Low Power Radio

Careers in Broadcast Techology - It's not all fun and games!

2011-12-31T07:30:00.000-08:00

Low power radio is an interesting, relatively low cost hobby and lots of fun but there is a serious side, too. It turns out that those of us with a technical bent are very much in demand in the broadcast, technology and regulatory sectors. Not only are we in demand, it turns out we're actually scarce - yep, that's right, geeks get paid!
     The Alabama Broadcasters Association recently announced that the organization is establishing a Broadcast Engineering Academy at the ABA office in Hoover, AL. “This idea was created out of pure necessity,” said Bill Ballard, ABA Chairman and President and General Manager of WIAT-TV in Birmingham, AL. “There is such a shortage of broadcast engineers that something had to be done." Visit the Alabama Broadcasters Association's home page and read the full write up of the academy
     Visit this Google search link to check for a broadcast association in your home state.
     At the national level, the Federal Communications Commission offers internship opportunities throughout the year, providing opportunities for interested students to increase their knowledge of the issues and technologies that are shaping the telecommunications market. As FCC Chairman Julius Genachowski said in his recent speech to Congress, "A powerful indicator of the growing significance of the tech sector to our broader economy came a few weeks ago when Apple surpassed ExxonMobil as the most valuable company in the world." Visit Student Internships at the FCC to learn more.
     Happy New Year!

The new SSTRAN AMT5000 - the high efficiency AM transmitter kit

2011-11-13T14:15:00.000-08:00

Our friends at SSTRAN are offering a new AMT5000 Transmitter Kit and low power radio enthusiasts on the web are taking notice.
     SSTRAN tells us that the new model is shipping right now and is avaialialble in the same dependable configurations, with "10 kHz channel spacing for use in North and South America. Includes enclosure and 120 Volt AC Adapter. All surface-mount ICs pre-soldered to the board."
     In telling us why this model can truely be called high efficiency, SSTRAN responds that "Transmitter range is a complicated issue that depends on the transmitter output power and the installation-specific antenna and ground losses. FCC rules limit the final RF stage power input to 100 mW. For any given antenna and ground system, the "best range" prize will go to the transmitter that is able to convert the largest portion of the 100 mW input power to output power."
     "The efficiency of the RF output transistor is the first part of the overall efficiency calculation. Output transistor efficiency is a measure of the amount of input power that is lost as heat in the output transistor. The AMT5000 transistor efficiency is 98%, so only 2% of the input power is lost as heat."
     "The AMT5000 has a built-in tuning coil in the form of an iron-powder core toroid coil. (The designer believes) Toroid coils offer major advantages over other coil configurations occupying the same physical volume, but only if the core material is properly chosen for the operating frequency and power level."
     "In summary, the overall efficiency of the AMT5000 will be equal to or better than any other Part 15 transmitter utilizing an internal tuning coil, and the overall efficiency will be essentially the best theoretically possible when using any conceivable super-efficient, externally tuned antenna system." (© sstran.com)
     Full specifications here: SSTRAN AMT5000 Specification Overview
     Web Article here: AMT5000 High Efficiency Pro AM Radio Transmitter Kit
     Web comments and discussions: part15.us/node/3004 | part15.us/node/2840 | part15.us/node/3064 and part15.us/node/3045

Low power AM transmitters in action

2011-10-31T09:15:00.000-07:00

Today's post brings us YouTube videos from several hobbyists who have built and operated some of the transmitters we have written about in the past - if you were curious about if and how these transmitters really work, look no further than Google's billion dollar baby.
We'll begin with a video from a hobbyist who built the Sci-Toys.com four-pin crystal oscillator transmitter, who reports "I started with the version here at sci-toys.com transmitter plans. The basic idea is to run a signal through a crystal oscillator, which when output to an antenna, sends radio signals at a fixed frequency (in our AM band's case, 1.0 and 1.2 MHz). See the schematic at crystal oscillator schematic." Nice work and a nice demonstration of a project that is often criticized on some message boards - sounds pretty good to me!
Next, will take a look at a couple of videos from the builders of a popular tube kit,
the iTx two tube unit, available from Vintage Components in the UK.

The first builder tells us of a "Home made vacum tube MW broadcaster demonstration - This is a kit which I purchased online and built onto the supplied PCB, it works extremely well and is called the iTx if I remember correctly. The unit can operate on between 27 and 90 volts dc with a heater voltage of 1.4 to 1.5 volts dc. An ac heater supply is unusable due to the hum created which totally blanks out the audio being broadcast."
Another video from an iTx kit builder here: A Nice kit to order and to make - iTx AM Tube Transmitter Kit

Many more videos about low power, home made AM transmitters can be found here: YouTube search AM transmitters Enjoy!

AM & FM Transmitter Lab Tests, Reviews and Commentary

2011-09-27T20:28:00.000-07:00

Please enjoy this survey of transmitter review sites, offering reviews and commentary about low power AM and FM transmitters
• Do It Yourself Broadcasting
"Transmitter images have links to their manufactures. Links to transmitter reviews are also provided when available."
• Transmitter Reviews & Commentary
"Our transmitter review and commentary section. Comments are welcome!"
• CRP Transmitter and Kit Reviews
"Low power AM and FM transmitter kits assembled and/or read about in my course of study. Provided to help decide whether it is really worth it to build a transmitter from a kit verses purchasing a pre-assembled transmitter."
• Part 15 Radio Product Reviews and Lab Evaluations
"Giving the Part 15 radio broadcaster the ability to learn about equipment and services that will assist in a positive low power broadcasting experience, offering information on the potential benefits and downfalls of the evaluated products."
• Low Power AM Transmitter Reviews
"Four low-power transmitter products that retransmit programmes on MW at low power, so that vintage radios can play authentic broadcasts."
• FM Transmitter Review.com
"A directory of FM Transmitters to help avoid frustrations while saving money! Over one hundred personal FM Transmitters sorted and categorized by features and available options - quickly search what matters most to you."
Some great arm chair engineering awaits...

Some late summer links for transmitter grounding and antenna information

2011-09-09T07:33:00.000-07:00

Where can I learn more about grounding my AM transmitter? Is an RF ground the same as lightning protection? Can I use a counterpoise instead of a ground rod? What's the best antenna design for me? How do antennas work, exactly?The answers to these and many more questions can be found on our late summer tour of great info sites. We'll start with our talented friends at smeter.net:
Ground characteristics, lightning protection grounds, radio frequency grounds, and practical grounding systems. Information about Earth characteristics, grounding material characteristics, benefits and practical issues related to grounding systems.
Also many small DOS software applicatons that will help you 'do the math.'

While you're there, stop over at the Antenna Design Information & Software pages, for a wealth of free antenna design information and software. As smeter.net says, "Good antennas contribute greatly to the communication abilities of transmitting stations."

Another point of interest on today's tour of interesting links would be
Antenna-Theory.com, the online source for understanding antennas. Introduction to antennas, antenna basics, types of antennas, antenna arrays, antenna measurements and many more antenna related topics

You might also like to see your tax dollars at work, over at the United States Army Signal course on, what else, Antenna Theory. Designed to teach the theory, characteristic and capabilities of the various types of radio antennas from high frequency to ultra high frequency, with field expedient antenna designs.

If your new to the low power world, you might prefer Antenna Theory Simplified, offering some simple techniques for better understanding of some terminology used and how it is applied in the antenna industry, providing the reader a wealth of knowledge that is essential for antenna selection and solutions.

Broadcast low power FM in stereo or mono? RESOLVED

2011-08-13T08:04:00.000-07:00

I've been watching the stereo vs mono low power FM debate for as long as I have been broadcasting. Not only have there been widely variant opinions, even real radio stations have tried going mono to improve reception.
     To add to this confusion, when the high powered FMs tried mono the results were mixed at best and the talent complained bitterly about the change. One example was Washington DC's WJFK during their "Guy Talk" era in the early 2000s. Howard Stern, Opie & Anthony and Don & Mike jabbered from 5:00 am  to 7:00 pm and the engineers hoped that switching to mono would improve signal coverage. The listeners complained, the talent freaked out and - worst of all - no real improvement in coverage. So what's the real deal?
     Fortunately, a real radio engineer has settled the matter once and for all using the tried and true argument-settler in technology arguments - math! Paul Thurst, radio engineer and blogger, just posted a great summary of his conclusions on his blog linked below. After running the numbers, Paul first answered the question for high powered FM stations - why doesn't switching to mono make a difference?
"Those stations tend to have a great deal headroom when it comes to power density, building penetration, multipath (picket fencing and capture effect)."
     So you really don't see a difference in range or coverage between stereo and mono in a mega-Watter. On the other hand, if you are working the low end of the power curve, either with licensed LPFM (10 Watts - 100 Watts) or are working under Part 15 rules (micro-Watts), it's a completely different story.
"On low power stations, stereo can be a great detriment to reliable coverage." and "For Class A and LPFM stations, it (stereo) should be turned off."
     Or, in the case case of purchasing a low power FM transmitter, look for a mono unit, skip the encoder or look for a unit that can run in either mode - example, the Whole House FM Transmitter 2.0
     Read Paul's entire post and check out some of his other information on his excellent engineering blog.
FM Stereo vs station coverage by Paul Thurst, on August 8th, 2011, posted on Engineering Radio blog at EngineeringRadio.us

Another round of readings in Electronics

2011-08-06T13:23:00.000-07:00

Exploring the digital attic, found some dusty old volumes you might find useful:
Need a quick circuit for a simple audio amp?
• Integrated Circuit Audio Amplifiers By Mike Martell N1HFX
Can there be too many readings about antenna coils?
• Construction of Antenna Matching Transformers
• Loading Coils for Low Power AM Antennas
General low power info
• Joe Carr's Radio Tech-Notes - What is a "Good Ground?"
• Hints for Low Power Broadcasters
• L P R Booklet
Hard core audio modulation for AM
• Modulation Transformers
Click here for a list of earlier posts featuring readings in electronics

Very simple low power AM transmitters

2011-07-07T21:52:00.000-07:00

UPDATE: Thanks to all who wrote to tell me that the links in this post didn't work - oops! Miss one little quotation mark and there goes the whole link - fixed!
A transmitter with fewer than 10 components? No, four transmitters with fewer than 10 components! Here are four ways to have fun with low power radio, quickly. Low-component-count transmitters probably won't deliver spectacular range and they will be a bit fussy to tune but enjoyment is virtually guaranteed. These circuits are easy to put together and fun to try. Be careful - I built one of these in the early 90s and I've been hooked ever since!
    One transistor transmitter - This circuit has a fairly low input impedence and will operate in the 1200 to 1600 KHz range. The frequency is adjusted with the variable capacitor G1.
    A more robust one transistor transmitter - Another circuit that works best on the 800-1200 kHz range, but with changes to the inductor L or the variable capacitor C1 it can transmit to the whole range of the AM dial.
    A 555 IC used as an oscillator - This circuit uses a 555 timer IC, resistors, capacitors, mic and an wire antenna. The 555 timer IC is used a free running multi-vibrator with the frequency pulled down to 500 - 600 KHz.
    A crystal oscillator based 1000 KHz transmitter - In this circuit, the transformer isolates the input from the oscillator and provides a better impedence match. The signal from the secondary coil modulates the DC power to the oscillator. A wire connected to the oscillator output works as an antenna. Another 1000 KHz crystal oscillator page

So, you might ask, where on earth would one get these components, even if there are less than 10? Your Low Power Radio blog has answers! The four suppliers listed below are great places to start your search:
    Dan's Small Parts & Kits is a legendary ham and hobbyist supplier from big sky country (Montana!). Dan's is a "money order or wait for your check to clear only" vendor, probably a key to his long term survival selling small electronic items at low prices. Far too many items to summarize - if it's for radio, it's here.
    Midnight Science, home of the Crystal Set Society. Here you'll find links to FAQs, science fair suggestions, and introductory articles, along with a nice selection of low power radio parts like alligator clips, brass binder posts, air variable capacitors, coil forms, diodes and toroids.
    Peeble's Originals comes from the mind of Mike Peebles who has been producing crystal radios, tube radios, transistor radio kits, and informative instruction articles, since 1988. Here you will also find capacitors, audio match transformers, fixed variable coils & coil forms, connectors, enclosures and other hardware.
    Science Toys offers a whole selection of fun science projects, kits, parts and supplies, as well as the crystal oscillators, audio transformers and other items needed for the crystal oscillator circuit above.

Enjoy!

The Mod Squad

2011-07-03T08:20:00.000-07:00

Curious about low power radio and interested in electronics? Perhaps you have one of these (or something similar) lying around and you'd like to try something fun. Here are some transmitter modifications for your study:
   • Belkin Tunecast II Mod (12 page PDF)
   • Belkin Tunecast F8V367 mod
   • Belkin Tunecast Auto Universal FM transmitter Mod
   • C. CRANE FM Transmitter mod
   • Radio Shack Stereo FM Transmitter (12-2051a) mod
   • Zune FM Transmitter Mod
   • More on FM transmitter mods by Tim Gray
   • Dozens of YouTube videos about FM transmitter mods
But, isn't it illegal to modify a transmitter or to operate a transmitter that has been modified? Short answer, no. When it comes to a hobbyist experimenting with a low power tramsmitter, the FCC rules are silent on whether the transmitter was purchased off the shelf, modified, built from a kit or made from scratch.
    So what's the deal with "FCC certified transmitter" etc.? The FCC requires that any transmitter that is sold to the public for use in the FM broadcasting band be type certified before it can be sold. Sold, not operated. Once you buy it, it's yours and you can do whatever you want with it - except sell the modified transmitters on ebay :) The operative rule for FM transmitters is very simple - the field strength can't exceed 250 uV/M at 3 meters. Most agree that equals a range of around 200 feet on a low priced portable. A car radio will pull in that signal strength at two to three times that distance.
    What sort of range will get the FCC upset? Well, the FCC speaks only in terms of field strength but the FCC's enforcement records are public and can be easily accessed here. As you can see, the FCC generally intervenes when the field strength reaches several times the permitted uV/M, often at distances greater than 3 meters. There are two reasons you don't have much to worry about if your modding a low power FM transmitter.
    First, a transmitter can only put out a fraction of the power it consumes. The most awesome transmitter imaginable would only deliver about 30% of it's input power as radio frequency output. When you are modding a transmitter that was designed to run on two AA batteries, you're not exactly going to burn a hole in the wall with the fearsome radio power you unleashed with a basic mod.
    Second, you are starting with a low power transmitter designed to be mass marketed. It's not like the manufacturer is going to toss in a bunch of pricey, high output components in the transmitter, just waiting to be unleashed by your mad mod. Far greater than the risk of being hauled away in irons by the FCC is the risk of being just a little disappointed in the results of your efforts.
    The good news is that most mod-able low power transmitters do start with a little extra punch, then the manufacturer reduces the signal power (called attenuating) to make sure the transmitter delivers well under the 250 uV/M @ 3M rule when mass produced. A good mod, plus a well matched antenna, can restore that extra power and get you closer to the top end of the limit.
    What is a "well matched antenna?" An effective antenna should start at a 1/4 wave (vertical) or 1/2 (dipole) wave length, then be adjusted to account for a peculiarity of radio frequency (RF) waves. To calculate wavelength in inches, divide 11811 by your frequency in MHz. For example, if I transmit on 87.9 MHz, 11811/87.9 = 134.37" and then a 1/4 wave vertical would be 134.37/4 = 33.6" but you need to make one additional adjustment. Radio waves travel on the surface of conductors rather than through the core, so RF moves about 5% slower. To adjust for this factor (called the velocity factor), we slightly shorten the antenna wire. 33.6 X .95 = 31.9" for a 1/4 wavelength antenna at radio wave speed.
    A dipole is simply two 1/4 wave length elements, one connected to the hot RF output and one connected to the ground side of the circuit (a nice place to pick that up is the negative battery terminal or power connector).

And there you have it, a little peek into the mad mod world... for research purposes only, of course.

FM transmitting antennas for low power radio

2011-06-29T06:38:00.000-07:00

We have many posts and links for AM transmitting antennas as AM antennas are hard to find and usually must be hand built by the hobbyist. FM broadcasters have a tougher time with regulation but antennas are easier to find - many nice units are available off the shelf at great prices.

	Low power quarterwave antenna, perfect for small FM stations, 20 MHz bandwidth, handles 15 Watts of power, vertical polarization, complete with mounting bracket. Easily mounts to your balcony, any metal railing or antenna mast. Small size and compact dimensions make this antenna easy to conceal, reducing risk of complaints or theft
	Efficient PCS028 FM band magnet base antenna, 200 watt power rating for transmission, comes with 18 feet of RG8 coax and PL-259 connector. Portable, easy to set up, easy to move, easy to conceal, great for temporary or mobile operations - an all around handy sky hook
	Low power PCS-0210 single circular dipole, no-tune operation makes this omni-directional antenna a good match for low power transmitters, the higher you raise it, the better your range. The ferrite balun used limits power handling to a couple of watts
	Low power single folded dipole, a wideband, no-tune FM antenna, complete with mounting bracket, easily mounts to balcony or antenna mast. Somewhat directional when mounted horizontally, omni-directional mounted vertically. Also limited to a couple of watts by the ferrite balun used.
	Thinking of doing it yourself? Check here for a number of antenna designs including Dipole, J-pole, Twin-lead, and Quarter wave ground plane designs with number of links provided at the bottom, leading to additional design sources regarding antenna construction

Before you connect to your antenna, consider using a dummy load for testing and tuning. You can easily build a dummy load with an RF connector and carbon resistors (not wirewound or metal film, these react differently at RF frequencies). One 1/4 Watt, 47 Ohm or 68 Ohm carbon resistor is fine for 10 mW - 100 mW transmitters, four 220 Ohm 1/4 watt resistors in parallel (220/4 = 55 Ohms) will work for 1 Watt units.

Real life low power radio stations

2011-06-19T16:53:00.000-07:00

As part of our continuining eforts to answer the question "Does anybody really do this stuff?" please to be enjoying some information from those who practice the art. Images and descriptions are the copyrighted materials of their respective owners - enjoy!

"Rhemaradio has returned to the Pacific Northwest and the Columbia River Gorge. With a new web domain, new site and updated studio and broadcast equipment.
After decades as a professional broadcaster (Marshall) and newspaper mogul (Alexis), my wife and I founded Rhemaradio in late 2005 and Marshall is now pursuing a career in voice acting and voice overs from his digital home recording studio (The VO-Factory)."

"Friday Harbor Tiny Radio - Our mission is to serve the town of Friday Harbor with local news, weather, sports, special events, and entertainment - all brought to you in glorious sandflea-powered Amplitude Modulated Monophonic sound.
Playing music by island musicians, ferry reports, weather, calendar updates and announcements, poetry and read aloud stories, local events, high school sports, commentaries, Old Time Radio, and island scuttlebutt.We are actively looking for (especially local) NorthWest indie artists who can use us to air and promote their music, comedy, and storytelling."

"Community Radio is coming to Buffalo, for those who demand that their radio serve as a collective forum where locally relevant ideas, opinions, news, and music are broadcast to the community, the actual options on our radio dial are few and far in between.
The important thing is to open up an independent, non-profit, community-controlled signal so that a forum can be created for the exchange of ideas, music, and information relevant to our city. Thanks to everyone who came down to the fundraiser and a special thank you to the bands/DJs who were so kind to donate their services."

"Serving Cuyahoga Falls-Chapel Hill Plaza Area, MRAM is a Part 15 Radio Service of Miles Robert Audio Project Recording Studio. Broadcasting 24/7 at 1500 on the AM dial, programming includes Local Talent from our Miles Robert Audio Project Recording Studio with NOAA Weather broadcasts when threatening conditions exist and newscasts on the hour.
Send us a note and include the Date, Time, Frequency, Signal quality and some details about what you heard as proof. We’ll verify your report and send you a card signed by the GM as proof of reception."

"PGCR is Pleasant Gap Community Radio, a FCC Part 15 authorized low power radio station at 87.5 MHz on the dial. As a Part 15 station, and not a traditional broadcast station, PGCR may or may not be 'on the air' at any given time. PGCR is the place to hear your favorite music and memories from yesterday through today, in addition to local news, weather, community information from around Pleasant Gap, PA and world news from the Feature Story News network."

Low voltage vacuum tube transmitter

2011-06-14T06:45:00.000-07:00

My analytics data tells me my visitors love tube projects! I recently located a low voltage tube transmitter project created by the famous electronics dude Joe Sousa, who tells us:

"Following the RadioMuseum tradition of home-made AM transmiters listed at the end, I have come up with this simple single tube version. I based the design of this simple transmitter on Gammatron/Gridless-Audion operation of the 1Zh37B Russian Subminiature Tube."

Next, Joe describes his VCO tuning approach:

"A matched capacitor and ferrite stick could have been recovered from a discarded AM transistor radio. This would give a fairly accurate frequency indication. In my case, the ferrite and capacitor came from different sources."

Joe goes on to describe his home-made chassis:

"The box is made of soft Bass wood and was bought ready-made at a local crafts store. I added the two wooden posts to support the ferrite stick, and removed the original brass clasp to fit the variable capacitor, after chiseling out the wood. The lid is kept closed with an embedded pair of neodymium magnets on one of the front corners of the box and lid."

Joe describes his power plan:

"The picture that shows the batteries includes a 0V battery for Bplus in the form of a shorted battery clip that was recycled from a dead 9V battery. The 1.5V cell you see with a 9V clip on it is used to run Bplus at 1.5V."

Read the full article, get the schematic and full construction instructions at the fabulous Radiomuseum.org forum - go there!

New (to me) Self Contained, Fully Assembled, Outdoor AM Tramsmitter

2011-06-05T09:32:00.000-07:00

UPADTE - The manufacturer responded promptly with: Our prototype transmitter has been operating continuously since it was built in 2006, except for short periods of power outage. It has proven to be a reliable design and a good product, and we have used it in both permanant installations and temporary ones where it is powered from an automobile cigarette lighter socket.

The pricing information is available at www.waynemillerassociates.com/GI/GI100ordering.htm This page includes the operator's manual for the transmitter, as well as the manuals for the accessories that are currently offered. The Sales link to our manufacturing partner is listed on the ordering information page.

Photo and quotes are
© Wayne Miller Associates, LLC, all rights reserved

I recently learned of another low power AM transmitter maker called WAYNE MILLER ASSOCIATES, LLC who tell us they offer a "Self-contained, pole-mount 100 milliwatt AM transmitter with synthesized frequency selection and very low distortion audio and 30 dB of automatic gain control."

According to the AM TRANSMITTER Model GI-100/1000 user's manual "The Model GI-100/1000 is a professional quality, low distortion AM transmitter unit that is designed for continuous outdoor use. It is FCC certified to operate in the standard AM broadcast band and can be operated unlicensed in accordance with Part 15 of the FCC code. Made in USA."

It's always exciting to discover a new vendor and I've sent the company an email asking about publically available pricing and ship dates - more when I have it!

Beginners guide to AM Transmitters, AM Antennas & AM Grounding

2011-05-26T18:39:00.000-07:00

We get a number of inquiries about low power broadcasting on the AM band. Let's take a quick look at the four critical areas impacting range in low power AM broadcasting: transmitter, based loaded antenna, a good ground and tuning. First is the transmitter type. Check to see what kind of transmitter is used and pay attention to how transmitter output is configured.

Is the transmitter a simple oscillator or is a buffer amplifier present? This is important because a simple oscillator will be very sensitive to small changes in the antenna, ground or surroundings. A simple oscillator will be a bit trickier to tune. A more sophisticated transmitter will have a final amplifier section that will protect the oscillator from the effects of local environment changes. Either can be made to work but it's important to know which is being used. Check the schematic and the circuit board to see if there are internal matching circuits (small inductors or a few capacitors) between the transmitter output and the antenna terminal. These low-tech approaches to antenna matching are great for transmitting across a room but not across the street. Jumper these items out of the circuit when tuning for maximum range.

The 3 Meter rule means loading the short antenna with an inductor coil and then tuning the assembly. Specific antenna construction projects here, here, here and here

Ground rods, ground radials and ground screens are all very helpful. The FCC won't count anything below ground so put some metal under the dirt. Six radials, ten feet long, will deliver at least 50% of the maximum benefit so start there. A ground connection to the transmitter more than a few inches long can result in an unbalanced dipole and an NOUO for violating the 3 meter rule.

Finally, tune the system by adjusting components. Changing the connecting point (tap) on the coil changes the inductance and can make fairly large-stepped adjustments. The antenna can be shortened slightly for fine tuning. The filament of a low current lamp will indicate the current level passing through the antenna when connected in series with the antenna and coil. A micro-ammeter can be connected in series with the antenna tuning circuit and the range should be in the low uA

Urgent Sponsor News - Appilan Technologies

2011-05-15T11:19:00.000-07:00

We just heard this from our sponsor and we hope you'll join us in giving Appilan your full support!

From Appilan's CEO - "We used to advertise heavily on a popular ad network, until one day the criterion for advertisers magically changed and we were blacklisted. Now, we can't run any network ad that links to Applian. Are ad networks blacklisting specific advertisers to protect other parts of their businesses?"

We released a new version of WM Recorder - the easiest, most powerful way to record millions of video and audio files from the internet - automatically!

We also released Replay AV - Radio on Steroids! Capture and schedule recordings for both Streaming Audio and Video.

Replay Converter is the easiest way to convert video and audio files. We've decided to lower the price of Replay Converter to just $9.95!

We have also updated Freecorder4 our versatile FREE audio/video recorder/converter - a great introduction to the Replay line of recording software.

These applications are great for managing content for Low Power Radio, as well as being just plain fun - Get some soon!

Updates for AM Transmitting Antennas & Grounding

2011-05-08T12:15:00.000-07:00

Spring time is antenna time. Better weather and more daylight gives us the chance to get out and play with our skyhooks. In honor of Spring, here is all the information I have handy on transmitting antennas and transmitter ground systems for the medium wave AM band. As always, be extremely careful of overhead and underground (call before you dig!) power lines and watch your step on that ladder...

AM Transmitting Antenna Articles

AM Transmitter Antenna Handbooks and Manuals

Medium Frequency Antenna Construction Plans
Excel spreadsheet Antennacalc.xls for use with 'Medium Frequency Antenna Construction Plans' above
The MWA Antenna Book
The Big Antenna Book, includes Carrier Current Tuning info
Antenna Section of Kyle Drake's Low Power AM Broadcaster's Handbook

AM Transmitter Ground Systems

Now you have the info - build it and they will listen - well, maybe...

This year's vanity post

2011-04-24T07:30:00.000-07:00

Web analytics reports tell us about blog visitors. If we create a blog that attracts significant visits, trends in the data emerge. When bloggers see positive trends we blab about those trends in vanity posts like this one. The trends for Low Power Radio are most encouraging!

First, your faithful blog author going through three jobs in two cities in 2010 meant posts that year were few and far between. How humbling it was to see visitors still using the (then) static content.

Equally humbling was finding we are an international blog with a surprising number of recent visits from countries like Canada, the Netherlands, the United Kingdom, Germany, India, Russia, Italy, the Philippines and South Korea - thank you! Finally, the staple of the internet - top ten lists - looks both predictable and interesting at the same time.

Top ten search terms:

low power radio
low power am antenna
talking house transmitter
low power radio stations
am transmitter amplifier
whole house transmitter
micropower radio station
set up a radio station
fm amplifier kit
fm transmitter hum

Our top ten posts:

Top ten referrers

Search Engine performance

About two thirds of our visitors arrive via a search engine, the balance linked from a referring site

82% search engine traffic came from Google
Yahoo and Bing each kicked in about 7%
All the others made up the remaining 4%

blogger.com and translate.google.com sent oodles of visitors but I think those are already counted under Google. If not, awesome!

It's encouraging to see that folks still appreciate some of our earlier posts while coming back to see our newer information. Our referrers represent a solid community of sites dedicated to low power radio and experimental broadcasting. The search engine activity indicates there are lots of interested folks out there looking for information.

AM broadcast band transmitter amplifiers for carrier current

2011-04-13T19:36:00.000-07:00

Most low power experimenters broacdcast through an antenna. Carrier current provides for broadcasting over a limited area by superimposing your RF signal onto an electrical power transmission wire. Nearby radios pick up the signal and the range extends along the wires carrying the signal. This topic was covered in an earlier post, titled Low Power Broadcasting with Carrier Current

One item not covered earlier was the amplifier needed for effective carrier current transmission. Experimenters who might have a Part 15 compliant AM transmitter won't get much range in carrier current without a low power booster amplifier able to push a watt or two of RF down the power lines.

Basic theory for an external final amp is to first match the 50 Ohm output of the transmitter to the input impedance of the amplifying transistor. You do a little power management and then you match the output to the 50 Ohms for a typical transmitter output. Included here for your review are four amplifiers from two designers, ranging from 1 Watt to three Watts of additional power. These circuits are fairly simple and reasonably tolerant of various approaches but do have the onerous component of winding several coils.

It wouldn't be fair to turn you loose on these projects without a little help for the coil winding part - please to be enjoying these helpful (and mercifully short) guides.

Stereo to mono the easy way, by Mike Sokol - guest post from 1996

2011-04-05T19:14:00.000-07:00

Searching for a way to combine stereo channels for my FM mono transmitter, I found this article back in 1996. I had a link to this information in my favorites for years until it finally came up "404." Thanks to the Internet Archive I was able to recover this seminal missive and present it here for you.

We’ve all been in a fix from time to time when we needed to sum two audio signals into one. Most of the time, it’s taking a stereo signal and turning it into mono."

I designed Bus’tr simply as an aluminum project box with 1/4” circuit jacks and 680 ohm build-out resistors. To use it, you just hook 2 outputs of anything you want to mix together into 2 of the jacks and the signal comes out the 3rd jack, simple as that.

Notice that all 3 jacks have a build-out resistor, allowing any two jacks to act as an input. You can substitute RCA jack for the 1/4” jacks if desired. For this configuration, be sure that the equipment you’re hooking together is rated at 600 ohm or less output impedance. Higher or lower impedances can be made to work by substituting different resistor values

I have also used lower resistor values when the source output voltage was higher than a line-out connection.

See the complete article by Mike Sokol

Low Power Broadcasting with Carrier Current

2011-04-03T11:29:00.000-07:00

Carrier Current Broadcasting injects an AM radio signal into a building or neighborhood electrical system. This strategy allow a low power, unlicensed station to broadcast to receivers near the electrical wires carrying the AM broadcasting signal. This can be a simple and relatively inexpensive means to start a radio station where the broadcaster has access to the electrical distribution system. Special equipment is used to connect an AM transmitter into the electrical system for broadcasting.

General information on Carrier Current:
AM Carrier Current Broadcasting from the short-lived Hobby Broadcasting Magazine, Part 1 and Part 2
Some interesting forum threads at Part15.us here, here, and here.
Carrier Current Broadcasting Theory from the mysterious LPB
Carrier Current Techniques an older but all-inclusive handbook, including transmitter and coupler schematics.
Radio Systems' Carrier Current page

Carrier Current Transmitter Plans
A Simple 2 Watt Tube Carrier Current AM Broadcast Transmitter
Build This: Carrier Current Audio Transmitter
Enhancing the Ramsey AM-25 (for carrier current use) by George Trinkaus
'Part 15' Broadcast Band Transmitter
As always, be careful around electricity!!!

The Sea Grant low power radio stations

2011-03-16T14:04:00.000-07:00

Low power radio continues to be a useful tool for Sea Grant Extension to reach a large audience traveling through a particular geographic location. Sea Grant Radio continues to broadcast messages about research pollution, septic systems, wildlife, marine research projects, the recruitment of volunteers and related events; as well as announcements about educational events and opportunities

A portion of Sea Grant Radio listeners responded to online surveys and indicated an interest in learning more about wildlife, research, events and educational opportunities. There is some evidence that radio listeners are attending events and facilities they hear about on the radio. Sea Grant Radio continues to be viewed as an attractive resource for partner educational agencies.

One of the best outcomes from the Sea Grant program is the wealth of information about the real-world use of low power radio. Please to be enjoying the excellent publications and web pages listed below:

Reaching target audiences
Tuning into low power radio

Great Bay area radio listener survey

K-YAK 1610 AM Low Power Radio
Oregon Sea Grant Low Power Radio Study
Low power radio as a high power education tool
Low power radio, and antidote for visitors looking but not seeing
Low-Power Radio Stations Warn Travelers About Zebra Mussels
Texas Sea Grant unveils Low Power Radio for Calhoun County coast
Woods Hole Oceanographic Institution Sea Grant Low Power Radio Project

Oh Canada! Very friendly to low power radio

2011-03-12T06:00:00.000-08:00

Canada is light years ahead in the area of low power radio and guess what, NAB, their commercial radio industry hasn't imploded yet!

Industry Canada exempts FM broadcasting transmitters from authorization when those transmitters meet the requirement of Broadcasting Equipment Technical Standards 1 (BETS-1). These transmitters are commonly called Low Power Announcement Radios or alternatively real estate radios.

According to BETS-1, “The maximum power output of the transmitter into its antenna, with no modulation, shall not produce a field strength level of more than 100 μV/m as measured at a distance of 30 metres, compared to the USA FCC standard of 250 uV/m at 3 meters. That might seem miniscule, but it could be said in a very crude way that Canada allows more than five times the power.

Learn more with Frequently Asked Questions on Low-Power FM Broadcasting from Industry Canada

One such operator is VankleekFM a privately owned Ultra Low Power FM transmitter located in the village of Vankleek Hill, Ontario. The owner of the service, Jean Sarrazin, maintains a license with Industry Canada to use the frequency, 88.7 as an unprotected, "local public information service" and describes the operation as follows.

As a low power station the service is exempt from most CRTC content requirements as long as it respects the CRTS's exemption order defined by the following criteria:

Operates between 88 -107.5 MHZ,
Field strength measurements at 30 metres must not exceed 100 uv/m
Meets all technical requirements of Industry Canada,
Originates all programming,
Does not rebroadcast the programming of another (broadcast) undertaking,
Does not broadcast religious or political programming,
Does not broadcast the same message on more than one transmitter.

I found a bit more information at an inactive but informative site called Radio XY - English Bay - kewl, eh?

Low power radio updates from around the web

2011-03-06T07:04:00.000-08:00

FCC Eyes Expanding Role of TIS • RadioWorld.com • by Randy J. Stine, 03.04.2011
(Three) petitioners contend that conditions have changed since the TIS (was initiated) in 1977, (one) petition asked to eliminate the limitation that confines TIS stations to areas near roads, several asked the FCC to consider use of “ribbon systems,” and some operators would like to include such things as Amber alerts, terror threat levels, NOAA weather forecasts, public health warnings and other information (more...)

Can You Do a Lot With 0.1 Watt? • RadioWorld.com • by James Careless, 02.01.2011
KPFK is turning to low-power AM transmitters to reach Hispanic neighborhoods in Los Angeles. “With a few LPAM transmitters and antennas, we can cover MacArthur Park,” says KPFK Program Director Alan Minsky. “About 50,000 people work in this area right now. That’s a big audience that can be reached in a very affordable manner” (more...)

Low Power Hour • kdxradio.com • by Carl Blare, © 2011
The Low Power Hour (LPH) radio program is hosted by Carl Blare and features news and conversations about legal, unlicensed, AM, FM and Shortwave broadcasting in the U.S., under Part 15 of the FCC Rules, welcoming hobbyists, professionals and equipment suppliers who pursue low power radio activities. The Low Power Hour (LPH) radio program is public domain, community audio. Submissions of your own low power interviews or other clips may be included in future editions of the LPH (more...)

MAXNET? Shortwave plus narrow band FM plus broadcast band FM

2011-02-25T22:38:00.000-08:00

(From the original marketing page) MAXNET is a broadcasting system consisting of a central Network Transmitter System: Model MX-1356, Range to 5 miles, PLL narrow band FM operating on 13.56 MHz, complies with Part 15.225. This main network transmitter sends out a signal which is picked up by each repeater.

The signal is converted to the FM broadcast band and transmitted to passing vehicles within the allowable radius of about 300 feet (approx. signal strength is 7.5uV/M). One repeater is installed every 500 to 600 feet long the highway or for each 300,000 sq. feet (approx. 7 acres) of desired coverage area within an unobstructed perimeter. All repeaters transmit on the same frequency, so as a motorist passes one repeater he approaches the next, providing seamless reception.

Easy to install solar powered repeaters are fully self-contained, no cables to run. A complete functioning system can be set up quickly
MAXNET network transmitter controls all repeaters and feeds the common audio signal without wires.
Installed multi-band audio processor makes MAXNET as loud and crisp as any major market station.

See the historical MAXNET marketing page, circa 1998, here
Could a similar system be set up today? Any Ideas?

Guest post from the distant past

2011-02-05T13:45:00.000-08:00

Back in the 28.8kbps, 640 X 480 internet days an experimenter in Greece put up a nice web page about his junk box AM transmitter. I stumbled upon it back then and found it really interesting, then it went 404 as all web pages from back then did when which-ever dial-up ISP folded. Thanks to the Internet Archive, I was able to relocate this lost gem and offer it to you now. A teaser follows, the entire work is linked below:

Simple low power AM transmitter

Since many people are looking for low power radio transmitter plans, I’ve decided to post the plan of the most simple radio transmitter I know. It is a little AM transmitter, a wireless microphone really, for the Medium Wave band (but it can be used for low power broadcast on the Short Wave band too). What is attractive in this circuit is its simplicity.You can’t expect much from such a little project, but, it’s a good and especially easy start broadcasting.

It won't cost more than 5-10 USD, the components are everywhere readily available (or, they can be cannibalized from any old AM portable radio). It can be constructed and tested in less than 2 hours. The transmitting power is subject to the transistor type one will use and the voltage of power supply, but it’s somewhere around 50mW, as far as I can tell. I found that my construction works best on the 800-1200 kHz range, but with changes to the inductor or the variable capacitor it can transmit to the whole range of the AM dial.

Christos Z. Konstas

See the entire web page here: Simple low power AM transmitter

FCC Enforcement Actions for Home FM Transmitters

2011-01-26T10:52:00.000-08:00

In our last post we looked at enforcement actions for AM operators and discovered two things:

There aren't very many enforcement actions against AM operators, only around four or five each year.
Enforcement actions centered on very high power operators and the configuration of the transmitter, antenna and ground wires with a focus on the "three meter rule."

Now, a look at the Low Power Radio mailbag tells me that there is similar interest in the FCC actions regarding FM operators, so this time around we'll get an overview of the FM notices and citations. I reviewed over 300 recent FCC actions against FM operators and there are two messages there, as well:

Unlike the actions against AMers, there are several actions each month against FMers so FMers are really getting lots of enforcement attention.
It's all about the field strength in microvolts per meter, folks, so that's what we really need to discuss.

So what is field strength and what are "microvolts" per meter or uV/m? The uV/m is a way to measure the practical power output of, in this case, low power transmitters. For AM operators, permitted uV/m is calculated based on the frequency being used with this formula: (24,000/F)/m at 30 meters, so the lower the frequency the higher the permitted power.

In FM operations there is no formula. FM field strength is limited to 250 uV/m at 3 meters, period. But a hobbyist might ask "what the heck does that mean for me? To arrive at a useful answer it's important to remember that in the FM world the field strength arises from two factors - the output power of the transmitter and the quality of the antenna match.

A transmitter with very low power output (in the microwatt range) could be matched with a very well constructed antenna and would probably violate the letter of the law. On the other hand, some certified FM transmitters have a rather high power output (perhaps 10 milliwats or 1/100th of a watt) but an intentionally poor antenna system to achieve the 250 uV/m rating. This is why FCC certified FM transmitters are usually certified as a complete unit including the antenna - and why changing anything on a certified FM transmitter voids the certification.

My survey of the 300 recent FM enforcement actions shows blatant disregard for the FCC limits (AKA "Pirate Radio" I guess) with field strength readings in the tens of thousands of uV/m at hundreds of meters away. I found only one action that seemed to be in the realm of useful for this discussion. The relevant portion is here:

The operation on frequency 107.7 MHz was measured at 1,381 microvolts per meter (uV/m) at 3 meters. This exceeds the allowable unlicensed limit of 250 uV/m at 3 meters established in Part 15.

So, at just a shade under six times the permitted field strength, we see an enforcement action. This was the lowest field strength enforced against in my review. But again, what does this really mean for a hobbyist? Transmitters are advertised to us with power output in watts, no one gives us field strength until we get busted! Here is what I have learned through experimentation and yes, I have been busted so I did get the field strength (more on that later).

I have connected a 10 mW (10 milliwats or 1/100th of a watt) transmitter to a well matched dipole and the absolute maximum range was 1000 meters using a car radio for reception that has a sensitivity of about 40 uV/m. What this tells me is that as long as you stay in the sub-watt power output area (10 mW, 100 mW, maybe even 1/2 watt with a not-very-good-antenna) you will likely fall below the enforcement threshold.

On the other hand, should you buy one of those FM blow torches off of ebay (2 watts, 5 watts and more), the number of enforcement actions in the FM band indicate you will likely be told to turn it off in a fairly short period of time. So, what's that like? My experience was that the quality of the enforcement experience is really up to you. As long as you are operating at a reasonable (even if not compliant) power level, not advocating sedition and are responsive to the FCC requests, the worst of the experience will be turning off your transmitter.

I received my NOUO back in 1997 so it's not online yet, but it looked just like the NOUO referenced above. My NOUO arrived by certified mail and I responded immediately. I shut down my transmitter and wrote back that the violation was inadvertent, that I was trying to adhere to Part 15 rules, that the transmitter was permanently off the air and that I would not violate FCC rules again in the future. I sent that letter certified mail as well and I received a very polite letter back thanking me for my cooperation and telling me that the matter was closed. Whew!

So for me the worst part was turning off my transmitter - it does hurt a bit to silence something we hobbyists tend to fall in love with. I think the message here is try to stay compliant no matter how frustrated you might be by the limited range because a silent transmitter has far less range than a compliant one!

That, and try AM whenever possible - more range, less enforcement - win/win!

FCC Enforcement Actions in the AM Band

2011-01-17T13:18:00.000-08:00

When discussing unlicensed low power radio, the topic of the FCC will inevitably come up, followed by the question "What would the FCC do if I..."

Fortunately, the FCC provides an easily accessible record of all of its enforcement activities. In reviewing recent FCC field actions we can learn from the mistakes of others and get a better idea of what to expect. You might also wish to review the FCC Enforcement Bureau Inspection Fact Sheet for general information about a station inspection. In this post we'll look at AM Band Enforcement Actions to see what kinds of violations the FCC has focused on in the AM band.

There might be two ways to look at this. Yes, there have been a number of enforcement actions over the past 8 years but, most are for outrageous power levels or blatlantly ignoring the 3 meter rule for antenna and ground. Other than that, there seems to be little enforcement attention paid to low power AM broadcasting.

A tip of the capacitive hat

2011-01-01T00:03:00.000-08:00

AM operators can further improve range by adding a little something to the top of the antenna called a capacitive hat.

Capacitive hats do not radiate a significant amount of signal. Instead, a capacitive hat increases the effectivness of the vertical radiator by assisting in distributing current along the full vertical length.

Without a capacitive hat, the RF current is stronger at the base of the antenna and decreases toward the top. For this reason, the upper portion of the radiator puts out very little signal.

A basic capacitive hat can be quickly made with several wires in the shape of a pyramid, supported by guy ropes. Some are made with two horizontal elements at the top of the antenna; small spokes of stiff copper tubing radiating out, with or without a perimeter wire or a hoop; or a metal disk.

A capacitive hat increases the effective height of the antenna with the beneficial side-effect of reducing the losses caused by nearby shrubs and buildings, especially where your antenna is taller than these objects.

Use at your own risk, of course, but a modest capacitive hat will not be likely be a compliance issue, there are no instances in the on line database of enforcement actions stemming from using this concept.

The how big, how long and how many of ground radials

2010-12-28T19:47:00.000-08:00

Medium wave broadcasters can gain significant range by adding ground radials the the base of a vertical antenna. AM transmitters use return ground currents and the ground (and radials) are part of the antenna system. An array of wires at or below the earth at the base of the antenna will improve the return path and increase range.

The signal strength scale is arbitrary and relative, based
on the maximum benefit derived from the highest possible
number of radials used during testing, either 120 or 60,
depending on the tester and the tests being performed.

Ground radials do not need to be much longer than the antenna is tall. A shortened antenna with loading coils will have a more compact "near field" where the majority of the antenna field is concentrated. The ground radials need only reach out as far as the near field extends. Field intensity decreases at the square of the distance from the base of the antenna.

When working with the upper end of the AM band, radials around 10 feet long should be adequate. For lower frequencies, consider extending the radials to 20 feet. Use heavy wire, around 12 ga., stranded or solid core, insulated or not, whatever is available inexpensively.

The optimum number of radials used appears to be subject to the principle of diminishing returns. Some recommend 60 or 120 radials but there is a high cost to using that many. Several hams have conducted controlled tests to determine the impact of additional radial pairs. I've plotted that data on the graph above. The benefit in additional signal strength appears to drop off quickly after 12 and 24 seem to yield 80% of the maximum possible benefit.

Field strength meter for FM transmitters

2010-12-12T13:22:00.000-08:00

It's old, it's crude and it's way too simple, it might not be sensitive enough and it might not work.

Still, it's cheap and quick and just might help with tuning an antenna.

Submitted for your review with no assurances!

It should probably be built in an RF resistant enclosure and the adjustment is strictly relative.

It should probably not be used in any arguments with the FCC.

More digital audio software

2010-12-04T17:56:00.000-08:00

MP3 Gain 550k - analyzes and adjusts mp3 files so that they have the same volume.
The MP3 VCR 6.2M - record MP3 streams off the web. Great for capturing content for rebroadcast.
Streamerp2p 360k - stream audio without a server.
1 by 1 94k - a small, fast and handy player which provides powerful tools to play tracks.
Peak Limiter 115k - enhances music recordings and digitized speech.
Audio Level Meter 385k - optimum setting of input levels for various sound recording functions.
Audacity 2.4M - free sound editor, record, edit, effects, unlimited undo.
Audio Stocker 8k - Audio Compressor and muxer plug-ins for WinAmp.
Weather Grabber 90k - get weather data.
Scanner Recorder 194k - sound activated PC recording utility.
Soliton 303k - a handy sound file attributes adjustment utility.
Ogg Drop XP 307k - drop zone utility for converting WAV files to the GPL OGG format.

The ins and outs of Audacity

2010-11-30T04:24:00.000-08:00

The free Audacity audio app is widely recognized as a phenomenal tool. The application is free but some feel the learning curve is steep. In order to help reduce the high non-monetary cost of learning to use this application, a variety of tutorials are offered.

Tutorial for creating your own bumpers and station ID files, our own perennially popular tutorial
audacity.sourceforge.net/manual-1.2/tutorials.html, tutorials and documentation from the developers
www.guidesandtutorials.com/audacity-tutorial.html, more thorough than you could ever imagine, from guidesandtutorials.com
ko6bb1.multiply.com/tag/audacity, recording and restoration tips from an Old Time Radio collector
Several video tutorials for Audacity here, courtesy of YouTube.com

How to use Audacity for Windows to record a basic podcast.

Chez Radio Procaster - one year later

2010-11-25T06:51:00.000-08:00

We ran an announcement for the new Chez Radio Procaster Low Power AM Transmitter a little over a year ago so we decided to follow up and see how folks like it after a year in the wild.

Customer Service
"I was ready to order the Procaster and had a few questions so I went ahead and emailed the company this Saturday. I was pleasantly surprised to get a quick, concise response on Sunday! Overall I was impressed with the companies speed of response and their straight forward answer."

Upon Arrival
The included mounting hardware, adequate cable, transmitter, studio to get me going, the TX (natch), the connection box with regulated 12V power supply, all the mounting hardware, and a surprisingly sturdy and easy-to-tune antenna.

Range
1/4 mile from the house, I was hearing everything like it was a commercial station. At 1 mile, everything was still strong and listenable then at 1-1/8 mile, it started to deterioate. I'm thinking if I really tuned this thing, it would probably push 1.5 miles

In Summary

Automatic Power Regulation
Built-in Audio Processor
Integrated Antenna Included
Has both F.C.C. (US) and Industry Canada certifications
May require audio isolation transformer depending on installation

User Tips

Some reviews from other sources:

For the FM enthusiast, here's a low cost kit option

2010-11-21T10:48:00.001-08:00

CANCK108 - Universal FM Transmitter with Mic and Line Inputs (Solder Kit)
"The CK108 offers an FM transmitter that provides both a built-in sensitive microphone and an RCA jack for line input. In the line mode, it can be easily connected to any audio source to broadcast the audio signal to any FM receiver within its range.

6V DC or 4 x “AA” size batteries, frequency adjustable from 88 to 108 MHz. Low power, can be operated under Part 15 of the FCC rules with a short antenna."

Order Page Here: CANCK108 - Universal FM Transmitter with Mic and Line Inputs (Solder Kit), there is a review here, and for more in depth info, see the Set-Up Manual, here.

Perhaps the least expensive AM transmitter yet!

2010-11-20T08:55:00.000-08:00

Our good friends at Chaney Electronics offer a pretty nice little AM transmitter kit that might be the ultimate low cost entry level transmitter kit. The AM Microphone Broadcast Station Kit - C6752 is a small but efficient, experimental AM broadcast station using a high-gain electret microphone, two transistors and a RCA jack so that you can also connect to the earphone output of your MP3 or CD player.

The reviewer over at the Christian Radio Project says..." it is very impressive for its cost and simplicity of construction and may potentially be a good candidate for use in a low-cost neighborhood AM station. It truly has all the makings of an effective and yet very simple transmitter..."

This review goes on to note that the tuning capacitor that comes with the kit can make adjusting the frequency frustrating but after all, this is a fully functioning transmitter for under $10.00

An easy way to cope with the supplied tuning capicitor is to use a long, non-conductive tuning stick (rod with a chisel tip at one end that will fit in the tuning slot of the capacitor) made of plastic, wood or similar material. The tuning stick should be long to keep your hand from getting too close and detuning the circuit.

This is a very basic kit and includes everything you need, clear instructions, a minimum of parts and simple assembly requirements.

MODS - If you would like to get a better variable capacitor, you will need to replace the 3.5 - 13 pf trimmer that comes in the kit with a better unit from a supplier like Dan's Small Parts and Kits or your local source. Connecting to a real RF ground, probably best to onnect to the negative battery terminal, will always boost range. A 12-18 volt power supply could be used in place of the battery. Adjusting (by sliding the iron powder rod in and out of the wire-wrapped cardboard sleeve) the loading coil connnected to the antenna would also kick out the range a bit.

Great source of tech info and operator tips

2010-11-10T06:25:00.000-08:00

ISS, or Information Station Specialists offers a nice collection of tech info and operator tips on their company web site.

The case studies section can be a great place to visit to get interesting ideas for niche uses of low power radio broadcasting.

The Operator's Zone section offers FCC info, interference advisories, FAQs and content guidelines.

Emergency funding resources describes Federal and state grant programs for organizations seeking radio transmitting equipment

On Tech Talk, you'll find articles on grounding and signal improvement.

ISS primarily focuses on what are commonly called TIS or Traveler Information Stations. These stations operate in the AM Broadcast Band (530 kHz - 1700 kHz), are limited to a 10 watt transmitter output power and the antenna height may not exceed 15 meters (49.2 feet). A TIS may not transmit commercial informationand this service is not available to individuals or groups - only to governmental entities and park districts.

Meet the Freedom Stik!

2010-11-07T14:49:00.000-08:00

A contributor over at Daily KOS just discovered the Scosche series of ultra low cost FM "play with it" transmitters. Before I send you over to check it, I should give you two warnings. First, I need to warn you that the folks at Daily KOS use extremely graphic language and if that's a problem, you might not want to go there...

The second warning is that tampering with a certified transmitter eliminates the certification. The KOS author suggests that adding a radiating element on the negative battery terminal (genius idea for more range, btw) is "still legal" and, well, er, ah, um, it's not. What that means is that certification is no longer a defense if the FCC comes by and tells you to shut it off. If you do cross paths with the FCC (and you'd be surprised what they will pursue, especially on the FM band) just do what they ask (usually 'turn it off,' in rare instances, 'give me that!')

And speaking of the FCC, here are the cert docs from an early ver - note photos, schematic and operation page. Nice! FCC Report on FMT-4, ID #RLQAT100

Here's a synopses from KOS, anyway - "Meet the SCOSCHE FMT4RA Fm Transmitter. $12. Walmart auto section... I figured out that the maximum usable range for stereo music was out around 400 feet, line-of-sight, clear day. ...what if a feller were to just dangle a quarter-wavelength piece of wire from the negative-most AAA battery connection?" Answer? It works great 8^)

Here's another report on the same kind of transmitter - and no graphic language. There are 31 posts in that thread and another thread here - all good stuff. A second follow up is posted here. A 5/8ths wavelength of wire attached to the negative side will work even better than the 1/4 or 1/8th wave approach the KOS contributor mentioned - a dipole does not have to be symmetrical, an unbalanced dipole will also work well. How to calculate a 5/8 wavelength? Use this online calculator for 5/8 wave verticals.

Tube transmitters for the nostalgic

2010-11-01T07:16:00.000-07:00

Some folks like these transmitters because they have a collection of antique radios to serve, some just like the warm glow. Here are two kits and two scratch-built units for your consideration.

	Our first kit comes from Vintage Components across the pond in jolly old England, order through their ebay store		Our second feature is a miniature AM broadcasting station, patterned after the 1939 Zenith model S-7000 Wireless Record Player
	Next a quite successful 6888-based AM transmitter. A 6AB4 or 6C4 is used as an audio preamp and the 6888 as the transmitting tube.		Finally, check out Phil's Old Radios' Li'l 7, a high-quality AM broadcast transmitter that you can build at home for less than $50.

The usual warnings apply here, the Vintage Components unit uses safer power sources, the other three transmitters will have mains voltage and current levels present in the circuit - use care!

Whole House FM Transmitter® 2.0

2010-10-27T05:23:00.000-07:00

The newest version of the WHole House transmitter hit the market a few months ago and user comments are coming in quite positive. First, the

facts: The Whole House 2.0 offers compact size, light weight and a user-friendly case design. The transmitter functions are displayed on a digital screen with blue backlighting and the unit covers entire FM band from 88.1 to 107.9 in 0.1 MHz steps, on both even and odd frequencies.

One of the more popular features is the Stereo/ Mono selection option, letting you broadcast in true stereo format with the right and left channels or to switch to mono to broadcast a little bit farther with less fidelity.

The bigest change is that the 2.0 now complies with FCC’s part 15 rules (FCC ID: XOAWH-FMT and for Canada it's IC.8728A-WHFMT) See the FCC Certification info here, some photos, etc., still available.

One observer recently commented that "the certification test data on the FCC website for the new Whole House transmitter is surprisingly complete. The highest field strength for the Whole House certification data is 183.7 uV/m at 3 m at 98.0 MHz using vertical polarization of the field strength measuring pickup antenna."

A user reports that "I've been using the Whole House 2.0 for a few months, and find it closely equivalent to the C.Crane in power, but with added feature of stereo/mono switch, which is useful for many users. It covers entire FM band and has a microphone input to be used as a wireless microphone complete with a belt-clip. It sounds professional."

Why Does My Transmitter Hum?

2009-12-20T06:57:00.000-08:00

Because it doesn't know the words!
Or, it could be that you are suffering from one of several technical causes of hum in transmitter circuits...
According to those in the know, these causes might include:

Power supply hum due to poor DC supply filtering
AC hum pickup in the transmitter audio due to poor shielding
Ground loops
RF induced hum modulation on the transmitted signal

What's the cure? Here are several links to technical articles dealing with hum reduction in audio and RF circuits:

Finesse Voltage Regulator Noise! from Wentzel associates
Hum reduction info from northcountryradio.com
Hum redux, from www.kenneke.com
Sound Card Interfacing from www.arrl.org
Hum Rejection from www.bluejeanscable.com
"Tweaks" - bottom of the article
Ground loops from www.epanorama.net
Breaking ground loops from www.epanorama.net
Hum Update from lists.contesting.com
Circuit tips - middle of the article
Power and grounding techniques
RF/RFI & Grounding

Happy Hum Hunting!

Miscellaneous updates

2009-11-28T11:10:00.001-08:00

A couple of quick updates as year end approaches...

The Talking House transmitter is now sold by a company calling themselves "I A.M. Radio" which is apparently a new marketing effort for the old "Radio Systems" company. Transmitters are now available to anyone rather than the limited distribution the old firm used but the price is still a total hallucination. Still best to buy off an auction site, it seems.

There is also another web site offering some TH info - here www.wwwrench.com/th5

Our friends at Part15.us have a nice four page thread authored by several experimenters who are trying to build shortwave transmitters, very interesting read titled Shortwave Part 15

Our friends over at hobbybroadcaster.net have really been growing fast, bringing together a couple of older low power sites and adding a web ring and a very active forum - get on over and check it out!

Major updates for some very handy software from Applian

2009-11-28T10:22:00.000-08:00

WM Recorder has always been a powerful streaming recorder but with this latest release it's gotten even better. WM Recorder 14 offers the ability to capture live streaming flash sites (like live sports or chat sites) and even has the ability to preview, pause, rewind and fast forward streaming Flash content. Additionally, WM Recorder 14 can capture Quicktime, Windows Media and Real streams.

Replay Media Catcher now has an incredibly useful new Video History tool that allows you to save previously viewed videos onto your hard drive. The video history tool keeps track of any videos watched on the PC that can be downloaded - even when Replay Media Catcher is closed. Just open the Video History tool and click save on any video you want to keep on your harddrive. We have also added a special "Record Audio" tool that allows Replay Media Catcher to record any audio your PC can play - even from encrypted sites - as a high quality MP3.

Replay Music added the capability to tag previously recorded MP3s (perhaps recorded using another program) and retag songs that weren't properly tagged the first time.

Replay Converter offers improved CD/DVD burning capability and the ability to change the video track speed. There is also a new a "remove audio track" option for video editing purposes.

Visit the Applian Technologies web site for more info

Low Power 250 mW FM Amplifier Kit

2009-10-26T06:42:00.000-07:00

Here at Low Power Radio the idea is, well - low power! True low power broadcasters are trying to reach a small group of local listeners without using the brute force approach of pirate radio. Maybe it's just more challenging, perhaps it's more enjoyable than looking over your shoulder and waiting to be told to take your station off the air. When it comes to hobby broadcasting, FM operators need to be particularly careful to keep the power down. If you've recently purchased a low power FM unit and feel you need just a little more oomph to get to the the next door neighbor's house, this little low power amplifier might be just what you need.
Click here to read about assembling this handy low power kit

The High Potential of Low Power Radio

2009-09-21T06:55:00.000-07:00

Bruce DeYoung is an authentic low power radio pioneer, putting low power radio to work in a variety of settings. Bruce's follow up reports, like the one linked below, provide powerful evidence of the surprising effectiveness of this underutilized medium.

High Potential of Low-Power Radio
By Bruce DeYoung
"New communication tools can enable audiences to receive customized information at their convenience. A case in point is the innovative use of low-power radio for outreach in the Pacific Northwest."

Read the rest of "High Potential of Low-Power Radio" by Bruce DeYoung in The Journal of Extension (JOE), the official refereed journal of the U.S. Cooperative Extension System.
Also interesting and on topic are the products and case study found in this article, Erie Landmark Radio - Short Distance Broadcast of Historical Messages from the Erie Landmark Company.

Low Power on Shortwave?

2009-09-19T13:27:00.000-07:00

Yes, in the USA, shortwave low power stations may operate in the 22 meter shortwave band from 13.553 MHz to 13.567 MHz, with a field strength limit of 10,000 uV (microvolts) per meter at 30 meters from the antenna. About 1.8 mW to 3 mW would be needed, depending on the antenna. Unlike low power AM medium wave, however, there is no limitation on the size or type of antenna, feedline or ground for shortwave low power stations.

It would be an almost unknown operation here in the US, as very few people own shortwave radio tuners and even fewer ever listen. In other parts of the world that might be different.

Here are some schematics, plans, illustrations and ordering information for low power shortwave transmitters:
---
Amplified modulation section design
---
No-coil design
---
Hartley Oscillator Kit info
---
Talking Pixie modified ham transmitter, and filter

In Depth: Talking House AM Transmitter

2009-09-08T17:27:00.000-07:00

Some have called it "one of the nicest transmitters you can't buy," but more on that in a moment. Good quality audio and multiple inputs and outputs make this a great entry level transmitter. A plug and play, AM band, 100mW transmitter, the Talking House transmitter has three really important features:

FCC certified, giving the user peace of mind
Self contained - everything you need is in the box
Self tuning, making set up easy and agile

Until a self-tuning transmitter was available, the biggest barrier to putting an AM operation on the air was tuning the antenna. Using patented technology, the Talking House transmitter automatically adjusts the inductance and capacitance of the antenna load to match the frequency and conditions. If you would like to try to squeeze out just a bit more range by building your own antenna there is a separate RF output for that, too. Learn more about this transmitter and its features and functions here:

- Company web site -

- User Review -

- Owners Manual -

- Tech Notes -

So, why can't you buy one? The company apparently only sells to Real Estate brokers or institutional buyers and has been unfriendly towards hobbyist inquries. Not to worry, however - it seems there is a steady supply of folks selling these on ebay, and at fairly reasonable prices compared to the published company list price.

The Well Grounded Broadcaster

2009-09-08T06:11:00.000-07:00

Low power broadcasters who use the AM band can really improve range and audio quality by installing an effective Radio Frequency (RF) ground system. A good RF ground system depends, in part, on a natural phenomenon called "ground conductivity." This refers to the electrical properties of minerals in the local soil. Read more at the FCC web site page titled "Map of Effective Ground Conductivity in the USA"

So how does a broadcaster construct an effective ground? Two transmitter manufacturers have provided some tips here:
Hamilton Rangemaster Grounding Methods
and in the PDF file of Ground Hints

Also some nice info from Information Station Specialists:
Why a Groundplane is Important, How It Works & Is Installed

Ham radio enthusiasts, especially those who work the 160 meter band (which is directly above the AM band at 1800 KHz) provide a rich source of helpful hints on setting up an effective ground system:
Grounding methodology
Good Ground is Hard to Find
Grounding in RF Environments

One last technical note and caution - true RF grounds should not radiate. Most conductors carrying RF current will radiate if not buried in the earth. This phenomenon means a long ground lead can cause compliance problems with the FCC. Instead of constructing an antenna with a ground, you might inadvertently build something engineers call an "off-center fed dipole." Building an off-center fed dipole could earn an FCC citation, like this one:
FCC Citation for Excessive Ground Lead

Help for Low Power AM

2009-08-09T08:12:00.000-07:00

The Xtal Set Society has updated their site and added numerous items to their helpful catalog, useful for low power AMers. Why do we care? A radio concept called reciprocity. Reciprocity means that receiving things should also work as transmitting things. Reciprocity is especially pertinent at the low power levels of, well, low power broadcasting.

If you've read about loading AM transmitters with air coils but you need a coil form, if you’re more sophisticated and want to try fine tuning with an air variable capacitor or if you are interested in winding a toroid core you can find parts and info here.

The catalog also features a handy calculator page for calculating calculations.

Little Known Sources of Kewl Stuff

2009-08-05T05:59:00.000-07:00

There are a number of reputable, well-know sources of goodies for us low power radio folks. Then there are some reputable, not-so-well-known folks who don't seem to get their name out there - so I'll do it for them. First on my list is Cana Kit, a Canadian firm who offers the popular and inexpensive Universal FM Transmitter with Mic and Line Inputs, pictured here. Many more Cana transmitters here.

Then there is DC Kits, who sells several PLL and VCO units on their website here.

Next is Ocean State Electronics, or OSE, who also offer both PLL and VCO products.

So, the only question left is, "With all these options, why aren't you on the air?"

Tutorial for creating your own bumpers and station ID files

2009-07-17T12:51:00.000-07:00

A great (I think so, anyway) tutorial for newbies - and oldies, too!

"This short tutorial will demonstrate how to create a station ID audio file to support station operations. Using the free audio editing application called Audacity and four small WAV files, we'll create an MP3 file that can be added to most playlists. Once you see how much you can do with this simple approach you'll be able to apply these techniques to make your own station sound more professional and more fun." Click here for the Tutorial

While you're at it, check out the Partners in Rhyme tutorials pages, too.

Low Power Amplifier Plans for AM Transmitters

2009-07-13T07:36:00.000-07:00

The other kind of low power broadcasting is called "carrier current" because this kind of broadcasting uses wires that are already present as an antenna. To learn more, check out "Carrier Current Broadcasting Theory" by LPB.

One of the requirements of this approach to broadcasting is just a bit more power, something that is almost impossible to do at 100mW on AM. Happily, a very smart radio engineer created a solution - the AMA 5000 low power transmitter amplifier for 100mW transmitters in the AM band! Most useful for punching another .5 to 3 watts of power into your carrier current system.

Some say the safest approach is the Neutral Loading Option, so check it out. Here's a quick way to get the FCC to come to your house - connect this amplifier to an antenna (don't). With that in mind, take a look at:

AMA 5000 PA Construction plans, including parts layout and PCB foil pattern

And remember, if you can't be good, be careful...

Partner Site Update - Part15.us

2009-07-06T17:55:00.000-07:00

Our friends over at Part15.us tell us that server problems have been getting them down but that all should be well shortly. The content was moved to a healthier machine and they are waiting for the DNS to catch up to the new location.

While you're waiting for that site to come back, check out some of the other links below and look at some of our earlier content here, in case you missed it the first time around.

Popular posts include Antennas, getting rid of hum and grounding. The least popular post is here - 1 view, and that was probably me. Oh well...

On the air for less than $10.00?

2009-06-21T19:49:00.000-07:00

If you’re interested in trying low power broadcasting without any big commitment, the BH 1417 chip is your friend - a cheap, effective little IC from ROHM. The very good news is that this interesting FM stereo transmitter chip is widely available in a variety of ready-to-use-and-abuse forms from your local discount store or ebay seller.

Sold as a "Car FM Transmitter Modulator for MP3 players" or some similar sounding name, these fully assembled (and often FCC Certified) transmitters can be an easy entry into experimental broadcasting. A sound source, a windowsill and perhaps a tiny bit of hacking and you're on the air.

On the downside, the range will be measured in hundres of yards, not in miles and how long these little set ups will last is anybody's guess. But, we're talking about cheap fun for beginners here, so let's have fun! Most of these low cost, low power transmitters use some form of this schematic, a suggested starting point from the manufacturer. What's exciting about these is first of all the low price. As Mad Magazine used to say, "CHEAP!"

Click here to see a sort of user review, some very minor hacks that increase range and random thoughts on powering this little guy with solar power

Today's Reading Assignment - Limited Area Broadcasting

2009-06-01T06:28:00.000-07:00

Please to be enjoying this comprensive white paper from Dr. Jack Gittings, foremost broadcast electronics expert, PhD from Standford, former chief hardware engineer at Cisco and professor at Stanford, who tells us that

The objective of limited area broadcasting is different from conventional commercial broadcast applications. Instead of trying to cover the maximum area possible, limited areas are chosen and a broadcast signal is focused on them. In the United States the FCC has defined limited area broadcast methods and limits under Part 15 of its Rules, which do not require either a license or notification for operation.

Enjoy the remaining 2000 or so words here: White Paper on Limited Area Broadcasting

Software for Low Power Radio

2009-04-05T07:29:00.000-07:00

Whether it's an audio editing application, an audio file scheduler or a way to stream your station over the internet, broadcasters need software. Our collection of software links can help you create programing, automate a station, and get on line. You will even find software that will help you recycle an old Win98 or, heaven forbid, DOS based PC and put it to use for your radio station.

Most software featured here is free, so why not give it a try, you'll be glad you did... or maybe you won't, but you won't know until you try - sort of like low power broadcasting!

And like hobby broadcasting, these simple applications can be addicting, so you have been warned.

Enjoy! Click here for: Software for Low Power Broadcasters

A Little Light Spring Reading - Updated with Tubes

2009-03-18T06:38:00.000-07:00

Spring is here, and the mind of the low power broadcaster turns to low power broadcasting! There aren’t any low power broadcasting courses at the local college and if you are one of our international visitors, there might not be any recognition of low power broadcasting in your home country at all.

Your low power radio blog is here to help!

Below you will find two publications written in the 1990s by dedicated souls who tried to fill the gap between what we know, and what we'd like to know, about low power radio.

Some will be a bit out of date, but all is free and you just might discover a few "ah-hah!" moments lurking in these learned tomes:

Low Power Broadcasting - Mission Edition The "extended version" of a book we brought you last year.

Handbook for Tube Based Part 15 and Low Power Transmitters If you think toobs are cool, this is the book for yoo, schematics, layouts, trouble shooting, antenna issues, grounding and all that good stuff. Sheesh! I finally fixed the link :-)

Be sure to check last year's spring reading post here for more reading fun.

Enjoy!

My Baloney Has a First Name

2009-02-13T08:10:00.000-08:00

A recent perusal of some of the radio blogs (some of which are linked on my blog) shows a disturbing trend. Lately I've noticed an increase of blatantly false information being disseminated by people who have chosen to oppose experimental broadcasting.

Crotchety hams, trolls and other digital malingerers have taken it upon themselves to declare that "the FCC is 'reviewing' part 15 (the regulations that govern low power radio) and other assorted nonsense.

Apparently deeply perturbed by the new opportunities inexpensive electronic technology provides to today's broadcast experimenter, these troglodytes are out to stop us from having fun. Don’t let this mental masturbation deter you from enjoying our hobby!

So what's an experimental broadcaster to do?

Read more at My Baloney has a First Name… Part 2

Still More Stolen Moments, Other's Radio Writings

2009-02-11T06:28:00.000-08:00

Before commercial radio turned into a cesspool of sociopaths, populated by uptight, back-stabbing, scum buckets, people used to get into the industry because they loved the technology. Please to be enjoying this delightful look back:

The Story of Bootleg Radio 1610
by Robert R. Kegerreis, 12.30.2008
"...With a mail order kit from Allied Radio that had been designed for electronic experiments, I began building a low-power radio transmitter. Technically the experiment was titled "how to build a phone oscillator." The kit contained one vacuum tube, a small electrical transformer, several resistors and capacitors, and a tuning coil. My job was to follow the schematic, place the components in the right place and solder them together. Then according to the instructions, by attaching a ground wire, antenna and microphone, I would be 'on the air'..."

Read Robert's entire article at Radio World

Fixing bad audio in low power transmitters

2009-02-10T06:02:00.000-08:00

The input for your transmitter can be A-OK and your PC Sound card output can be working great, but you're not happy with the sound quality. Perhaps there's too much treble, not enough bass, scratchy high notes or other "ear sandpaper."

There are several possible causes of bad sound. There might be an impedance mis-match. The peak to peak volume levels from the PC sound card might be too high or low. There can sometimes be RFI from the PC leaking through the sound card and into the transmitter. The lack of audio input buffer amplifiers on the audio input side of most low cost transmitters can be a problem, too.

Read more about fixing bad audio here

Low Power Radio Podcast

2008-11-06T20:49:00.000-08:00

Hosted by Sam Bushman with Co-Hosts Carlton Bowen, Curt Crosby, Shawn Henry and invited guests, Liberty Roundtable explores A variety of local, state, and national political topics. A refreshing, unique and independent perspective. Political conversation that cuts through the spin and fluff to the heart of today's key political issues.

This week, Sam and friends planned a short chat about low power radio that Sam found so interesting he devoted the rest of the show to the topic.

Hear the podcast here - http://www.audiocanyon.com/lrtaudio/lrt20081106a.mp3 - the low power radio discussion starts at about nine minutes and twenty seconds in (0:9:20).

Thanks to Sam and his guest!

Beware of Low Power FM Radio Scams

2008-10-28T06:25:00.000-07:00

A recent FCC Consumer Advsiory warns:

"The Federal Communications Commission (FCC) has learned of scams that apparently target low power FM (LPFM) station applicants.

Applicants report they have received e-mails or letters offering to “jet start” an LPFM station or telling them to buy equipment or services that may not be useful or necessary. Perpetrators of these scams may refer to the equipment or station as a “Part 15 device” or “Part 15 transmitter.”

Part 15 devices or transmitters are low power, non-licensed transmitters. Examples of these types of transmitters are cordless phones, baby monitors, garage door openers, wireless home security systems and hundreds of other types of common electronic equipment that utilize very little power. Operators of Part 15 devices are not required to obtain a license from the FCC to use them.

Perpetrators of these scams advertise the Part 15 devices as a means to start an LPFM radio station. Some perpetrators have advised potential applicants to use the perpetrator’s expertise/services (for a fee) to prevent FCC rejection of their applications."

Read the rest of Beware of Low Power FM Radio Scams here

Learn more about LPFM here

Bill Moyers Journal eppy about LPFM, including Video

How to Build an AM Band Transmitting Antenna

2008-10-17T10:35:00.000-07:00

After "Which transmitter should I use?" the most pressing question for low power broadcasters is "How do I build an antenna?"

A fellow by the name of Ernie Wislon who ran a mail order company called PanAxis Productions back in the 70s and 80s wrote a definitive manual on low power AM transmitting antennas - including extensive theory and formulas. Alas, Ernie retired, sold the company and the manual went out of print.

Imagine my joy when I discovered an old photo copy of this manual, originally entitled "Construction Plans, Medium Frequency Antennas."

So, I scanned all 14 pages, cleaned the images up as best I could and used the old "Splitz" application to put the scanned pages in a format that is readable over the web and also added links to clear images of the formulas.

So, enough chit-chat, please to be enjoying Construction Plans, Medium Frequency Antennas

Virtual Audio Cable - the Patch Cable INSIDE your PC

2008-10-06T19:53:00.000-07:00

Just gave VAC a look, super nice app and well worth the registration fee.

http://software.muzychenko.net/eng/vac.html

I lifted this image from the help file to clairify the functionality for those unfamiliar with this software:

From the manual:

"Virtual Audio Cable can be used to:
Connect two or more audio applications into a chain where each next application receives an audio signal produced by a previous application. For example, you can connect a player application to an audio processor and then connect a processor to an analyzer or a meter application to investigate the audio signal.

Intercept the digital audio signal from applications playing it to MME/Wave, DirectSound or WDM/KS Audio ports. For example, you can connect Real Audio Player to Audacity and record any portion of played sound in real time, without a quality loss. Or you can use it to route input and output signals to/from Skype from/to some recording/playback applications.

Record pure digital audio data produced by applications that don't create WAV files, sending audio only to MME/Wave, DirectSound or WDM/KS Audio device in real time.

Digitally mix several audio sources together and route resulting audio stream to a recording application, digitally distribute (share) an audio stream among several recording applications, convert audio data from one format to another in real time or bring a multi-client feature to any audio device that has not such feature."

Kewl!

Two useful circuits for low power broadcasters

2008-09-09T20:24:00.000-07:00

The LM386 amplifier and a parallel port controlled relay switch

The LM386 universal audio amp is really handy for boosting audio before feeding the transmitter. Low power AM transmitters love to get hot audio, the more the better. Giving plenty of oomph in the audio will give the modulation section plenty of signal voltage to work with and that will better modulate your carrier wave.

Some low power broadcasters who are disappointed with their range are simply under-driving the modulation section. Drop an LM386 booster amp in your audio chain and see what happens!

There are many ways to get your hands on an LM386 booster amplifier. You can pick up a chip and build your own from scratch, using LM386 Booster Amplifier plans like these. You can order an easy-to assemble-kit from an electronics vendor. Either way, it's an uber simple solution!

A parallel port controlled relay switch can be the centerpiece of a simple station automation system. The relay can switch various audio sources and provide an easy way to bring NOAA Weather Radio, local TIS stations, police scanners and other odd ball audio sources into your station playlist.

Connected to any old PC, managed using anything from home automation software to a DOS batch file, the parallel port relay can easily manage all of the connections you can throw at it. Just like the LM386 Booster Amplifier, you can build a simple relay from your junk box using parallel port interfacing plans, or you can order a nice, eight-relay kit.

Put it all together, it spells lots of fun for almost free :-)

Best Low Cost Transmitters for Beginners

2008-09-01T05:56:00.000-07:00

I get a few emails each week asking for a recommendation, and it's hard to go wrong with one (or both!) of these time honored gems. Each inexpensive transmitter kit is simple to assemble and comes with an excellent assembly manual that will help you learn about the technology while putting together a set up that will provide hours of fun.

VEC-1290K Kit, AM Radio Transmitter with Antenna Tuner
"The VEC-1290K is easily setup to broadcast in the AM broadcast band between 540 and 1710 kHz. Accepts audio from standard line-level or microphone-level sources. Delivers good modulation depth and linearity. Features a professional quality epoxy PC board, with solder mask and silkscreened parts legend to make assembly a breeze!" Can be operated under Part 15 of the FCC rules with a 3 meter (9'8") antenna and a power supply input equal to or less than 100 mW. The assembly manual is linked from the product page, and you can read a review here and another review here.

CK108 Kit - Universal FM Transmitter with Mic and Line Inputs
"The CK108 offers an FM transmitter that provides both a built-in sensitive microphone and an RCA jack for line input. In the line mode, it can be easily connected to any audio source to broadcast the audio signal to any FM receiver within its range. 6V DC or 4 x “AA” size batteries, frequency adjustable from 88 to 108 MHz. Low power, can be operated under Part 15 of the FCC rules with a short antenna." Order Page Here, there is a review here, and for more in depth info, see the Set-Up Manual, here.

Where to get, or how to build, an antenna

2008-08-31T07:31:00.000-07:00

No doubt about it, the antenna is your connection to your listeners. A good skyhook will help even a mediocre transmitter deliver your broadcast. A bad, or poorly matched antenna will silence even the best transmitter.

For AM broadcasters, the challenge is truely daunting. How to stuff a 500 foot long wavelength into a 10 foot antenna? Fortunately there's plenty of help. Carl the AM antenna guy will custom build an antenna for you.

If you're a do-it-yourself person, a nice 14 page manual on several diffeent approaches can be found at "How to Build an AM Band Transmitting Antenna." Kyle lays out all you'll need to know in the antenna building section of his popular web site.

Miles Roberts Audio, Operator of MRAM 1500, offers these low power AM antenna construction plans

There are also some specific instructions for building the Manteca Magnum antenna here and there's an animated GIF movie to show how it all fits together. An older version of a base loaded vertical antenna is listed here. You might also want to read the The MWA Antenna Book, lovingly reconstructed on Part15.us

FM broadcasters have a much easier time with antennas, it's the FCC that turns out to be the problem there. For those interested in buying an antenna ready-made, the FM DX Antenna Company offers many options. If you would prefer to build your own, try PCS Electronic's Guide to FM Antennas.

Basic Electronics for Low Power Broadcasters

2008-08-28T06:15:00.000-07:00

It might be a snarky post on a forum, maybe you just bought a transmitter and need to add a power supply, perhaps you'd like to boost an audio source just a bit to peak your modulation. No matter what the cause, we hobby broadcasters have yet to be offered plug and play solutions for any and every challenge our hobby brings.

Hackers know scripts, tweakers know drivers and we need to know basic electronics.

With that in mind, please enjoy our Low Power Radio Classic Electronics Reading Room

Some Unusual Transmitters Available Now

2008-07-23T08:21:00.000-07:00

The MW-250 broadcasts a rich warm vintage tube sound using cathode modulation for better frequency response, Pi-Network Design for antenna matching, maximum efficiency, and minimum harmonics. Delivers 100 milliwatt legal power limit. Hammond cabinet with vintage black wrinkle finish. Standard RCA jack accepts inputs from cd and mp3 players, computers, boom-boxes, cassette recorders, broadcast audio consoles.

PCI MAX is a small digital FM transmitter in the form of a PCI PC card that plays audio files from a PC through radio waves to a radio receiver. Install this card into your PC as you would any other PC card, install software and broadcast. Software gives full control over frequency and power. Additional output power and superior audio quality can be obtained by using external power source. Coupled with MP3 player and scheduling plugins this becomes a fully automated radio station.

FCC Certified transmitters

2008-07-22T19:51:00.000-07:00

Some of the information we've looked at in the last few blog posts indicates it just might be possible to set up a low power radio station that generates a little bit of income through advertising revenue.

I've discovered that two of the most important elements of setting up a money-earning station are publicity and promotion. In my summary of the Oregon Sea Grant research, for example, it was shown that small signs promoting a low power radio station increased listenership a whopping 40%.

The problem is that publicity and promotion will also attract scrutiny and in the radio world that means an FCC field inspection. A great way to have a near a worry free FCC field inspection is to use an FCC certified transmitter.

Here is a quick review of some of the certified transmitters on the market today. Both AM and FM units are shown but keep in mind that a certified FM unit will have more limited range.

Talking House plug and play AM transmitter. Available in one-each quantities through ebay.	The TransAM-100™ Talking Billboard Low Power AM Radio Station for advertisers.	Procaster outdoor AM transmitter, from chezradio.com	Hamilton RangeMaster AM1000, a long history of service.
UX350-EX USB FM Transmitter, Stereo unit, innovative USB connection to a PC, sold by CanaKit.	Info Radio low power FM transmitter, sold by the manufacturer, informative web site.	FMT Digital FM Transmitter , stereo, original product from the C. Crane Company	ACC100 FM Mono Transmitter, PanAxis design now sold by Progressive Concepts, available in Stereo.

What is a Legal Transmitter for Low Power Radio?

2008-06-23T07:21:00.000-07:00

Must I buy a certified, ready made transmitter or can I build a kit?
Can I build my own transmitter from scratch?
Can I build and sell my own transmitters?
How many low power transmitters can I own or make?
What makes a transmitter legal?
Will I be fined for broadcasting?

Questions, questions, questions, flooding into my email inbox daily. Good questions and happily, there are good answers - from the best possible source - the FCC :-)

Any and every question you might have about low power broadcasting and the law are in the FCC publication with the snappy title of "Office of Engineering and Technology (OET) Bulletin 63" also known by another snappy (and much more descriptive) title of "UNDERSTANDING THE FCC REGULATIONS FOR LOW POWER, NON LICENSED TRANSMITTERS" (I don't know why they have to shout!)

Go there, and learn

Mix Radio Network Offers New Service Package

2008-05-25T06:59:00.000-07:00

Jon Benjamin, Operations Manager at the Mix Radio Network writes "I have been a part 15 enthusiast for a long time with our station "Surfside 1640" and wanted to pass along some exciting news to low power broadcasters who want to grow their stations."

The Mix Radio Network, DAT and Bandwidth Daddy have joined forces to give you...

FULL SERVICE Radio Station Coverage
- Fully legal music licensing and Shoutcast stream hosting.
- FREE 24/7 Updated National Weather from The Mix Radio Network
- - Listen here: http://mixovernight.srpradionetwork.com/
- FREE Station IDs from Digital Audio Tracks!
- - Listen here: http://www.wzfb.com/Dat_Audio.mp3
- DAT was the voice of the SaveNetRadio.org PSA campaign. Sound familiar?
- - Listen here: http://www.wzfb.com/savenetradio

Read more about the Mix Radio offer here

Spring Reading Opportunities for the Technically Inclined

2008-05-01T06:12:00.000-07:00

Spring is here, and the mind of the low power broadcaster turns to, well, low power broadcasting!

Many folks who are interested in learning more about the hobby find that there are really very few ways to, well, learn about the hobby. There aren’t any low power broadcasting courses at the local community college. If you are one of our international visitors, there might not be any recognition of low power broadcasting in your home country at all. Your low power radio blog is here to help!

Below you will find several publications written in the 1990s by dedicated souls who tried to fill the gap between what we know, and what we'd like to know, about low power radio.

Some of what you will read will be a bit technical as most of the authors are engineers. These files are PDFs of scans in graphics mode so the files are a couple of MBs in size for those of you on thin pipes. Some will be a bit out of date, but all is free and you just might discover a few "ah-hah!" moments lurking in these learned tomes:

Low Power Broadcasting
Broadcaster's Guide to Radio Sation Development
Carrier Current Techniques
The Big Antenna Book
Engineer's Trade Secrets of Radio

Enjoy!

Opportunities for the Commercialization of Low Power Radio

2008-03-16T07:58:00.000-07:00

Today I'm delighted to share this fascinating, in-depth study of opportunities for the commercialization of low power radio. The writings in the link below offer an intriguing summary of several detailed investigations and include a short one-minute video, a simple 10-page pamphlet describing low power broadcasting and a 12-page scholarly research report By Dr. Bruce DeYoung of Oregon Sea Grant. Neat stuff!

Bruce's research showed that there is a gap in available visitor information about local business services and a lack of convenient access to messages about safety and recreational etiquette. Because of significant media consolidation and the use of automation in the operation of local radio stations, that gap has grown far wider in the years since Dr. DeYoung's initial study.

The conclusion of the Oregon Sea Grant study was that low power radio is a viable way to bridge this growing information gap by broadcasting short, preprogrammed messages over a limited area. Visitors tuning in from cars or boats will hear messages about a particular locale, attraction or facility.

Be sure to check out the preliminary audience statistics in the report - aggregate 60% acceptance with no promotion other than on-site signage - WOW!

Affordable radio exposure for local businesses is an exciting option for low power radio that has been little explored over the years. The success of various local weekly and monthly free newspapers offering low-cost advertising seems to indicate tremendous opportunities are waiting for us!

Read all about it here: Oregon Sea Grant Low Power Radio Study

Real Life Low Power Radio Stories

2008-03-11T07:36:00.000-07:00

Yes, Virginia, there really is a low power radio. And now you know... the rest of the story!

"Spurred on by the success of its low-power radio promotion this summer outside New York's Holland Tunnel, Atlantic Records has created a separate department dedicated to the burgeoning world of 100 milliwatt--1/10 of a watt--radio outposts. Atlantic's division for low-powered radio ventures will be headed by Bob Kranes, former PD at WBCN Boston and WLIR (now WDRE) Long Island, N.Y."

Read more about it here: Atlantic Records Low Power Radio

Imagine a bank using "a low-power AM radio transmitter designed to broadcast repetitive, pre-recorded sales messages directly from a bank office to cars in line waiting for drive-in window service."

Read more about that here: Drive Through Radio

Your diligent editor is searching the globe (well, at least the web-globe) for more, so stay tuned...

Chain-chain, Chaaaaain

2008-03-08T05:47:00.000-08:00

The audio chain, where you can really make a difference in how your station will sound. And, ain't it great to be alive in the new millennium? When I was a kid any one of these items would cost hundreds of dollars, back when that was real money - now, these high-tech toys are almost free!

Stolen Moments - Other Readings on Low Power Radio

2008-03-01T06:01:00.000-08:00

A blogging tradition unlike any other, where you use other peoples' content to make your own blog look good :-)
• Peer-to-Peer Low-Power AM Broadcasting
"The idea is to use legal unlicensed low-power AM transmitters operating at Part 15 levels, under 100 milliwatts, to set up a radio network that pulls its content off a central repository."
Read more at http://www.mediageek.net
• John Anderson on Freak Radio Santa Cruz: the State of Media in 2008
"John Anderson recently joined Skidmark Bob on Santa Cruz’s long running unlicensed station to dish about topics at DIYMedia.net."
Read more at http://www.mediageek.net
• AM / FM Band Broadcast Transmitters
Radio and Wireless "recently found a number of sources of FM transmitters that exceed the F.C.C.'s part 15 regulations."
Read more at http://www.eskimo.com
• Microradio Broadcasting: Aguascalientes of the Airwaves
"Radio was introduced to the Western world by Guglielmo Marconi in 1895. By 1907 interest in the technology had reached the general population."
Read more at http://www.thirdworldtraveler.com

New Transmitter from Chezradio.com

2008-02-19T18:47:00.000-08:00

"ChezRadio manufactures low power Part 15 AM transmitters which can be used license-free and without content restrictions. Broadcasts from these AM transmitters can be received on any AM radio. ChezRadio transmitters feature easy non-technical setup and are simple to use - just plug and play!"

"For 2008, ChezRadio introduces the new flagship unit, the Procaster. This low power AM transmitter delivers professional quality and 'big station' sound. Uses include community radio, retirement communities, churches, marinas, campgrounds, businesses, emergency broadcasts and more. The 42 channel Procaster features internal Hi-Fi audio processing, balanced audio inputs, heavy-duty construction and high quality electronics."

"Best of all, this complete broadcasting system is FCC 15.219 and Industry Canada RSS-210 certified when used with the included antenna. Certification with the authorities provides peace of mind and credibility in business."

Learn more at Chezradio.com

Click here to read a user review

New product announcement from EDM electronics

2008-02-16T09:07:00.000-08:00

I just received word of this innovative new transmitter

"We though it may be of interest to you and your readers that we will be making our LED Classic FM transmitter kit available in a 1mW/10mW option as from next week. Basically you will be able to flip a small switch on the pcb and limit power to 0dBm or 10dBm. We feel that this should bring the transmit range more inline to that allowed to users in the USA and Canada under part 15 rules. Price shipped around $120US. This includes pcb, enclosure and psu."

"Our new EDM-TX-LCD transmitters are doing very well and have received excellent reviews from various other Radio boards and customer letters. This is a very high performance (SNR hitting the 80dB mark) unit in the audiophile class which will also be evident by comparing the specifications on our site - www.edmdesign.com check under the "Specs" link. This unit has fully adjustable power levels in two ranges (1-10mW), (2-100mW) by means of an onboard pot."

Welcome

2008-02-15T10:43:00.000-08:00

One of my predessors said it best

"Will my flea-power station change the world? With dozens of cable TV channels, zillions of web sites, plus videos and video-games and CDs, in addition to more high-power radio stations than ever before, people have a lot of choices for stuff to look at and listen to. Don't be too optimistic or too pessimistic about the effect your station might have. It is better to light a single candle than to sit and curse the darkness. "

Crash Korr, MWA