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Low power AM circuits of James R Cunningham

100 milliWatt AM Transmitter Schematic
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10 Watt AM Transmitter Schematic
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3-12 Watt AM Tube Transmitter Schematic
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James Cunningham regularly published booklets of radio instructions, schematics and station plans, intended to help missionaries set up gospel radio stations.
     Titles included Low Power Radio Broadcasting and The Big Antenna Book
     At one point in time, James also manufactured and sold transmitters, carrier current load tuners and other assorted sundry hardware items.
     One surviving document tells the story of the Cunningham Transmitters Model CM 30 - 50, an AM transmitter manufactured for export.
     The low power AM transmitter schematics to the right all come from Low Power Radio Broadcasting, Missionary Edition.
     James passed away in 2005, as announced on his gospel radio MSN group, shown here in the Internet Archive.
     Many of the left menu links still connect to archived copies of other projects and information. For example the two-part series titled "Solving broadcast problems" discusses how to deal with the kinds of RF / audio chain problems common to low power broadcasting efforts.
    You'll find lots of interesting articles and comment on topics like carrier current, antenna tuning and general low power radio information.

Radio waves rediscovered, Tesla was right!

You might have already read that the sometimes maligned and often misappropriated legacy of the good Mr. Nikola Tesla received a positive jolt in the news.
     An enterprising group of baby entrepreneurs took a long-known radio hobbyist factoid, slapped on the unicorn start-up bromide 'patented' with an IPO-ready name and proclaimed themselves the master of a new energy source.
      First, here is the 'amazing' news story, from a more sober source that nicely identifies the underlying reality of this so-called new idea, circa 2015.

Freevolt Grabs Energy from the Air

"The Freevolt captures ambient RF waves and converts them to DC electricity. Very low power devices can run exclusively on the energy extracted by the Freevolt... This is ideal for remote applications like smart sensors on bridges or buildings, and for home safety products such as smoke detectors and security sensors."
     Perhaps the Freevolt team was reading this article on the up and down Rex Research, back in 2011.

Manos Tentzeris' Ambient Energy Antenna

"Researchers have discovered a way to capture and harness energy transmitted by such sources as radio and television transmitters, cell phone networks and satellite communications systems. By scavenging this ambient energy from the air around us, the technique could provide a new way to power networks of wireless sensors, microprocessors and communications chips."
     Or, maybe they were inspired by this article, also courtesy of Rex Research, back in 1989

Joe Tate's Amazing Ambient Power Module

"The Ambient Power Module (APM) is a simple electronic circuit which, when connected to antenna and earth ground, will deliver low voltage up to several milliwatts. The amount of voltage and power will be determined by local radio noise levels and antenna dimensions"
     Whether "Free," "Amazing" or simply "APM," the current excitement confirms the veracity of the 36 Chinese Strategems, specifically, "Take something old, bring it to the present day and call it your own."

      Once again, Tesla is proven to be ahead of his time - he only needed to live long enough for our 'through thin air' power transmission requirements to drop down to the milliamp level. Freevolt is an exciting development but far from new.

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A summary of FCC enforcement actions on the AM band, and more

Image © part15lab.blogspot.com, all rights reserved
Call this the Internet is too damn big, part two.
     A blog popped up last year on my favorite topic, local area broadcasting, and I just found it.
     The good people at Part 15 Local Area Broadcasting have kindly created Part 15 LAB, the Part 15 Local Area Broadcasting Blog at part15lab.blogspot.com
     The Internet being too big seems to work both ways, as this intrepid blogger hasn't found me yet, either. Having not found me, and sharing my affection for transmitting on the AM band to avoid FCC scrutiny, a wonderful blog post was written on a summary of FCC enforcement actions on the AM band.
     This well done, if perhaps mis-titled post, can be found here NOUO Notices of Unlicensed Operation, and reaches the astute conclusion that:
"There have been only 7 instances of the FCC shutting down supposed Part 15 AM broadcasters in the past 3 years... Compare this to the estimate of 1,000's of FM broadcasters receiving NOUO's in the same time frame."
     Well said! Also found on Part 15 Local Area Broadcasting are posts on the FCC Ground Conductivity map and a great tutorial on Zara station automation software, along with links to Neighborhood Public Radio and more!

      Visit Part 15 Local Area Broadcasting for some excellent low power radio info!

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