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Why Does My Transmitter Hum?

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:

Editor's note:  Dead links were recently updated with links to the original content found at the awesome, link saving Internet Archive!

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!

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Get on the Air with One Click, Buy a Transmitter Bundle from Amazon.com

Many hobbyists agree that the F-S variable power 0.1 to 0.5 W FM Transmitter is one of the best transmitters for the price.  Add the convenience of a selection of premium quality accessories and you can literally be on the air with a single click.
     No need to search the web for FM broadcast antenna, FM transmitter antenna plans or FM broadcast antenna diy, this great combo includes an F-S Electronics RangeBooster 2.0 Ground Plane Antenna. 
     Connect your antenna to the transmitter with your included ultra low-loss  (55.4 db/100m), 8 mm diameter,  rugged class 8D broadcasting cable and add your programming with the included 6 foot heavy duty stereo audio cable. 
     Necessary adapters are included, too - a simple and cost-effective solution to increase your range, minimize signal loss and maximize your broadcasting enjoyment.
     Peace of mind with the lifetime warranty.

Check out these reviews from real users:

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• "I am able to get more range with the external antenna"
• "Set up was so easy. The sound quality was awesome. I love this transmitter!"
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