Frankly, I've been out of school far too long to do a decent job of
designing a filter. I've included a link on filter design below if you want
to slap a few components together. Or you could simply go to your local
electronics supplier and tell them that you've got a buzzing in your radio
caused by something switching DC and you want to insert a low pass filter or
an RF choke in the DC line.

This will help you design a lowpass filter:

http://www.radio-electronics.com/inf...ter-design.php

However, simply wrapping your +12v line through a ferrit ring will serve the
purpose.
wrote in message
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On Monday, December 17, 2012 11:42:00 AM UTC-5, Dan Marotta wrote:

Either or both of these of the proper values and connected in the proper
way will greatly reduce or eliminate RF interference.


Thanks Dan for for your input. Since exercise is good for the brain,
inquiry minds want to know how to determine proper capacitor and RF choke
values and how to connect correctly.