08-24-2011, 12:23 PM
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Join Date: Jan 2011
Originally Posted by Wire Weasel
With many radios, if you put one of the slow color-changing LEDs in the meter the LED actually makes an awful noise that sounds like motor gears grinding away as it changes colors.
I have thought of putting a small capacitor across the leads to see if that would filter out the noise but I don't have any extra or junk radios around to try it on and don't want to tear into either of my good radios just to make this experiment.
Has anyone here come across this and tried or done a fix for the noise?
It's worse in some radios and makes no noise in others. The noise is picked up and passed along in the audio circuits. You can both hear the noise through your speaker and the noise is transmitted out too and is very annoying.
They are never a problem when putting them in outboard power/swr meters for meter lighting and looks neat in them.
Seems to me that the solution would depend on finding which specific circuit inside the radio is picking up the interference. Those little color-changing LEDs work by way of PWM, which means they are fed a rapidly oscillating signal, the duty cycle of which determines the brightness of each LED. That signal is what is being picked up by some part of the radio's internal circuitry. Since the source of the interference is inside the radio chassis it will likely be very difficult to get rid of. One possibility is to enclose the LED assembly itself in a metal shield.