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Old 16th April 2011, 07:34 AM   #1
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Default Radio Interference

If anybody is hearing RF OR a radio station
this is for you..


it's based on the reactance of a capacitor

1\ 2 PI F C

this gives you the ohms seen By ac in the capacitor at the given frequency


anyhow
if you simply place .1uF ceramic capacitors on your inputs to ground.

the noise will stop !
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Old 16th April 2011, 09:27 AM   #2
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http://www.sengpielaudio.com/calculator-RC.htm
here's an online calculator

ok using the calculator you can see that at 20khz the cap looks like 79.57 Ohmns to ground
this would roll of some of you HI's in a full range system

to the radio signal it's a straight short to ground

.01 should be tried first : especially in full range application because
.01 at 20 khz = 795.7 Ohms

Last edited by ElecronicsEdC; 16th April 2011 at 09:39 AM.
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Old 21st April 2011, 07:10 PM   #3
cviller is offline cviller  Denmark
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Thanks for the info. I actually had a mexican radio station on my chip amp while I was living in San Francisco.
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Old 21st April 2011, 07:37 PM   #4
AndrewT is online now AndrewT  Scotland
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Quote:
Originally Posted by ElecronicsEdC View Post
If anybody is hearing RF OR a radio station
this is for you..


anyhow
if you simply place .1uF ceramic capacitors on your inputs to ground.

the noise will stop !
100nF seems far too high for RF attenuation.
Most will use an RC time constant of 100ns to 1500ns.
1k0 source resistor normally requires a 100pF to 1n5F to achieve those RC values.

0u1F cuts far too much treble.
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