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Author Topic: RFI IN EQ/LIMITER  (Read 3823 times)
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KB5MD
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« on: December 12, 2009, 05:55:29 PM »
Need suggestions as to methods for getting rid of RFI in an EQ/Limiter/Compressor.  Input and output cables are shielded and unit works fine when transmitting into a dummy load but not when its to the antenna.  RF seems to be getting in via the output cable.  Anyone else had this probloem?   Huh Huh
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N2DTS
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« Reply #1 on: December 12, 2009, 06:26:37 PM »
Clamp on ferrite things they use on much electronics are easy.
I got thousands free at work.
Dont forget the AC line cord.

I never seem to have RF in the shack, even though the antenna is over the house.
Good grounds, a resonant antenna, no tuner, everything mounted in cabinets (which are grounded).

I did use a bunch of those things on my flex ins and outs though...

It seems to me that the rf field strength would have to be very high, or the grounding very poor to get RF into things.

I 'can' run 700 watts carrier and well over 2kw pep with the antenna drirectly above the shack up about 50 feet without issues.

Brett
 


 
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Jim, W5JO
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« Reply #2 on: December 12, 2009, 06:34:21 PM »
Move the antenna farther away Roy.   Cheesy
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kc6mcw
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« Reply #3 on: December 12, 2009, 06:44:27 PM »
Are you using unbalanced audio cables? My RFI went away when I changed to balanced cables.
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ke7trp
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« Reply #4 on: December 12, 2009, 08:45:08 PM »
Yep. This curred my problems.   I used balanced XLR to XLR cables. Then an audio technica Low to high impedance converter at the transmitters.  This solved all my issues. 

C
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n2bc
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« Reply #5 on: December 13, 2009, 08:55:22 AM »
Place an isolation transformer on the output.  A small 600:600 ohm audio transformer will isolate the audio ground.

I run all the audio outputs (PC & various receivers) through an 8 channel line level mixer then into a set of amplified speakers.  Each of the inputs and the output run through an isolation transformer.  No problems with RF. 
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KB5MD
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« Reply #6 on: December 13, 2009, 12:24:53 PM »
The balanced cable did the trick...Thanks guys! Grin Grin Grin
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K5UJ
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« Reply #7 on: December 13, 2009, 11:10:25 PM »
Quote from: N2DTS on December 12, 2009, 06:26:37 PM

Good grounds, a resonant antenna, no tuner, everything mounted in cabinets (which are grounded).
 
These things almost never or never have anything to do with RF distorting baseband audio.  I have experienced cases where "ground" or grounded cabinets made matters worse.  For an excellent paper on dealing with RF in the shack where it is not wanted download this file by Jim Brown and read it. 

http://audiosystemsgroup.com/RFI-Ham.pdf

73

Rob
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"Not taking crap or giving it is a pretty good lifestyle."--Frank
kc6mcw
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« Reply #8 on: December 14, 2009, 10:41:34 PM »
Good article...
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