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RFI and Faraday cages

GOYA said:
Yep. I made them myself. Microphone cable with Switchcraft plugs and the shield is only attached on the source end.

I was in the midst of trying a grounded foil cage when CB guy stopped transmitting.
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Noise rejection is better with the shield grounded at each end. Myself, I'd experiment with going from the mic cables and floating shield to coaxial style cable, something like Belden 1694A that has heavy copper braid and a foil shield. The braids work better at low frequencies EMI while the foil works better for RFI.

From Blue Jeans Cable...

The two points that jumped out at us when we examined these data were (1) the consistency of the shield type hierarchy--double braids outperforming the braid/foil cables, braid/foil outperforming the single braid, and the single braid outperforming the "quasi-balanced" unbalanced cable, and (2) the very close correlation between the shield resistance (inverse of conductivity) and the cable's performance.

The 1800F performed miserably, which was no particular surprise. First, it isn't a coaxial cable and therefore isn't well-suited for use in an unbalanced circuit. Second, it was wired in a manner which, though popular with some users, makes no apparent electrical sense. None of this should be held against 1800F, which, when attached properly to balanced connectors and used in a balanced circuit, is a truly superb cable.
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Note the 1800F is the typical "mic" cable style cable with two inner conductors surrounded by braid shield, although technically it is for AES/EBU balanced digital signal. The connection style they refer to often discussed in audio circles --one wire of the twisted pair to the center of the RCA plug, one to the outer ring, and the shield attached to the outer ring but only at the "source" end of the cable.

The tests focused primarily on low frequency 60Hz hum hence the double braids performed better. Later they suggested a braid + foil combination if RFI is a problem, hence the Belden 1694A, again with the "quasi-balanced" microphone-style cable considerably worse than the rest.

Complete article: http://www.bluejeanscable.com/articles/humrejection.htm
 
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If you can find this character, report him. You are only allowed a maximum of 5 watts going to the final, which amounts to about 3.5 watts out on a really, really good tuned CB. A lot of these characters use linear amps going into the 100 watt output area, so they are all over the place. Defending yourself from this is almost imposssible. I had a radio station that was located several miles from me and it took several complaints to the FCC to get these people to align their transmitter. They were all over the dial! Communications electronics is my background and I do know a bit about this stuff. I have repaired and maintained several transmitters in my time and they were spot on for maintenance and operation, not like you find now a days.
 
The guy didn't broadcast at all today. At least while I was home.

The amp with the meters definitely had charged caps. I had just turned it off within 10 seconds of when I noticed the meters jumping. But I didn't hear any output then.

BTW, what I hear sounds an awful lot like an adult talking on the old Charlie Brown cartoons. Muffled and smeared.
 
Interesting.

One other thing I'd suggest: make a 1/4 inch TRS connector where all three contacts are shorted together, essentally a grounding plug.

When the guy's transmitting, look at your system with and without this shorting plug in the Rane input.

If it's the same with or without the plug, it's probably not the input.

If it stops with this plug in place, the RF is inserting itself through the input.

I agree with you on the chassis ground: it shouldn't matter.
 
pilotprose said:
If you can find this character, report him. You are only allowed a maximum of 5 watts going to the final, which amounts to about 3.5 watts out on a really, really good tuned CB. A lot of these characters use linear amps going into the 100 watt output area, so they are all over the place. Defending yourself from this is almost imposssible. I had a radio station that was located several miles from me and it took several complaints to the FCC to get these people to align their transmitter. They were all over the dial! Communications electronics is my background and I do know a bit about this stuff. I have repaired and maintained several transmitters in my time and they were spot on for maintenance and operation, not like you find now a days.
Click to expand...

Assuming, of course, that one has something more than pure speculation of an amplifier being used.
 
I'm pretty sure I have some foil shield coax around here. I'll see if I can find it and give it a trial.
 
Strangely and pleasantly quiet around here. I kinda wish he'd transmit so I could test some things.
 
Apparently the guy has stepped his transmissions way down. I've heard him once in the last 10 days or so. And it was while the stereo was on but not playing anything. Just barely heard him. I can live with that.
 
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