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I live within 2 miles of a fairly powerful AM/FM radio station. I can hear the AM station coming through my powered subwoofer. The subwoofer cable is 25' long and new from Blue Jeans, their LC-1 cable. One suggestion I've received is to purchase some RF chokes and wrap the subwoofer cable a few turns around the choke. Sounds good on paper, but I can't imagine being able to wrap this cable around anything smaller in diameter than my thumb. Of course, I don't know how large these RF chokes are, but the few I have seen weren't even easy to wrap phone wire around. Other suggestions ? Is there where balanced cable connections shine ?


Thanks,

Bill
 

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Quote:
Originally Posted by storman /forum/post/14274884


I live within 2 miles of a fairly powerful AM/FM radio station. I can hear the AM station coming through my powered subwoofer. The subwoofer cable is 25' long and new from Blue Jeans, their LC-1 cable. One suggestion I've received is to purchase some RF chokes and wrap the subwoofer cable a few turns around the choke. Sounds good on paper, but I can't imagine being able to wrap this cable around anything smaller in diameter than my thumb. Of course, I don't know how large these RF chokes are, but the few I have seen weren't even easy to wrap phone wire around. Other suggestions ? Is there where balanced cable connections shine ?


Thanks,

Bill

So what else can it do make coffee?
I was picking up the sodden Evil scum of the Earth BBC radio Solent on the surrounds earlier this year, for two nights in row I think. I hate I hate the scum of Earth rotten evil BBC there scum and that made me, made as hell.



So this is rather uncommon what you’re talking about, could be atmospherics cursing the scum of Earth radio broadcasts, you sure it wasn’t the evil scum BBC maybe scum “World Service” the BBC is scum.
 

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Are you sure it's the cable and not just getting into the sub itself?


I think there are ferrites that can be snapped around the cable if it is that.


Or, else, you could try to make a different cable from RG-6 coax and some F>RCA adapters and have a try with that. RG-6 is inexpensive but well shielded, and the adapters are only a few bucks each at Radio Shack.


If you talk nice to the "cable guy" he'll probably make you a 25' cable for no charge. Then all you need are the adapters.
 

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Search the "Archive 2" for a thread:

"Radio tower 2000 yards from location of theater causing interfierance"

by Beezee

it has some good links in interference troubleshooting
 

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I also seem to remember a AVS member mention last year that he had breaker 19 “rubber duck” coming though his sub, now that was funny.
 

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If the cable is the pickup point, your best bet is probably to go to a braid/foil combo shield rather than a double-braid shield like the LC-1. A foil layer in the shielding is highly effective at reducing RFI. I'd recommend something like Belden 1694A.


Kurt
Blue Jeans Cable
 

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If you can unplug the cable to the sub at the sub and the radio station goes away then that confirms the problem is coming in through that cable. If the station is still there then it is likely that it is coming in through the power line. Both are common. Radio Shack has split cores that snap around the cable. Normally they are large enough to handle cable sizes as large as RG-8. Here is a link to the cores.
http://www.radioshack.com/search/ind...w=ferrite&sr=1

Basically the wire is acting like an antenna and then a marginal connection in the sub acts like a rectifying junction and detects the AM signal. The Ferrite acts like a choke to radio frequencies and it should be placed as close to the entrance to the sub as possible. Shielded cable may or may not fix the problem, the ferrites should fix the problem and with smaller cables the cable can be looped through the ferrite a couple times to increase the choke effect. Sometimes more than one ferrite may be needed. This is a common problem faced by Amateur Radio operators and Ferrites have pretty much been the most effective solution as they do not require any physical changes to the actual offended equipment.


..Doyle
 

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I've had many issues with RF interference from both strong AM & FM. Using the ferrites and actually playing around with the positioning of the AC power cord helped the most.(Especially with VCR's and powered speakers) The more expensive audio cables made less of a difference than addressing the AC power cord itself did. Hope this helps.
 

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Quote:
Originally Posted by DoyleS /forum/post/14286680


This is a common problem faced by Amateur Radio operators and Ferrites have pretty much been the most effective solution as they do not require any physical changes to the actual offended equipment.

Not all ferrites are created equal. The AM broadcast frequencies are at the very lower limit of effective ferrite performance and even then requires a special manganese-zinc mixture just to provide an additional 20 -30 Ohms impedance at 1 MHz. I doubt the units from Radio Shack are those type units, especially since they are unspecified.
 
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