Hey Guys..Im having very frustrating problem concerning RF interference..I basically live right under a 900 foot tall TV/Radio transmitter and weather radar dome. This is a pain in the butt for my system. I constantly get RF hum on my sub even though I have everything hooked up through a monsterpower power conditioner power strip and decent cables running throughout the system. (It was much worse and with all speakers before the conditioner). The sub still hums and makes listening to music and watching movies a lot less fun. What can I do to alleviate this issue? Is there some sort of line level filter that can help? I can't think of anything else I can do.

Yes either a line level filter (although it may TAKE out that actual freq range, meaning you wont hear LF effects in that range)

You could switch to a Passive Sup with an external Amp, with some have better sheilding than Active Subs.

A better Cable? Like a Quad Sheild, you could even try a DIY where you can externaly ground it.

If you literly live under a tower, aside from that, and the problem dont go away, you may be SOL.

I've got a similar problem with AM signals; my room has electronic equipment that sprays RF throughout (computer UPS, VCR, DTV set-top box), and about 30 feet away, medium-tension power lines.

But living right under a broadcast tower?? Man, you're talking tens of thousands of watts of RF energy. If it were me, I'd be moving. Fast.

I can't think of anything else I can do.

Move.

I am moving a few blocks over (college town) in september so hopefully that will help some.

G'day all, RF breakthrough issues of these types are very difficult to solve especially due to the enormous RF power levels involved!

As a Ham Radio operator myself I've had to solve a few similar issues myself over the years. The ferrite chokes are quite useful for these kinds of suppression applications. This is an excellent technical reference http://audiosystemsgroup.com/RFI-Ham.pdf Regards, Felix (vk4fuq) aka catman.

I am moving a few blocks over (college town) in september so hopefully that will help some.

Yes it will IMO - you are getting direct radiation into all exposed parts of your system at present. In your current situation you are so close, no amount of ferrite rings and line filters will completely solve it without affecting performance. Take heart from the fact that your power conditioner had an impact on the situation - moving further away will dramatically reduce the field strength and can only help.

Good luck

John

Have you tried moving to another outlet for the power ? One on a different circuit , or moving the sub to a different location or sheilding it some more with a better ground .

Barney

There are books and volumes on the subject of RFI, like this..

http://www.arrl.org/catalog/?item=9892#top

So many variables many of which are trial and error until you find the right combination that gets rid of the problem. One big factor is knowing the frequency of the fending source of RF getting into your system. I was killing my next-door neighbor's subwoofer with my transmissions on the HF band between 15 and 25 mHz (I'm a ham radio operator too). Finally I tried a ferrite core I removed from an old TV flyback transformer, wrapped the sub's signal cable through the core about 8 to 10 times, and that took care it completely. Spent an afternoon of experimenting to find the cure. Good Luck!

It is weird because I can't seem to isolate the problem..It was better when I had my equipment further away from my outside wall but with the furniture and my new tv im stuck with where it is now. The weird part is that it will go a couple of weeks without any hum then all of a sudden it will be terrible. Also, as Im typing this is was strong and all of a sudden cut off. The problem with trying different outlets it that I only have one that is grounded in my room where my system is..I live in a home that was built in 1914. I would be more concerned about this if I wasn't moving in a few months..its just a nuisance at this point. Could the length of my sub line cable have to do with it? Im assuming it's just acting like an antenna at this point and the longer the cable is the more rf it will pick up.

G'day all, one little thing that happens from time to time on my system is that some of the interconnects although superb cable, have RCA connectors that tend to be slightly loose on the RCA sockets and sometimes they tend to work loose and the shield goes open circuit as a result, although things still work as a signal earth is picked up somewhere else.

However when this happens, bad RF breakthough from my Ham Radio stuff is the inevitable result. I've learn to recognise the symptoms instantly! It's worth checking! Regards, Felix aka catman.

If you could surround the equipment with metal screen (like screen door material) basically making a Faraday cage this may reduce RF interference in the electronics. The RF is coming through the air not the power, most likely. If your sub has a built in amp, wrap the sub.

Thanks for the advice guys..i will say that it also hurts FM reception and it has made me really appreciate the tuner in my sx-535 as it picks up stations perfectly with no antenna whereas my ss receiver is still slightly fuzzy with an antenna, and I'm right in the middle of a city

I had a problem like that in 1972. I was living in a suburb of Cleveland which had an FM radio station, the tower and transmitter of which were only about one third of a mile from me (I could see the tower from my bedroom window after dark and went right past the thing on my way to school in the morning). The signal from that station was incredibly strong, forcing its way into my TV on channel 6 (even though the station itself was on 92.3 MHz), between stations on a cheap stereo FM radio I had at the time, and to make matters even worse, it got into a solid-state stereo tape deck and could even be heard, believe it or not, on the 10-meter band of the receiver (a Hallicrafters SX101A Mark III) I had in my Novice ham radio station.

I was pretty much stuck with the situation the three years I lived in that suburb (I didn't move there by choice; the explanation is very long and OT for this thread), but once I was able to leave (in August 1975, IIRC) and return to my former city of residence (another Cleveland suburb some 15 miles east of the station in question), my interference problems ended, thank goodness. I now live in a small town with no local stations of its own (it is basically served by the Cleveland stations, although my town isn't considered a suburb of the city); however, there is one station in the next town south of here (by five miles or so) that runs 1kW days/0.5kW nights. I don't have any problems with interference from that station, although it does appear at two spots on the digital AM/FM tuner in my stereo system: 560 and 1460 kHz, the latter being the station's fundamental frequency. Poor shielding, I guess (the stereo system is an Aiwa bookshelf unit made in 1999).

I'm not familiar with the Cincinnati area, but I do know they have several 50kW stations (WLW, WCKY, et al). One of them might be the one giving you all that interference you speak of, especially if you are literally under the towers. I had an aunt who lived in a Cleveland suburb where almost every TV and FM tower for Cleveland's stations was located. She was so close to the stations (within a mile or two) she could often get very good color TV reception just using a piece of wire on the antenna terminals, or even no antenna whatsoever.

Speaking of Cincinnati's WLW-AM 700 (The Big One), this all reminds me of the story of when that station first went on the air in the 1930s, with a 500kW signal. The signal was so strong it was illuminating light bulbs that weren't even in sockets! :yikes: This caused a huge outcry in the area, especially from farmers who complained they couldn't shut off the lights in their henhouses at night. The problem was solved shortly thereafter when the FCC changed the rules for commercial AM radio stations, declaring the maximum output power of any such station shall be no more than 50 kW.

I think lots of ferrite core filters and/or a really good EMI filtering surge protector will resolve your problem.

This is what a ferrite core looks like on a cable:
http://upload.wikimedia.org/wikipedia/commons/thumb/1/12/Ferrite_core.jpg/800px-Ferrite_core.jpg

You can buy the clip on type (they are half moons that close together to form a circle around the cable.

Years ago I lived next to long distance high power lines and experienced problems similar to what you're seeing/hearing. Installing EMI filtering and lots of ferrite cores did the trick.

You'll probably need to put a core on every power cord in the system (just before it enters the component), as well as both ends of the analog audio cords. For the subwoofer RCA audio cable in particular, you may need to double up the cores on each end.

You can frequently find a batch or "lot" of ferrite cores on ebay for a nice price. Otherwise, they can get expensive quick.

If after you do that, you still have a problem, I would get a surge protector or power conditioner that has heavy EMI filtering.

I have a frustrating RF issue that I have isolated to my turntable, i.e. turntable connected to phono stage = 5ghz buzz; disconnect the turntable analogs from the phono stage = blessed silence.

Could these ferrite clip-ons on my phono to phono-pre interconnects help?

Thanks,
James

Wow, you can hear 5 gigahertz!?! Impressive.

8-)

I would suggest you start the troubleshooting by double checking that your turntable is plugged into the same outlet as your preamp/amp/receiver and the TT is grounded properly.

Check the cables and ground points for oxidation. Try different cables between the TT and preamp (including a new ground cable).

If none of that works, you could try ferrite cores, but there's no guarantee they will resolve your issue.