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Picking up radio waves on my Amp

Discussion in 'Amps and Cabs [BG]' started by spliffnriff, Apr 3, 2003.


  1. I am not sure if this is an amp issue or a bass issue, but last night when I was jamming at a club I belong to, when I pluged my bass into the amp, I was picking up radio signals! It was annoying the group, and it was frustrating to me. :mad:
    Does anyone know why :confused: :confused: this happens, and how to get rid of the noise??
    Thanks
     
  2. bentem

    bentem

    Oct 18, 2002
    Rockville, MD
    some of my friends who have those little squire amps that come in strat poacks pick up french radio in the middle of the night. Ive never heard of it happenng on a bass amp.
     
  3. This is a Fender 200 watt Bass amp.
    I am thinking it might be my bass???
     
  4. Try a different (better) cable from bass to amp.

    Chris
     
  5. Why does this happen? Not sure about the electronic explanation, but...

    I had a similar experience when I purchased my current amp (used Eden WT600). I was trying it out before I decided to buy it. I plugged into it, turned up the gain a bit, and..... I could hear a radio station thru the speaker. :meh: It was quiet (you had to be right next to the cab in a quiet room) but it was definitely there.

    Went outside for a look, and sure enough, there was a radio transmitting antenna verrrrrry close to the church in which I was testing the amp.

    Since my amp isn't used near a transmitting antenna anymore (as it was in the church), it never acts like a radio receiver.

    Wish I had a solution other than "Play in a different club":meh:
     
  6. stephanie

    stephanie

    Nov 14, 2000
    Scranton, PA
    I have that problem at home with my Squier amp. I sometimes pick up radio stations...sometimes even ppl's phone conversations :eek:

    I thought it had to do with the grounding?
     
  7. I think grounding and shielding can have something to do with it, my cheap 15 watt fender used to pick it up every now and then. My guitarist has gone through three wahs that all eventually pickup radio signals.
     
  8. BoiNtC

    BoiNtC

    Nov 25, 2002
    NYC, USA
    I have the same problem when I run through my friends Ibanez Soundwave(orsomethingwave... 60watter) at church and through a Bass Pod, without the Pod, it'll be fine, but once I use the Pod I pick up Radio Disney :p I dunno how to fix it but I just lowered the volume on my pod a bit... and turned up the amp a bit more to make up for that...
     
  9. Petebass?
    Joris?
    Mark Reccord?
    Bob Lee?
    :confused:

    (apologize for those electronic types I missed...)

    These guys might offer a bit of insight on the radio receiver thingy.
     
  10. rumblethump

    rumblethump Supporting Member

    Mar 25, 2000
    Pioneer CA. 95666
    I've had the same thing happen with my old Acoustic 360. I agree, I think it happens due to proximity of a high power transmittor. In my case it was a Ham radio operator.
     
  11. Eric Moesle

    Eric Moesle Supporting Member

    Sep 21, 2001
    Columbus OH
    It could be any one of the following:

    - Lack of shielding on the bass itself.
    - Bad cable from instrument to amp.
    - "Dirty" power to the amp carrying lots of RF interference (let's hear it for those Furman power conditioners . . )
    - Really cheap amp, poorly designed.
     
  12. How does this happen? Simple - we're all bathing in radio frequency energy pretty much all the time. If you can pick it up with a radio, then it's all around.

    All you need is a Detector of some sort (diode) to take AM radio out of the air and turn it into an audible signal. Your standard cheap amp uses components that have bandwidth way out into the RF region (op-amps most notably), mix that with a badly shielded input cable or a speaker cable that is long enough to be an antenna and you'll get radio frequency signals coming out of your speaker.

    It has more to do with shielding than grounding.

    Here are some things to try:
    Use a better cable from bass to amp.
    Tie a simple knot in the power cord right up next to the back of the amp. This puts a small common-mode choke on the power line.
    Go to Radio Shack and by some split-ferrite cores that can be snapped around your cable or power cord, like you see on some computer cables. These may fix it.

    If you really want to know how this is possible, build yourself a crystal radio. It works with no batteries! The power going to the earphone is coming straight out of the RF in the air!!!! That gives you an idea of what we've all been bathing in for the last 100 years or so.

    Chris
     
  13. Thanks for the science of it, throbbinnut!!

    Interesting...
     
  14. Thanks guys, I will start the process of elimination tests:D :D
     
  15. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    Hi Spliff,

    Do the amp and bass controls have any effect on how loudly the radio station is picked up? Does it happen when nothing's plugged into the amp input? These questions could help locate where it's getting into the audio circuitry. It's probably not coming from the bass unless you're really close to the transmitter, or if it's an active bass with maybe a little circuit defect that causes it to demodulate RF signals.

    As Chris mentioned, just a little non-linearity can cause a diode effect that demodulates an AM radio signal. Make sure your grounds and shields are good and make good contact with each other.

    You'll know it's really bad when you can watch CITY-TV on your bass amp. ;)

    If it appears to be getting in through an amp input, you can probably have a technician put a small-value disk capacitor and a ferrite bead on the input wiring to help decouple RF to the chassis instead of the audio circuitry.

    Audible radio interference can be a little mysterious to track down. One evening about 22 years ago I was helping a friend complete his recording studio in a nice old brick mill building in Connecticut. We had been playing some music over the control room monitors while we worked but left the system on for a while after. We started hearing a radio station picked up through the system; I turned up the CR volume on the Loft console to try to hear it better and figure out what it was. The only AM transmitter within 20 miles was about five miles away, and after sundown it was only 250 watts anyway, and besides, it didn't really sound like a commercial radio station.

    So jokingly I pointed out to my friend that hey, he's Polish, I'm half Polish, and the board was built by a guy with a Polish last name. So it had to be Radio Warsaw, right? Hah hah, yeah. Like anything in there would pick up shortwave anyway.

    About 30 seconds later came the top of the hour, and a male announcer came on and said it was the North American service of Radio Warsaw. Ed and I looked at each other, and I swear our jaws were hanging down to the floor in astonishment. Then we broke out in laughter.

    Within ten or fifteen minutes the radio station faded away, and we never again heard any radio signal being picked up by the control room system.
     
  16. Hey Bob,

    I think CB radio types call that "Talking Skip" (where there is 'ducting' or a type of containment of radio waves in the atmosphere, causing it to travel insane distances...)

    Maybe I'm mixing it up with acoustic 'ducting' in the ocean. I used to be a sonar technician in the Navy. 10 years ago I knew alot about how sound travels thru the water....doppler... 'f' sub 0 (base freq), harmonics, etc.....

    Don't mind me. Sound and radio are similar but different. Or something.



    :confused: :meh: :bassist:
     
  17. rickbass

    rickbass Supporting Member

    I had an incredibly crappy Silvertone 2x12" that thought it was a radio.

    If I owned it now, instead of in the late 60's, I'd use it and just call myself a "rap artist." :D
     
  18. Thanks for all the info. My bass manufacturer was kind enough to offer a ferrile bead, which I will install. I will also bring in my own cables from now on!
    I read an article, that the cable does not make a difference, and that cheap ones are as good as expensive ones, except when you use long cables.
    Either way, I will be doing both.
    Thanks again for all the insight and help.

    Bob, if you pick up any spy signals......:D
     
  19. :D :D
     
  20. leanne

    leanne

    May 29, 2002
    Rochester, NY
    I have this problem sometimes. It seems to depend on everything--bass, amp, and cab. I pick up FM radio, there's a big tower near my house. But the funny thing is that the station I get on the amp, I can't get on the radio. (A lot of stations don't come in here because of the tower)

    It is worst if I have one of the pots one of my basses turned all the way in one direction. Also, I slightly changed the direction my amp faces and moved it over a few feet, and I hardly ever pick up the station anymore.