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Picking up radio on my bass?!!

rainbowreality

rainbowreality

Guest
May 28, 2013
48
0
#1
Hi,

Recently I've started to be able to pick up a pirate radio station via the guitar. It is the guitar because when I turn down the pickup volume it goes away.

It's very faint but annoying as hell! Also it only happens when I visit my brother who lives 80 miles from me. There's shielding on the inside but it's quite some age now.

Any ideas anyone?
 
#2
Are you sure its the instrument and not the amp?

What you are experiencing isn't that uncommon, at least not for me. The practice spot I used for one of my bands had a guy in the neighborhood with a HAM radio that I could pick up through my cab. It was creepy, you could only hear one side of the conversation.
In the place I use now the guitar players sometimes pick up radio stations through their amps.
It just depends if you are near something that broadcasts in a way that affects your stuff.
 
#3
I wouldn't mind so much if the music this radio played was any good. It is weird, like hearing an awful station from the after life!

What makes me think it's the bass is when I unplug it, the station stops, ditto when I hold the strings. Unless they simply act as the aerial?
 
#6
This is interesting. The same thing started happening to me in the last few weeks (that I noticed anyway). I'm personally starting a process of elimination (change the bass one week, one of my pedals the next week, etc.) until I discover the culprit. :ninja:
 
#11
If the ground is ok, then it may be that the pickup that receives the signal has a resonance in its circuitry. You say the cavity is shielded, but the shielding may be marginal (i.e. sprayed or painted on shielding vs. copper foil lined). Another solution is to re-wire the pickups changing the length of the leads from one component to another. That should change the circuitry resonance to reduce the picked up signal. If the pickup is active with a built-in preamp and the resonance is in the pickup, and if the manufacturer is unwilling to help, then that may be too hard.

There's a good possibility that the radio transmission your hearing is a low-power transmitter that is close by. You could probably build a directional radio detector and ranging tool to locate the transmitter. Or, try to catch some identification from the transmission and talk to the FCC. If you know a Ham operator, they might help you out with ID'ing the culprit's broadcast frequency and maybe the location. It all depends on how much of an irritation you find it to be.

Lloyd Howard
 
#15
I have a Marshall 2203 that tends to do this. On the rare occasion anymore I play guitar for a gig or jam, I take a long guitar cord, make one loop in it close to the amp, and hang the loop off the amp stand, adjusting the size of the loop until the radio station goes away. This turns the guitar cord into a form of a bandpass choke that eliminates the radio signal.
 
#16
Doggone it, Rainbowreality, now I have Mexican Radio (by Wall of Voodoo) stuck in my head.

iiipopes said:
I have a Marshall 2203 that tends to do this. On the rare occasion anymore I play guitar for a gig or jam, I take a long guitar cord, make one loop in it close to the amp, and hang the loop off the amp stand, adjusting the size of the loop until the radio station goes away. This turns the guitar cord into a form of a bandpass choke that eliminates the radio signal.
Click to expand...

This reminds me of an old idea I've heard that tying a knot in a cable would block lightning from traveling down it.
 
#18
Thanks for all the feed back, ideas and solidarity!

I'm going to do a total insulation of the cavity, fresh wiring of the pots, Jack socket and bridge earth using the shortest lengths of cable possible. And just to make sure tie a knot in the audio cable, if none of that works I'll admit defeat!
 
#19
How do you know that the guitar is the source of the radio?

What model is your amp?

Certainly the guitar/cord is the antenna, and there is stuff you can do to make it a less efficient antenna, but unless there is some sort of diode in your guitar there is no circuit to form a radio detector.

It is much more likely that your amp has some issue. Like the input jack grounding is poor. I have a Mesa Boogie guitar amp that uses a very low resistance on the input to the first gain stage. It picks up radio in some cases because of the hi-gain design. Some amps will kill radio signals by isolating the input jack from the chassis with a fiber washer, then a capacitor ties the return side to chassis to dump radio level frequencies, and the return(ground) side of the input jack is directly wired to the groundpoint at the first gainstage.

All kinds of amp design, amp fabrication, and amp degridation (loosening, corroding, stray wire contact...) can cause an amp to turn into an AM radio when an antenna (guitar and cord) are attached.
 
#20
That's interesting! Do you have any schematics for the input stage? I.E what diode is used? Does that mean you could build a simple unit to use as a radio suppression to plug the guitar into and then output to the amp?
 

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