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Radio Interference - Can't solve it

#41
I've had a few active bases over the years and I still have one up in the cave, but I've always used EMG and I've never had that problem. Maybe it's because with the active EMG products you rid yourself of the ground completely. But I'm hardly an expert.
 
#42
Somewhere between twenty and twenty-five years ago I was playing lead guitar in a praise band with a Marshall 2203 head that, well, let's just say it had been repaired from "overuse" before I purchased it. So who knows what was starting to let go internally. But oh, what a tone! I digress. At one service I started getting a local radio station coming through the speaker cab. I reverted to the old broadcast engineer's trick: I took a very long guitar cord, made a loop near the input jack, and adjusted the size of the loop until the radio signal went quiet. I was using an amp stand, so I hung the loop over the arm of the amp stand tucked under the corner of the head so it would stay secure for the duration of service.
 
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#43
iiipopes said:
At one service I started getting a local radio station coming through the speaker cab. I reverted to the old broadcast engineer's trick: I took a very long guitar cord, made a loop near the input jack, and adjusted the size of the loop until the radio signal went quiet. I was using an amp stand, so I hung the loop over the arm of the amp stand tucked under the corner of the head so it would stay secure for the duration of service.
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i was today years old when i heard of this trick! :wideyed:
 
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#45
Well, been doing some poking around. I've reached out to the radio station and have been in touch with someone there who's helping me out and seems pretty interested in a positive outcome for me.

One thing I have since learned (and addressed in one of my basses) is that the shielding in the pickup cavities needs to be electrically connected to the shielding in the control cavity. However it had no impact on the radio signal. :-(
 
#47
Amateur radio hams call this an “ugly balun”. The diameter of the coil and number of loops affects the frequency that gets attenuated. But this is only going to work if the problem signal is coming from the bass to the amp or interface across that cable—which I think is unknown in this situation so far.
 
#48
JKos said:
If you are picking up an FM station, there is something else going on with a lot is energy that isn’t FM. Demodulating FM just doesn’t happen that easily.
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What else could be going on?


SharpCat said:
Amateur radio hams call this an “ugly balun”. The diameter of the coil and number of loops affects the frequency that gets attenuated. But this is only going to work if the problem signal is coming from the bass to the amp or interface across that cable—which I think is unknown in this situation so far.
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Sounds like I need to get an amplug or something similar to see if I'm getting the interference without the instrument cable.
 
#49
BaileyMan said:
One thing I have since learned (and addressed in one of my basses) is that the shielding in the pickup cavities needs to be electrically connected to the shielding in the control cavity. However it had no impact on the radio signal. :-(
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too bad that wasn't the answer but yeah;

all too commonly i see instruments where the factory puts the black shielding paint in the pickup cavities without bothering to actually connect it to ground, thereby turning it into "antenna paint" :meh:
 
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#50
I tried a headphone amp. A Rushead Bass Max by Valeton (seems like a great little piece of gear, btw). I'm still getting radio signal. It seems as though something in all of my active basses is acting like an FM antenna.

The technician at the radio station is going to reach out to some guitar techs and see if he can help figure out what's going on. I thought I'd check in here.

Any thoughts on what could be acting as an FM antenna or why something might be doing so?

Thanks!
 
#51
BaileyMan said:
It seems as though something in all of my active basses is acting like an FM antenna.
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Your active basses are not demodulating an FM signal. They are not tracking the frequency of the transmission to decode the audio signal from the frequency modulated transmission. They are receiving an AM signal emanating from the station/transmitter. Perhaps not on purpose.

Are you sure the station doesn’t also broadcast on AM?
 
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#52
JKos said:
Your active basses are not demodulating an FM signal. They are not tracking the frequency of the transmission to decode the audio signal from the frequency modulated transmission. They are receiving an AM signal emanating from the station/transmitter. Perhaps not on purpose.

Are you sure the station doesn’t also broadcast on AM?
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Just confirmed. Only FM and cell signals from that tower. They don't broadcast on AM.
 
#54
JKos said:
Your active basses are not demodulating an FM signal. They are not tracking the frequency of the transmission...
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It's not impossible. I once picked up an FM station on an amplifier I was building. The process by which it happens is called "slope detection". There are articles on the web that explain it better than I can.

Reid
 
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#55
SharpCat said:
If they have an AM spurious emission at -46dB on a 50,000 watt transmitter, that's still over a watt of AM power, and you're really really close.
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I'm not really sure what all this means or how to apply it. Based on info from radiolocator.com it says it's a 6000 watt transmitter. How would one know if they have an AM spurious emission?
 

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