CB / Am radio interference

Yes_me

Member
Apr 30, 2022
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Hi there. Any suggestions would be welcome. My turntable and preamp combination are receiving interference. I can hear a CB / Am radio user when the units are powered on. The turntable earth is connected to the preamp earthing point and there is very little noise apparent. Whenever the radio user transmits, I hear a very loud buzzing with his voice speaking in the background.
I am very frustrated so any help would be appreciated.
 

ifor

Well-known member
Dec 3, 2002
104
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Do you by any chance have a TT/tonearm combination with an aerial (unshielded tonearm wires), such as a VPI?
 

Yes_me

Member
Apr 30, 2022
4
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Thank you for your answers. I am using an Optonica turntable with an Audio Technica pickup. It is linked to an HQ RIAA preamplifier then into an AUX imput of a Denon micro-system. If I disconnect the earth lead, I still receive RFI but with added noise due to the turntable not being earthed. The suspected CB radio could possibly be a Radio AM. The fault only occurs when the turntable and preamp are being used.
 

Gray

Well-known member
There's a possibility that the CB man is making illegally high powered transmissions.
Here in the UK there used to be a department that would track down and stop dodgy transmissions (But good luck with trying to arrange anything like that in these cash-strapped days).
If you haven't already, you could disconnect the TT from the preamp to see if you still get the breakthrough (with preamp output still going into the Denon).
That would tell you whether the TT or preamp is susceptible.
Then you might be able to try different TT / preamp where necessary.
Ultimately there may be nothing you can do to prevent it.
(I reckon the fault is with him not you - not that that's any consolation to you, as you're the one with the problem :().
 
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Yes_me

Member
Apr 30, 2022
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Just an update. This is difficult to diagnose because the radio user is not around every day or night ! I have found that I always receive noise, even if the turntable is switched off. If I disconnect the turntable, I think the noise stops but I am still not 100% certain.
I contacted Ofcom and they were not at all helpful. Their investigation concluded that "equipment may have a lack of immunity to radio frequencies".
 

djh1697

Well-known member
Nov 27, 2008
127
21
18,595
Try some "ferrite beads", or "ferrite rings"

I am not sure where you would locate them from these days with the demise of Tandy and more recently Maplin. They *MIGHT* resolve the issue.

Optonica is a brand I haven't heard of for a long time, although I did sell some in the early 1980's. . I'd say try and put a bead as near to the turntable output cable as you can, BUT do not let it put weight on the cable, otherwise, you may damage the arm wiring.

The shop I worked at also sold CB's and we did not have this issue.

If that doesn't work try the phono amplifier end.

 

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