Engine RPM noise on CB radio

[krokus]

Having lost track of what you have tried, have you tried running the radio and no whip? (Leaving everything else connected.)

In your recent video, I hear some whines that sound like a mixture of clocks, and control signals.

A spectrum analyzer would be very useful, or some other HF receiver.

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[secretspy711]

Yes, when I disconnect the antenna, all noise goes away.

I borrowed a HackRF SDR from work, tuned to the CB band, but didn't see any difference with the engine on vs off. Whatever RFI is being picked up, either it's outside the CB band, or the SDR just isn't seeing it for reasons I don't understand. The former supports my hypothesis that this radio simply isn't filtering very well.

I permanently moved the antenna to the fender. It seems like it's working a bit better here and there's no question about ground plane at this location. While driving around a little today, it definitely seems like the noise is worse when driving through neighborhoods with vertical surfaces that reflect RF, compared to main roads where structures are further away. When driving on main roads, I can sometimes reduce the squelch to 3 without having noise break through. When I get into a neighborhood, I have to keep the squelch on at least 4. But if I turn the engine off, it all goes away and I can take it down to 2. (Max is 7).

I'll keep using it for a while, but I may buy a Cobra or something else.

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[Fowler]

Time for a new CB! Too bad you cant find an old Motorola Mocat 40 CB It had push pull audio and an extender circuit to help eliminate interference. Great rig.

 

[james1941]

Did you ever find the problem. I have the same set up and same problem.

 

[secretspy711]

I determined that this CB is just more sensitive than my last one. All my attempted fixes may have helped very slightly, but I don't think I could ever eliminate it while using this radio. It works well enough for Jeep trail rides with the LO/DX setting and squelch set appropriately.