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Cooling Fan noise through CB

Old 11-06-2018, 11:05 PM
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Default Cooling Fan noise through CB

I just got an external speaker for my CB (so I can actually hear things now) and it's made me aware that my CB picks up a slight "whine" when the electric cooling fans kick on (running triple electric radiator fans). It's not horrible, but I'd like to cure it if I can.

I've done some reading and it seems first off I need to rewire my CB to go directly to the battery (currently I'm tapped off the cigarette lighter outlet in the dash). I also read about people putting electrolytic capacitors across the fan leads (as close to the fan as possible) and in the leads to the CB (close to the CB unit). Anyone have any input on this? Further suggestions? The antenna is a through roof mounted NMO base with a base loaded 49" whip (has a solid ground path between the cable housing and the body).
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Old 11-07-2018, 05:38 PM
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Good choice on antenna and placement.
Disconnect the antenna from the CB, do you still hear the whine? If so it's likely coming from the power wires. You can try putting some some ferrite beads on the wire leads, loop the wires through the beads as many times as you can.
I would try powering the CB directly from the battery first and see how that goes.
Also try some RF bonding, running braided ground strap from the exhaust to the "frame" and from the hood to the body.
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Old 11-07-2018, 08:17 PM
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Originally Posted by prerunner1982 View Post
Good choice on antenna and placement.
Disconnect the antenna from the CB, do you still hear the whine? If so it's likely coming from the power wires. You can try putting some some ferrite beads on the wire leads, loop the wires through the beads as many times as you can.
I would try powering the CB directly from the battery first and see how that goes.
Also try some RF bonding, running braided ground strap from the exhaust to the "frame" and from the hood to the body.
Well shoot, I disconnected the antenna from the CB unit and ALL noise is gone. So now what?
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Old 11-07-2018, 08:30 PM
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You can try rerouting your wire.
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Old 11-08-2018, 07:53 AM
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Originally Posted by CLSegraves1 View Post
Well shoot, I disconnected the antenna from the CB unit and ALL noise is gone. So now what?
choke(s) on the power wire for the fans
choke(s) on the antenna coax
RF bonding (ground straps) for hood, exhaust, engine, hell even try bonding the fans (carefully)....the more the merrier.

Or switch to GMRS or ham radio.... they don't have quite the RFI issues that CB has and they are better in almost every way!
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Old 11-08-2018, 10:00 AM
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Originally Posted by prerunner1982 View Post
Or switch to GMRS or ham radio.... they don't have quite the RFI issues that CB has and they are better in almost every way!
X10. FM modulation produces a much clearer cleaner signal than the AM based CBs. You get a much higher power ceiling (max of 1500 watts on HAM bands and 50 watts on GMRS) than the 4 watts CBs are limited to and access to repeaters to greatly extended local communication ranges. It does require a license on both bands but the tech license is really cheap (I paid 10 dollars to take the test and I'm good for 10 years) and the GMRS license only requires you to pay the fee and all the paperwork can be done online, no test required.

-KK6RBI
-WQYH678
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