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Power Prongs Causing Continuity Between Ground and Antenna?

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chuckellis
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Name: Chuck Ellis

Power Prongs Causing Continuity Between Ground and Antenna?

Post by chuckellis » Friday, 07 July 2017, 21:10 PM

Hey, guys. I just bought a Cobra 29 LTD classic. I've tested the continuity for my 102" whip antenna and coax. Steel car with grounding bonds throughout the vehicle. Everything on the system that should have continuity has it, and everything that should be open is open from the coax up front to the antenna and base. I plug the coax into the back of the CB and everything still reads the same until I plug in the power.

As soon as I plug in the power, I have continuity between the base and the antenna all down the line. I checked the power feed from the 12 power to the back of the three prong plug for the unit and there's nothing. If I test the power prongs on the back of the CB, I get almost full continuity. I popped open the back of the unit to see if there was a short, and there's a small, flat, yellow capacitor soldered to the back of each prong leading to a ground spot on the back of the unit. That seems to be where the continuity is coming from.

If I unplug it, everything goes back to normal. Hots have continuity, grounds have continuity, but between the two, they're open. Radio turns on and seems to function ok. I've done calibration procedures and messed with the antenna length using washers, but my SWR pegs off the charts every time I key the mic.
I'm a complete noob here, so any help would be greatly appreciated.

Thanks!
Chuck


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MDYoungblood
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Re: Power Prongs Causing Continuity Between Ground and Antenna?

Post by MDYoungblood » Monday, 10 July 2017, 18:25 PM

Hello chuckellis,
Welcome to the forum. Plugging in the power plug is creating a circuit so I don't see a problem there. If there isn't a shorted center conductor in the coax then there isn't a problem there either. Since you are saying the radio pins the SWR meter when keyed turn the modulation off via the dynamike and try the SWR one more time. Get the antenna adjusted for the best SWR.
As a new member could you post a intro in the "Welcome to the Forum" topic, viewforum.php?f=89 , so others can say "Hi", thanks.

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