Keying mic breaks squelch

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SVTotem

SVTotem

Well-known member
Joined
Jul 29, 2010
Posts
199
Location
Orlando, FL
Well that is what it sounds like.

New ham here. Kenwood TM-71A. Arrow 2m/70cm J-pole.

I removed my two banded from the jeep to bring it inside where I could spend some time learning its features and frequency programming. I picked up the J-Pole and 25' cable to eventually mount the antenna in the attic. When I hooked up the antenna I found that any attempt to transmit on M or H in either band results in a loud sound similar to breaking squelch. It is ok on L. I thought the antenna was too close and moved it to another room, but no change. I remounted the radio in the jeep and all was fine.

Any ideas?
 
I have seen something like this happen before.  Turned out I had the power wires from the power supply routed too close to the radio.  Rerouting the power wires straight out and away from the antenna connections fixed it.  Having a antenna analyzer would be good to check the frequency and SWR on the antenna but I don't think that is the problem. I am assuming the power supply is adequate for a 50 watt radio?  Ed/K3CAV
 
Like Ed said, the problem is RF or noise getting into the 12 volt power lines or the microphone cord when you transmit.  First thing to check is the power supply capacity - is the voltage sagging out of spec when you transmit?  Low voltage means less regulation and filtering inside the radio, so outside noise and RF picked up by the power leads becomes more critical.

RF interference can be reduced or eliminated by moving the antenna further away from the radio and it's mic and power cords.  In a car, the metal body provides shielding between the antenna and the radio, even though they may only be a couple of feet apart.  A naked antenna in the same room as the radio and power supply doesn't have the same isolation.
 
Problem solved. Thanks guys.

I had the radio sitting atop the power supply and the excess power cord coiled up next to the PS.

I am a very new ham trying to find my way. My near term goal is to build a go box using a gator box rack system. I can see that I will need to be mindful of cord placement.

I will participate in a field day later in the month and should pick up a lot there.

Thanks again
Bill
KJ4FWN
 
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