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RF getting into transmit signal

Dec 10th 2011, 19:43


Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
I have been told by a couple of ops that my signal is difficult to read due to stray RF getting into my signal on 15 meters. What exactly is this? How can I identify it? What can I do about it? I am in a usually very quiet area. I live full-time in my motorhome and am camped in Big Bend National Park for 3 months. There are no broadcast stations anywhere near me. We are so remote there is no cell reception, no commercial radio or TV stations within range, and, of course, no industry. My motorhome is connected to commercial power and the HF rig, an older FT-747GX into a G5RV, is running off the 12 volt system in the vehicle. I was told today that my signal was nearly unreadable due to this problem. I shut it off and fired up the mobile rig in my personqal vehicle, an FT-897 feeding into an ATAS-120 antenna. I was told that I still had RF on my signal but that it was improved. What gives?? I have never had any reported problems on other bands. Please help! Thanks!! 73 de Tom KD6TR
Dec 10th 2011, 22:55


Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
The problem they are reporting is probably RF feedback into your audio. That causes a kind of squirrelly distortion of your audio that can be hard to copy. It would be caused by a strong RF field near your rig (and your mic) that would be different on different bands.

General things to try: (1) Be sure your rig is well grounded. In your case, ground it to your motorhome frame. Make sure all your radio gear uses the same ground connection. An additional ground rod might or might not help. (2) Move your antennas further away from the rig. Maybe you can change the antenna orientation. Keep coax or other feed line away from your operating position - especially the mic. (3) Try filtering on the mic cable and other wiring to your rig (power, CW key, etc.). Type 31 ferrite cores are probably best - you need multiple turns.

I hope this helps!

73 Martin AA6E
Dec 17th 2011, 04:05


Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
High Swr .....above 1.8 : 1 and the antenna too close to the operating position will also cause Rf in transmitted audio.

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