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TX DUP signal problem 200D?

Posted: Fri Oct 05, 2018 4:55 pm
by G3ZQH
After several years of relatively problem-free use of my 200D I recently have a problem (or maybe not?) with a very poor quality TX signal as seen on the DUP panadapter. When I hit tune, I see many spikes either side of the main frequency- I have attached a screen shot to show an example on 40m. I have re-loaded the firmware (v4.9) and PSDR (v3.4.9), which made no difference at all. Now, the strange thing is that when I have asked for comments on my SSB signal quality, every response has been that it is a good clean signal with excellent audio! So, this makes me question what I am seeing in the DUP window.

So, my question: is this a real TX problem (something physically broken) or is it a fault in the DUP panadapter display of my TX signal? And, how would I be able to check this?

Any help appreciated.

73 Dave G3ZQH

Anan 200D screenshot DUP TX 40m.jpg
Anan 200D screenshot DUP TX 40m.jpg (265.71 KiB) Viewed 3178 times

Re: TX DUP signal problem 200D?

Posted: Fri Oct 05, 2018 6:52 pm
by DL2XY
Hello Dave.

These are 100Hz sidebands.
Please check your power supply for defective filter capacitator or rectifier. Maybe you can try another supply.

Another possibility is an antenna problem leading to high common mode currents which will flow through rectifier of the supply.
That would modulate the carrier with 2*50Hz mains frequency which may look exactly like your spectrum. You may try to transmit into a dummyload to confirm.

Regards Walter

Re: TX DUP signal problem 200D?

Posted: Fri Oct 05, 2018 7:59 pm
by G3ZQH
Hi Walter
The problem is still there with a dummy load. However, it mostly affects 40m and 30m- the other bands have only very small sidebands -60dB or lower. Unfortunately, I don't have a spare power supply, but I have confirmed the voltage and checked internally with no evidence of any problems. So I suspect the PSU is OK, but will try to source a second unit. Do you any other thoughts for possibilities?
73 Dave G3ZQH