Cross Band Interference with Flex 6600M and Elecraft KPA500

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  • Updated 2 weeks ago
  • (Edited)
I have a strange thing happening in my SO2R setup with my 6600M and Elecraft KPA 500 / KAT500 setup.  When running High Power in a contest (i.e. 500 watts), I normally have the KPA500 on Slice A (Antenna 1) while still using Slice B (Antenna 2) at 100 watts.  In this configuration, I can transmit on Slice A at 500 W and have very little interference on Slice B which is great.  However, surprisingly, when I transmit on Slice B at 100 Watts, it almost totally wipes out Slice A.  In this example, I have Slice A on 20 CW and Slice B on 15 CW.


The strange thing is that this only happens if I have the KPA500 in "Operate" mode.  If I have the KPA500 in "Standby" or "Off", I don't have the problem.  In other words, having the KPA 500 in "Operate" on Antenna 1 (even though I am not transmitting) causes RX on Slice A it to be wiped out when transmitting on Slice B (Antenna 2).  

I have tried different band combinations (e.g. 40 and 20, etc.) with the same results.  Also, I do have external Bandpass Filters on both slices (Dunestar).  The Flex 6600M, KPA500, and KAT 500 all have separate ground wires running to my common station ground point.


Has anyone else experienced this or have any suggestion what I might try?  Like I said, it is not a problem when the amp in in standby or off but it is surprising to me that having the amp in operate would affect RX on that slice.


73,

AL, K0AD
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Al Dewey

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Posted 3 weeks ago

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K3SF

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hi Al

Would be good to have a better description or wiring diagram of the setup. That includes antennas, antenna switches and how things are run to and from flex to the amp and then the antennas.  

I am not able to visualize your setup based on the problem description.

i would look to see if some configuration to determine if the cause maybe RF going somewhere you think it is not.

also transmit and receive antenna configuration on the flex


Paul K3SF

For example here is my RF distribution setup


(Edited)
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Al Dewey

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I'll try to put something together.  Probably a good exercise anyway.  May take a few days.

73,

AL, K0AD
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Kari Gustafsson

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Hi, I had a similar experince with 2 x OM2500A in SO2R. When one in Operate mode I got rf feedback to other slice and also detected rf on power meter of the amp. De-taching PTT send cable to the amp avoided the phenomena. But no good solution in a real live contest .Unfortunately I forgot how I solved the problem.