PGXL: Low SWR on CW. High SWR on USB. Same Ant, Freq and Drive power!

KM6XX

PGXL with 3.4.10 driven by a 6600 running SSDR 3.1.11. At the same frequency (~14.202) and same drive power (~46W) I get ~1200
https://www.youtube.com/watch?v=3kpf6H3ZUWk
W and a 1.5:1 SWR with a CW tone. However, using USB I get a "HIGH SWR RFP" warning in the PGXL utility.  This is new.  I've never seen this issue before. See the attached video.  Any ideas?

Sergey KN7K

KM6XX

DL4RCE

Please read the changes of the update to the PGXL software, there is an update also to SWR related / protection stuff. 73 Volker

Al K0VM

DL4RCE

"Fast SWR Protection: The Power Genius XL hardware protection system, designed to prevent damage due to high SWR events, is now more sensitive and reacts faster."

Dan-N7HQ

Sergey KN7K

Tim - W4TME

Cabral, please open a HelPDesk ticket for your issue are suggested by Dan so we can address this issue for you.

KM6XX

Dan-
Thanks for the detailed explanation.  I believe you are correct in the issue is related to the antenna system.  I did a battery of tests on my feed line system with a dummy load to rule out possible issues with the 8" coupler penetrating the wall of my shack, the Davis CMC and various feed line sections that make up the antenna system.  All of these components tested out fine under high power. 

However, having the manifest itself during USB transmissions and not during  constant CW transmission had me believe it was  RF in the shack.   

Do you have any data that suggests the directional couplers are susceptible to wide band RF current vs narrow band?

Also, I have a AM radio tower about a mile from my shack and the signals at 780kHz are outrageously high. Do you know of the directional couplers are susceptible to external RF?


That being said, I changed my antenna feed system based on a paper on End Fed Half Wave antennas to reduce the likely hood of stray RF in the shack. It recommends a  0.05 Lamda  length of coax from the feed point to the CMC.  I found some interesting results:
1. With a 14ft length of coax (0.05Lamda) between the system passed! Please note the SVSWR was 1.36:1.
2.  If I reduce the length by about 3ft, the unit systems fails with "High SWR RFP".  The SVSWR was 1.26:1.
3. Reducing the length further reduces the SVSWR and the system fails.

This begs the question, Why would the lower SVSWR lengths fail if the there is less reflected power?

I don't believe it is moisture, as I live in Arizona and it is very warm and dry right now.

I'll do the help desk ticket right away.

KM6XX

Will do Tim.

KM6XX

My Ticket : Request #36978