High SWR on 160m

Larry Burke

After 30-45 minutes of FT8 operation on 160 (typically calling a DXpedition under less than ideal conditions - one sequence on, one off) the SWR meter on the PGXL will take off, max out and the amp indicates High SWR. Meanwhile, an external SWR meter shows no change to the antenna's actual SWR. So it sounds like something taking place internal to the PGXL, possibly heat related. Shutting the amp off (using the switch on the back of the amp) then turning it back on seems to cure the problem for a while. Anybody else experience this?

Stan VA7NF

Often on 160/80 even a high power balun will overheat. For example our 80M OCF Dipole has a 3KW balun but over heats at 1KW CW. The signs are a slowly increasing SWR which drops if CQ is paused for 30 seconds.

Mike-VA3MW

Stan brings forward something that requires investigation. I was going to say the same thing.

Can you tell us more about your station please.

• What sort of power are you using?
• What temperatures are you seeing on the PGXL when this happens?
• What is your 160M antenna and is the typical SWR you are seeing?
• Are you using a high power tuner at all?

With your other SWR meter, I assume you have that installed between the antenna and the PGXL (sorry, I have to ask)? :)

Can you recreate this situation while testing into a dummy load at the same power? If so, then we need to open a support ticket for you. If you don't have a high power dummy load, they aren't very expensive to add to the shack and a very good tool to help diagnose a problem.

Larry Burke

The power is 1500 watts out of the PGXL.

I didn't note the temperature, but will the next time this happens.

The antenna is a 160m vertical fed with LMR400. There is an SWR meter, surge protector and antenna switch between the PGXL and the antenna.

There is no tuner.

Yes, the SWR meter (PowerMaster) is between the PGXL and the antenna.

This doesn't happen very frequently. Only in a situation where I have been operating for a long period of time. Typically I notice it after I have been calling a station on FT8 where it requires significant time to "get through". And it's a surprise when it happens so I didn't think to observe the temperature, but will next time. I do not have a high power dummy load.

Building on Stan's comment, it is possible that the coupler for the PowerMaster, which is remote from the actual meter, may have a component in it that is overheating. I would kinda expect to see some unusual readings on the meter if it were the PowerMaster acting up. I have a barrel connector ready to bypass the coupler the next time this happens. It is also possible that the surge protector is overheating.

For now, I am just curious if anyone else has noticed similar behavior. In the meantime, I'll keep these comments in mind should this occur again. I don't particularly want to generate a support ticket yet, given I still need to do a bit more investigating and because the problem is fairly infrequent.

Mike-VA3MW

Many thanks for the excellent update that really helps to paint the picture.

Keep an eye on it and if we need need to, we can open a ticket. I'll also have Dan Q have a look at this for his comments and to see if he sees something unique.

My setup is similar through a Power Genius / Antenna Genius than a pair of LP100 probes / 50:75 balun / RG11 -- 160M mostly vertical with elevated radials.

73