Radio: it's not just a hobby, it's a way of life

Current Operating Frequency and Mode

OFF AIR for storms, probably for much of the week if the forecast holds

Hot Spare GW3UEP class-E amp is in the bullpen if needed for this weekend’s Field Day message event

– Posted in: 630 Meter General Topics, 630 Meters

I’m a big fan of the GW3UEP class-E amp and use two of them in conjunction with my W1VD zero degree combiner.  That system has been very reliable for a very long time but what if I lost a PA during the Field Day event this weekend?  I can run uncombined at nearly 3db less power while I frantically replace components on the ailing amp but I decided it made the most sense to build a spare amp that I can keep in a hot-swap state.  So here it is:


Note that most of this amp is built from recycled materials, the exception being the WIMA pulse-rated caps (red and blue) that I picked up at Tanner’s in Farmer’s Branch, TX for under $5.  I normally use silver-dipped mica caps but since the WIMA’s were available in the values I needed, I decided to try them.

As a test I ran the PA up to about 30V on the drain at nearly 6 amps and was able to get about 165 watts out at nearly 92% efficiency into a 50 ohm load.  That’s REALLY good.  Even better, the IRF540 didn’t seem to mind the abuse and I was able to maintain a carrier for 5 minutes with minimal heating or changes in drain current as components were stressed.  The KW oil filled dummy load was as warm as I had ever felt it.

These results are not necessarily typical but I run huge heat sinks and fans on my home brew PA’s and I am obsessed with well-matched loads so I tend to get away with things that someone else might not.

Hopefully this amp won’t be needed this weekend but its here if it needs to be pressed into service.