Harry: Are these values on a dummy load or feeding the KAT500 or antenna direct?
I just quickly checked my KPA500 into a dummy load at 500 watts output. The currents run from 14.0A on 20M to a low of 11.5A depending on band. This is done with 500 watts output as shown on my Bird 43 and Bird 50.5 ohm load in TUNE mode which I have set for 20 watts tune power on all bands from my K3S. The HV runs 60.0 volts or a bit higher under load and 74.5 volts at no load. The amp is sourced from 240VAC.
With the amp feeding the KAT500 and a 1.5:1 or better resolved match on the antenna system, the currents run from a high of 16.4 amps to 11.7 amps. Again depending on band and SWR values.
Yes the amp is more efficient on some bands, and the load impedance will affect the PA current. As to fans, I run mine in NOR and let the amp take care of itself. Fans do ramp up when running FT-8 at 500 watts.
73 Bob, K4TAX On 8/2/2019 6:03 PM, W4HWD wrote:
HI, I'm new here and new to Elecraft. I have to KPA/KAT500 combo and love it! I do have a question about PA current though... On all bands except 20, when running full power out, my HV sits around 64v and PA current is stable between 10 and 12A. FAn takes it's time coming on and amp just loafs along. On 20, however, even at lower power output levels, the PA current is high and the fan comes on and steps up quickly! At full 500W out on 20, HV is 62v and current runs as high as 16A! Even at 300w out the current runs around 13A, higher than any other band at full 500w out. Question is, is this just how it is or do I have something amiss on 20m? Antenna is doublet 60' in the air and this antenna is the one I use on 80, 40 and 20, so don't think I can blame the antenna. Tuner loafs along during all this, and SWR is no worse than 4:1 on any of these three bands. Harry W4HWD -- Sent from: http://elecraft.365791.n2.nabble.com/ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to rmcg...@blomand.net
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