[Amps] KPA1500 Efficiency vs. RF-Kit B26

[Jim Brown]

On 7/11/2021 9:25 PM, Adrian wrote:
> I imagine the KPA1500 has a temperature display, what FT8 session RF out 
> power level can it sustain, without exceeding 50 deg C if you know ?

Why 50 deg C? The microprocessor controlling the fans (there are 
several, in the outboard PSU and in the RF deck) sample operating 
temperatures and increase fan speed as needed. I usually cruise at 
around 1kW on 6M WSJT modes, where the amp is least efficient, and where 
long TX times with 40% duty are the rule, and around 1.5kW on HF.

On 6M, the software speeds up the fans as needed as the indicated temp 
passes about 64 C, and holds below that for as long as I want to run. 
When I'm contesting on HF, always at 1.5kW, I've seen temps at 90 C, the 
fans run faster, I'm happy, and the amp is happy.

To put this in perspective, N6TV and I are both serious contesters, so 
when we're contesting, we're going full bore, balls to the wall! So is 
my neighbor, K6XX, who is a mfg engineer at Elecraft, with 
responsibilities for the KPA1500.

73, Jim K9YC