[Elecraft] KPA500 Temps?

[Wes Stewart]

When you put the KPA500 into transmit there is some fixed (FET) drain current 
regardless of whether you are driving the PA or not. Likewise, the power supply 
is supplying this current.  So the efficiency is zero and all of this DC power 
is converted to heat, not RF.  Efficiency increases with drive.

So what you are doing is poor practice.  Furthermore, IMD performance of the 
driver (K3) is likely better at higher power. It's for sure better at 20W than 10W.

Wes  N7WS


On 1/16/2017 7:22 AM, cx7tt at 4email.net wrote:
> For the NAQP cw party this past weekend, I ran low power. Rather than
> 'stress' the K3s with 100W, I chose to run 6W thru KPA500, giving me 100w.
>
> During a one hour run period, 125+ Qs on 15m, I noticed the KPA500 temp
> at 51C which surprised me. Idle temp in the shack is generally around 33
> to 35C. I expected much lower temp at 100w output.
>
> Why the higher temp and is it not related to power out?
>
> 73
> Tom
> HP1XT
> ___________________