The duty cycle of FTx is 43.3% and may be less than RTTY or PSK
depending on the transmit:receive ratio; or long winded SSB.
I've run the KPA1500 at or near legal limit into a resonant antenna on
Ftx, for hours at a time without issues. It will warm the shack and I
suggest headphones, the fan can make some noise.
The lower output that you run, the less efficient the amp is, which is
total power used (presented as heat) to output power. Sometimes (30M),
that's the cost (the K3/4 won't produce the US legal limit of 200 watts,
without the amp).
73,
Rick nk7i
On 11/10/2023 11:14 AM, Victor Rosenthal wrote:
I don't have a kpa1500, but I recall someone from Elecraft saying that
since the efficiency decreases when power is reduced, backing off the power
does not reduce the heat load.
Victor 4X6GP
On Fri, Nov 10, 2023, 16:28 Pete Smith N4ZR <pete.n...@gmail.com> wrote:
I started operating FT8 while my KPA-1500amp was out for repair. Now
it's back and raising a question:
Operating with just my K-3, set at 100 watts, I would see 100 watts
indicated on its meter through the whole 15-second FT8 transmission..
When I drive my amp, it only needs 30 watts for full CW power (on 24
MHz), but the amp indicates 1200 watts input for the whole FT8 transmit
cycle. I'm wondering if I should back off to protect the
amp,considering the duty cycle is so high - on the other hand, the
temperature reading profile of the amp seems to be pretty much the same
as on CW.
73, Pete N4ZR
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