Rich, Dave, and all,
This is 'usual' behavior for the K2 - it seems the power shifts by about 5
watts in high power mode. It is present, but not noticable in low power
mode because the shift is only about half a watt which is a smaller
percentage of the power setting.
Checking the schematic, it seems this is controlled by the VPWR signal which
is an output from the 8 bit DAC. It would seem to me that each DAC step
should be about 0.5 watts (128 watts/256 steps), so even with a DAC
uncertainty of +/- 1, the power should vary by only 1.5 watts assuming that
the DAC input value is held constant (I don't think that is possible). My
guess is that there is an additional uncertainty in the firmware calculation
of the power to be transmitted that causes the remaining part of the
variation. The present region of uncertainty appears to be +/- 5 DAC steps
if my math is anywhere close to correct.
Perhaps Wayne can comment and tell us if the firmware loop can be tightened
a bit to reduce this power varaiation. I don't drive an amplifier, but for
someone who is driving an amp with say 50 watts from the KPA100, the real
varaiation is 10% and for a 1500 watt amp, the final output variation is
about 150 watts!!!
I really can't see this as a problem in actual operating practice (there is
little difference in transmitted signal between 1350 watts and 1500 watts),
but it can make meters 'dance' which may be quite disconcerting.
73,
Don W3FPR
----- Original Message -----
Sounds like both K2's I have had. 38xx and 44xx. The output jumps all over
the place. My amp does not like it either. When I posted about it, the
response I got was that is "normal".
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