Posted by
Jim McCook W6YA on
Aug 24, 2019; 6:45pm
URL: http://elecraft.85.s1.nabble.com/KPA-1500-Power-Output-Variation-tp7654657.html
I'm using my K-3 with the KPA-1500 and have a problem with extreme
changes in power output with a given drive level on 40m CW. This
happens to a lesser extent on other bands with different antennas. My
40m antenna is tuned to 7.025 where SWR is 1.1:1. On 7.000 it is 1.4:1
and at 7.050 it's 1.3:1. Within that range of frequencies the output
_without_ the tuner at a given drive level (30w) varies from 1300w to
well over 1700w. Using careful _tuner_ settings it's only slightly
better. I have to reduce drive to 24 or 25w to get below 1500w,
depending on the temperature of the amplifier (power output varies a lot
with temperature changes). Higher temp = lower output.
I have tried to compensate in the segments where output is excessive by
using manual settings via the Utility. This has helped slightly, but
still isn't adequate. I've resisted using ALC because of concern for
generating distortion. Having to ride the drive level from the K-3 is a
PIA, especially during contests.
It seems to me a good answer would be to have higher input attenuation
so drive requirement would be higher, maybe around 70+ watts. I'd
expect changing drive level by the same number of watts (5 or 6) would
not affect output as much. I'd also assume the power output would not
vary nearly so much with a given drive level.
Is this a possible solution? I've also understood that most
transmitters (even the K-3) have cleaner output near highest rated output.
Help!
Jim W6YA
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