[Elecraft] K3S TX current

[ab2tc]

Hi,

I have recently made a discovery during a routine checkup that my K3S draws
*much* more TX current on 20 m than any of the other bands. Using Data A
FSKD mode at the 100W level it draws about 22A versus 16-18 A on all other
bands. DC voltage from the Powerwerx SS-30DV is 14.2V as measured at the
binding posts. The K3S voltmeter indicates 14.2V in receive and 13.7V in
transmit mode. Current is measured with the K3S built-in ammeter (~1A in
receive). Power output is 100-102W as measured with an LP-100A on all bands
40m - 10m. TX IMD is not noticeably affected as measured using the built-in
2-tone generator. I measure maybe 33dB (5th order worst case) below PEP on
40m slowly worsening to 30dB on 10m, all within acceptable limits for a
solid state 12VDC powered transmitter.

What's up with this? I don't know how long this has been been a "problem" as
this is not something I routinely monitor. My much older K3 (with the old
bipolar PA) does *not* exhibit this behavior. Is this indicative of a
problem with the 20m low-pass filter perhaps? All measurements are done with
a Ridge Electronics dummy load. All RF connections are tight and the LP-100A
indicates 1.01 SWR on this dummy load in all cases. BTW my serial # is
10480, which is an early serial #. It was back to Elecraft twice in its
first year for fixes to the transmit signal path to improve TX IMD.

Knut - AB2TC

PS. I am not worried about the electricity bill, but whether this is
indicative of a potential future serious failure.



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