Following up on an exchange I had some time ago with Larry, I couldn't
figure out why his LP100A watt meter was reading low - even after he had
calibrated it in his shop. With some help from Don W3FPR, I got it
figured out and offer this for future reference to others who may
experience the same confusion.
There is a procedure on page 49 on the K3 manual to calibrate the power
out on the K3. After doing this you calibrate "per-band" using a
procedure on the same page. I didn't realize the K3 power meter is not
absolute. In other words, this procedure on page 49 is what tells the
K3 power meter how much 100 watts really is (actually 50 watts is used
for the test).
I had calibrated my K3 watt meter some time ago against an MFJ-949E
antenna tuner watt meter. (OK stop laughing). Turns out the MFJ unit
and another cheapo SWR meter I had here were both way off. The MFJ
reported 100w when the true output was more like 70. As a result, even
though my K3 watt meter read 100w, in perfect agreement with the MFJ,
both were wrong.
I re-calibrated, per Don's suggestion, using the LP100A as the
reference. Now 100w on my K3 shows 100w on the LP100A and 125 watts on
the MFJ. As an added bonus, my amplifier now puts out full power as it
was being under driven before.
--
Buck
k4ia
K3 # 101
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