[Elecraft] K3 and LP 100A calibration

[Buck k4ia]

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