David,
You are chasing your tail since you are trying to use all those
wattmeters - they will all be different.
You say that you are using a wattmeter between the KPA100 and the KAT100
- that in itself can lead to a variety of readings. The only thing you
can really trust is a good dummy load. The DL1 is good.
Because of the scaling done in the KPA100 for the output of the
wattmeter to the K2, you can calibrate it at low power. Disconnect the
power cable from the KPA100 and power only the base K2. Now, you can
use your DL1 dummy load and do the calibration at 10 watts (the power
control is a lot easier to use with no PS connected to the KPA100). Be
certain your KPA100 wattmeter is balanced first (do that into a good 50
ohm dummy load or it will not be correct - use your DL1). Then set the
KPA100 forward power pot so the K2 display matches the power calculated
from the DL1/DMM reading. You may have to make several trials to
average things out, but once calibrated that way, your KPA100 wattmeter
will have greater accuracy than the run of the mill wattmeters - and it
will be accurate on both the low and high power scales.
If you do it right, you can judge the accuracy of those external
wattmeters by comparing them to your KPA100.
You can expect some variation from band to band because the diodes are
not entirely linear with frequency. Pick one band and stick with it
while doing the calibration. Attempting to calibrate on several bands
is an exercise in frustration. I like to use 40 or 30 meters, but if
your operation is mostly on 20 meters, then that may be a better choice
for you.
If you are attempting to compare wattmeters with a live antenna,
remember that common mode current on the feedline can also have some
influence, and the amount of influence may be vastly different from one
meter to another - as I said, the only thing you can trust during these
calibrations is a known dummy load.
73,
Don W3FPR
David Wilburn wrote:
Ok, I got all kinds of numbers off of the DL1. The Bird seems a touch
low, showing 80 - 100w across all bands. Every time I measure it a
different way, I get different numbers. Very frustrating. The W1
quit after about 5 min. The MFJ meter gives one reading, the Bird
another, using the DL1 and doing a calculation, goes crazy on 10&12m
but more stable, and once again different on others. Friend is going
to loan me his Bird, think it is a 4309, and we will see what it
shows. I have put the Bird between the K2 & the KAT100, and
transmitted and then ID'ed, and got the 80 - 100w. Am I chasing my tail?
Dave Wilburn
K4DGW
K2/100 - S/N 5982
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