Jeff Liebermann wrote:


About 20 years ago, I was involved in a wattmeter calibration party.
Mostly, we were trying to product frequency versus indicated power
graphs. Should be simple enough. Right.

Because of erratic readings, it was decided that everything needed to
have the contacts cleaned and tarnish removed. Someone dug out some
silver polish, which made the slugs and couplers look nice and shiny,
but also coated them with a layer of wax. The readings stabilized
only after everything was wiped with alcohol patches to remove the
wax.

That was why I used some old greenbar computer paper.


After that, we found that many of the slugs produced seriously
inaccurate readings. Dig out the Model 43 data sheet and it says
+/- 5% accuracy. Ok, 5% of what? Calling Bird support determined
that it was 5% of full scale. Therefore, if I use a 100 watt slug to
measure a 25 watt transmitter, and 5% of 100 watts = 5 watts, 25 watts
indicated could be anywhere between 20 and 30 watts. So, we ran the
graphs mostly at full scale with a few spot checks 1/2 and 1/4th of
full scale. A Telewave 44A (no slugs required) turned out to be quite
good (specified accuracy +/- 6% of FS) above about 200 Mhz, but
required using the included calibration chart for lower frequencies.
Also, my collection of battered Radio Shack VHF/UHF VSWR meters were
amazingly accurate (in the ham bands).

There was some discussion that a light bulb dummy load and light meter
was more accurate, but we didn't have time to verify the claim.


For their market, the Bird was good enough. As long as the
'Federation of Chicken Chuckers' were in a good mood.


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.