On Thu, 4 Dec 1997 11:47:09 -0600 w5hvv@aeneas.net (Roderick M.
Fitz-Randolph) writes:
>_________________________________________________________________________
>Hmmmmmm, Steve, it is my considered opinion that you have been smitten
>by the My-wattmeter-is-more-accurate-than-your-wattmeter syndrome.
>Please
>note that syndrome means that there doesn't appear to be any basis in
>fact for the symptoms (from a medical dictionary).
>
>I have, over a career of nearly 40 years as an electronics engineer,
>had
>occasion to use many Bird wattmeters. I have found that even when
>they
>came straight out of PMEL, that they often will not give the same
>power
>readings with another one set up side by side with it and alternately
>using the same crystal unit.
>
>In addition, I have almost never found one that gave the same reading
>on two separate but identical crystal units. I believe that the
>problem
>is most often the crystal units, themselves. I personally see no
>justification for the apparent snobbery that Bird wattmeter owners
>appear to have.
>
>As for the accuracy of my Drake W4 wattmeter, I have taken the time
>and
>effort to determine its accuracy with a 1500 watt mil-spec dummy load
>and a tektronix scope (by measuring the voltage at the dummy load) and
>I am satisfied that it is accurate within 5%. Perhaps that is a
>fluke.
Rod, as an engineer I am sure that you would agree that your test
equipment, unless calibrated against a NITS traceable standard, is as
much of a crap shoot as anything else discussed here recently. Just
because it has the TEK or HP name on it means diddly otherwise.
Going back to days of yore I remember the problems that National Radio
had in testing the NCL-2000 amps. The Waters loads were junk and changed
readings based on oil temperature. Next we tried the Drake ....another
mistake since it said the NCL was putting out 1600W on 10M.
We finally were able to scrounge a Bird meter and load from the military
division and that became our standard.
Please note that military and most real world commercial testing
specifies the Bird as the standard. Our Navy or USAF inspectors at
National would have had us hung if we tried to use a Drake, Swan or even
a Collins meter....the testing specs said Bird....period.
Like 'em or not they are the standard. That's not to say other meters are
bad; some such as the Mirage MR-1 are very accurate.....but you know what
they use for the reference in those magazine tests...3 guesses. Sounds
something like the Indiana Pacers coach's name.
I have 4 Bird's here. Also a Vectronics, a Mirage, 2 Daiwa's and a home
brew. I keep the brand X meters in line just to keep an eye on the VSWR;
if I need to know what is really going on I use a Bird. They have not
failed me yet....1.8MHz to 2.3 GHz.
Do I really care if my power is within 5% or 3 % of full scale
accuracy...nope. What I do care about is that it is repeatable, day in
and day out.... something I cannot say for Brand X meters with component
aging, heat and assorted other problems.
73 Carl KM1H
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