[Elecraft] OT: Bird watt meter?

[Ron D'Eau Claire]

Guess this is the "real world" talking. Your experiences are =
interesting,
but I've never tried calibrating one of them. I know the FCC field =
engineers
used them to check transmitter outputs for spec. Maybe it's consistency =
that
is important there. The tech sets a transmitter 50 watts, and then FCC =
notes
that his meter says 50 watts too <G>.

After answering the original question I checked the Bird spex and they =
claim
5%. That happens to be no better than any of the common good quality =
"Ham"
wattmeters.

I agree about dropping them from a tower. Done that <G>.=20

Back in the 1950's I was not away of ANY RF power meter suitable for =
field
use at any tolerance other than the Bird. The only other method I saw =
back
then was a thermocouple RF ammeter driving a dummy load, and the results
were never better than 20% or so. Since you square the current reading =
the
multiplied it by the impedance of the load, you squared the ammeter =
error
too.

Ron AC7AC

-----Original Message-----
> Bird meters are only good to plus or minus 5 per cent, presumably of=20
> full scale. -Stuart
> K5KVH
>
>
If you are lucky. I calibrate Birds at a nist lab. All are limited to =
+/-
!0% of full scale or more. They are very nonlinear on frequency. I
personally have never understood the reverence for Bird meters. The only
pluses I can give them is no power required for operation and you can =
drop
them from a tower and they will survive. I would never rely on them for
anything but peaking a signal or a VERY general  output indication.

Roy AB7CE