[Elecraft] Wattmeters (WAS: no subject)

[Ron D'Eau Claire]

In addition to Vic's "spot on" comments, Bird elements, like any precision
device, need to be checked and calibrated regularly if they are to be
depended upon.

In commercial shops we at least compared several from time to time to be
sure they all agreed with each other and, if not whether it was the element
(usually the case) or the meter that was at fault. They went to a
calibration lab for adjustment every year or two. 

The elements can be thrown out of calibration by being bumped around in the
tool box, where too many of them hang out when not in use. After dropping an
element, most users stick it back in and, if it registers power, heave a
sigh of relief thinking "it wasn't hurt". Hmmmmm....

The most accurate method most Hams have of measuring RF power is to use a
rectifier/voltmeter combination. That's because the accuracy of the peak
voltage measurement is dependent upon a DMM that the Ham uses regularly and
which can be easily checked with decent accuracy in a number of ways. For
power levels beyond the limit of the metering circuit a simple voltage
divider such as the Elecraft DL1 uses can be pressed into service. If you
aren't sure about the accuracy of the divider, run a test at a power level
that you can measure both directly and through the voltage divider to
confirm its accuracy and, if there is an error, determine the needed
correction. 

As for the MFJ guy who dismissed the Bird meter, he may have gone to the
same sales seminars I attended in the 1970's. The one where they teach you
this: 

Your prospect says, I have a Whiz-Bang unit!" 

The salesman looks genuinely interested and say, "Oh, really? Which model?"

You say, "It's the mega-plex Mark Five!"

He shakes his head slowly, saying, "Oh...that model...is it still working?"

Nothing like the "inferred condemnation". 

Ron AC7AC