[Elecraft] Power Measurement Instrument

[Ron D'Eau Claire]

A less-expensive and much more versatile option to the OHR WM-2 is the
nice r-f power meter described by Hayward, W7ZOI and Larkin, W7PUA, in
the June 2001 issue of QST. It is based on the Analog Devices AD8307
chip and looks like it can be built for under $50 using all new parts.
I'm currently collecting the parts for mine, so I haven't built it yet.
But every test instrument that Wes, W7ZOI, has described that I have
built works exactly like he predicts. I am bringing it up now because I
see a number of posts about power measurement options on the reflector. 

It does NOT require any exotic gear to calibrate and, unlike most
"commercial" watt meters and kits, allows measurements of very low
powers. This meter will measure r-f  levels down to less than -70 dBm
(that's less than 0.1 NANOwatt!) and up to +50 dBm (100 watts) and show
a response flat within 1 dB to 500 MHz when built as shown. 

As usual, Hayward includes a lot of information about test setups for
using the device to test low-level oscillators, evaluate filters when
used with a signal generator and for evaluating impedance matches in
transmission lines. His "workshop" experiments showing how to use a new
test instrument have always been a fun exercises of their own that have
never failed to teach me something.

Ron AC7AC
K2 # 1289