[Elecraft] K3 construction tools:RF Pwr meter 1 mW to 5W, Sig Gen 50uV on 20m or 40m

[Don Wilhelm]

Rich,

Yes, you can buy an HP435A with sensors for big bucks, and you will have 
power measurement accuracy over a wide range.  But there are other less 
expensive ways (homebrew) ---

Have you considered building an RF Power Meter?  Take a look at the one 
published by Wes Hayward W7ZOI and Bob Larkin W7PUA in QST June 2001 (pg 
38ff) and available in the Member's Only section of the ARRL website.  
There is additional updated information on Wes's website 
http://w7zoi.net/Power%20meter%20updates.pdf.

That meter, properly constructed, will measure down to about -70 dBm and 
with the companion 40 dB power tap, it will measure up to 100 watts (+50 
dBm).  When calibrated it can provide very good accuracy.  It does 
require two known signal levels to calibrate (the Elecraft XG1 or XG2 
will provide that), and if the front end is well shielded  (see Wes's 
updates)  it will be accurate and if carefully constructed, it is good 
up to at least 200 MHz, more likely 500 MHz.  An analog meter can give 
reasonable readout, but there is provision for attaching a DMM for more 
precision.

This meter is not only good for measuring 1 mW, but even goes down to 
the nanowatt region.  I like mine, and use it frequently.  Use batteries 
mounted inside the enclosure, do not even think about powering such a 
sensitive instrument from an external supply if you want the isolation 
it needs for low level signals.

The other good  and convenient meter (actually computing SWR and power 
meter) is the Tandem Match - An Accurate Directional Wattmeter 
(originally published in QST January 1987), which is still a very good 
meter - without the coupler, it will measure power from -20 dBm (10 
microW) to +32 dBm (1.5 watts) and with careful construction should be 
good to 500 MHz.  With the coupler, its high frequency end is determined 
primarily by the coupler.  This is an older design by Elecraft's own 
John Grebenkemper KI6WX (his call was KA3BLO at that time).  FAR 
Circuits has boards, but I caution you on these boards - they do not 
have through plated holes and some traces need to have continuity from 
one side of the board to the other, so you must solder many components 
on both sides of the board (ask me how I know!).

73,
Don W3FPR

Richard Hill wrote:
> I'm struggling to find a 1 mW to 5W capable RF power meter.  I have a DL-1, but think it is not useful at 1 mW.  
>   
>