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Tuesday, May 13, 2008

Calibrating my W7ZOI/W7PUA Power Meter

In the course of testing my 20 meter DSB rig, I discovered that the chart I prepared for my
W7ZOI / W7PUA power meter had some problems. In my first effort to get some calibration points, I used a simple diode and cap peak reading signal probe to measure voltage across 50 ohms, but I may have neglected to convert from peak to RMS before calculating the power. That would certainly mess up the chart!
This morning I used my old Heathkit SG-8 signal generator and my HAMEG (20 Mhz) 'scope to get a couple of points for my graph of the response curve (line) for my meter.
I drew the new line, then used my trusty HW-8 at 1 watt to see if my chart was accurate. It was right on the money!
I look forward to happily measuring milliwatts with this very FB piece of test gear. See the June 2001 issue of QST for more details. Thanks to Wes and Bob for the great project. And thanks to Thomas in Norway for sending me the AD8307 chip.

1 comment:

  1. Howdy,
    Big 73s from Chiba, Japan. I listen to your Soldersmoke podcasts on a little MP3 player that I found laying on the street and took home and gave a little love and cleaning up.
    I operate as 7J1AWL here, QRP for the last year or so. Just built the ATS3B and a seeming multitude of other gear. I really appreciated hearing your family anecdotes about the swimming pool, geothermal chicken, and DX with your zipcord antenna. Whoo hoo! I have erected my share of semi-stealth antennae here in a variety of apartments and know your excitement when scoring DX.
    I'll keep listening.
    Very best 73,
    Jonathan KC7FYS/7J1AWL


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