Had several interested in the Ten Tec power meter kit reuse as a QRP one. A
little summary of the kit might be of general interest.
The stock kit has two frequency pickups (HF toroid and VHF strip line), and
two power scales on each pickup, 20 watts FS and 200 watts FS.
My paper in the "QRP Amateur Radio Club International Quarterly" for Fall 1996
describes the kit, and its construction. It also shows that you can make the
QRO kit, into QRP with a Full scale range of 20 watts in place of 200, or 2
watts in place of 20. It is all done by having known sources of low power,
and using the four cal pots, (two for HF, and two for VHF). First verify the
kit is working as built by following TT set up to 20 W and 200 W. Then, with
known sources, or a known good Bird meter set up a 2 watt HF signal on Bird,
and then sub the TT meter in place of the Bird, keeping coax the same, etc.
Readjust the 20 watt pot (if on 20 watt scale, and with a 2 watt source, HF),
to 2 watts. Do the same for any other range you want to modify. You must
have a known 50 ohm dummy load, of course, and either a Bird or source you
trust to be a certain power, or another known good power meter borrowed for
the test. Alternately, the handbooks show how to make a diode RF voltage
probe for HF, and measure power by measuring RF voltage across 50 ohm load.
We are not doing laboratory accuracy, but a perfectly adequate measure for the
wide variety of antennas, and efficiencies that typical hams use.
Ten Tec provides an excellent manual for assembling each of their kits.
If you build exactly to their instructions, you should have very good and
identical results to commercial power meters built into rigs, or better
quality Antenna matching units. There is one toroid made up of two cores
glued together for wider HF band coverage. The primary is the coax line, and
turns of a secondary provide the pickup of HF signal.
For VHF, you have the pickup lines etched right on the board, making this an
easier assembly. This is a straightforward kit, if you have a couple of tip
sizes on the soldering iron, and is a nice weekend project, with time left
over.
Hope that is helpful,
Stuart K5KVH
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