QRP Mod for Model 1202

From the Ten-Tec Reflector September 9, 1999

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 straight forward 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