The FT817 is a deservedly popular transceiver, used by thousands of QRP enthusiasts around the world and
immediately recognised by the amateur microwaver as a modern replacement for the ageing IC202 or FT290 “prime movers” of yesteryear.

I’ve used a couple of IC202 transceivers (one an S model) for over fifteen years and have been very pleased with their performance as a microwave IF, except for one feature … the poor frequency display of ten kHz per dial division. In the past few years, my microwave transverters have been improved so much, with features such as hi-stability OCXOs, that their frequency stability and resetting accuracy now exceeds that of much of my old VHF gear. Hence I thought it was about time I treated all the transverters to a more modern
IF transceiver.

In late March 2004 I purchased a new FT817 and was immediately impressed at how Yaesu could pack so much into so little!

My 3.4, 5.7, 10 and 24GHz transverters are designed around DB6NT transverters, constructed from Michael’s excellent kitsets and driven by 120 milliwatts of 144MHz from an IC202S. My 23cm old DEM transverter is driven at 10 watts input by an aged TS700, while my recently acquired 47GHz gear, bought from a
“retired millimetre man”, requires an FT290 at 3 watts. Apart from the 23cm transverter which uses a separate PTT line, all the others require a switching voltage on the coax connecting the IF transceiver to the microwave transverter. The 47GHz transverter send/receive is controlled by a positive voltage on TX while the others are switched by a positive voltage on RX.

A look through my (almost complete) collection of Microwave Update Proceedings found a couple of relevant articles in the 2002 edition … one by Paul Wade, W1GHZ,
(1) and the other by that UK expatriate Dave Robinson, WW2R. Dave’s article (2) provided me with the solution to the problem of switching the transverters no matter what the configuration (IC202S or FT290).

The final outcome was the unit shown in the photographs … a versatile and switchable interface between the FT817 and the microwave transverters. This little unit allows the FT817 to directly replace either IC202 or FT290 type transceivers with no modifications at all required to the microwave transceivers. A facility to adjust the RF input to the transverters is also included, as well as a near foolproof protection circuit for those who have been known to get the 12V DC input leads the wrong way round … a potentially disasterous event when out /portable!

Apart from a little mechanical ingenuity, most of this article relies entirely on other people’s work. My thanks go to Dave, WW2R, for the basic circuitry.

The complete interface is a little smaller than the FT817. If a larger enclosure were used, extra DC and IF output sockets could be fitted, enabling use with several transverters at the same time.