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.
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
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 Michaels 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
by Paul Wade, W1GHZ,
(1) and the other by that UK expatriate Dave Robinson, WW2R. Daves
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
Apart from a little
mechanical ingenuity, most of this article relies entirely on other
peoples work. My thanks go to Dave, WW2R, for the basic circuitry.
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.