My thanks to Walter, Mal, Mike, Wolf, Paul, Geri and Bob for the response
to my 706 query. I have not checked the web sites yet but will do so in the
next day or so.
One or two related comments :
Argo assisted reception of my 180 kHz CW signal shows a slight frequency
shift on long "dots". However, the divide by 100 gives the obvious
reduction from the drift measured at 18 MHz.
I attempted to locate an ICOM TCXO unit but was told that they were no
longer available.
As suggested, the problem is a thermal one. Like Mal, I run the 706 at the
1-2 Watt level,into a dummy load, before the divider chain. At this power
level the exercise is an extremely inefficient one - about 30 Watts has to
be removed from the little black box ! Some tests at higher power levels
did not improve the situation.
To date, I have been keying the 706. This encourages plenty of fan cycling
and internal temperature change. As an experiment, I intend to leave the
transmitter turned on and key a later stage in the chain. Hopefully, this
will keep the fan operating all of the time and improve the frequency
stability a bit. Again, as suggested by Mike, I may have to further
encourage the fan to run continuously.
I had a look under the appropriate cover in the hope of packing some
polystyrene or similar material around the crystal osc. However, there
appeared to be a decided lack of surplus space.
Again, my thanks to all who so willingly responded to my inquiry.
73,
Kevin, ZL4MD
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