And here is the QDX transmitting FST4W-1800:
Note that the tone spacing is only 0.089 Hz, and the QDX is tracking these accurately and cleanly.? Pretty amazing!?
But there does remain a frequency drift issue, caused by temperature rise during the transmit cycle.? I'm measuring slightly less than 1Hz drift during the thirty minute transmit time. This won't affect most modes, but will be a problem for FST4W-300/900/1800.? Either a GPSDO or an OCXO will probably be required to improve the already good temperature stability, and I doubt if either of these would make sense in a standard QDX (cost / size / power / diminishing returns / etc.)? But there are always other ways to do this, so we shall see...
And again, thank you Hans!
--
Paul Elliott - WB6CXC
