Hi all,
I've just completed my second QDX - this time using the RWTST method for T1. Just over 5W or so on bands with a little compression of some LPF inductors, so all good. On some bands I need to reduce the supply to about 10V to keep the power down to 5W.
However I've noticed it consistently drifts +1 or +2 Hz on 20m WSPR. The drift is present on 30m to a lesser extent. Current draw on 20m for 5W into a dummy load is about 1A. As I reduce the supply voltage and power, the drift is still there, but reduced. Lowering the supply voltage to about 7V for say 3W output on 20m still results in +1 Hz drift on most spots.
On opening up I found T1 was quite hot (I guess about 60 C or so). My hi-bands QDX has no such drift - so I was wondering if this could be my TCXO not working as it should (or just not being able to handle the rate of increase in temperature on tx) and whether the RWTST method results in more T1 heating.
My high bands QDX does about 4 to 5W on 12V on all bands with the earlier method of winding T1 with no issues. Current draw is similar - always under 1A.
I've thought about reverting to the previous method of winding T1 or providing some kind of heat sinking or active cooling - any ideas re this or if my TCXO is not working as it should?
Thanks,
Steve
