Two problems: Look at the switch-on drift. It drops by about 10Hz in the fist couple of seconds! It's got the separate power regulator for FET PA. A heatsink and ?1 coin glued on to the crystal and still it 'chirps'.
Ian,
Have you tried with NO PA voltage?
That looks more like a voltage change than temperature related. It seems to stabilise too quickly.
The second problem is the frequency. The U3S readout shows 28.000.770 MHz, but I'm clearly transmitting a full 20Hz low. (Remember, Chris's grabber is not 20 Hz out.)
Is that related? It looks as if it might start correctly but quickly shoots down.
I've tried all the tricks regarding park frequency (150.000.000)? and
And all possible park frequencies? Once the rapid drop is cured maybe you'll get the heat drift down.
73 Alan G4ZFQ
the ref frequency has settled to 27.004.555, cal step time 20 240. The rig is in the U3S case on a shelf with a stable temperature and a decent 3A power supply.
