I think I several hours building mine from an ARRL handbook design of some
sort, then maybe a half hour a day for a couple of weeks with a 50 Watt lamp
for heating and a fan for cooling until I tweaked the drift with various
N750, etc. ceramic caps. A real challenge but whatever drift I have now is
virtually nil . I think I quit tweaking at about 200 Hz "cold" to "warm"
drift. BTW, my transmitter is a hetrodyne affair, 5.0 to 5.2 MHz VFO + keyed
crystal oscillator, both feeding Mini-Circuits DBM.
If you are interested, I can put to schematic what I ended up with as I need
to do it anyways for my own reference.
kb8tl at arrl dot net
Bob