Interestingly, if I remember correctly, Scott described at one time on the
reflector that the TCXO did not have better stability than the earlier
crystal oven. They moved to the TCXO because the ovens were becoming
unavailable.
Sounds right to me. However, I made the change primarily to have better
start-up stability without having to leave the power supply running 24/7.
From a cold start, the OCXO's frequency makes a relatively large excursion
until it comes up to temperature. That said, I found Ten Tec's TCXO to be
significantly more stable than the OCXO ever was. After the mod, I don't
believe I saw more than a 20 Hz change in frequency at 14 MHz -- even from a
cold start.
If Ten Tec no longer carriers that particular TCXO, many inexpensive
replacements are available with 0.5 ppm accuracy or better. The difference
in price is generally a function of the TCXO's phase noise spec and absolute
stability required.
Paul, W9AC
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