[Premium-Rx] Frequency Standards

[J. Forster]

GandalfG8 at aol.com wrote:

I used to use an ovened crystal standard with distribution amp, built in-house
by Siemens in the UK,  but there was always the niggling doubt as to how well
calibrated it actually was.

That's a problem if you operate stand-alone. Hence the need for a receiver.

> When the Z3801A GPS units became available that seemed like the ideal answer,
> and probably still is, but I just couldn't resist the rubidium unit. I've
> realised that it's as easy to get hooked on nice test gear as it is on
> radios:-)

Tell me about it !! Just as expensive too.

> This particular Racal standard is quoted as having an accuracy of plus or
> minus 5 parts in 10 to the minus 11 per month, or 5 in 10 to the minus 10 per
> year, and I doubt that it's even two years old yet.

That's somewhat better than the specs on crystals, but in my experience crystals
are very often 10x better than spec if you let them run for a long time (months
or years). My crystals have been running 5 years plus and are about as good as
Rbs. BTW, Rbs are really crystals, locked to the Rb cell.

> Other than having a desire for things being spot on, or as good as possible
> anyway, I think it will take quite a while before that degree of drift is
> going to matter much for me.

True. Unless you are doing very special stuff (like physics research), 1 in 10 E
10 is just fine.

> What is the recommended calibration interval for something like this?

I don't know the 'official' schedule. I just tweak my unit if the freq. goes off
more than 1 in 10 E 10. The frequency always increases, so I move it down 2 in
10 E 10. Easy.

Take care,
John

> regards
> Nigel


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