On 12/18/2011 12:00 PM, Charles P. Steinmetz wrote:
Ed wrote:
My 04E must be less stable than yours. I was monitoring a fully
warmed-up Efratom FRK rubidium and saw a drift of ~ 0.04 Hz (i.e. 40
counts) over two hours after I turned on my 1992 from standby. Are
more than one type of oscillator used for option 04E? Mine is a
model 9462.
There are actually two Racal part numbers that you sometimes see in
documentation as being used for Option 04E -- 404386 and 454879. The
9462s in the US military contract 1992s that I have seen (pretty much
all of the 1992s one sees in the US are from the mil contract, IME)
are marked "9462 454879." I have not seen an oscillator marked
"404386," so I do not know if these are Model 9462 oscillators or
another model.
Mine is marked "9462 454879 Rev A"
As with any crystal oscillator, there is no doubt a range of both
stability and warm-up drift in the 9462s you find, but IME not a very
large variation. (I'm assuming that you clocked the warmup after the
1992 had been in standby -- plugged in with the red power button "on"
-- for a week or more [preferably for a month or more].)
Yes, mine was always in standby mode. It was probably running for many
months like that.
An oscillator with greater warm-up drift will not necessarily be less
stable, after warmup, than one with less warm-up drift.
Agreed. But it was annoying to leave it in standby mode and then still
have some drift. At first, I thought the drift was due to the rest of
the unit warming up. I was quite surprised when my tests showed that
the drift was 100% due to the oscillator. Using an FRK as an external
reference, I can turn on my 1992 (not from standby) and immediately
measure my Z3801A as 10.000 000 000 MHz.
Ed
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