[time-nuts] HP 5065a Rb ref update and question on time scale
magnus at rubidium.dyndns.org
Sat Oct 1 04:53:44 EDT 2011
On 30/09/11 17:46, cdelect at juno.com wrote:
> The time scale selection is to match the offset in each particular
> receiver section and thus put it on frequency. Once there you can use the
> chart to determine offsets from the value you use.
> The synthesizer setting by virtue of how its designed does not allow one
> digit changes! You have to use one of the settings from the chart in the
> manual to get you within the C-field range when tuning!
> Also after a synthesizer change you have to wait a long time (or remove
> and replace the red wire powering the synthesizer) for the operation
> light to reset.
I had one HP5065A with a totally non-standard setting. I put that
setting on paper and instead chose a standard one writen down on the
front panel. This gave me the wrong frequency, so I looked it up in the
table of the manual and tried a few others until I settled for one
giving me good frequency compared to by Thunderbolt locked to GPS. I the
trimmed the C-field up for the last piece. Once I decided to got this
route, it didn't take too much time to hit the spot. You are really lost
without the table with it's offset ordered sets of settings.
There is a few hidden aspects to the synthesizer settings. The factor m
and n which reshape 5 MHz to 5,312.. MHz using m/n*5 MHz is not listed.
The n factor is n=10000-TW where as m is about 1.6 times n. The m factor
determines the loop gain in that PLL lock. However, it is only part of
the story, but it is interesting to note that there is a loop within a
loop in this rubidium where as the 5,312... MHz synthesis is done using
other methods in most other rubidiums. Dividing by 16 and mix up with 5
is not too uncommon.
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