[time-nuts] HP 5065a Rb ref update and question on time scale

paul swed paulswedb at gmail.com
Sat Oct 1 14:05:46 UTC 2011

Indeed on my 5065a 8714 seems to be the right number. With the cfield I
could trim to the gps just fine and hit the stability specification. By the
table thats says I am -250 parts. OK, it works.
But I would think I should be at 9999 or 0 offset by the table even though
its not exactly zero.
Second item is that if I adjust the lsd I would believe I should shift a
bit. But it seems to have a much larger effect.
As Corby said it doesn't actually matter.
Just not making much sense though with your math maybe I need to run the
numbers and see whats really going on. In that respect its much like the CS

I am curious that maybe back in 1974 atomic time was one thing and then a
correction was done that makes it -250 from what it was. Maybe a historical

On Sat, Oct 1, 2011 at 4:53 AM, Magnus Danielson <magnus at rubidium.dyndns.org
> wrote:

> On 30/09/11 17:46, cdelect at juno.com wrote:
>> Paul,
>> 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.
> Cheers,
> Magnus
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