[time-nuts] HP 10811 versions for 5065A

[Magnus Danielson]

Hi Corby,

On 2020-07-20 19:55, cdelect at juno.com wrote:
> Magnus, You mentioned:
>
>  "The produced noise is at least 10 dB worse than you
> would expect. This impacts long term stability response as I have
> reported earlier."
>
> Can you refer me to the info you posted earlier or elaborate?

I posted comments on this, with the thread "5065A phase-noise" starting
on 2020-01-12.

I wrote amongs other this:

> So, then for the replacement kit, the 10811 is really good, now isn't
> it? Well... turns out that the wide noise is around 12-13 dB worse than
> the old 00105-6013, it's only as one gets to the closed in noise that it
> raises up, and it is quite respectable. I've not measured this open-loop
> yet.
>
> So, none of them is stellar in the phase-noise department.
>
> I've noticed that the 0565-6097 has a rather crude adaptation of the
> sine into the TTL input of a 7474 flip-flop setup to act as divide by 2.
> You have a series inductor and capacitor into a voltage divider-chain
> that sets the midpoint. I am not quite sure that this provides good
> noise properties as it squares up.
So, I'm even saying it's 12-13 dB worse than the 00105, not the 10 dB I
recalled.

I also measured the long-term stability and compared after/before some
different measures.

My conclusion from these measurements was that the 00105 was
flicker-noise limiting, and through fairly quick hacks I could work
around that and get significant improvements. So, the 00105 assembly
does not provide a clean enough 5 MHz phase-noise for the 5065A
reference. For the 10811 case, the output assembly degrades the signal
more than necessary, as was obvious from the phase-noise measurements.
Even my quick and dirty hacks illustrated for the 00105 what was a key
performance limiting factor which should be dealt with.

I have not had time to do additional test, but I have a few ideas.

Cheers,
Magnus