[time-nuts] HP 5061 zeeman frequency experiance

paul swed paulswedb at gmail.com
Tue Oct 4 09:31:04 EDT 2011


Magnus

But does anyone have comments on the meter approach HP suggested.
I really need to understand whats semi normal for  old tube.

I suspect I may be sitting near the noise floor of the system.

As for the network analyzer I just happen to have a HP 8505 so may give this
a try. Suspect I will see the fingers but very close to the noise floor.
Regards
Paul.

On Tue, Oct 4, 2011 at 3:06 AM, Magnus Danielson <magnus at rubidium.dyndns.org
> wrote:

> On 04/10/11 04:56, paul swed wrote:
>
>> Hello to the group.
>> Still working on the 5061 with a 5060 tube. Have home brewed a new CS oven
>> controller thats appropriate to the 5060 tube and its working quite well.
>> 2
>> op amps and a couple of transistors. It handles the 5060s higher current
>> needs. Average current is 650 ma at 98 ohms for the thermistor.
>> The zeeman frequency is still bothering me. Granted I may be dealing with
>> a
>> weak tube.
>> But I can adjust the cfield and get the various peaks. But they are
>> small. The normal HP meter is a 50 ua movement.  Using a 25 ua larger
>> scale
>> meter to monitor the beam current results in,
>>
>> No modulation 8 ua
>> Driving 42.82KC at +1dbm I actually see the meter drop to 7.5ua.
>> Then adjusting the cfield to 20 ma I can see the middle peak at 8.5 ua
>> maybe
>> a little higher.
>>
>> Is this the peak? Or better question whats a normal old CBTs beam current
>> and the peak expectation.
>> I am wondering if I simply am way down at the edge of usability.
>> I can adjust the ionizer and get a higher reading just unsure were to stop
>> at. Burn something out perhaps like the ionizer is the risk.
>>
>> The other thing is that there is still a drift. You can see the system
>> lock
>> for about 3-5 minutes then slowly become unstable and slip 5ns. Depending
>> on
>> the zeeman peak used it goes right or left. The green op light stays on
>> however so the slips awfully small.
>>
>
> With a very small trick you can sweep your tube using a network analyzer
> and a mixer.
>
> Take the Port 1 of your network analyzer and sweep around 12,6 MHz which
> you insert in replacement of the synthesis frequency. Hook the 10 MHz of the
> crystal to the network analyzer input for additional stability. Use the
> detected signal (as amplified) and control a mixer which takes a bit of the
> 12,6 MHz and feed that to Port 2 of the network analyzer. That way you
> modulate the amplitude.
>
> Should give you an overview of the 7 peaks, there spreading and their
> location.
>
> Note that this also works for spectrum analyzers having a sweep output, as
> no phase is recovered this way anyway.
>
> Cheers,
> Magnus
>
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