[time-nuts] Re: HP 5065A, no 2nd harmonic.

[Germán Herrera]

Hi there

I don't have much experience with the HP5065A, but one I did this very 
same issue on my Efratom FRK-L. Turns out the thermistor controlling the 
resonator cavity temperature was broken and the cavity temperature was 
off. This caused loss of resonance lock, and by definition, loss of the 
2nd harmonic.

Reaffirming what Bob says, there a number of other factors that might 
cause the issue.

Cheers,
German

---
Germán Herrera
Responsable IT
Ingeniería
SES Sistemas Electrónicos S.A.| Espinosa 1045 (C1405AMM) | Buenos Aires 
| Argentina
W: +54 11 54538426 | Email: g.herrera at ses.com.ar

On 2021-11-19 10:47, Bob kb8tq wrote:
> Hi
> 
> Well backing up a bit, why does a 5065 have a second harmonic?
> 
> Very quickly:
> 
> The stuff in the physics package creates an absorption notch. You
> interrogate this notch with a phase modulated locally generated 
> microwave
> signal. When the signal is at the right frequency it dumps photons and
> you get a signal in the photo diode. That signal has the (audio) second
> harmonic in it when you are doing everything just right.
> 
> Yes, there’s a lot of hand waving in there, but that’s the really fast 
> version.
> 
> Since a lot of “stuff” is involved, there are a number of ways to loose 
> the
> second harmonic.
> 
> Bob
> 
>> On Nov 18, 2021, at 7:48 PM, Jared Cabot via time-nuts 
>> <time-nuts at lists.febo.com> wrote:
>> 
>> Hi,
>> Your help is appreciated. We can keep this on-list for now I guess, on 
>> the chance it helps someone in the future.
>> 
>> Jared.
>> 
>> ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
>> On Friday, November 19th, 2021 at 08:25, paul swed 
>> <paulswedb at gmail.com> wrote:
>> 
>>> Jared I would be happy to see if I can help remotely. We may want to 
>>> take this offline or not. Others may find it interesting.
>>> Regards
>>> Paul
>>> WB8TSL
>>> 
>> 
>>> On Thu, Nov 18, 2021 at 12:56 PM Jared Cabot via time-nuts 
>>> <time-nuts at lists.febo.com> wrote:
>>> 
>> 
>>>> Hi all,
>>>> 
>> 
>>>> I have a 5065A Rubidium Standard that was working ok, but has lost 
>>>> the 2nd harmonic.
>>>> My voltages are all ok, the physics package hasn't overheated and I 
>>>> have replaced the usual resistors on the lamp assembly (and it was 
>>>> running fine afterward for a while), the lamp illuminates, and I've 
>>>> done the procedure to remove cell flooding.
>>>> All readings on the 'circuit check' switch are nominal, apart from 
>>>> the 2nd harmonic position. No matter what I do, I can no longer get 
>>>> it to raise above 0.
>>>> However, when I first turn the unit on, the needle drops to 0 and 
>>>> flicks a little before settling on 0 and staying there.
>>>> 
>> 
>>>> Can someone help me get this unit up and running again?
>>>> 
>> 
>>>> Thanks!
>>>> Jared_______________________________________________
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