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

[Bob kb8tq]

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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