[time-nuts] Antique Rubidium Standard Questions

[paul swed]

Some pix of the rg would be great

On Wed, Apr 25, 2012 at 11:43 PM, Ed Palmer <ed_palmer at sasktel.net> wrote:

> Paul,
>
> Good suggestion, but I don't think pop rivets had been invented when they
> built this thing! :-D   It's built like a piece of mil-spec equipment.
>  When I google for individual parts, I keep tripping over NSN numbers.  Now
> that I look closely at it, I realize that the case is just the case with no
> electrical connection between it and the circuit other than the BNC jacks
> on the front panel.  The concept of 'chassis ground' is an unknown concept.
>  I don't think there's even one chassis ground lug anywhere.  Even when I'm
> poking around inside the unit, there are no live wires that I can touch,
> everything is insulated.  The build quality is very high.
>
> But now that you've got me thinking about it, I think there's something
> weird about the grounding in the physics package.  I've got to take another
> look at that.
>
> Thanks!
>
> Ed
>
>
> On 4/25/2012 8:59 PM, paul swed wrote:
>
>> Ed look for pop rivetted ground logs. Famous for going bad. HP even used
>> them.
>> Drill em out and put real bolts and lock washers in
>>
>> On Tue, Apr 24, 2012 at 7:34 PM, Ed Palmer<ed_palmer at sasktel.net>  wrote:
>>
>>  Paul,
>>>
>>>
>>> On 4/24/2012 5:24 PM, paul swed wrote:
>>>
>>>  When all else fails check the grounds. Especially 40 year old screws.
>>>>
>>>>  Been there, done that.  This unit had multiple problems with bad
>>> soldered
>>> ground connections.  I went through the unit and resoldered everything
>>> that
>>> looked the least bit odd.  I didn't find any screws that were
>>> electrically
>>> significant.  Maybe I should look again!
>>>
>>> Ed
>>>
>>>  On Tue, Apr 24, 2012 at 6:13 PM, ed breya<eb at telight.com>   wrote:
>>>
>>>>  Ed,
>>>>
>>>>> Tuning the cavity should peak everything - it just maximizes the
>>>>> excitation power at the microwave frequency, so you get the most output
>>>>> from the Rb light wavelengths. A mechanical cavity resonator will have
>>>>> a
>>>>> very wide (compared to the modulation frequencies you're looking for)
>>>>> bandwidth, so unless something happened to it physically, it should be
>>>>> OK
>>>>> as originally built or adjusted. However, you may want to look at the
>>>>> multiplier chain and SRD bias circuit components and adjustments -
>>>>> those
>>>>> could have drifted quite a bit over forty years, limiting the microwave
>>>>> power due to being off-frequency, or having poor multiplication
>>>>> efficiency.
>>>>>
>>>>> I'm guessing that the second harmonic is indeed present, but just
>>>>> buried
>>>>> in the noise, and the loop still can "lock" because of the further
>>>>> signal
>>>>> processing, even though you don't see the evidence - remember it's a
>>>>> lock-in amplifier capable of digging a tiny signal out of the noise. If
>>>>> you
>>>>> go through the multiplier and check and tweak things, you may get more
>>>>> excitation power and signs that it's getting back to normal. Once you
>>>>> get
>>>>> enough power, if the Rb cells are still good, the second harmonic
>>>>> signal
>>>>> should show up large enough for the circuit to detect sufficient S/N
>>>>> ratio
>>>>> and provide a valid lock indication.
>>>>>
>>>>> Ed Breya
>>>>>
>>>>>
>>>>> Ed Palmer wrote:
>>>>>
>>>>> Could the drift be at least partially responsible for the lack of
>>>>> second
>>>>> harmonic?  A message on the list (
>>>>> <http://www.febo.com/******pipermail/time-nuts/2006-******
>>>>> April/020562.html<http://www.febo.com/****pipermail/time-nuts/2006-****April/020562.html>
>>>>> <http://www.**febo.com/**pipermail/time-**
>>>>> nuts/2006-**April/020562.html<http://www.febo.com/**pipermail/time-nuts/2006-**April/020562.html>
>>>>> >**)
>>>>> said that you could peak the second harmonic by adjusting the cavity
>>>>> tuning.
>>>>> If the cell and the cavity are out of sync would that kill the second
>>>>> harmonic?  How close to they have to be?  If this thing has a cavity
>>>>> tuning adjustment I haven't found it.
>>>>>
>>>>
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