[time-nuts] Re. DIY atomic "resonator"
magnus at rubidium.dyndns.org
Tue Apr 11 12:22:45 EDT 2017
On 04/11/2017 05:54 PM, Richard (Rick) Karlquist wrote:
> On 4/11/2017 12:31 AM, Andre wrote:
>> Has anyone else either built an atomic clock around a bare Rb lamp
>> module "core" or attempted
> Not a DIY project, but I was the RF designer on the HP 10816 rubidium
> standard, which never made it to product introduction (a half dozen
> working pilot run units were built in 1982). I would say this task is
> probably beyond the scope of a DIY project, at least for most
> The Rb lamp drive circuit (particularly getting the
> lamp to light up) is very challenging.
There would be none. It would be replaced by a laser. That has its own
set of "problems" but different.
> The step recovery diode multiplier is very challenging.
Today you would not go the SRD route in synthesis.
Besides, SRDs can be hard to find these days.
> The photodetector and loop integrator is non trivial.
I'd expect the loop integrator to be done in digital, which eases up on
some of the design problems.
> The synthesizer is the one thing that is easy in 2017.
> The oven is also no simple thing to get
> low tempco. Unlike a crystal, you have a lot of heat being
> generated by the lamp, etc. The lamp needs to be at a different
> temperature than the other cells.
Going down the laser-route, the balance of temperature between the cells
is no longer a relevant problem. Further, the lamp and its heat is gone.
> You have to keep the tip
> off at the lowest temperature to keep the Rb in place and not
> "flood" the cell and block the light. Etc., etc.
You still have this problem, but not as a lamp problem but only for the
resonance cell part.
> This is in the category of projects where if you were qualified
> to do it, your time is far too valuable to do it for the amount
> of money you would save.
This is the type of project you do not to save any money, but to spend
Even if done in a much more modern fashion, avoiding several of the
traditional problems, there is plenty of issues to solve and handle.
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