[time-nuts] Frequency Electronis 5608A standard

[Magnus Danielson]

Hi,

On 2019-02-03 23:07, John Ackermann N8UR wrote:
> I've been playing with a Frequency Electronics 5608A "Frequency 
> Standard." It's a 2U rack mount beast with battery pack and a module 
> labeled as a 10 MHz Rb standard, and another as a 5 MHz VCXO.
>
> I originally thought that the VCXO was a cleanup oscillator for the 
> Rb, but that doesn't seem to be the case.  As best I can tell, the Rb 
> module accepts a 10 MHz *input* and its output is a control voltage 
> that goes to the VCXO.  The 5 MHz VCXO goes through a doubler to send 
> 10 MHz to the Rb, and has distribution for a bunch of 5 MHz and 1 MHz 
> outputs on the rear panel.  There are no 10 MHz outputs.
>
> The "LOCK" indicator on the front panel lights up.  Early tests 
> indicate that the short term stability is pretty good, but it has a 
> bathtub shaped aging curve that's more like a crystal than an Rb.
>
> Google doesn't turn up any hits on this model number.  Has anyone here 
> encountered one of these guys and know what it was used for, or have 
> info on the design?

I have encountered one and helped a fellow time-nut to debug-it.

Yes, you input 10 MHz into the rubidium and it outputs the OCXO EFC. 
It's very obvious and not too hard to follow the signals around with a 
bit of tinkering once the 10 MHz input part is clear.

Turned out that the rubidium part had a really bad part (thin-film based 
"chip") which was not easily replaceable.

I kind of like it. No clue what it was used for.

I was unable to get it to run, so no measurement of performance. Pitty.

Cheers,
Magnus