[time-nuts] DDS in GPSDO design?

[Michael Tharp]

On 05/27/2012 07:10 PM, Magnus Danielson wrote:
> How far off? What Rb do you have?
>
> Most Rb:s not having a EFC input should be possible to modify for EFC in
> one way or another, since the C-field needs to be applied regardless.

I don't know how far off it is. It's an Efratom 102100-001, which 
there's very little information about. Most of what I know is from a 
time-nuts post from 2006 (!) -- the pictures from that thread can be 
found here: http://nixie.ramdac.be/

It's likely that it could use a tune-up because mine could not get a 
lock when I first powered it up. I did the smart thing and twiddled 
every single trim pot (after marking the original positions, bah) hoping 
to get the sweep frequency in the right place. It was only after I gave 
up and walked away for a few minutes that it locked. Now it locks in 
under 3 minutes every time but I'm sure the 10mhz output could use a trim.

The outputs available through the main connector are 10MHz out, vreg 
voltage, active-low lock indicator, Rb lamp voltage, and "xtal monitor" 
which sweeps over a large range while it's looking for a lock. That 
sounds nice, but even if it were pullable it would probably interfere 
with the ability to lock to Rb. There are several internal headers but I 
can't find any documentation on this particular model so their function 
is a mystery to me.

Probably the intelligent thing to do would be to look for a good 
pullable OCXO rather than designing around what I have. Wouldn't be much 
fun, of course.