[time-nuts] Racal 9420 OCXO

[Dan Rae]

On 8/23/2011 1:09 PM, GandalfG8 at aol.com wrote:
> Hi All,
>
> This is quite a common oscillator, with variants used in a number of Racal
> receivers or offered as high stability options for Racal counters etc, but
> although the specs are widely available I've not found anything from Racal
> that  might be considered to be a user manual.
>
>
Nigel, I took the liberty of correcting the part number in the header.  
They are quite common, also quite often go wrong, so beware if you buy 
any off ebay...

I don't think Racal released circuit diagrams of any of their ovens.  I 
have traced out the circuit of the rapid warm up oven found in a lot of 
receivers, the 9442-12 and have fixed those, there is a ceramic cap that 
frequently goes wonky.  The two 9420s I have fixed were just broken 
wires; they seem to have used PVC insulated wire which degrades...  I 
haven't done the homework on those yet.

The 9420s I have do have an EFC input as well as a stabilised Voltage 
out to feed it, and in the receivers I have that use it [RA1795] the 
fine setting is done from that, coarse setting from the top adjustment.

So yes, in theory they could be used as a basis for a GPS disciplined 
standard, but a quick eBay search shows a lot of more modern and 
probably better quality 10 MHz OCXOs from China...

Dan