[time-nuts] Racal-Dana 1991 w. Option 4C - what is that ?

Larry McDavid lmcdavid at lmceng.com
Fri Jan 20 12:18:32 EST 2012


Racal Option 04C is not an ocxo. I received a Racal 1999 counter 
advertised with "ovened" frequency standard but when I examined the 
actual part installed, it was a simple modular oscillator, a NDK 23-9134 
with only a single adjustment. It was not stable with room temperature 
and devilish to adjust.

I complained to the Hong Kong seller and they sent me a Racal Option 04A 
module as a replacement, which is oven controlled, but not the Racal 
"High Stability Option 04E." This was a big improvement over the Option 
04C (which is not described in any Racal literature I've found) but 
still showed significant ambient temperature sensitivity and again had 
only a single adjustment. I have subsequently replaced that with a Racal 
9462 ocxo, the ocxo furnished as Option 04E and that has both COARSE and 
FINE adjustments.

I now have a Racal 1992 counter/timer running with Option 04E, measuring 
10 MHz from a HP Z3801A GPSDO. My current 15°F overnight room 
temperature variation causes about 0.003 Hz change in displayed 
frequency when counted with a 10-second gate period. The FINE frequency 
adjustment is easy to adjust (with due care) and has no backlash or 
short-term drift that I've seen. Others have reported "click-stops" and 
short-term drift after adjustment but I've not seen that.

One does occasionally find Racal 9462 ocxo offered on eBay. Also, one 
sometimes finds non-operational Racal instruments offered at low price 
but which to have Option 04E installed. I convinced one seller to remove 
the Option 04E module (the Racal 9462) and sell just that with much 
lower shipping cost.

There is also what is evidently an older Racal frequency standard module 
similar in appearance to the 9462 but which has screws attaching the end 
plate rather than the soldered-can 9462; one of those is seen from time 
to time on eBay from the UK but I have avoided that.

I believe the Option 04C was provided only to get the counter running 
and that this option was offered as a low-cost solution to users who 
planned to supply precision 10 MHz input to the rear panel frequency 
standard connector.

The Racal 9462 ocxo is in a "hermetic" can with glass feed throughs, 
with the can end cap soldered in place. I don't know what is inside the 
9462 as I have not tried to open one. The can is not actually hermetic 
because the interior is exposed when the adjustment cover screws are 
removed to adjust the frequency. Those screws have a rubber o-ring in a 
groove under the head of the screw so when the adjustment cover screws 
are in place, the interior is well sealed. The ocxo itself actually 
operates at 5 MHz and there is a small PWB on the end, soldered directly 
to the feed through pins, that doubles the output frequency to 10 MHz. 
I've acquired several 9462 ocxo of various age and there are both PTH 
and SMT versions of the frequency doubler PWB.

The Racal Option 04E ocxo, the Racal 9462, seems to work very well for 
its intended purpose.

Is the Racal 9462 ocxo, their Option 04E, actually in a double oven, 
like the HP 10811? I don't know.

If interested, I have pictures of the exterior of these options.

There was a Racal Option 04R, a Rb standard, but I've never seen one.

All of these options interchange easily within the Racal 199n counters 
and perhaps other Racal models as well. While there are Racal ocxo that 
operate on 12 volts, all the ones I've seen operate on only 5 volts and 
have a single cable to apply power and output 10 MHz. The are very easy 
to replace.

Yes, like everyone else here, I'm working on a FEI FE-5680A. Who can 
resist that?

Larry W6FUB



On 1/20/2012 6:45 AM, cfo wrote:
> Hi Nuts
>
> I just bought a Racal-Dana 1991 (german eb..) , with options
> 01 : Inputs in back
> 4C : Unknown ? , but maybe some OCXO (i hope)
> 55 : GPIB
>
> Does anyone know what option 4C could be ?
> I hope some super nice OCXO option from USAF , they have bases in .DE
...

-- 
Best wishes,

Larry McDavid W6FUB
Anaheim, CA  (20 miles southeast of Los Angeles, near Disneyland)




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