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

[Larry McDavid]

The Racal 9462 ocxo uses a temperature-controlled 5 MHz crystal 
oscillator inside a sealed can. On the outside end of the can is a small 
circuit board that doubles the output frequency to 10 MHz. The ocxo 
cable comes from this circuit board so the output to the counter is 10 
MHz. The Racal 9462 operates on 5 vdc and the cable has only three 
wires, two of which are provided by a shielded cable for the 10 MHz signal.

Depending on the age of the ocxo, this doubler circuit board can be 
either PTH design or (on later units) SMT design.

My understanding is that a 5 MHz crystal is inherently more stable than 
a 10 MHz crystal so better overall performance is achieved by using a 5 
MHz crystal and doubling the output to get 10 MHz.

I have pictures of these OCXO if you are interested.

The Racal Option 04C is a really, really simple 10 MHz oscillator whose 
performance is terrible! It is not described in any Racal publication I 
have found and I think it was offered to customers who bought many 
counters for use in applications where an external precision 10 MHz 
source was to be used; the Option 04C allows the counter to operate 
poorly until connected to an external precision 10 MHz source. Option 
04E provides the Racal 9462 and there are other ocxo versions, such as 
Option 04A, that offer better performance than 04C but not so good as 
Option 04E.

Larry


On 1/30/2012 9:24 AM, cfo wrote:
> On Fri, 20 Jan 2012 09:18:32 -0800, Larry McDavid wrote:
>
>
>> 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 have been looking for a Racal 9462 ocxo , for my Racal-Dana 1991
> counter. I will prob. use my Tbolt anyway , and save the money.
>
> But i'm confused ... Is it a 5 Mhz or a 10 Mhz unit.
>
> I have found pictures of one claiming it's 5Mhz
> http://www.jbtech.de/parts/racal_dana/9462.html
>
> But i have also received a picture from jaap , with a racal 9492 , where
> it clearly says its a 10Mhz unit.
>
> Can anyone clarify ?
>
> I think there was an "option" that enabled the use of "other ocxo values"
> is that why a 5Mhz can be used , in some 1991's ?
>
> If i ever decide to get a OCXO , i would like to get the "right one".
>
> Regards
> CFO
>
>
>
>
>
>
>
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-- 
Best wishes,

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