[R-390] Some Crystal Info

[Bob Camp]

Hi

If you rummage around long enough, there is a military specification  
on all of the crystals in the R-390. It's pretty specific about the  
load, temperature, and tolerance of each crystal. They even go into  
stuff like spurs, resistance, aging, and  motional parameters. What  
makes it *very* confusing is that after the military standardized  
everything we all started using the mil designations to refer to the  
crystal packages rather than what's inside ....

All of the military crystals were designed under contract out of Ft.  
Monomoth. The agency involved changed names so often it's sometimes  
tough to figure out who is who. Some of what was done is reported in  
the Proceedings of the Frequency Control Symposium. A lot of what was  
done was published in separate reports. Most of those are *tough* to  
find these days. Occasionally you will find references to them in the  
FCS papers.

Bob
KB8TQ


On Oct 22, 2007, at 10:42 PM, Tony Casorso wrote:

> Hi everybody. Sorry that my image thread got so long. I'm still  
> looking at the problem but I'll keep the details to myself and only  
> post here if I make some headway.
>
> For a while now I've been wondering what the difference between a  
> CR36/U and a CR27/U crystal was. I found a reference to them in an  
> old paper that is only available to paying members of IEEE. I  
> believe the paper is from the 1950s as it is full of tube  
> oscillator circuits. I started a new job in July and it turns out  
> that I have access to all of the IEEE papers. This one is called  
> "Design Data for Crystal Oscillators" By H.E. Gruen of the Armour  
> Research Foundation. It says that the CR18/U, CR27/U, and CR36/U  
> crystals are all designed for 32pf loads to be used in parallel  
> resonant mode (antiresonant mode in the paper). The difference  
> between them is that the CR18/U is not for use in ovens while the  
> CR27/U is for oven applications at 75 degrees C and the CR36/U is  
> for oven applications at 85 degrees C.
>
> Hopefully someone will find this information useful.
>
> Cheers,
>
> Tony
>
>
>
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