[R-390] Ovens and Synchronization

[Roy Morgan]

At 04:14 PM 8/7/2004 -0500, you wrote:
>Hey guys,
>
>         Lets talk about the crystal ovens in the 390A.

Ok, let's do.

>   I seem to remember
>it is common practice to not use them anymore for the sake of longevity.

Yes, a number of people turn the ovens switch off.  I seem to remember the 
ovens being described in the manual(s) as provided for *very* difficult 
temperature environments (like unheated places in the arctic.)

>My R-1051 experience ...  without the oven the stability the 1051 is known 
>for goes down the toilet.

But, but... do you NEED 10  cycles dial accuracy??

>  The crystal in the oven was designed to work at a specific
>temp to be stabile.  There is a nice flat spot in the curve up around 85C

The crystals may well be quite stable at whatever temperature they are at, 
but not as accurate as at the rated temparature.  If the crystal 
temperature wanders up and down (with ovens off), the frequency may drift 
enough to cause trouble in *SOME* modes of operation: for instance 
mulitplexed RTTY reception with very narrow shifts.  Do you do that with 
your receiver?

>Is this not the same with the crystal deck, calibrator xtals and maybe to a
>lesser degree the PTO in the 390A?

Yes, it is likely the same.

>Looking in the Y2K manual it seems recommended to fire them up a few hours
>before an alignment but then go back to the practice of turning them off for
>our day to day ops....seems that would negate the alignment.

I presume you mean run the ovens for a few hours before an alignment.  I 
would suggest you turn them off, leave them off, and do the alignment after 
a warmup with the ovens off.

It might change the frequency alignment of the PTO a bit.  But I would 
expect any such change to be well within the adjustment range of the zero 
set mechanism.  If the end point spread changes too much, that is another 
story.

>   Wouldn't one be better off doing the alignments in the state one would 
> normally operate the radio?

Yes, I agree with this.

>I pulled the whole IF deck apart for complete cleaning....

I think you mean the *R*F deck.

>Gear train works like a swiss watch....love that Mobil 1

'Sounds like you are well on the way to having a better-than-new radio.. 
keep going!

Roy


- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
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