[R-390] RE: Ovens

[Michael Murphy]

I think the calibrator in the ART-13 uses an old FT-243 pin spaced 200 kHz
crystal. No oven there! Plus they definitely are aged. My guess is that Fair
Radio should have some. That ought to get you within a couple of kc after
zero beating WWV!

Bob was starting to talk about SL-cut crystals which are normally required
to hit frequencies much below 1 MHz and are somewhat less stable than
AT-cuts, hence the requirement for ovens etc..

Mike Murphy WB2UID


----- Original Message -----
From: "Bob Camp" <ham at cq.nu>
To: "Laird Tom N" <LairdThomasN at JohnDeere.com>; "R-390 HF Receiver List"
<r-390 at mailman.qth.net>
Cc: <Llgpt at aol.com>
Sent: Monday, August 09, 2004 8:54 PM
Subject: Re: [R-390] RE: Ovens


> Hi
>
> The calibrator crystal would be a bit tough to do as a "stable at room
> temperature part". The 200 KHz  frequency is low enough that you can
> not do it as an AT cut in that holder. The HR202 oven is actually a
> pretty good little unit. It will hold a couple degrees during fairly
> major external changes. Since it's a plug in it's easy to replace if it
> runs away. It's not all that different than the units you wold see in
> the older two way radio sets.
>
> One interesting thing you could do would be to replace the first LO
> crystal with a room temperature unit and then replace the calibrator
> crystal with a cell phone TCXO and a digital divider. You would have a
> more accurate calibrator. What ever you did would fall into the
> category of easily reversible modification if it was all in a
> replacement oven plugin. Next step up would be to phase lock the first
> LO to the TCXO.....
>
> As you pointed out "why spend the extra money".
>
> Take Care!
>
> Bob Camp
> KB8TQ
>
>
>
> On Aug 9, 2004, at 11:26 AM, Laird Tom N wrote:
>
> >> From all that I have read over the years, I agree; don't use the oven.
> > For the semi-purest. You can buy crystals for HR202 from mhelectronics
> > that are designed for room temp. Although, the consensus is "why spend
> > the extra money".....
> >
> > Tom Laird WC9M
> > Moline, IL.
> >
> > -----Original Message-----
> >
> > My 3 cents
> > Don't use the ovens period!
> >
> > Les  Locklear
> >
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