[R-1051] Frequency standard module

[jan at skirrow.org]

This is extremely useful info Bob. Thanks!

Jan


At 05:50 PM 5/13/03, you wrote:
>Hi,
>
>There are several generations of frequency standards out there for the
>R-1051. More or less:
>
>1) Early production parts with BT cut crystals in them - properly made.
>
>2) Early production parts with AT cut crystals in them - properly made.
>
>3) Later production and replacement parts with who knows with in them - made
>by the "paint by numbers" approach.
>
>So what does this all mean in plain simple English:
>
>A BT cut crystal has a parabolic temperature coefficient and it peaks at the
>operating temperature. An AT cut crystal is a third order curve and it hits
>a local minimum at the operating temperature. If you turn on your cold radio
>and the frequency goes up as it warms up you have a BT cut crystal. If it
>goes down in frequency you have an AT cut crystal. More or less forget about
>replacing BT cut crystals ....
>
>A properly made frequency standard should have the oven set to match the
>individual crystal used to build it. This isn't to hard to do. You simply
>move the temperature and watch for a minimum frequency if it's an AT or a
>maximum if it's a BT. A frequency counter that will read out to 0.01 Hz is a
>nice thing to use when you do this. Once the oven is set to this point it's
>temperature stability *should* be as good as it's going to get. This should
>minimize post warm up drift. Most radios that take a *long* time to warm up
>have ovens that are off temperature.
>
>If you have one of the weird late production or replacement oscillators then
>it may never have been set to temperature ever. It also may or may not set
>properly when you try to adjust it. There's along story about the source of
>these parts, but this post is already a bit to long anyway ...
>
>Since the inside of the oven is the hottest part of the radio it's not to
>surprising that parts in there fail from time to time. You may fix one
>problem only to cause another. Probably your best bet on a dead oscillator
>is to simply find another one.
>
>     Enjoy!
>
>         Bob Camp
>         KB8TQ
>
>
>
>----- Original Message -----
>From: <jan at skirrow.org>
>To: <r-1051 at mailman.qth.net>; <r-1051 at mailman.qth.net>
>Sent: Sunday, May 11, 2003 7:53 PM
>Subject: Re: [R-1051] Frequency standard module
>
>
> > At 11:25 AM 5/11/03, James A. (Andy) Moorer wrote:
> > >If someone sends me a copy, I'll scan it and put it on the web site.
>Sounds
> > >like a good thing to make available.
> >
> > I'm curious ... what is the problem people are having with this module?
> >
> > I ask, because I have six freq std modules - in three versions, and only
> > two are what I would call serviceable. One or two 'sort of' work. They
> > oscillate, but way off the correct frequency, but then will usually pop in
> > after they warm up a bit. The others are dead - and the problem seems to
>be
> > the crystal. These are an unusual cut, I don't know what the electrical
> > specs are, and I don't know if they can be rehabilitated.
> >
> > I have spent some time on the problem, but haven't been able to find any
> > explanation, other than bum crystal. I've got on my (endless!) list of
> > things to do to rebuild the circuit with a modern crystal style - has
> > anyone tried this?
> >
> > If anyone has a fix, I'd sure like to know!
> >
> > Jan Skirrow, VE7DJX
> >
> >
> > _______________________________________________
> > R-1051 mailing list
> > R-1051 at mailman.qth.net
> > http://mailman.qth.net/mailman/listinfo/r-1051
> >
> >
> >
>
>
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