[ARC5] ARC-5 Crystal Question

Fri Aug 13 11:39:42 EDT 2010

It's just as Henry says; You connect it to directly to the coil socket with
short leads.  Any GDO relies upon an external inductor which is all a
crystal is electrically when operating in its parallel resonance mode (less
the DC path which the GDO doesn't care about).  Of course the crystal
represents a lot more inductance than the coils and likewise the tuning
capacitance of the GDO represents more shunt capacitance than the crystal is
likely to see in a real circuit.  But it still oscillates readily and you
can spin the tuning dial while watching the meter to maximize the reading.
You won't find a peak per se, but usually the oscillation gets stronger at
one end of the dial or the other.

The post-Millen GDO's started using smaller coil sets whose pin dia and
spacing match that of an FT-243 so it's particularly convenient to use one
of those units to check crystals.  I have built small adaptors that adapt
other crystal holders to the FT-243 both for use in equipment and for use
with my GDO.  The smaller transistorized GDO's are particularly useful to
have in your bag at the hamfest, flea market, or surplus store. I picked up
just such a unit recently very cheaply because it was missing all its
coils.  It won't "GDO" but it makes a dandy portable crystal checker.  In
fact, that's what I used to check the crystal in my ARC-5.

BTW, if you leave the sensitivity control at one setting, you can test a
whole batch of crystals at one time for relative activity.  I do this to
identify sluggish crystals.  The more active the crystal, the higher the
meter reading.

Dennis AE6C

On Fri, Aug 13, 2010 at 7:18 AM, Henry Mei'l's <meils at get2net.dk> wrote:

> You just bring leads from the xtal pins to and into the coil plug socket
>  --
> I've done the same thing as Dennis with several GDO's  (including Millen
> and
> Eico) over the last many years
>
> Don't know if Dennis this any differently - he can tell us.
>
> Henry
>
>
> ----- Original Message -----
> From: "J. Forster" <jfor at quik.com>
>  To: "Dennis Monticelli" <dennis.monticelli at gmail.com>
> Cc: "Discussion of AN/ARC-5 military radio equipment."
> <arc5 at mailman.qth.net>; <jfor at quik.com>
> Sent: Friday, August 13, 2010 3:07 PM
> Subject: Re: [ARC5] ARC-5 Crystal Question
>
>
> > How did you hook it to your GDM?
> >
> > -John
> >
> > ===========
> >
> >
> >> OK.  Curiosity got the better of me.  After reading the thread again, I
> >> pulled the 8870Kc unit out of my T22 and hooked it up to my trusty grid
> >> dip
> >> meter, which I use as a crystal checker.  It oscillated just fine.
> >>
> >> Dennis AE6C
> >>
> >> On Wed, Aug 11, 2010 at 9:35 PM, Henry Mei'l's <meils at get2net.dk>
> wrote:
> >>
> >>> I actually did try to get an '8000kc'/kHz  ARC-5 xtal to ocscillate
> >>> (Think
> >>> I
> >>> lashed together a Pierce, (triode/grid-to-plate) breadboard setup).
> This
> >>> xtal didn't oscillate -- but on the other hand I don't recall whether I
> >>> ever
> >>> tried to use it in its intended function, so it might have been
> >>> disfunctional in all respects.
> >>> But as Dennis writes, why shouldn't they oscillate?
> >>> Easy enought to find out.
> >>>
> >>> Henry
> >>>
> >>>
> >>> ----- Original Message -----
> >>> From: "J. Forster" <jfor at quik.com>
> >>> To: <arc5 at mailman.qth.net>; <milsurplus at mailman.qth.net>
> >>> Sent: Thursday, August 12, 2010 5:10 AM
> >>> Subject: [ARC5] ARC-5 Crystal Question
> >>>
> >>>
> >>> > Out of curiosity, does anybody know if the quartz crystals, used to
> >>> spot
> >>> > check the transmitter frequency, will oscillate? In the Tx they are
> >>> only
> >>> > used as very narrow band filters.
> >>> >
> >>> > Thanks,
> >>> >
> >>> > -John
> >>> >
> >>> > ===============
> >>> >
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