[ARC5] crystal control

[Dennis Monticelli]

While I have not tried it,I think going to an injection locking scheme
would work out better than replacing the VFO with another circuit and
trying to pass signal awkwardly through it.  With this scheme the 1626
osc circuit would remain as-is and free-run as usual.  An external
crystal osc would inject sufficient energy into the free running
oscillator (probably via cap coupling) so as to cause it to lock to
the external frequency reference.  Post-lock the drive level should be
able the same as before, and best of all the originality is preserved.
 For this scheme to work the free running frequency of the VFO should
be reasonably close to that of the crystal meaning only "ham band"
command sets would be suitable and the VFO dial would need to be set
in the vicinity of the rock.

Dennis AE6C


On 1/26/13, Mike Everette <radiocompass at yahoo.com> wrote:
> The ARRL Handbooks from about 1960 through 1967 or 68 had an article that
> had originally appeared in QST in 1959 perhaps, by Lew McCoy I think, which
> also showed a method of crystal-controlling a Command Set.  I built one of
> these, and it worked, sort of; but unless one unlocked the main padder
> condenser on the VFO tank circuit to peak things up as the article said to
> do, it didn't give a lot of drive to the final.  I was warned by someone
> with experience against disturbing that VFO padder.  Doing so would utterly
> destroy the VFO calibration and tracking.
>
> So, I suffered along for a couple or three weeks calling many CQs but making
> few contacts; probably had all of four or five watts going to the antenna at
> best.  The Novice band on 80 in those days was wall-to-wall signals at night
> and pulling anything out of the mess was tough.  Then I had the chance to
> borrow a DX-40, and used it until I upgraded five months later.  Making
> contacts was much, much easier.
>
> When I gave back the DX-40, with an upgraded license I resurrected the
> Command Set and this time used the VFO as ARC, God and Nature intended.
> Everything worked much better that way.
>
> I wonder if anyone ever got that Handbook conversion to work right...?
>
> As for stability of the stock Command Set in mil service, the tuning caps
> are made from some kind of super-alloy with an absolutely zero temperature
> coefficient.  I have read of people testing the oscillators on the bench and
> finding that they will hold frequency to amazing standards... like maybe a
> couple of cycles a week?  Even in an airplane, under vibration and extreme
> temperature change, they would hold very close.  The problem with the
> Command Set system was actually the receivers... and not the receivers
> themselves, but rather that the "aviators" could not keep their hands off
> the coffee grinder control boxes.  If they didn't hear anything, they'd
> start cranking and get the receivers off frequency.
>
> One historian, I forget whom (Gordon White?), asserted that this was what
> may have caused the lack of coordination among the fighter, dive bomber and
> torpedo squadrons at Midway.
>
> 73
>
> Mike
> W4DSE
>
>
>
> --- On Sat, 1/26/13, radio_man at wbsnet.org <radio_man at wbsnet.org> wrote:
>
>> From: radio_man at wbsnet.org <radio_man at wbsnet.org>
>> Subject: Re: [ARC5] crystal control
>> To: "john rose" <brokenthumb at live.com>
>> Cc: ARC5 at mailman.qth.net
>> Date: Saturday, January 26, 2013, 4:08 PM
>> Jon,
>>
>> Little 1 page article, p.62, in CQ "Command Sets"(1957)by
>> Henry, WØFVD (at
>> that time) for making a crystal control adaptor for the
>> transmitters for
>> Novice operation.  Was a little plug in module that you
>> could unplug and
>> put 1626 back in for VFO operation.  Looks pretty
>> simple, dunno if worked
>> very good or not.
>>
>> 73
>> Rod
>> KØEQH
>> >
>> >
>> >
>> >
>> > I have been searching the archives to answer this
>> question, it seems that
>> > no one asked. CQ magazine October 1965 was a
>> ‘special’ devoted to surplus.
>> > Gordon Eliot White wrote two articles the second of
>> which is “Crystal
>> > Controlled Command Sets”. During WW2 the Naval
>> Research Laboratory
>> > modified some Rx and Tx for crystal control. Receiver
>> schematics are laid
>> > out for the modified 12K8 circuit and delayed
>> AVC.  What was not discussed
>> > was any circuitry to convert the TX “to make the
>> calibration crystal
>> > control the frequency”. Does anyone know if this was
>> ever published? Is it
>> > still available?  Mr. White?
>> >
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