[MRCA] Recrystalling a TBX-8

Tue Mar 14 06:32:52 EDT 2017

Hi Garret,
Another application you could use for the crystal, would be in the
accessory crystal calibrator that goes with the -8.  I have seen them pop
up from time to time.
I found that the earlier model receivers pulled so hard on strong signals
that netting the receiver to the transmitter was very hit or miss, and
almost always miss if on CW trying to work the outside world where people
use tight receivers.   A weaker signal, like from an LM, let me get it
right on.  Maybe the -8 receiver behaves differently.
Have fun working it out.  I always loved taking my TBX set out for
demonstrations.
http://www.mrca.ar88.net/photo_gallery/History_Fair/HF_2011.html
RF

On Mon, Mar 13, 2017 at 11:40 PM, Garret Scott <scottgs at bellsouth.net>
wrote:

> Hi Rob,
>
>
>
> You are correct, except that the TBX-8 has a 3-tube transmitter.
> Oscillator (3A4), Modulator (3A4) and Power amp (2E22), …and, if you read
> the manual, they say it’s really a four-tube transmitter, with the 4th
> tube being a neon bulb for CW side-tone generation.  Whatever…
>
>
>
> But yes, it lends one to believe that an FT-243 would be fine in the 3A4
> oscillator, and that the giant crystals are just a vestigial element of the
> original TBX design.
>
>
>
> At any rate, I’ll be finding out real soon.  Fortunately, I have some
> sacrificial crystals to test with before I plug in any good ones.   I so
> agree on not really needing crystals, except actually I don’t entirely
> agree. I found out the hard way during our Secret City Special Event
> Station last year, that while setup with lots of busy activity from the
> public, National Park Service, and other hams, and then a large WWII
> reenactment around us, well I discovered that once all of that
> action-packed excitement hits, with the soldiers and vehicles and artillery
> and stuff, …well I kind of forget how to work the radios.  Things like
> crystal calibration points, charts, and netting to other stations and
> things just seem to vanish and I’m left staring at the radio.  So, I’m
> thinking that switching to a crystal and netting the receiver to it should
> be easier.  At least I think it would be.  At any rate, I have a lot of
> crystals, so I’m going to try it and see.
>
>
>
> Thanks for the thoughts and advice.
>
>
>
> Garret
>
> W8BUG
>
>
>
>
>
> *From:* Rob Flory [mailto:farmer.rob.flory at gmail.com]
> *Sent:* Monday, March 13, 2017 5:38 AM
> *To:* Garret Scott <scottgs at bellsouth.net>; mrca <mrca at mailman.qth.net>
>
> *Subject:* Re: [MRCA] Recrystalling a TBX-8
>
>
>
> Hi Garret,
>
> Doesn't the TBX-8 have a 2-tube transmitter, unlike the earlier models
> with the single 837?  The characteristics would be quite different.
>
> I never really found any advantage to operating the earlier TBX on crystal
> control.
>
> Rob
>
>
>
> On Mon, Mar 13, 2017 at 12:15 AM, Garret Scott <scottgs at bellsouth.net>
> wrote:
>
> Hi Al,
>
> Yes, those crystals are really scary. They would seem more appropriate in
> Frankenstein's lab than a portable radio.
>
> Thanks for the input.  That's exactly what I was thinking about.  I don't
> want to destroy perfectly good (and soon to be rare) 80m ham band crystals.
>
> Garret
> W8BUG
>
>
>
>
> -----Original Message-----
> From: MRCA [mailto:mrca-bounces at mailman.qth.net] On Behalf Of Al Klase
> Sent: Sunday, March 12, 2017 8:13 PM
> To: Military Radio Collectors Association
> Subject: Re: [MRCA] Recrystalling a TBX-8
>
> Hello Garret,
>
> I played with one of those years ago, and was kind of freaked out by the
> crystals, they're big, and appear to be heat sinked to the chassis.
> Fearing that it might be the kind of oscillator that breaks crystals,  I
> installed a # 49 pilot lamp ( 2 volts, 60 mA) in series with the crystal,
> and used FT-243's without a problem.
>
> YMMV,
> Al
>
> On 3/12/2017 5:52 PM, Garret Scott wrote:
> > With all this crystal talk, I've been prompted to think about crystals
> > for the TBX-8.
> >
> > Any one experienced with this or with those funky giant round
> > CG-40024-A crystal holders which they use?
> >
> > Just wondering if a typical fundamental crystal on 3885 Kcs will go in
> > there and work.
> >
> > Thanks,
> > Garret
> > W8BUG
> > scottgs at bellsouth.net
> >
> >
> >
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> --
>
> Al Klase - N3FRQ
> Jersey City, NJ
> http://www.skywaves.ar88.net/
>
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