[ARC5] [MRCA] Zenith Radio ART-13?

[Christopher Bowne]

My Zenith ATC/T-47/ART-13 has M1 through M6 stenciled in white paint on the end 
where the nameplate is, come to think of it, the T47/ART-13 is also stenciled on 
in white paint, will have to start looking for the various mods.  I believe I 
have the 1 kc resolution MO.




________________________________
From: Mike Morrow <kk5f at earthlink.net>
To: mrca at mailman.qth.net
Cc: arc5 at mailman.qth.net
Sent: Mon, November 26, 2012 2:38:34 PM
Subject: Re: [MRCA] Zenith Radio ART-13?

I wrote:

> The T-47A/ART-13 has all these improvements, plus a dynamotor DC control 
> power interlock to top cover removal, plus a vernier scale on MF/HF VFO 
> dial B that allows the VFO to be set at one-tenth of a minor dial scale 
> division. Thus, the calibration book for the T-47A is tabulated for 
> MF/HF VFO settings at 1 kHz increments throughout its entire operating 
> range. The earlier transmitters are calibrated for only 5 kHz increments 
> up to 8 MHz, and for only 10 kHz increments when higher than 8 MHz. The 
> T-47A cal book is thus about twice as thick as one for an earlier model. 
>
> So...IMHO Collins did *not* make the best version of this transmitter 
> system. That honor goes to Stewart-Warner Corporation's T-47A/ART-13.

Jeep wrote:

> Correct me if I'm wrong, here.  Both my ATC and my ART-13 were upgraded 
> at some point to have the vernier dials.

There's nothing too odd there.  It appears that a few (but very far from
most) of the USN units got a VFO dial B upgrade.  **Sometimes** one will find
USN units with a full upgrade to the T-47A that was performed as part of the
conversion to the T-412/ART-13B (but most often not).

That and other upgrades were usually indicated by a modification stamped in
paint on the unit.  If anyone has the official documentation for the military
mods made to these units, I'd be interested (as well as getting copies).  My
T-47A is stamped M-5 and M-6 in red paint, and M-5 in white paint.

I suspect that hams also performed swaps of the dial B vernier back plate.

> My late-model Navy ART-13 (yep... T-47/ART-13) has the 3-tube CFI-MCW
> module in it.

That's the 8Q-2.  Many early ATC units were later upgraded to the 8Q-2,
which requires a cal book change in addition to MCW-CFI unit replacement.

> The "A" model calibration book, as stated, is arguably twice as thick
> owing to the additional settings.  That said, either book works with
> either unit, with the caveat that the accuracy is superior with the
> "A" model book.

Well, at least the precision of VFO dial B adjustment is better with the
vernier scale.

The cal book data is essentially identical in all cal books, although it
is provided to an oder of magnitude greater precision for the T-47A
cal books.  Aside from that, selection of the proper cal book requires
knowing whether the 8Q-1 or the 8Q-2 MCW-CFI unit is installed.

> Also, an additional indicator of who made the unit is that Collins units 
> have their logo molded into the chassis casting in the area of the audio 
> and CFI-MCW modules. Both mine have it...

That's not surprising for a typical USN transmitter.  For the USAAF
T-47A/ART-13, none of which were made by Collins AFAIK, it would be!  :-)

What information is shown on the nomenclature plates for your two units?

> Question is, do only S/W units come with the 3-tube CFI-MCW module?

No, the 8Q-2 MCW-CFI is a Collins design.  Zenith and Stewart-Warner simply
reproduced it in their units, since it was the latest design.  I suspect
that all of the 8Q-1 units were built by Collins.

Only T-47A units had the VFO dial B vernier scale as original equipment.
IF Stewart-Warner was the only maker of the T-47A, which I believe, then
only Stewart-Warner units had the desirable VFO vernier scale dial at time
of manufacture.

> Were these modules used universally later on?

Yes.  It appears that the 8Q-1 was short-lived in new manufacture.

> I know the A-model had an interlock installed and the vernier, of course,
> and perhaps the T/R relay assy. but what else is there?  Looking at the
> late-issue AFTO that covers all three variants,  I'm still trying to see
> material differences.

The only visual clues are that **all** T-47A/ART-13 units will have the 8Q-2
MCW-CFI unit, the dynamotor control power cover interlock switch (on left
side under top cover), the VFO dial B vernier scale back plate, and the
MT-283/ART-13 mount hardware that engages the MT-284/ART-13 shock mount.
For a smaller detail, the cal book tray should have a rubberized chain
and loop designed to attach to the spine of the cal book to prevent loss.
If it has a LF/MF oscillator unit, it should be the O-17/ART-13A three-band
200 to 600 kHz unit rather than the O-16/ART-13 six-band 200 to 1500 kHz
unit.  The vernier back plate is the first external characteristic I look
for, followed by the control power interlock switch.

I've seen some vague description somewhere that the T-47A had some
individual component upgrades, but there are none that can be detected
from examination of the schematics of the T-47A vs. T-47.

If one examines the schematics of the T-47/ART-13, T-47A/ART-13, and 
T-412/ART-13B, it will be found that the dynamotor control power interlock
switch that was added to the T-47A design is S117.  However, if a T-47A
has been converted to a T-412/ART-13B, there will be yet another S117...
the LF Extended Range switch that adds a 220 uuf capacitor to the plate
circuit of V-102 in order to allow MF operation as low as 1670 kHz on
crystal control from the CDA-T oscillator unit.  That's a little sloppy.

Mike / KK5F

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