[MRCA] Zenith Radio ART-13?

[Mike Morrow]

For the USN, the ATC was made by Collins (COL-52286 or COL-52286-A) and
the ATC-1 was made by Zenith (CZR-52286-A).  The ATC-2 (CG-52286-A) by GE
was proposed but cancelled.  These became the T-47/ART-13 on new units
after the JAN system came into service in 1943.  Many units that were
made before then JAN system became a T-47 by simply changing their nomenclature,
often with a crude yellow paint stencil.

For the USAAF, there is the improved AN/ART-13A.  Every T-47A/ART-13
transmitter that I've ever seen has been made by Stewart-Warner (CWS).

The T-412/ART-13B is a modification of earlier ATC, ATC-1, T-47, or T-47A
transmitters.  That added the CDA-T LF/MF/HF crystal oscillator unit (ten
A/B channels above 1670 kHz and four LF/MF channels), plus a "LF Extended Range"
switch that allowed MF crystal control down to 1670 kHz.  The best T-412 should
be one converted from the improved T-47A design, yet most that I've seen were
made from older USN models, many of which had *not* been upgraded to T-47A
functionality.

FWIW, the ATC started out with the 8Q-1 MCW-CFI unit (two-tube) and poorly
shock-resistant mounting rails.  Most USN ATC, ATC-1, and T-47 units were
later upgraded to the 8Q-2 MCW-CFI unit (three-tube), along with the improved
MT-283 plus MT-284/ART-13 shock mounts.  Some of the VFO calibration points
points are different for 8Q-1 versus the 8Q-2 units, so the proper calibration
book depends on which MCW-CFI unit is installed.

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.