[Milsurplus] ART-13 differences

[Mike Morrow]

John asked:

>What is the difference between a T-47/ART-13 and a T-47A/ART-13?


The main difference between a T-47A/ART-13 (USAAF) and a T-47/ART-13 (USN)
is that the T-47A has a vernier scale on VFO dial B which the T-47 lacks,
allowing it to be precisely set to tenths of a dial division.  As a result,
the calibration book of the T-47A shows VFO dial B data in 1 kc increments
from 2.0 to 18.1 mc, while the T-47 calibration book only shows VFO dial B
data in 5 kc increments below 8.0 mc, and in 10 kc increments above that.

The T-47 calibration book will show LF/MF oscillator VFO data from 200 to
1500 kc, on the assumption that a USN O-16/ART-13 is installed, while the
T-47A calibration book will show LF/MF oscillator VFO data only from 200 to
600 kc, on the assumption that a USAAF O-17/ART-13A is installed.   Both the
O-16 and the O-17 VFO dials G lack the vernier scale that the T-47A has on
its MF/HF VFO dial B.  Regardless, the calibration book data of the O-16 is
in 2 kc increments, while the O-17 is in 1 kc increments.   The calibration
book for a T-47 will be marked "AN/ART-13," while the book for the T-47A
will be marked "AN/ART-13A."

In addition to this, the T-47A has a safety interlock switch on the
transmitter top cover that drops out DC control power to shut down the unit
and dynamotor when the top cover is removed.  The T-47 has no such thing.

There are doubtless other small circuit component value differences, but
those I mentioned are by far the most significant.

The T-47 is appropriate for USN applications, such as the T-47 and ARB
combination, or the T-47 and R-105/ARR-15 combo officially known as the
AN/ARC-25.  The T-47A is appropriate to USAAF/USAF application of the BC-348
(AN/ARR-11) and T-47A in the combo known as the AN/ARC-8 (IMHO, by far the
best airborne HF set in the world during and after WWII).

It appears that the T-47 with LF/MF oscillator O-16/ART-13 used the CU-25
and -26/ART-13 external LF tank coils, while the T-47A with O-17/ART-13A
used the CU-32/ART-13A.  The CU-32 is about the same size as the T-47A!  The
USN version normally used DY-11 or -12/ART-13 dynamotors, while the USAAF
version used DY-17 and -17A/ART-13A dynamotors.  What little I've found out
seems to indicate that eventually the DY-17 or -17A was used by both the USN
and USAAF.

Likewise, early USN ATC and T-47 units used a slide-type mounting like that
of the GP-7 or ATD (the MT-161/ART-13, IIRC), but later it seems the USN and
USAAF settled on the MT-283 and MT-284/ART-13 mountings.  Has anyone on the
list ever come across those old-style mountings?

Personally, I think the T-47A is the better unit for the reasons noted
above.  I'm putting together both a AN/ARC-8 and a AN/ARC-25, so I have
both.  To me it is important to keep USN stuff separated from the USAAF
stuff.  A T-47A with R-105, or a T-47 with an O-17, just seems wrong!

Mike / KK5F