[ARC5] Nomenclature Taxonomy - AN/ART-13B

[WA5CAB at cs.com]

OK.  I stand partially corrected.  However, a photograph of T-412/ART-13B 
is in T.O. 12R2-2ART13-1 (27AUG52) and subsequent revisions through 26SEP68.  
I also noticed (again, having forgotten it) that addition of the dynamotor 
interlock switch ("first S117") to NT-52286 or T-47ART-13 is Modification M1 
(and replacement of  the 8Q-1 CFI with 8Q-2 is M2).  Other differences 
between T-47A and the earlier models are that the LOCAL-REMOTE switch is 
mechanically different.and the transmit-receive relay assembly is different (the 
later one is backwards compatible).

Final revision of T.O. 12R2-2ART13-2 was 25JUN58.  One puzzling thing I 
noticed in it is that according to the Equipment Supplied list for AN/ART-13B, 
T-412/ART-13B was issued with both MX-128/ART-13 and CDA-T.  However, the 
majority of the text implies that if a T-47A went through the 10 to 20 hour 
conversion process to install a CDA-T, it should have gotten a new nameplate 
and "second S117".

In a message dated 6/25/2011 2:20:02 AM Central Daylight Time, 
kk5f at earthlink.net writes: 
> >In the case of T-412/ART-13B, however, there was a significant 
> difference 
> >in capability (the crystal oscillator).  So not only the component 
> >nomenclature but also the set nomenclature was changed or incremented.
> 
> There is *no* difference in the T-47A/ART-13 with CDA-T oscillator and the
> T-412/ART-13B other than:
> 
> (1)  The T-412/ART-13B has an "EXTENDED LOW FREQUENCY" switch on the front
>      to allow crystal operation in the CDA-T as low as 1670 kHz.  That
>      switch, "second S117", adds C151 in the plate LC circuit of V102.  
> But,
>      S117 is a careless error.  The "first S117" is the dynamotor control
>      power interlock switch to top cover removal that was added to the
>      T-47A/ART-13.  It was apparently overlooked when C151 was added to
>      make the T-412.
> (2)  Although manuals refer to the T-412/ART-13B as a modification of the
>      T-47A/ART-13, many T-412/ART-13B units were modified USN T-47/ART-13
>      or ATC or ATC-1 units which had neither the "first S117" dynamotor 
> control
>      power switch, nor the vernier scale on VFO dial B that allowed dial
>      settings at 0.1 of each minor dial division.  Those were the main 
> changes
>      between the USN T-47 and the USAAF T-47A.  However, sometimes one can
>      find T-412/ART-13B units that are modifications of USN ATC or T-47 
> units
>      that had been upgraded to have the same characteristics as the T-47A. 
> 
> 
> >Plus I have to add that a T-47A with an installed CDA-T is not a DOD or 
> >USAF modified unit.  USAF modified units got a T-412 nameplate.   Those 
> units 
> >without the T-412 nameplate were done by a contractor for Pan American or 
> 
> >done by some other non-DOD activity (including hams with the mod kit).
> 
> USAF modified units got a T-412 nameplate *only* if they had the EXTENDED 
> LOW
> FREQUENCY circuitry in addition to the CDA-T.  There are no T-412 units 
> that
> lack this switch.
> 
> The USAF T.O. 12R2-2ART13-1 (15DEC56) defines the AN/ART-13B as T-47A with 
> CDA-T,
> and does not list the T-412.  The USAF T.O. 12R2-2ART13-2 (30MAR56) also 
> defines
> the AN/ART-13B as T-47A with CDA-T, but does list the T-412 and address 
> the
> EXTENDED LOW FREQUENCY switch. 
> (http://bama.edebris.com/manuals/military/an-art13/ )
> The T-47A/ART-13 with CDA-T without the "second S117" EXTENDED LOW 
> FREQUENCY switch
> is an AN/ART-13B without the change of external nomenclature that was done 
> for the
> T-412 units with that switch.  These were military units, not post-WWII 
> surplus
> or commercial 17H-2 units used by the airlines.
> 
> The only thing that the T-412/ART-13B tag guarantees is the presence of 
> that
> second S117 and C151, along with the CDA-T oscillator.  The T-412 can be a
> modified USAF T-47A, or a modified USN T-47 or ATC in several variations.
> 
> Mike / KK5F
> 

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