[MRCA] Calibration book

[D. Platt]

Mike Morrow wrote:
> William C Taylor wrote:
>
>   
>> I'm trying to find a calibration book for my transmitter. It's a
>> T-47/ART-13 with O-16 Oscillator and 8Q-1 MCW-CFI unit.>>   
>>     
>
> Jeep wrote:
>
>   
>> Looks like there's one on Ebay, now.
>>     
>
>
> Well...no, there's not one for the transmitter described.
>
> The auction at:  
>
> http://cgi.ebay.com/ART-13-transmitter-CALIBRATION-BOOK-/220663938167
>
> is the cal book for an AN/ART-13A (T-47A/ART-13 and O-17/ART-13A).
> These use the 8Q-2 MCW-CFI.
>
> This calibration book will differ from the correct cal book as
> follows:
>
> (1) This book is more than twice the thickness of the cal book for
> the AN/ART-13 (T-47/ART-13, not T-47A), because it has cal data at
> 1 KC intervals throughout the tuning range.  This is because the
> vernier scale above VFO dial B on the T-47A allows greater precision
> in setting the VFO than does dial B on the T-47.  The T-47 cal
> book present cal data intervals ONLY at 5 KC in the lower bands, and
> 10 KC in the upper bands.
> (2) The cal book present cal data for the O-17/ART-13A LF/MF oscillator,
> which is 200 to 600 KC.  It will not have cal data for the full range
> of the O-16/ART-13 (200 to 1500 KC).
> (3) All T-47A units normally have the 8Q-2 MCW-CFI sub-assembly.  Thus,
> calibration points shown for the T-47A will generally NOT agree with
> cal points appropriate to a unit with the earlier 8Q-1 MCW-CFI unit.
>
> The auction cal book is interesting since it is a US Navy issue book.
> Most such transmitters used by the USN were T-47 units.  This does
> indicate there was enough use of the USAAF's improved T-47A model in
> the USN by the late 1940s for a specific cal book to be issued by naval
> authorities.  I knew the USN later used the CU-32/ART-13A LF/MF external
> tank coil, and DY-17 and DY-17A/ART-13A dynamotors, so this book verifies
> that the T-47A also saw later Navy use, in addition to their T-47.
>
> The $60 auction start price for a poor condition cal book is, IMHO,
> a little high.  It's in Australia.
>
> Mike / KK5F
>   
I just compared all three book versions and what Mike says is, of 
course, correct.  The difference is that the A model has the vernier, as 
mentioned, and the calibration points take this into effect.  However, 
one can use the "A" model book for 2-18 MHz and interpolate for a 
slightly better accuracy. Or, simply go to up or down to the bracketing 
whole kilohertz.  What I've done on two units, not "A" models, was to 
remove and replace the rotating calibration plate with one from a junker 
A model VFO knob.  I am going to try and make a universal decal or 
stick-on to convert any older plate to the "A" plate with vernier 
calibrations.  Can't hurt......!

Jeep/K3HVG