[Milsurplus] Bendix TA-12

[Mike Morrow]

> Can anyone tell me the frequency coverage of the Bendix TA-12G
> transmitter? I’m trying to make some equipment ID cards for a
> radio display and can’t find my TA-12 manual. Note this is for
> the G model, not the more common B or C.

It's not likely that your TA-12 manual would have helped.  The TA-12G is the last and most refined of the TA-12 series, with some improvements in the PA output tuning capacitor configurations and a small "wave meter" neon indicator to help assure correct MF channel 1 tuning.  The TA-12G is built by Northern Electric Company, and it should have come with a heavy paper calibration graph stowed under the transmitter case.

The first three TA-12G channels have the same frequency range as the TA-12B.  The fourth channel is as shown below.

Ch. 1 -  300 to   600 kHz  TA-12B  TA-12C  TA-12G
Ch. 2 - 3000 to  4800 kHz  TA-12B  TA-12C  TA-12G
Ch, 3 - 4000 to  6400 kHz  TA-12B          TA-12G
        4800 to  7680 kHz          TA-12C
Ch. 4 - 4370 to  7000 kHz  TA-12B
        5750 to  9000 kHz                  TA-12G
        7680 to 12000 kHz          TA-12C

Frequency coverage overlap of the three remotely-selected HF channels allows more flexibility for using channel frequencies relatively close to each other.  The TA-12B has the best channel overlap but coverage stops at 7000 kHz,  The TA-12G has less channel overlap but coverage stops at 9000 kHz.  The TA-12C has NO channel overlap, but coverage stops at 12000 kHz.  Unfortunately, that was not especially useful in the WWII era, nor was it supported by the associated RA-10-series receiver whose coverage ends at 10000 kHz.

The RA-10DB receiver's coverage is;

Band 1 -   150 to   400 kHz
Band 2 -   400 to  1100 kHz
Band 3 -  2000 to  5000 kHz
Band 4 -  5000 to 10000 kHz

I have always admired this particular Bendix system.  I have:

RA-10DB LF/MF/HF manually-tuned receiver with dynamotor and
        with MR-11D loop relay unit
MR-9B   Receiver control box
MN-20E  DF Loop
MN-52B  DF Loop control box

TA-12B  MF/HF four-channel transmitter
MT-53B  MF tank coil
MT-51C  Transmittee control box
MP-28BA Modulator/dynamotor

Plus other ancillary items.

It seems a pretty good compact 1940-era system that provided a four-channel HF communications set with some LF/MF DF capability.

Mike / KK5F