[Milsurplus] Bendix MN-20E Loop (and use with RA-10DB/TA-12B system)

[Mike Morrow]

Clete wrote:

> Question:  What's the MN-20E loop used with?
> It can be mounted on either the top or bottom of
> the aircraft.
> I'd like to find a spline cable or something to turn
> it with.  Anyone have any ideas?

The MN-20E is a general-use loop that, like its larger diameter brother
MN-22, was used in many Bendix installations requiring a manually-operated
DF loop. The most common use would be with the MN-26** RDF.  But I've got
mine for a Bendix RA-10DB and TA-12B system I've just about collected
(I still lack the MS-18B mic jack box).  The RA-10DB/TA-12B system is
made up of:

MN-20E    RA-10DB Receiver DF Loop
MN-52B    Control Box for MN-20E DF Loop
MP-28BA   Modulator with Dynamotor and Mount
MR-9B     Control Box for RA-10DB Receiver
MS-14B    System Junction Box
MS-18B    Microphone Jack Box for TA-12B Transmitter
MT-31C    Tuning Meter for TA-12B Transmitter
MT-51C    Control Box for TA-12B Transmitter
MT-53B    MF Tank Coil for TA-12B Transmitter
RA-10DB   Receiver with Dynamotor, Mount, and Loop Relay Unit MR-11D
          150 to 400, 400 to 1100, 2000 to 5000, 5000 to 10000 kHz
TA-12B    Transmitter with Mount
          Ch 1:  300 -  600,  Ch 2:  3000 - 4800,
          Ch 3: 4000 - 6400,  Ch 4:  4370 - 7000 kHz

The RA-10DB serves both as communications and RDF receiver, because
it includes the Loop Relay Unit MR-11D which accepts the RF feed
from the MN-20E loop.  But also part of the loop installation is
the MN-52B Loop Control Box above, which has the mechnical indicator
dial and crank, as well as switches to cause the MR-11D to select
the loop.

The RA-10DB/TA-12B was not a bad set for serving a broad range of
aircraft radio needs.  It was much more versatile than the common
three-receiver, two-transmitter MF/HF ARA/ATA or SCR-274-N.

The spline cable that goes between the MN-20E and the MN-52B control
box is just the common larger spline type that were used in many
sets of that vintage, including the MN-26*, SCR-269-*, AN/ARN-7,
AN/ARN-6, SCR-**-183 and -283, RU-**, ARB, and many other sets.  It's
a lot easier to find than the smaller MC-215 type used in "command set"
and trailing wire antenna BC-461 controls and a few other places.
Robert/WA5CAB sold me the last few I've obtained, and probably knows
the best designation to apply to the larger spline.

Mike / KK5F