[ARC5] FT-310-A and AN/ARR-1 VHF Homing Adapter

[Mike Morrow]

> I have a BC-946 with a FT-310-A in the drawer.  What was this supposed to 
> power?

Robert wrote:

> Originally intended for use with AN/ARR-1 (Navy ZB-1 or -2).  That's 
> apparently what the BC-946 was procurred for use with.

Just to throw in a little technical history notes, just for fun:

All of the broadcast band versions of the Type K receivers derivatives except
the RAV CBY-46103 came with this power adapter box as standard equipment:

ARA       CBY/CCT-46145 Receiver CBY/CCT-62036 Power adapter for ZB-* Homing adapter
SCR-274-N BC-946-B Receiver      FT-310-A Power adapter for AN/ARR-1 Homing adapter
AN/ARC-5  R-24/ARC-5 Receiver    MX-20/ARC-5 Power adapter for AN/ARR-1 Homing adapter

All of these BCB receivers had as their only purpose for existence their use with
the VHF homing adapter, although one could argue that the MF loop antenna connections
of the R-24/ARC-5 *could* have been used with a DF loop like the DU-*...but that's
very unlikely.

The BCB receiver could be installed in a standard three-receiver rack in place of
the beacon band unit, since it was unlikely that where the VHF homing adapter was
being used, a LF/MF beacon band receiver would have any value.  The ZB-* or AN/ARR-1
homing adapter could be connected to the BCB receiver through the power adapter with
a three-conductor cable, nt-49133/PL-*56 at the power adapter end and nt-49062/PL-*63
at the homing adapter.  The BCB receiver antenna terminal could remain connected
to the BCB output of the homing adapter at all times, since actual BCB recption
would have no value.  This arrangement eliminates the need to use the homing adapter
system's control box and antenna switch box.  The BCB receiver's standard CBY/CCT-23251
or BC-450-A three-receiver or C-26/ARC-5 single-receiver control box that was
previously used by a beacon band receiver could now serve as the only controls
needed for the VHF homing system.  I've never found any official diagrams showing
the obvious electrical details of this arrangement, but AFAIK no recovered USN
aircraft using the ARA with ZB-* combo have had the ZB-* pilot's control box and
antenna switch box present.  I believe that the standard early-WWII carrier aircraft
using the ARA/ATA command set likely all had a BCB CBY/CCT-46145 installed in place
of a beacon band CBY/CCT-46129 in their three-receiver racks, and a ZB-* VHF
homing adapter near by.

There doesn't seem to be much likelihood that there were many SCR-274-N systems
that used the JAN equivalent of the ZB-*, the R-1/ARR-1.  Had there been, the
installation could have been exactly like the ARA with ZB-*.  There has been
some speculation that the US Army P-38G flight that shot down IJN Admiral Yamamoto's
aircraft in April 1943 may have used the AN/ARR-1 as the "special navy compass"
that is mentioned in at least one pilot's memoirs.  However, unless the flight
was at great altitude, the range of the YE/YG VHF homing beacon would likely
have been far too short to support the 600 mile inbound trip unless ships with
YE/YG beacons had been staged along the way.  AFAIK, there's never been any
evidence of that.  It's sad that such a simple technical detail like this remains
unresolved after 69 years...just what was that "special navy compass"?

The AN/ARR-1 was used on B-29 aircraft in the Pacific, but it was connected
to the AN/ARN-7 ADF, according to pilot manuals I have for the B-29 and B-29A.

A large percentage of AN/ARR-1 components found today have US Army order numbers
on them, so many homing adapters seem to have been procured by the USAAF.

It is also unlikely that many ZB-* or AN/ARR-1 homing adapters were ever used
with the R-24/ARC-5.  About the time the AN/ARC-5 saw delivery the improved
all-in-one-box AN/ARR-2 VHF homing receiver was available for installation in
the USN's AN/ARC-5 receiver racks.  The most common AN/ARC-5 receiver control
box, the C-38*/ARC-5, has a dedicated section that provides full controls for
the R-4*/ARR-2.

For USN aircraft before, during, and after WWII the ZB/YE-YG homing system was
one of the most important radio systems in use.

The MX-20/ARC-5 power adapter is frequently found on actual service-use
receivers other than the R-24.  It could have been used to power an LM-*
frequency meter for in-situ adjustments, or one of the rare O-4/ARC-5
CFI units.

73,
Mike / KK5F
(Corrections, observations, and opinions welcomed, as always.)