[ARC5] Command Set Navigators

[Mike Morrow]

I wrote:

>I've just about concluded that a complete SCR-274-N set
>ought to include the BC-946-B and the R-1/ARR-1 (with
>Signal Corps markings).  I need to locate plugs for the
>connector (PL-74?) for the power adapter and the large
>connector on the R-1, plus a MC-415 BCB control box dial.

I've identified everything that it takes to add the AN/ARR-1 to an existing SCR-274-N installation:

AT-5/ARR-1   Homing Antenna
MT-2/ARR-1   Mount for R-1/ARR-1
R-1/ARR-1    Homing Adapter (234 to 258 MC)
BC-946-B     Receiver (.52 to 1.5 MC)
DM-32-A      Dynamotor for BC-946-B
MC-415       Dial for BC-450-A Control Box (.52 to 1.5 MC)
FT-310-A     Power Adapter (standard on BC-946-B)
PL-56        Connector to FT-310-A (5-pin)
PL-63        Connector to R-1/ARR-1 (8-pin)
PL-259       RF to/from AT-5/ARR-1, RF to BC-946-B (3 total)

The power cable from the BC-946-B to the R-1/ARR-1 should be wired:

PL-59 pin 25 to PL-63 pin 46 ( +24 vdc)
PL-59 pin 35 to PL-63 pin 41 (+250 vdc)
PL-59 pin 27 to PL-63 pin 52 (Ground-Common)
PL-63 pin 40 to PL-63 pin 52 (Sets R-1/ARR-1 to normal sensitivity)

The standard SCR-274-N utilized a BC-453-B, BC-454-B, and a BC-455-B in a three-receiver FT-220-A rack.  When the R-1/ARR-1 homing system was to be used, doubtless there was no need for the beacon band BC-453-B.  The BC-946-B could be installed in place of the BC-453-B, the power and RF cables from the R-1/ARR-1 connected to BC-946-B, and the dial changed on the BC-450-A control box.  That's all that's necessary.

Thus, it is very simple for the original users (the USAAF) or collectors (us) to add the AN/ARR-1 to the SCR-274-N, since the control and relay boxes are eliminated.

It appears to me that few if any USAAF installations of the R-1/ARR-1 utilized the control and relay boxes of the AN/ARR-1.  They would be completely superfluous.  As several have noted, it appears almost (or all) USAAF R-1/ARR-1 units come with metallic covers over the R-1's connectors that would otherwise go to the control or relay boxes, and even the one well-used USN-marked R-1/ARR-1 that I have has those covers.

I was fortunate to find the exact connectors needed (PL-56, PL-63) in my collection.  Now all I need is the MC-415 BCB control box dial.  But I wonder if any were ever actually made.  I know BCB dials exist for the ARA and the AN/ARC-5.  But SCR-274-N control box dials are noticably different in styling in comparison to AN/ARC-5 equivalents.  No pictures of the MC-415 appear in the manuals for the BC-946-B.  The unique (for SCR-274-N) FT-310-A power adapter is always standard on the BC-946-B, but the associated unique MC-415 seems not to have been packed in the box with the BC-946-B.  Maybe none were ever made.

I'm also looking for a manual or copy (preferably Signal Corps) for the AN/ARR-1.

I also wrote:

>I would enjoy hearing other list members' speculation why,
>on so many Signal Corps R-1/ARR-1 units, the antenna input
>coil assembly has had the mica insulation broken, and most
>of it removed.  In addition, the 2 uuF capacitor C132 across
>part of the coil is always found removed.

That should have been "C134", not "C132."

Mike / KK5F