[ARC5] 274-N rack used for APW-11??

[Mike Morrow]

Dave wrote:

> There's got to be a good story behind this rack:
>
> http://www.ebay.com/itm/290939973405

Not that I know of.  Apparently the AN/APW-11 was, as the early
JAN RT component number of RT-122/APW-11 suggests, being designed
near the end of WWII.  The RT-122 was made to fit in a rack that
was *almost* mechanically identical to a SCR-274-N transmitter
rack. 

Wayne wrote:

> I have an APW-11.  It was used as part of the guidance system
> for the Matador cruise missile.

The AN/APW-11 is a "Control Beacon (Remote Control and Telemetry)" but
it was also sometimes called a Bombing Air Radar Guidance System.
It was developed shortly after WWII and was primarily installed in
piloted aircraft.  It is a S-band radar tracking beacon that communicated
to a ground tracking radar, upon interrogation, the heading, speed, and
altitude of the aircraft by using audio tones.  This helped ground
control get the aircraft to the proper location for weapons delivery.

Some other components in the system were:
RT-122*/APW-11 or RT-447/APW-11 
AT-171/AP 
C-400*/APW-11 
C-2460/APW-11 
MT-622*/APW-11

I have a pilot's manual ("dash 1") for the B-57 Canberra bomber that
briefly describes the AN/APW-11 that it carried, but not in much detail
because the classification of AN/APW-11 information was higher than that
of the aircraft dash 1 manual.

One may find many references to the AN/APW-11 being installed on manned
and unmanned experimental aircraft, and missiles, to enhance ground
tracking, but I suspect that was a case of making do with an existing
system that was originally intended for other service.

> It is more or less the same width as a 274-N receiver but it's
> taller and a couple of inches longer.

The RT-122* or RT-447/APW-11 is **exactly** the same width and
length of a SCR-274-N **transmitter**.  It also has unit hold-down
pins at the bottom of the front panel that are identical to those
found on SCR-274-N transmitters.

The RT-122* or RT-447 is 1.5 inches less in height than a SCR-274-N
transmitter.

> Also, note that the rack for sale on ebay does not have the
> bent parts that slide over the dynamotor mounting section of
> a 274-N receiver.

The MT-622*/APW-11 rack for the AN/APW-11 is mechanically almost
identical to the SCR-274-N transmitter rack.  It is not based on
command set receiver dimensions in any way.

> Also the APW-11 has a couple of guide pins in the back, clearly
> designed to slide into the holes on the rack. 

True, but the most important item to note is that the power
connector on the rear of the RT-122* or RT-447 is essentially 
identical to that on a SCR-274-N (not AN/ARC-5) transmitter,
EXCEPT that it is ROTATED 180 degrees.  The alignment pins prevent
inserting an AN/APW-11 unit into a SCR-274-N transmitter rack.

Trying to kludge a SCR-274-N rack for use with the AN/APW-11,
or an AN/APW-11 rack for use with an SCR-274-N, requires
re-orienting the rear connector and a lot of other things as
well.  SCR-274-N racks are far more common than AN/APW-11 racks.

The RT-122*/APW-11 units are neat little sets that are heavier
that a SCR-274-N transmitter.  I've seen them at hamfest flea
markets in that past 20 years for as low as $5.  I've even
bought a couple.  They are early cold war relics, but not much
else.

Mike / KK5F