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Duxford Radio Society

Imperial War Museum, Duxford, England 

Equipment Summary



APS-13 Tail warning radar front

RT-34/APS-13 Tail Warning Radar (USA)

The RT-34/APS-13 is a low power UHF tail warning radar transmitter/receiver which was used in Allied aeroplanes such as the P51 Mustang and also the
P-38L, P-47D, P-61, P-63, P-82D in the later stages of the war.

The equipment operates at 420 MHz with a receiver IF of 30 MHz and is powered by an internal rotary generator which is supplied from the aircraft 27V dc system.

The electro-mechanical construction is all aluminium, and the equipment uses all miniature glass valves except for the voltage stabiliser which is a VR105V (0C3).  The PA is two 6J6s.

Three modified APS-13 were employed as the primary radar altimeter fuse in the ‘LittleBoy’ atomic bomb dropped on the Japanese city of Hiroshima.
This APS-13 equipment, serial number 13711:CRV, was manufactured by RCA, Camden, New Jersey, USA under a  contract number  458-DAY-44 (1944).

This equipment example is in excellent condition and appears to be complete mechanically and electrically and is in working order.
This equipment has been cleaned and repaired and is now functioning, although the pilots cockpit warning unit is not held in the DRS collection.


APS-13 inside top view
APS-13 underside view
APS-13 system components 1
APS-13 system components 2
APS-13 sectional plan view of tail fin with antenna
APS-13 cockpit installation

Colour photographs of the APS-13 control panel in the cockpit of a P51D Mustang can be found at the following web site:

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updated 29-8-2006