[Milsurplus] Setchell-Carlson 591, AN/CRR-1, SCR-578 Rescue Radio

[Mike Morrow]

I've recently acquired an interesting aircraft beacon band receiver, a Setchell-Carlson Model 591.

The most common of these types of receivers are the BC-1206-C and -CM units (Setchell-Carlson Model 524), which use 28 vdc as B+.

A less common unit is the  R-76/ARR-13 (Setchel-Carlson l Model 512), which has a 278 kc select switch, runs off 14 vdc A+, and whose manual specifies an RCA AVA-126 vibrator supply for B+.

The Model 591 looks similar to the receivers above, but uses 1.5 vdc loctal tubes and has cloth carry handle and battery pack straps attached to the case.  A special battery pack (+67.5, +1.5, and -7.5 vdc) that has the same width and depth as the receiver is to be strapped under the receiver.  The receiver has Signal Corps stamps on it, and the manual indicates that it is 1943 vintage.

Fred Chesson's page at http://pages.cthome.net/fwc/AN-C.HTM indicates that this unit was known as the AN/CRR-1, with battery BA-244/U, for use with the 500 kc emergency/rescue Gibson Girl transmitter SCR-578.  This is the first time I've heard of the military pairing up a LF/MF portable receiver with the SCR-578 (and presumably, the later AN/CRT-3).

The use of a beacon band receiver in this service raises some questions.  The Model 591 has no BFO and thus can copy A2 and A3 signals only.  The upper frequency coverage ends around 420 kc, just at the point that the merchant marine MF morse band started, and well below the 500 kc that the SCR-578 uses.  I wonder if it was intended that LF/MF A2 or A3 signals would be transmitted from the rescuing force on frequencies below the maritime morse band.   Most common WWII merchant marine radio consoles like the Radiomarine 4U transmitted A2 in the merchant marine MF band, but generally could not transmit below 420 kc.  What entity would be transmitting to the parties in distress, and how would they know which frequency to select?

Mike / KK5F