[Milsurplus] Secrets of the R-23 and R-24/ARC-5

[Mike Morrow]

The R-23 and R-24/ARC-5 receivers had some interesting uses intended.  They differ from the earlier ARA/ATA (CBY/CCT-46129, -46145) and SCR-274-N (BC-453-*, 946-B) equivalents in potential application.

1.  They have push-terminals and a switch for a loop antenna.  The DU-* or DW-* DF loops could be used.  Much more likely a ZB-* or AN/ARR-1 homing adapter could be optionally connected through these terminals, but since the AN/ARR-2 homing receiver was available from about the same time that the R-24 was, it is unlikely that the ZB-* or AN/ARR-1 homing adapter was ever used with an R-24.  (These loop connections were present on the 1940 RAV liaison CBY-46102 and -46103 receivers, but were eliminated on the 1940 ARA command CBY/CCT-46129 and -46145 receivers.)
2.  They have a specially LP-filtered AF output from the cathode circuit of the 12A6 output stage.  Not present in R-25, -26, -27.  This AF is used by the MX-19/ARC-5 audio adapter plug-in panel.  It provides for connection and use of the R-23/-24 as a MF localizer receiver to the R-43/ARN-9 "Air-Track" (improved ZA-*) ILS.  The R-43 also contains a 90 to 95 MHz glide slope receiver, output to an ID-24/ARN-9 cross-needle display.  This ILS was abandoned by the USN by 1944 in favor of the grossly superior USAAF SCS-51 ILS.  It is unlikely that the R-23 or -24 ever was utilized with the AN/ARN-9 ILS.
3.  They have AGC with modified tube lineup, as do R-25, -26, -27.

In the front panel plug-in space, one of four devices may be found:

1.  C-24/ARC-5 Local control panel.  Panel provides no audio outputs.
2.  MX-19/ARC-5 Audio adapter panel.  Used only to connect R-23, -24 to AN/ARN-9 ILS.  System was abandoned in 1944.
3.  MX-20/ARC-5 LV/HV power out adapter panel.  Supplied standard on R-24.  Used to provide power to ZB-* or AN/ARR-1 homing adapter, or O-4/ARC-5 crystal-controlled calibration frequency indicator (CFI), or LM-* CFI.
4.  MX-21/ARC-5 Remote control adapter panel.  Supplied standard on R-23, -25, -26, -27.  Completes LV power circuit to permit power control from remote.

These were just a few notes to refresh a couple of obscure features of the R-23 and R-24/ARC-5 navigation receivers.  Although the R-24 was designed to support a DF loop, a VHF homing adapter, and a instrument landing system, it in fact did none of those things.  That's why they all appear unused until hobbyists got a hold of them.  

The same can be said for the SCR-274-N BC-946-B.  The ARA CBY-46145 is the only command set BCB receiver that saw real application to the war effort.

Mike / KK5F