[ARC5] ZA navigation radio?

[Mike Morrow]

The USN ZA instrument landing system was developed in the mid-1930s and had a commercial designation of AIR TRACK.  It used an MF localizer signal around 300 kHz and a VHF glide slope signal around 100 MHz.  The ZA contained the glide slope receiver and the aircraft's RU-* or ARA was the localizer receiver.  The ZA processed these signals and displayed the results on a crossed needle indicator.

The ZA equipment advanced to the ZAX, which ultimately was designated AN/ARN-9.  R-87/ARN-9 was the glide slope receiver and the aircraft's R-23*/ARC-5 was the localizer receiver, which required use of the MX-19/ARC-5 audio adapter panel installed in the front of the R-23*/ARC-5.  Both of the R-23*/ARC-5 and R-24/ARC-5 navigation receivers connect filtered low-level audio from the cathode of the 12A6 to the adapter panel connector for use by the ILS.  Two localizer transmitter beams were modulated with one of two low frequency audio tones that the MX-19/ARC-5 sent to the R-87/ARN-9.

The AN/ARN-9 is the ILS to which various AN/ARC-5 manuals refer.  It was significantly more difficult to use than the USAAF's RC-103-A VHF localizer and AN/ARN-5* UHF glide slope receiver, so the USN very wisely abandoned the ZA, ZAX, and AN/ARN-9 by 1944 in favor of the USAAF's system.  Also the ZA and AN/ARN-9 glide slope was parabolic rather than linear which was inferior.to the USAAF system.

Manuals and components for the ZA system are not too rare, but surviving manuals and components for AN/ARN-9 appear to be nonexistent.  The only item I've ever seen is the ID-29/ARN-9 cross needle indicator.

Jack Antonio is the world's leading expert on the ZA.  He has put together probably the only existing complete ZA ILS system.

ZA components are often stamped in white paint with the aircraft type in which it was designated for use...usually a large patrol aircraft like a PBY.

Mike / KK5F

-----Original Message-----
From: Paul Thekan <pfthekan at gmail.com>
Sent: Dec 24, 2023 12:56 PM

Merry Christmas...

I came across a Test Oscillator CDE-60050 for " ZA series equipt" Not sure
if this preceeded the ZB radio...or this is something completely different.

Tnx
Paul
N6FEG