I had several opportunities 1967 to 1970 to visit the avionics field maintenance building at Blytheville AFB.  That was a SAC base, and almost all aircraft there were B-52 and KC-135 aircraft.

 

There was always RT-279/APX units for the AN/APX-25 under repair.  AFAIK, all RT-279 units were RT-82/APX-6 units which had been modified by Stewart-Warner for use with the KY-95/APX-25.  They still had "AN/APX-6" boldly marked on the front panels.

 

Mike / KK5F

-----Original Message-----
From: Francesco Ledda <frledda@att.net>
Sent: Dec 15, 2022 7:57 PM
To: <scottjohnson1@cox.net>
Cc: ARC-5 Mail List <arc5@mailman.qth.net>
Subject: Re: [ARC5] APX-6 IFF

 

In Europe, the APX-6 was in service with many legacy airplanes until the late 70s. There were airplanes like the T-33, C119, HU-16 and F-86K that were never upgraded as they were EOF in the early 70s, but for budgetary reason kept flying.  APX-6, APX-25, ARN-21, ARN-6, APG-30, ARC-33, ARC-27 were abundant and cheap in the surplus market…
 
Best, Francesco K5URG
 


Sent from my iPad

On Dec 15, 2022, at 18:15, scottjohnson1@cox.net wrote:

It was indeed the KY-95, and some older APX-6 transponders were field modded to work with the KY-95 (which had the mode 2 code settings on its front panel, the added SIF control box gave Modes 1 and 3.

 

Pulled one complete from an ex-RCAF Dakota, it was evidently still being used up to 1975 by the Canadians.

 

Scott  W7SVJ

 

From: arc5-bounces@mailman.qth.net <arc5-bounces@mailman.qth.net> On Behalf Of Doran Platt
Sent: Thursday, December 15, 2022 2:43 PM
To: ARC-5 Mail List <arc5@mailman.qth.net>
Subject: [ARC5] APX-6 IFF

 

In 1961, the APX-6, although, I think, were still in use, had been eclipsed by the APX-25 IFF system incorporating the  KY-25A (or was it 95?) IFF/SIF encoder. The two units look very much alike. By then Mode II (mil only) selective code, was necessary. The coder had a 6 bit  selectable address yielding a two letter identifier.....wowee!!

Jeep K3HVG

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