11-A/APN-12 IFF Transceiver -- What is this??
 

Military Radio
Military Radio model 11-A/APN-12. This is a 15 tube radio, with an eye tube.
The radio looks to be in good condition, and looks to be complete. It operates
on 115 volts AC, or 26 volts, DC. I have not tried it to see if it works. It
has no rust, and is very clean inside. Would make a nice piece of history. Only
$40. See picture

http://southeasttexas.com/uploads/ACFB8B6.jpg
~
Can someone tell me what this is and what it does?
Also approximate worth?

Thanks in advance.

John

John posted, in part:

Can someone tell me what this is and what it does?


IFF is Identification, Friend or Foe. You have the airborn end of the system.

In early systems, which I believe is where this would be, age-wise, that
transponder would automatically transmit a signal in response to having
received an "Interogation," aka "Challenge" from a radar station. There were
only three possible responses to an interogation: 1,2, or 3 blips. These
would be seen on the Radar Station "B" scope next to the echo return signal of
the radar. That's the one with the circular trace.

Each day a different one of the three codes would be assigned.

An aircraft that sent no IFF signal or a wrong one, would be assumed
unfriendly.

As late as the 60s this type of IFF was in use. I was once a civilian
employee/operator at an operational RADAR station. The secret IFF code of the
day was not given to us. We tracked aircraft and gave the grid coordinates and
IFF status to the Airforce on special lines. They decided if it was friend or
foe.

It seems silly now, but at the time it was serious stuff to report "I have a
bogey on my gadget and the parrot's sqawking 1" or 2 or 3.

Don

Close, but there's a bit more to the story. As the other person alluded
to, modes are actually a set of bracket pulses, spaced a number or
microseconds apart amount corresponding to each "mode". The "squawk
codes", binary count pulses imbedded between the bracket pulses, are
decoded by ground or airborne interrogators so that the "code" can be
read out on a radar scope, etc.

Military Mode 2 came about in the mid-50's with the advent of the APX-6
(later the APX-25) transponder and accomplanying KY-95 SIF (selective
identification feature)encoder. Early Mode 2 was the descreet daily or
mission code and preset on the ground and had 2 digits up to 77. On
newer transponders, mode 1 and 3 codes can/could be set/re-set in the
cockpit, to include altitude encoding with the modes now labelled as
Mode A/B/C (and D). Codes now consist of 4 binary digits up to 7777.
The military is the only entity authorized Mode 2/B. I don't know if
mode 2/C and 4/D can be reset by the aircrews in modern acft, though.
Well, enough of this. Any help??? de K3HVG

JOHN7714 wrote:

Military Radio
Military Radio model 11-A/APN-12. This is a 15 tube radio, with an eye tube.
The radio looks to be in good condition, and looks to be complete. It operates
on 115 volts AC, or 26 volts, DC. I have not tried it to see if it works. It
has no rust, and is very clean inside. Would make a nice piece of history. Only
$40. See picture

http://southeasttexas.com/uploads/ACFB8B6.jpg
~
Can someone tell me what this is and what it does?
Also approximate worth?

Thanks in advance.

John

Don't Know if you got an answer John. If not, these were rigs we used in
the dark ages (pre plug and play) to get on 1296. Used 2C39As for rf
out and had to tweak the cavities to get it in the ham band.

Cheers es 73,

Scott W7GSM

JOHN7714 wrote:
Military Radio
Military Radio model 11-A/APN-12. This is a 15 tube radio, with an eye tube.
The radio looks to be in good condition, and looks to be complete. It operates
on 115 volts AC, or 26 volts, DC. I have not tried it to see if it works. It
has no rust, and is very clean inside. Would make a nice piece of history. Only
$40. See picture

http://southeasttexas.com/uploads/ACFB8B6.jpg
~
Can someone tell me what this is and what it does?
Also approximate worth?

Thanks in advance.

John