[Milsurplus] ABK IFF Puzzle

[J Forster]

Hi Bruce,

Thanks. If the manual turns up, I'd like to chat w/ you about getting a few
pages copied out. Do you remember if the frequency is swept by a motor driven
capacitor located between the chassis? If so, as a kid I had a British unit of
similar electrical design, but radically different implementation.

Best,
-John

================

Mike Morrow wrote:

> Bruce MacMillan <radio at telus.net> wrote:
>
> >This topic was discussed recently on the arc5 mailing list John. I
> >believe it was purposely marked as a receiver only to mislead the other
> >side.
> >
> >"The SCR-595-A IFF was simply a US Navy ABK Mark III IFF, without any
> >Army nomenclature applied to the RT unit.  The SCR-695-A Mark III/G IFF
> >unit was the BC-966-A.  The nameplates of all of these units bore the
> >description of "RADIO RECEIVER" to mislead the other side.  But the USN
> >ABK units also bear USN component numbers starting with "43" which is
> >the component code for a "receiver-transmitter."  Not too consistent
> >or deceptive!"
>
> The quoted text above comes from one of my recent postings.  It's probably
> best to attribute any direct quotes to the original writer, just in case
> someone wants further information from that source or even wishes to say
> that the information is full of crap. :-)
>
> I have a manual for the ABK (and I have an ABK-5 unit), but unfortunately
> I'm in the middle of a move and my 40 linear feet of tech manuals are in
> moving boxes and won't get properly re-organized for some time to come.
> The RF portion of Mark III IFF sets like the ABK was essentially a simple
> receiver that was triggered into oscillation (and therefore transmitted a
> return) upon receipt of an interrogation signal.  The frequency of operation
> swept from 157 to 187 MHz using a capacitor driven by a gear box off of the
> integral dynamotor unit.  The dynamotor also drives the response code keyer.
> Six different response codes could be selected at the pilot's control box.
>
> Some of the IFF gear from WWII is pretty interesting in concept.  Not all
> were receiver-transmitters.  The AN/APX-15 on some B-29s was a signal
> processing amplifier that detected fluctuations in the output from the
> AN/APG-15 S-band tail-gun laying radar set.  The set would warn the operator
> when fluctuations characteristic of reflections from the rotating propellers
> of Japanese aircraft were detected.  Clever and very simple, but I've never
> read any reports of how effective it was.
>
> Mike / KK5F
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