[ARC5] Re: [Milsurplus] History of Ham Mods: Opinions?

[Bob Macklin]

FWIW:

In the mid 50's I worked on the USAF Mark VII weapon. It had 2 radar
altimeters. 2 barometric altimeters. and 2 mechanical timers.

The last item was a CONTACT fuse.

Bob Macklin
K5MYJ
Seattle, Wa,
"Real Radios Glow in the Dark"
----- Original Message ----- 
From: "Mike Hanz" <AAF-Radio-1 at aafradio.org>
To: <cosmoline at aa4rm.ba-watch.org>
Cc: "ARC5" <arc5 at mailman.qth.net>; "Milsurplus"
<milsurplus at mailman.qth.net>; "Thomas Adams" <quixote2 at ix.netcom.com>
Sent: Monday, June 16, 2008 9:55 AM
Subject: Re: [ARC5] Re: [Milsurplus] History of Ham Mods: Opinions?


> Marty Reynolds wrote:
>
> >>To elaborate, there were four of the APS-13s in each weapon, in both
> >>Little Boy and Fat Man - all having a different set of frequencies to
> >>avoid interference.. There was an averaging system to account for spin
> >>of the bomb casing in flight. The weaponeer could have switch selected
> >>an alternate set of frequencies if Jacob Beser (the RCM officer) had
> >>identified potential interference.
> >>
> >
> >Mike I've read the 'averaging' was that 3 of four sets had to agree on
> >altitude.  Provoking.  I've wondered just how with VT electronics.
> >
>
> It was a little more complicated than that, Marty.  Remember that this
> weapon was built with WWII electronics, and they often failed in
> flight.  The task was to design a weighted system that would tolerate
> the failure of any two of the APS-13s while ensuring that the fuse would
> operate properly with any remaining two, so two had to agree that it was
> at the proper height, not three.  Their decision logic was used
> elsewhere in the weapon - called "series/parallel" logic, but the
> electronics used delay lines and gated times to detect coincidence.  The
> four APS-13s were turned on by a set of six redundant barometric
> switches that "voted" their output in a similar way to turn on power
> when the weapon reached 17,000 feet.  This also reduced the ECM exposure
> time of the weapon.  There was no backup fusing system, at least for
> Little Boy.  Tests had shown that the gun weapon was essentially
> "self-assembling" on contact with the ground, so that was the backup
> plan.  The whole process was started by a set of eight mechanical timers
> in a "Clock Box" that initially limited anything happening for 15
> seconds after it left the bomb bay...they were worried about radar
> reflections from the B-29 triggering the weapon in the event there were
> multiple failures of the baro switches and radars.
>
> 73,
> Mike
>
>
> _______________________________________________
> ARC5 mailing list
> ARC5 at mailman.qth.net
> http://mailman.qth.net/mailman/listinfo/arc5
>