On Fri, 08 Aug 2003 21:09:57 GMT, Guy Alcala
wrote:

"The Air Force also conducted a quick look evaluation of a potential APR-26
replacement in April [1966]. An HRB-Singer 934-1B missile warning receiver
was installed in 62-4416 and test flown at the Sanders facility, which had a
Fan Song missile guidance simulator not available at Eglin.

And there we were in June 1966 sitting on the ground at Eglin with the
F-4C WWIV waiting for range time on the SADS and cancelling for rain
when another site was available. Here I thought and was led to believe
the Eglin SADS was the only one available..

The 934-1B
differed from the APR-26 in that it analyzed the modulation characteristics of
the C-band [i.e. radar L-band] guidance signal to differentiate between SA-2
missile activity and missile launch modes, while the APR-26 simply looked for
an abrupt amplitude increase. The HRB-Singer set performed well, but the Air
Force was already committed to a large APR-26 procurement and saw no
compelling reason to buy another system to perform the same function.

Shame they didn't have to stand up before a couple hundred pilots and
say we see no compelling reason to give you a better system that would
give you more confidence and might save your life! Welcome to the
realities of the Vietnam War..

Only
after the Wild Weasel III F-105s were in combat was it learned that the
APR-26's design was based on possibly faulty intelligence regarding the
amplitude increase. This led to numerous incidents of flase lower
threat-level 'activity' indications when 'missile launch' should have been
displayed. The APR-26 was later modified to analyze the guidance signal and
the improved sets redesignated APR-37."

The original story I heard in June 1966 at the APR-25/26 class at
Keesler and later from the tech reps was the missile guidance signal
was feed into a dummy load. That caused the Activity Light to come on.
Then when they launched and switched to active guidance at a higher
power the Launch Light came on. Another variation on that was they
interrogated the missiles at low power before launch that gave the
Activity and then went high power to guide giving Launch light. No
mention at all of how the missile was quided until I took the
APR-36/37 factory course in 1968 at ATI/ITEK in Palo Alto, CA. Here
they went into the guidance pulse train and what the APR-37 looked at.
They talked like this was recent intel and here the info had been
around for years.

This was separate from the QRC-317 SEE-SAMS/QRC-317A ALR-31, which was
eventually incorporated into the APR-25 ('SPOT SAM') and turned it into the
APR-36 (the 'centered in both beams' A/S light).

I'm not sure how the ALR-31 was tied into everything else on the
F-105. I saw the circuit boards with a zillion surface mounts ICs on
them and I was in awe. It made the APR-26 and 36 look like crystal
radios. I remember a control box on the left rear panel. Little meter
about 3/4 inch across that indicated beams centered when the needle
centered sticking up in the center. How anyone could see the thing
while flying was beyond me.

Jenkins, further on his his
section on the Weasels, also seems to mention the same mod you call the
'Bowman', although not by name. The description certainly fits:

"A separate modification provided the capability to correlate a C-band missile
guidance signal received by the APR-26 to a specific E-F band signal displayed
on the APR-25 azimuth indicator."

I've seen the explanation of the mod somewhere on the net or in a
book. I can't find it now on the net, but I might have it saved to a
CD. Bowman might not be the right spelling, but sounds close to that.
He was an airman at Korat ECM shop when he got the idea. He was kind
of a legend when I got to Korat in Nov 1968. Went on to work for
ATI/ITEK..

BTW, how was this displayed by the strobe? I've seen references elsewhere to
dashed versus solid lines or something similar, but nothing authoritative.

I don't remember what the article said. If it worked during self-test
on the weasels I don't remember seeing it. Flashed the strobe on and
off is as close as I can get.