Vietnam era F-4s Q

Guy Alcala wrote:

Buzzer wrote:

On Fri, 08 Aug 2003 08:35:18 GMT, Guy Alcala
wrote:

The AS light on the APR-36/37 was the simple version of the ALR-31 on
the weasel which I think had been around for a couple years.

You're right and I was misremembering. It seems that APR-37 was essentially
the APR-26 with that modification, but that APR-26 itself wasn't improved.
Here's what I've got, from Jenkins' book on the Thud:

"The Air Force also conducted a quick look evaluation of a potential APR-26
replacement in April [1966].

Not to disparage Jenkins, who's done great research on the F-105, but
"potential replacement in April (1966)" doesn't track well with my
experience. I arrived at Korat in May of '66 and at that time the
APR-25/26 was just being initially installed in the operational jets.
We had maybe a dozen airplanes out of 40 or so with the "vector" gear.
Installation of the entire fleet wasn't completed until mid-June. I
hadn't even seen or been briefed on the RHAW gear while in training at
Nellis through April of '66. To be seeking replacement before initial
installation doesn't make any sense.


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. 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. 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."

I'm not a "squeaks and beeps" EW, but here's what I was taught about
the sequence for the SA-2. The initial TDU (Threat Display Unit) light
were for "Lo" indicating a low PRF (pulse recurrence frequency), as
you got lit up with both beams of the Fan Song (Az & El), you got a
"Hi" for high PRF. When missile data upload was taking place, another
frequency was employed (that's where an EW could tell you more) you
got an "Activity" light and when command guidance signals were
received, indicating control signals to the missile airborne, you got
the "Launch" light.

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). 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."

While the "correlate a C-band missile guidance signal to a specific
E-F band signal" tracks with what I said above regarding "launch"
lites, it doesn't equate with what the definition of the AS light was.
The AS (azimuth sector, but colloquially the "aw ****" light) meant
you were illuminated by both the horizontal and elevation beams of the
Fan Song at high PRF. It literally meant that you were the designated
target for that particular missile system. It did NOT relate to a
missile actually being launched.

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

Yes, different frequency bands displayed different strobes. A Fire Can
was a solid strobe, a Fan Song a three dash line, and something else
(CRS strikes here) for an AI (air intercept) radar.

In the high threat arena, the 25/26 was notorious for degenerating
into a big "spider" in the center of the scope.


Ed Rasimus
Fighter Pilot (ret)
***"When Thunder Rolled:
*** An F-105 Pilot Over N. Vietnam"
*** from Smithsonian Books
ISBN: 1588341038

You got most of it correct. Initial acquisition was usually done by SAM in
Low PRF therefore you got a Low light, Switching to High PRF changed the
light to High. If you were in both AZ and EL sectors you got the AS
(Acquisition Sector) light. Launch for the SA-2 was done on acquisition of
additional signals in a two step process. Lights and tones for warning.
Not the most accurate indicator, but the only one we had.

Different strobe types were for frequency differentiation. Can't say more,
besides I forgot the break points. Too many systems in the head since then.

Les
F-4C(WW),D,E,G(WW)/AC-130A/MC-130E EWO (ret)


"Ed Rasimus" wrote in message
...
I'm not a "squeaks and beeps" EW, but here's what I was taught about
the sequence for the SA-2. The initial TDU (Threat Display Unit) light
were for "Lo" indicating a low PRF (pulse recurrence frequency), as
you got lit up with both beams of the Fan Song (Az & El), you got a
"Hi" for high PRF. When missile data upload was taking place, another
frequency was employed (that's where an EW could tell you more) you
got an "Activity" light and when command guidance signals were
received, indicating control signals to the missile airborne, you got
the "Launch" light.

Ed Rasimus wrote:

Guy Alcala wrote:

Buzzer wrote:

On Fri, 08 Aug 2003 08:35:18 GMT, Guy Alcala
wrote:

The AS light on the APR-36/37 was the simple version of the ALR-31 on
the weasel which I think had been around for a couple years.

You're right and I was misremembering. It seems that APR-37 was essentially
the APR-26 with that modification, but that APR-26 itself wasn't improved.
Here's what I've got, from Jenkins' book on the Thud:

"The Air Force also conducted a quick look evaluation of a potential APR-26
replacement in April [1966].

Not to disparage Jenkins, who's done great research on the F-105, but
"potential replacement in April (1966)" doesn't track well with my
experience. I arrived at Korat in May of '66 and at that time the
APR-25/26 was just being initially installed in the operational jets.
We had maybe a dozen airplanes out of 40 or so with the "vector" gear.
Installation of the entire fleet wasn't completed until mid-June. I
hadn't even seen or been briefed on the RHAW gear while in training at
Nellis through April of '66. To be seeking replacement before initial
installation doesn't make any sense.

As noted below, this was the WWIII fit, and they were just starting procurement.
The question was whether they'd confirm
procurement of the APR-26 or go with the HRB-Singer set. Almost no sets of either
type had yet been fitted to trials a/c, and only a few of the APR-25/-26/IR-133 to
the F-100F WWs.

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. 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. 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."

I'm not a "squeaks and beeps" EW, but here's what I was taught about
the sequence for the SA-2. The initial TDU (Threat Display Unit) light
were for "Lo" indicating a low PRF (pulse recurrence frequency), as
you got lit up with both beams of the Fan Song (Az & El), you got a
"Hi" for high PRF.

H'mm that seems a bit off. Normally, fire control sets search at a lower PRF, then
track at a higher one. FWIW, the first available site I could find credits Fan
Song C/E with the following PRFs:

PRF 828-1440 Search. 1656-2880 Trk.

Fan Song B and F would show similar differences in PRF, although the specific
numbers would probably be different. You need the lower PRF for search/acquisition
to eliminate second time around range ambiguity, which also allows you to use
longer (hence more powerful) pulses. But you lose range resolution, so once
detected the radar will normally switch to a higher PRF for tracking (same with the
F-4, btw).

So, Low PRF would indicate general search mode, High PRF would indicate tracking
_somebody_ (at shorter range). That at least would be the case with the APR-25.
While you'd undoubtedly BE in both beams while the radar was tracking you or
someone close to the same LoS (as Marshall mentions in his LB II book, tracking
usually had to done manually after pods arrived), the PRF lights wouldn't be
indicating position in the beam per se, but just the radar PRF, a far simpler
procedure. Location in the beam sweep was a later addition -- That was what the
ALR-31 (and the same or similar circuit in the APR-36, attached to the A/S light)
would do. From the Air & Space article Bob referenced:

"Klimec set out to improve on the existing RHAW system, which only told you that a
SAM was looking, or launching, and gave only a general bearing to the radar source.
At this early stage in anti-radar development, before specially designed missiles
that home in on radar signals were available, the target still had to be visually
acquired and attacked with conventional weapons like rockets, guns, or bombs.

"The Fan Song was one of the first electronic scanning radars--it directed its
energy without having to move its antenna. "The way the Soviets built the Fan Song
was to have [one] radar that tracks both the aircraft and the missile," Klimec
says. "It would scan across 20 degrees and then go off the air, because you had to
shut the radar down in order to preclude any kind of problems with the energy
coming back inside and blowing out equipment--and then it would fly back, come back
on again, and scan 20 degrees, and go off the air."

"The radar cycled several times per second and was directed so that a targeted
aircraft was located at the center of the scan sector, which enabled the missile to
be maneuvered freely inside, while the target was simultaneously tracked by the
radar.

"So it dawned on me that if we could detect when the radar came on, and we could
determine when the aircraft was illuminated on the radar in the main beam, and we
could detect when the radar shut down to fly back, we could calculate the position
of the plane relative to the scan sector," Klimec says. It was known that the Fan
Song took about 100 milliseconds to complete a scan, so if an aircraft was
"painted" by the radar 50 milliseconds after the radar turned on, the aircraft was
in the mid-point of the scan sector. "And the aircraft ordinarily did not get to
the center of the sector unless somebody put him there--and since the tracking scan
system could only track one aircraft to make an intercept on one aircraft, if you
found yourself in the center of the scan sector and you found you stayed there,
then you knew somebody had selected you as a target," he says.

"After design engineers devised equipment to verify Klimec's theory, he began
monitoring the Eglin Fan Song simulator's emissions from the top of a hangar. "I
talked on the phone to the radar site and got them to move it a little bit, and we
verified that we could detect when the radar came on to start the scan, we could
detect when it went off the air, and we could detect when we got the large spike of
energy as the main beam came by," Klimec says. Klimec's innovation eventually
allowed fighter crews to know whether or not they were targets and to take action
only if they were."

So, prior to the ALR-31/APR-36, you might be in one or both beams and getting High
PRF, but not be in the center of the Fan Song sweep because it was actually
targeting some other a/c close to the same angle between the radar and you, leading
to unnecessary maneuvers and high pulse rates. You'd also pick up the L-band
guidance signal, again without necessarily being the target.

When missile data upload was taking place, another
frequency was employed (that's where an EW could tell you more) you
got an "Activity" light and when command guidance signals were
received, indicating control signals to the missile airborne, you got
the "Launch" light.

Right, the guidance used the C-band dish on the left of this picture (the E/F or
G-band tracking antennas are the horizontal and vertical troughs):

http://fas.org/nuke/guide/russia/airdef/fan_song2.jpg



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). 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."

While the "correlate a C-band missile guidance signal to a specific
E-F band signal" tracks with what I said above regarding "launch"
lites, it doesn't equate with what the definition of the AS light was.

I know, you're misinterpreting what I wrote. The A/S and the above mod are two
separate things. Here's what I'm talking about (again from the Air & Space article
Bob pointed out):

"As tactics were developed in the air, field modifications to the Wild Weasel
systems continued on the ground. A key weakness of the equipment was that if
several SAM sites were displayed on the scope and the light that signaled a launch
was illuminated, there was no way to know which site had fired and from which
direction the SAM was coming. "I heard the crews complaining about that," says
Weldon Bauman, who in 1967 was a junior enlisted technician at Takhli. "And I
thought Well, if I knew more about the signal, then maybe we could do something
about it." Bauman became a Wild Weasel legend for devising a system similar to Bob
Klemic's but that sidestepped cumbersome and lengthy procurement procedures and
could be hot-wired into the aircraft in the field immediately. But to do it, he
first needed access to sensitive data about the nature of SAM site radar emissions,
and after convincing an EWO to escort him into the intelligence section, he got the
information he needed. "I sat down and got the real-time data--the same day then
was real time," Bauman says. "I found out what they were seeing and then went back
and designed a circuit and it worked." When activated, Bauman's modification
cleared the scope of all information except for a blip that indicated the launching
site. Tom Wilson, a former F-105 EWO, marveled at Bauman's ingenuity and his
modesty. "This kid had two stripes, and he was so damn smart it was unreal," Wilson
says. "When I asked him how he came up with the mod, he said, "It was real easy.
Just three little parts wired into the line for the scope, and a switch, and it was
done.' "

The AS (azimuth sector, but colloquially the "aw ****" light) meant
you were illuminated by both the horizontal and elevation beams of the
Fan Song at high PRF. It literally meant that you were the designated
target for that particular missile system. It did NOT relate to a
missile actually being launched.

Right, see above.


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

Yes, different frequency bands displayed different strobes. A Fire Can
was a solid strobe, a Fan Song a three dash line, and something else
(CRS strikes here) for an AI (air intercept) radar.

In the high threat arena, the 25/26 was notorious for degenerating
into a big "spider" in the center of the scope.

Thanks. BTW, in the case of say a two-ringer growing to a three, did the strobe
extend in from the periphery, or out from the center? I've always assumed it was
the latter (looking similar to a PPI display), but I've never seen a source I trust
which says which it was.

Thanks,

Guy

Guy Alcala wrote:

Ed Rasimus wrote:

Guy Alcala wrote:

"The Air Force also conducted a quick look evaluation of a potential APR-26
replacement in April [1966].

Not to disparage Jenkins, who's done great research on the F-105, but
"potential replacement in April (1966)" doesn't track well with my
experience. I arrived at Korat in May of '66 and at that time the
APR-25/26 was just being initially installed in the operational jets.

As noted below, this was the WWIII fit, and they were just starting procurement.

OK, WW III was the F-105F. And the elaboration that it was
pre-deployment of the system helps, but it still doesn't make sense to
be seeking a replacement before you've operationally employed the
already purchased equipment. Things were happening fast in EW at that
time, so maybe that's the excuse.


I'm not a "squeaks and beeps" EW, but here's what I was taught about
the sequence for the SA-2. The initial TDU (Threat Display Unit) light
were for "Lo" indicating a low PRF (pulse recurrence frequency), as
you got lit up with both beams of the Fan Song (Az & El), you got a
"Hi" for high PRF.

H'mm that seems a bit off. Normally, fire control sets search at a lower PRF, then
track at a higher one.

So, Low PRF would indicate general search mode, High PRF would indicate tracking
_somebody_ (at shorter range). That at least would be the case with the APR-25.

About ten minutes after that post above, an aging synapse fired and I
recalled that 25/26 didn't really deal with Azimuth/Sector, but the Lo
PRF was search and the Hi PRF was switching to track mode.

So, prior to the ALR-31/APR-36, you might be in one or both beams and getting High
PRF, but not be in the center of the Fan Song sweep because it was actually
targeting some other a/c close to the same angle between the radar and you, leading
to unnecessary maneuvers and high pulse rates. You'd also pick up the L-band
guidance signal, again without necessarily being the target.

When missile data upload was taking place, another
frequency was employed (that's where an EW could tell you more) you
got an "Activity" light and when command guidance signals were
received, indicating control signals to the missile airborne, you got
the "Launch" light.

Right, the guidance used the C-band dish on the left of this picture (the E/F or
G-band tracking antennas are the horizontal and vertical troughs):

http://fas.org/nuke/guide/russia/airdef/fan_song2.jpg

Here's what I'm talking about (again from the Air & Space article
Bob pointed out):

"As tactics were developed in the air, field modifications to the Wild Weasel
systems continued on the ground. A key weakness of the equipment was that if
several SAM sites were displayed on the scope and the light that signaled a launch
was illuminated, there was no way to know which site had fired and from which
direction the SAM was coming. "I heard the crews complaining about that," says
Weldon Bauman, who in 1967 was a junior enlisted technician at Takhli. "---details snipped---

No ****! You bet we were complaining. It was a "good news/bad news"
kind of thing. We were glad the RHAW gave us info, but really wanted
more detail. Discrimination between radars in the saturated
environment of Pack VI was important and knowing where to look in a
split-second to acquire the missile visually was critical to survival.

Thanks. BTW, in the case of say a two-ringer growing to a three, did the strobe
extend in from the periphery, or out from the center? I've always assumed it was
the latter (looking similar to a PPI display), but I've never seen a source I trust
which says which it was.

You are correct. The "origin" of all strobes was the center of the
scope. The strobe extended outward in the direction indicated by the
integration of signal strength from the several antennae on the
aircraft skin. Lot of folks never really broke the code that the
length of strobe (1-ring, 3-ring, etc.) was signal strength not
proximity to the emitter. There was some correlation, but technically
it was strength not range.

In less saturated areas, we could often work a single Fan Song and get
station-passage, just like flying over a VOR. On the nose, on the
nose, then swing to the tail. Good way to find a likely spot to leave
some CBU.


Ed Rasimus
Fighter Pilot (ret)
***"When Thunder Rolled:
*** An F-105 Pilot Over N. Vietnam"
*** from Smithsonian Books
ISBN: 1588341038

Ed Rasimus wrote:

Guy Alcala wrote:

Ed Rasimus wrote:

Guy Alcala wrote:

"The Air Force also conducted a quick look evaluation of a potential APR-26
replacement in April [1966].

Not to disparage Jenkins, who's done great research on the F-105, but
"potential replacement in April (1966)" doesn't track well with my
experience. I arrived at Korat in May of '66 and at that time the
APR-25/26 was just being initially installed in the operational jets.

As noted below, this was the WWIII fit, and they were just starting procurement.

OK, WW III was the F-105F. And the elaboration that it was
pre-deployment of the system helps, but it still doesn't make sense to
be seeking a replacement before you've operationally employed the
already purchased equipment. Things were happening fast in EW at that
time, so maybe that's the excuse.

Yes, they had multiple systems in concurrent development, and were essentially trying everything.

snip

So, Low PRF would indicate general search mode, High PRF would indicate tracking
_somebody_ (at shorter range). That at least would be the case with the APR-25.

About ten minutes after that post above, an aging synapse fired and I
recalled that 25/26 didn't really deal with Azimuth/Sector, but the Lo
PRF was search and the Hi PRF was switching to track mode.

Yeah, I thought you might be conjoining APR-25/-26 with -36/-37.


So, prior to the ALR-31/APR-36, you might be in one or both beams and getting High
PRF, but not be in the center of the Fan Song sweep because it was actually
targeting some other a/c close to the same angle between the radar and you, leading
to unnecessary maneuvers and high pulse rates. You'd also pick up the L-band
guidance signal, again without necessarily being the target.

When missile data upload was taking place, another
frequency was employed (that's where an EW could tell you more) you
got an "Activity" light and when command guidance signals were
received, indicating control signals to the missile airborne, you got
the "Launch" light.

Right, the guidance used the C-band dish on the left of this picture (the E/F or
G-band tracking antennas are the horizontal and vertical troughs):

http://fas.org/nuke/guide/russia/airdef/fan_song2.jpg

Here's what I'm talking about (again from the Air & Space article
Bob pointed out):

"As tactics were developed in the air, field modifications to the Wild Weasel
systems continued on the ground. A key weakness of the equipment was that if
several SAM sites were displayed on the scope and the light that signaled a launch
was illuminated, there was no way to know which site had fired and from which
direction the SAM was coming. "I heard the crews complaining about that," says
Weldon Bauman, who in 1967 was a junior enlisted technician at Takhli. "---details snipped---

No ****! You bet we were complaining. It was a "good news/bad news"
kind of thing. We were glad the RHAW gave us info, but really wanted
more detail. Discrimination between radars in the saturated
environment of Pack VI was important and knowing where to look in a
split-second to acquire the missile visually was critical to survival.

One hopes they gave Bauman a DSM. Rare for enlisted, but not unknown. They gave one to Senior
Chief Radarman Nowell, the senior controller on U.S.S. Chicago in 1972 (aka "The Voice of Red
Crown"), for his controlling of 13 successful interceptions. Admittedly, he was only the second
navy enlisted man to be awarded one, but Bauman's work would seem to be as important. Googling I
see that he's an inductee of the Association of Old Crows Hall of Fame for "Missile
Warning/Launch Circuits."


Thanks. BTW, in the case of say a two-ringer growing to a three, did the strobe
extend in from the periphery, or out from the center? I've always assumed it was
the latter (looking similar to a PPI display), but I've never seen a source I trust
which says which it was.

You are correct. The "origin" of all strobes was the center of the
scope. The strobe extended outward in the direction indicated by the
integration of signal strength from the several antennae on the
aircraft skin. Lot of folks never really broke the code that the
length of strobe (1-ring, 3-ring, etc.) was signal strength not
proximity to the emitter. There was some correlation, but technically
it was strength not range.

Thanks. I knew that that generation of RWRs indicated signal stength rather than range. What was
the problem with crews not being able to grok it? I assume they were told what the strobe length
represented, so was it a cognitive problem in combat, i.e the brain is used to seeing a vector
length represent distance, so they automatically reverted to that under pressure?


In less saturated areas, we could often work a single Fan Song and get
station-passage, just like flying over a VOR. On the nose, on the
nose, then swing to the tail. Good way to find a likely spot to leave
some CBU.

Better you than me, although flying directly overhead is probably fairly safe as you'd be inside
SA-2 minimum range. It's a damned good thing that they didn't have any shorter-ranged SAMs
(co-located with the SA-2s), or I fear you would have only been able to do this once, if that ;-)

Guy

On Sat, 09 Aug 2003 06:05:51 GMT, Guy Alcala
wrote:

As noted below, this was the WWIII fit, and they were just starting procurement.
The question was whether they'd confirm
procurement of the APR-26 or go with the HRB-Singer set. Almost no sets of either
type had yet been fitted to trials a/c, and only a few of the APR-25/-26/IR-133 to
the F-100F WWs.

HRB-Singer set test Apr 66
F-105 weasel test flying Jan 66 Deployed May-Jun 66
F-4 weasel flying sometime before June 66
Didn't find out APR-26 might be faulty until after Jun 66..

Ok. They took a chance with the APR-26 since it was flying and ended
up being wrong..

It might have also been a maintenance thing keeping the 26 over the
Singer. Simple transistors against (maybe) multi-layer ic type boards
that would require extensive tech rep or depot support.

H'mm that seems a bit off. Normally, fire control sets search at a lower PRF, then
track at a higher one. FWIW, the first available site I could find credits Fan
Song C/E with the following PRFs:

PRF 828-1440 Search. 1656-2880 Trk.

Makes me wonder now. Did they "flip a switch" and double the prf? Or
did the prf double because the aircraft was in the box and two beams
at the same prf were hitting?

"The Fan Song was one of the first electronic scanning radars--it directed its
energy without having to move its antenna. "The way the Soviets built the Fan Song

Tech school memory - Lewis scanner. English name for soviet radar
scanning? English name for U.S. developed radar technique in late
40's-50's. Not further developed by U.S. because it was inefficient
use of power.

Thanks. BTW, in the case of say a two-ringer growing to a three, did the strobe
extend in from the periphery, or out from the center? I've always assumed it was
the latter (looking similar to a PPI display), but I've never seen a source I trust
which says which it was.

Center going out as you got closer to source.If I remember right on
the APR-25 a really strong signal would cause the signal to go to the
outer edge of the scope and curl back in a loop. Lots of strong
signals - lots of loops..

Factory schools on equipment were interesting. Fresh off the drawing
boards and the solder still cooling.G
APR-36/37
Student - What does that circuit do?
Instructor - I don't know.
Student - What does the engineer that designed it say?
Instructor - He can't remember..

Buzzer wrote:

Center going out as you got closer to source.If I remember right on
the APR-25 a really strong signal would cause the signal to go to the
outer edge of the scope and curl back in a loop. Lots of strong
signals - lots of loops..

See my previous regarding proximity vs signal strength. Sure, as you
get closer, you get a stronger signal, but the parameter was strength.

No looping. The strobe went out to the limit of the display, that's
all.


Ed Rasimus
Fighter Pilot (ret)
***"When Thunder Rolled:
*** An F-105 Pilot Over N. Vietnam"
*** from Smithsonian Books
ISBN: 1588341038

On Sat, 09 Aug 2003 16:12:58 GMT, Ed Rasimus
wrote:

Buzzer wrote:

Center going out as you got closer to source.If I remember right on
the APR-25 a really strong signal would cause the signal to go to the
outer edge of the scope and curl back in a loop. Lots of strong
signals - lots of loops..

See my previous regarding proximity vs signal strength. Sure, as you
get closer, you get a stronger signal, but the parameter was strength.

Probably why I set the sensitivity of each freq band to x db that
would give y deflection. Instead of x number of yds from sam site
would give a certain deflection since not all sam sites put out the
same exact power?G

No looping. The strobe went out to the limit of the display, that's
all.

Must have looped on the bench due to the loopy technician.

Buzzer wrote:

On Sat, 09 Aug 2003 16:12:58 GMT, Ed Rasimus
wrote:

Buzzer wrote:

Center going out as you got closer to source.If I remember right on
the APR-25 a really strong signal would cause the signal to go to the
outer edge of the scope and curl back in a loop. Lots of strong
signals - lots of loops..

See my previous regarding proximity vs signal strength. Sure, as you
get closer, you get a stronger signal, but the parameter was strength.

Probably why I set the sensitivity of each freq band to x db that
would give y deflection. Instead of x number of yds from sam site
would give a certain deflection since not all sam sites put out the
same exact power?G

No looping. The strobe went out to the limit of the display, that's
all.

Must have looped on the bench due to the loopy technician.

I have a vague memory of seeing a photo or film of an APR-25 display
somewhere, which IIRR did loop. Maybe this was film of a bench test, and
you'd never get close enough to a site in flight for the signal strength to
be great enough for that to happen?

Guy

Guy Alcala wrote in message ...
Buzzer wrote:

On Sat, 09 Aug 2003 16:12:58 GMT, Ed Rasimus
wrote:

Buzzer wrote:

Center going out as you got closer to source.If I remember right on
the APR-25 a really strong signal would cause the signal to go to the
outer edge of the scope and curl back in a loop. Lots of strong
signals - lots of loops..

See my previous regarding proximity vs signal strength. Sure, as you
get closer, you get a stronger signal, but the parameter was strength.

Probably why I set the sensitivity of each freq band to x db that
would give y deflection. Instead of x number of yds from sam site
would give a certain deflection since not all sam sites put out the
same exact power?G

No looping. The strobe went out to the limit of the display, that's
all.

Must have looped on the bench due to the loopy technician.

I have a vague memory of seeing a photo or film of an APR-25 display
somewhere, which IIRR did loop. Maybe this was film of a bench test, and
you'd never get close enough to a site in flight for the signal strength to
be great enough for that to happen?

And now I have confirmation of APR-25 looping. I finally got my hands
on a copy of Thornborough's "Iron Hand", which is indeed chock full of
good stuff as Ed said. In it there's an account by an F-4CWW guy of a
mission on Night Four of LB II, which I had previously read in the 2nd
edition of Thornborough's "The Phantom Story", by Bill McLeod (and
which have been the vague memory that was nagging me, rather than a
photo or film):

"The EC-121 called us about a minute before the last B-52 was clear
and told us that we were the last a/c remaining in the target area,
and made it plain that they thought that we should get out of there.
As soon as I answered the EC-121, Red Crown came up on Guard and
announced 'SAM, SAM, SAM!', which was followed by Don's calm voice
from the rear cockpit saying 'We're the target'.

"The APR-25/-26 lit up with a classic full-system launch with a strobe
that went clear to the edge of the scope and part way back to the
center, the launch audio started screaming and two SAMs lifted off at
our eleven o'clock. I kicked my left rudder to put hte strobe and
missiles at twelve o'clock and fired both Shrikes at the guy, then
rolled into an inverted slice and pulled the a/c towards the ground
with at least 4-5g. As soon as the nose was well down, I rolled out
part of the bank and reacquired the two SAMs over the canopy rail."
rest of account snipped

I don't know if the APR-25 was adjusted incorrectly so that it was
oversensitive, or if it was operating correctly and they were really
that close/the signal was that strong. McLeod mentions that they'd
been orbiting at about 18,000 feet, and his account implies that they
were offset several miles from the site at the time the SA-2s were
fired.

Guy