Singapore down selects three fighters...

On Fri, 17 Oct 2003 23:57:18 -0600, Scott Ferrin wrote:
On Sat, 18 Oct 2003 05:13:12 +0100, ess (phil
hunt) wrote:

On Fri, 17 Oct 2003 23:49:37 GMT, Thomas Schoene wrote:
"phil hunt" wrote in message
rg
On Thu, 16 Oct 2003 13:14:32 -0600, Scott Ferrin
wrote:

That's assuming the Typhoon can detect an LPI radar.

What's that, and how is it different from other radars?

LPI = Low probability of intercept. Usually a psuedo-random spread-spectum
signal that looks like random noise to a typical radar warning receiver.

Do you (or anyone else) have any estimate on how effective this is?

Here's something from Gulf War 1. In the book Gulf War Debrief by
Airtime Publishing they were interviewing a Tomcat pilot. He made the
comment that whenever the Iraqis detected a Tomcat's radar they'd
split but they never seemed to react to the F-15s (F-15s got the
majority of the kills, Tomcats got a chopper I think). Later I read
that the F-15s that went to the Gulf had LPI radars.

That suggests to me that the radars that Iraq had in 1991 counldn't
detect LPI radars. However, Iraq didn't have the best radars in the
world not even then, and the electronics industry is more advanced
today than it was (12 years is roughly 6-8 doublings of
performance/price, according to Moore's law). How effective would a
modern LPI radar be against an adversary using detectors which are
roughly as sensitive? Bear in mind that it's output signal cannot
truely look like random noise (it must be stronger, or the receiver
wouldn't be able to do anything useful with it). Also, the signal
reaching the receiver will be billions of times weaker than the
signal reaching the target. It therefore follows that the signal
reaching the target *at the relevant frequencies* will be billions
of times stronger than background random noise.

I suppose the question I'm asking amounts to: assuming equal
technology on both sides, can radar signals (from an aircraft radar,
or ground-based radar) be detected by an aqdversary (e.g. either an
aircraft, or anti-radiation missile)? Obviously when there's a wide
technology disparity, the answer to the question becomes most
obvious.

BTW, does anyone know of a good web resource on radars? (Most of the
stuff I can find from Google is a bit basis).

--
"It's easier to find people online who openly support the KKK than
people who openly support the RIAA" -- comment on Wikipedia
(My real email address would be if you added 275
to it and reversed the last two letters).

On Sun, 19 Oct 2003 03:57:04 -0400, John Keeney wrote:

"phil hunt" wrote in message
...

LPI = Low probability of intercept. Usually a psuedo-random
spread-spectum
signal that looks like random noise to a typical radar warning receiver.

Do you (or anyone else) have any estimate on how effective this is?

I don't know for a demonstrated (to me) fact, but in theory, it's danged
good.
Current LPI radar is one that has been adapted to spread spectrum technology
which works well in radios and is hard to direction find against: good clues
that it can be made to work as radar and is hard to intercept.

Anti-radiation missiles such as HARM or ALARM can detect radars. Can
they only detect older radars, or would they have some usefulness
against LPI radars too?

--
"It's easier to find people online who openly support the KKK than
people who openly support the RIAA" -- comment on Wikipedia
(My real email address would be if you added 275
to it and reversed the last two letters).

"phil hunt" wrote in message
. ..
On Sun, 19 Oct 2003 03:57:04 -0400, John Keeney
wrote:

"phil hunt" wrote in message
...

LPI = Low probability of intercept. Usually a psuedo-random
spread-spectum
signal that looks like random noise to a typical radar warning
receiver.

Do you (or anyone else) have any estimate on how effective this is?

I don't know for a demonstrated (to me) fact, but in theory, it's danged
good.
Current LPI radar is one that has been adapted to spread spectrum
technology
which works well in radios and is hard to direction find against: good
clues
that it can be made to work as radar and is hard to intercept.

Anti-radiation missiles such as HARM or ALARM can detect radars. Can
they only detect older radars, or would they have some usefulness
against LPI radars too?

From what I've read around the web, ALARM has just underwent a seeker
modification that can cope with any known radar transmitter. Whether that
includes LPI etc, I don't know, and doubt it'll be published for some time?

On Sun, 19 Oct 2003 07:01:01 GMT, Guy Alcala
wrote:

phil hunt wrote:

On Thu, 16 Oct 2003 13:14:32 -0600, Scott Ferrin wrote:
[regarding the F-35]
Weight and apparently they think the big wing isn't necessary. Weight
is the main issue for the STOVL version.

That makes sense.

To be specific, the navy version has the most fuel and is thus the heaviest
version, but it needs a larger wing (adding weight again) to make a carrier
approach at a sufficiently slow speed. The extra weight naturally decreases
performance in other areas, as well as boosting the cost and complexity (it
folds). If you don't need it, why pay for it or haul it around? Some countries
(e.g., Australia) may well want/require the extra range, but ideally would prefer
to have the larger wing in a non-folding version. Since they'd likely have to
foot the bill for the development and production of that all by themselves, it's
unlikely to happen.

You have to keep stealth in mind. The Typhoon likely wouldn't get to
USE it's superior manueverability (assuming it will have it).

If the F-35 is using its radar, the Typhoon will probably be able to
detect it. If neither plane is using radar, there is no advantage to
stealth.

It also assumes that the a/c aren't getting any info from offboard sensors, which
is increasingly unlikely. Stealth matters, especially for BVR. Depending on the
particular situation, it may or may not be more important than other factors. In
the situation you describe above, it would matter a lot.

Guy

The CTOL version does not have STOVL capabilities, so weight is no as
much of an issue.

Al Minyard

"phil hunt" wrote in message


BTW, does anyone know of a good web resource on radars? (Most of the
stuff I can find from Google is a bit basis).

If you don't mind some math, I'd look at EW 1010 on the Journal of
Electronic Defense website. You'll have to register, but it's easily worth
it. It will give you a fairly good tchnical overview or radars, EW systems,
electro-optics, etc.

http://www.jedonline.com/default.asp?func=ew101

In their discussion of LPI radar, they talk about Random Signal Radars,
which really do use a random (not even pseudo-random) signal. It works
because the emitter keeps a copy of the signal it sent and can compare it to
the time-late return and extract a useful signal. The RWR can't do that
nearly as easily because it doesn't know what was sent. So for an equal
level of technology, the radar wins.

--�
Tom Schoene Replace "invalid" with "net" to e-mail
"If brave men and women never died, there would be nothing
special about bravery." -- Andy Rooney (attributed)

On Sun, 19 Oct 2003 03:58:21 -0400, "John Keeney"
wrote:


"Scott Ferrin" wrote in message
.. .
On Sat, 18 Oct 2003 05:13:12 +0100, ess (phil
hunt) wrote:

On Fri, 17 Oct 2003 23:49:37 GMT, Thomas Schoene
wrote:
"phil hunt" wrote in message
g
On Thu, 16 Oct 2003 13:14:32 -0600, Scott Ferrin
wrote:

That's assuming the Typhoon can detect an LPI radar.

What's that, and how is it different from other radars?

LPI = Low probability of intercept. Usually a psuedo-random
spread-spectum
signal that looks like random noise to a typical radar warning receiver.

Do you (or anyone else) have any estimate on how effective this is?


Here's something from Gulf War 1. In the book Gulf War Debrief by
Airtime Publishing they were interviewing a Tomcat pilot. He made the
comment that whenever the Iraqis detected a Tomcat's radar they'd
split but they never seemed to react to the F-15s (F-15s got the
majority of the kills, Tomcats got a chopper I think). Later I read
that the F-15s that went to the Gulf had LPI radars.

I had not heard that, do remember a source?



Yeah. It was one of the more recent issues of either Airpower Review
(the Blue publication that has since been discontinued) or Internation
Airpower Review (the silver one) by Airtime Publishing. Sorry I
can't be more specific but they're boxed up and in storage. Basically
it said that around the time of the first gulf war F-15Cs were being
upgraded with the capability and then when the war started (or the
buildup I guess) they were the ones that got sent.

On Sun, 19 Oct 2003 07:01:01 GMT, Guy Alcala
wrote:

phil hunt wrote:

On Thu, 16 Oct 2003 13:14:32 -0600, Scott Ferrin wrote:
[regarding the F-35]
Weight and apparently they think the big wing isn't necessary. Weight
is the main issue for the STOVL version.

That makes sense.

To be specific, the navy version has the most fuel and is thus the heaviest
version, but it needs a larger wing (adding weight again) to make a carrier
approach at a sufficiently slow speed. The extra weight naturally decreases
performance in other areas, as well as boosting the cost and complexity (it
folds). If you don't need it, why pay for it or haul it around? Some countries
(e.g., Australia) may well want/require the extra range, but ideally would prefer
to have the larger wing in a non-folding version. Since they'd likely have to
foot the bill for the development and production of that all by themselves, it's
unlikely to happen.

You have to keep stealth in mind. The Typhoon likely wouldn't get to
USE it's superior manueverability (assuming it will have it).

If the F-35 is using its radar, the Typhoon will probably be able to
detect it. If neither plane is using radar, there is no advantage to
stealth.

It also assumes that the a/c aren't getting any info from offboard sensors, which
is increasingly unlikely. Stealth matters, especially for BVR. Depending on the
particular situation, it may or may not be more important than other factors. In
the situation you describe above, it would matter a lot.

Guy


Any idea why no vectoring nozzle on the A and C? With both PW and GE
having tested round ones it seems like a no brainer.

On Sun, 19 Oct 2003 19:07:01 GMT, Thomas Schoene wrote:
"phil hunt" wrote in message
rg

BTW, does anyone know of a good web resource on radars? (Most of the
stuff I can find from Google is a bit basis).

If you don't mind some math, I'd look at EW 1010 on the Journal of
Electronic Defense website. You'll have to register, but it's easily worth
it. It will give you a fairly good tchnical overview or radars, EW systems,
electro-optics, etc.

http://www.jedonline.com/default.asp?func=ew101

This looks useful, thanks.

In their discussion of LPI radar, they talk about Random Signal Radars,
which really do use a random (not even pseudo-random) signal. It works
because the emitter keeps a copy of the signal it sent and can compare it to
the time-late return and extract a useful signal. The RWR can't do that
nearly as easily because it doesn't know what was sent.

Indeed it doesn't. But, OTOH, it does have a *much* more powerful
signal to work with.


--
"It's easier to find people online who openly support the KKK than
people who openly support the RIAA" -- comment on Wikipedia
(Email: , but first subtract 275 and reverse
the last two letters).

"phil hunt" wrote in message
. ..
On Sun, 19 Oct 2003 03:57:04 -0400, John Keeney
wrote:

"phil hunt" wrote in message
...

LPI = Low probability of intercept. Usually a psuedo-random
spread-spectum
signal that looks like random noise to a typical radar warning
receiver.

Do you (or anyone else) have any estimate on how effective this is?

I don't know for a demonstrated (to me) fact, but in theory, it's danged
good.
Current LPI radar is one that has been adapted to spread spectrum
technology
which works well in radios and is hard to direction find against: good
clues
that it can be made to work as radar and is hard to intercept.

Anti-radiation missiles such as HARM or ALARM can detect radars. Can
they only detect older radars, or would they have some usefulness
against LPI radars too?

Anti-radiation missiles are in the same boat as any other DFing receiver,
the work on the same principles as other radio receivers, not magic.

Scott Ferrin wrote in message . ..
On Sun, 19 Oct 2003 07:01:01 GMT, Guy Alcala
wrote:

phil hunt wrote:

On Thu, 16 Oct 2003 13:14:32 -0600, Scott Ferrin wrote:
[regarding the F-35]
Weight and apparently they think the big wing isn't necessary. Weight
is the main issue for the STOVL version.

That makes sense.

To be specific, the navy version has the most fuel and is thus the heaviest
version, but it needs a larger wing (adding weight again) to make a carrier
approach at a sufficiently slow speed. The extra weight naturally decreases
performance in other areas, as well as boosting the cost and complexity (it
folds). If you don't need it, why pay for it or haul it around? Some countries
(e.g., Australia) may well want/require the extra range, but ideally would prefer
to have the larger wing in a non-folding version. Since they'd likely have to
foot the bill for the development and production of that all by themselves, it's
unlikely to happen.

You have to keep stealth in mind. The Typhoon likely wouldn't get to
USE it's superior manueverability (assuming it will have it).

If the F-35 is using its radar, the Typhoon will probably be able to
detect it. If neither plane is using radar, there is no advantage to
stealth.

It also assumes that the a/c aren't getting any info from offboard sensors, which
is increasingly unlikely. Stealth matters, especially for BVR. Depending on the
particular situation, it may or may not be more important than other factors. In
the situation you describe above, it would matter a lot.

Guy


Any idea why no vectoring nozzle on the A and C? With both PW and GE
having tested round ones it seems like a no brainer.

I believe the decision was based upon cost, weight, and need; not
including one is cheaper, lighter, and since the primary role is
strike, not required.

Brooks