pt@dciem (Paul Tomblin) (03/13/91)
From: cognos!geovision!pt@dciem (Paul Tomblin)
The recent discussions of Air to Air antiradiation missles, fighter radars
and AWACS brought back an old memory.
I remember reading some time ago that the F-14 could turn off it's radar,
and the pilot and back seat guy would still see stuff on their radar
screens from the other radars around, such as the carrier, the AWACS, and
other fighters with radars on. At the time, I sort of assumed that there
would have to be some sort of wireless data link, but now I'm wondering it
that is correct, or if what the article really meant was that the F14 radar
just passively used the reflections from other radars.
The stated reason for doing this was to not give away your postion as you
closed in to a target. Can you launch phoenix or whatever with the radar
off, or would you sneak up behind someone and scare the bejeezus out of them
when you suddenly lit them up seconds before you launch your missles?
(I know turning off your radar in the ACM game (from comp.sources.x)
can be quite effective if your target is busy engaging someone else, but if
he's busy looking out he will probably see you before you get close enough
to do damage. Now if someone would just add AWACS to that game...)
--
Paul Tomblin, Department of Redundancy Department. ! My employer does
The Romanian Orphans Support Group needs your help, ! not stand by my
Ask me for details. ! opinions....
pt@geovision.gvc.com or {cognos,uunet}!geovision!pt ! Me neither.stevew@wyse.wyse.com (Steve Wilson x2580 dept303) (03/18/91)
From: stevew@wyse.wyse.com (Steve Wilson x2580 dept303) In article <1991Mar12.232220.29870@cbnews.att.com> cognos!geovision!pt@dciem (Paul Tomblin) writes: >I remember reading some time ago that the F-14 could turn off it's radar, >and the pilot and back seat guy would still see stuff on their radar >screens from the other radars around, such as the carrier, the AWACS, and >other fighters with radars on. At the time, I sort of assumed that there >would have to be some sort of wireless data link, but now I'm wondering it >that is correct, or if what the article really meant was that the F14 radar >just passively used the reflections from other radars. Naaaaah! The basic way a radar works is that you send out a pulse and measure the time until you see the reflection. How can you do this if you aren't the emitter(taking into account that we're talking about the speed of light here and nano-seconds count! ) If such is the case then it is done via data links. It would be quite reasonable for something that is already making alot of radio noise like AWACS to also send out an encrypted data stream in the clear that the planes received and re-displayed to the weapons officer. Steve Wilson
gary@gatech.edu (Gary Coffman) (03/18/91)
From: ke4zv!gary@gatech.edu (Gary Coffman) In article <1991Mar12.232220.29870@cbnews.att.com> cognos!geovision!pt@dciem (Paul Tomblin) writes: > >I remember reading some time ago that the F-14 could turn off it's radar, >and the pilot and back seat guy would still see stuff on their radar >screens from the other radars around, such as the carrier, the AWACS, and >other fighters with radars on. At the time, I sort of assumed that there >would have to be some sort of wireless data link, but now I'm wondering it >that is correct, or if what the article really meant was that the F14 radar >just passively used the reflections from other radars. While you can get a bearing from passive reflections, I don't see how you could get range or closing speed information without tight coordination with the illuminating radar. It's necessary to know the precise timing and frequency of the particular radar pulse you are receiving to derive range and doppler information. It is conceivable that, if you are between the illuminating radar and the target, you could sample the pulse as it passes you and recover the information necessary to process the reflection. That would seem to be a relatively unlikely situation however. Gary
daveg@tiberius.clearpoint.com (Dave Goldblatt) (03/20/91)
From: daveg@tiberius.clearpoint.com (Dave Goldblatt)
In article <1991Mar18.135333.19904@cbnews.att.com> stevew@wyse.wyse.com (Steve Wilson x2580 dept303) writes:
From: stevew@wyse.wyse.com (Steve Wilson x2580 dept303)
Naaaaah! The basic way a radar works is that you send out a pulse
and measure the time until you see the reflection. How can you do
this if you aren't the emitter(taking into account that we're talking
about the speed of light here and nano-seconds count! ) If such is
the case then it is done via data links. It would be quite reasonable
for something that is already making alot of radio noise like AWACS
to also send out an encrypted data stream in the clear that the planes
received and re-displayed to the weapons officer.
This is what the F-14 does. It has the ability to receive radar information
from an E-2C in the region, and thus "run silent". :-) Very convienient
when the 'Cat is skimming the wavetops sneaking up on someone!
I don't think you can have it both ways at the same time, however; it's
an either/or situtation.
-dg-rh@craycos.com (Robert Herndon) (03/22/91)
From: rh@craycos.com (Robert Herndon) Since the original article <1991Mar12.232220.29870@cbnews.att.com> mentioning that he thought an F-14 could turn off its radar and still see stuff on its radar screens from all the other radars around, I have seen two apparently knee-jerk "nope, can't be done" responses, and no positive responses. While certainly the task would be non-trivial, it is certainly not impossible, either, although the F-14's radar proper might not be running the radar screen. Such an ability would be most useful for many reasons. First, it means that most aircraft in a mission could maintain radio silence. This would help deny the enemy passively obtainable information on how many planes the flight contains, and what kind of planes the flight has (if planes other than the F-14 can also do this). Second, radar & ECM take power. Why waste it, even if you do have lots? ECM in particular requires pods which normally generate their own power from the airstream (read "drag"). Third, though there are probably other solutions for this, why clutter up the spectrum so much with every aircraft's radar? It is that much more junk the radar and ECM systems must notice and decide to ignore. As to how it can be done, I'm sure there are E&M, radar, and ECM persons who are much more familiar than I on this topic, but: 1) Every combat aircraft these days has multiple receiver antennas. Timing information correlated from three on a signal source gives notice and bearing, which in a dogfight situation is 80% of the battle. (viz. "Modern Air Combat"; in 80% of all fighter-fighter kills, the victim is taken unaware; only 20% occur after initial engagement has failed to produce a kill.) 2) If the emitter's characteristics are known to the receiver, then much more could be gleaned. If the emitter's frequency and velocity are known, doppler analysis should provide rate of closure; if its strength & relative position are known, then the strength of the reflection can provide approximate range/size information. It seems that if all characteristics of the emitter are known, then anything the radar can normally ascertain should be ascertainable. It also seems like there are lots of tricks that can be played to ensure that friendlies know emitter characteristics while unfriendlies don't; e.g., slave radar frequency-scan to the IFF transponder codes, so that friendlies can reliably ascertain information about the emitter, etc. Anyone with more knowledge care to comment? -- Robert Herndon -- not speaking officially for Cray Computer. Cray Computer Corporation 719/540-4240 1110 Bayfield Dr. rh@craycos.com Colorado Springs, CO 80906 "Ignore these three words."
henry@zoo.toronto.edu (Henry Spencer) (03/22/91)
From: henry@zoo.toronto.edu (Henry Spencer) >From: stevew@wyse.wyse.com (Steve Wilson x2580 dept303) >>... or if what the article really meant was that the F14 radar >>just passively used the reflections from other radars. > >Naaaaah! The basic way a radar works is that you send out a pulse >and measure the time until you see the reflection. How can you do >this if you aren't the emitter(taking into account that we're talking >about the speed of light here and nano-seconds count! ) You can get quite good radar information if you know exactly where the emitter is and when it is sending out pulses. This is called "bistatic radar" and has been a research topic for quite some time. It's harder than conventional radar but there is nothing impossible about it. I don't believe it is actually in use, however; in the case mentioned, I believe the F-14s are getting the story by datalink from radar aircraft. -- "[Some people] positively *wish* to | Henry Spencer @ U of Toronto Zoology believe ill of the modern world."-R.Peto| henry@zoo.toronto.edu utzoo!henry
scott@graft.Berkeley.EDU (Scott Silvey) (03/22/91)
From: scott@graft.Berkeley.EDU (Scott Silvey) daveg@tiberius.clearpoint.com (Dave Goldblatt) writes: |> From: stevew@wyse.wyse.com (Steve Wilson x2580 dept303) |> |> If such is |> the case then it is done via data links. It would be quite reasonable |> for something that is already making alot of radio noise like AWACS |> to also send out an encrypted data stream in the clear that the planes |> received and re-displayed to the weapons officer. |> |> This is what the F-14 does. It has the ability to receive radar information |> from an E-2C in the region, and thus "run silent". :-) Very convienient |> when the 'Cat is skimming the wavetops sneaking up on someone! Interesting ... how is this done? Is it just directional information? Is this a current tactic for F-14's (terrain-level flight)?! I always thought F-14's much prefered high-altitudes except, perhaps, when attempting to avoid radar missiles. The data-link concept that Steve Wilson mentions above is currently being developed for the navy. AirForce AWACS already employ something along these lines. The idea is to enable fighters to see everything the ships and AWACS can see without having to emit radar signals themselves. The data encryption is done through an indecipherable spread-spectrum signal. I think the Marines want it too, but I'm not sure what radar equipped aircraft they use other than FA-18's. /-----------------------------------------------------------------------------\ | Scott Silvey | Ronald Reagan to surgeons in emergency ward after | | scott@xcf.berkeley.edu | being shot: | | | | | Flames to /dev/null | "Please tell me you're Republicans." | \-----------------------------------------------------------------------------/
norton@manta.nosc.mil (Scott Norton) (03/25/91)
From: norton@manta.nosc.mil (Scott Norton) [Please watch the amount of quoting; I've edited out 15 lines of unnecessary intro from two previous articles. This sort of thing is very time-consuming, so I'd appreciate it greatly if everyone can exercise discretion when quoting. -- CDR] There is a technique called bistatic radar, where the transmitter and receiver are not in the same place. It's not easy, particularly if you want accurate range AND bearing. I recall the phrase "pulse-chasing" to describe the problem of pointing your receive antenna at the transmitted pulse as it speeds along. But if you can tolerate some losses due to looking occasionally in the wrong direction, or from a large beamwidth, it is do-able. But I can tell you that the F-14 has a data link called Link-4A, that allows the E-2C or ship controller to send targets and orders to the F-14. Link-4A is also used for automatic carrier landings, flying the aircraft down to the deck (the last command given is a full-throttle and climb, in case the tailhook misses a wire. My office is now working on the follow-on data link, Link-16, as part of the Joint Tactical Information Distribution System. LT Scott A. Norton, USN <norton@NOSC.MIL> JTIDS Ship Integration Officer