Raptor - invisible to AWACS?

Anything goes, as long as it is about the Lockheed Martin F-22 Raptor
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popcorn

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Unread post07 Apr 2011, 06:26

Makes one wonder how stealth aircraft with directional data links (eg. IFDL, MADL) know which direction to aim their transmissions.. will appreciate any hint how this would work. :whistle: :whistle:
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SpudmanWP

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Unread post07 Apr 2011, 06:49

The members of the flight are in constant contact (via datalinks) and are updated to each others location.
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Unread post07 Apr 2011, 09:24

SpudmanWP wrote:The members of the flight are in constant contact (via datalinks) and are updated to each others location.


That's the big question really, what mechanism is involved that enables jet A to know where jet B, C and D are in 3-dimensional space at any point in time so A can shoot of a stealthy directional burst to his buddies &vice-versa. Its not like Link 16 whose transmissions are like ripples in a pond and accessible by anyone with compatible equipment.
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Prinz_Eugn

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Unread post07 Apr 2011, 17:16

My guess is that the links are directional, but not that directional. You don't need to be THAT careful. You'd also eventually have AWACS in the back being able to call out locations for other friend aircraft if need be.
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Unread post07 Apr 2011, 20:48

It could well be that an initial broadcast is used until the connection is established and from then on directional transmissions are done, with possibly new broadcasts if contact is lost. That's at least how it could work.

Haven't read the entire thread, but one if the questions at the beginning was how the F-22 communicates with AWACS, the answer is it doesn't. It only receives broadcasted transmissions.
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lamoey

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Unread post07 Apr 2011, 21:06

davidjoe897 wrote:If the Raptor has a gps jammer, it is invisible to gps,too.


GPS satellites don't see the vehicle being positioned. As far as we are considered, the satellite is a dumb radio transmitter that sends out a constant signal. The GPS receiver uses the signal from 4 or more satellites to determine its own position.
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Unread post08 Apr 2011, 01:30

popcorn wrote:
SpudmanWP wrote:The members of the flight are in constant contact (via datalinks) and are updated to each others location.


That's the big question really, what mechanism is involved that enables jet A to know where jet B, C and D are in 3-dimensional space at any point in time so A can shoot of a stealthy directional burst to his buddies &vice-versa. Its not like Link 16 whose transmissions are like ripples in a pond and accessible by anyone with compatible equipment.


Prinz_Eugn wrote:My guess is that the links are directional, but not that directional. You don't need to be THAT careful. You'd also eventually have AWACS in the back being able to call out locations for other friend aircraft if need be.


Scorpion82 wrote:It could well be that an initial broadcast is used until the connection is established and from then on directional transmissions are done, with possibly new broadcasts if contact is lost. That's at least how it could work.

Haven't read the entire thread, but one if the questions at the beginning was how the F-22 communicates with AWACS, the answer is it doesn't. It only receives broadcasted transmissions.


I'm guessing but I think that the transceivers involved almost certainly resemble single or small numbers of aesa radar elements. It would allow narrow LPI beams to be projected essentially directly at friendly aircraft (so frequency and pulse width agile as well if you like), much like the single beam individual target track that aesa lpi radars can do, except for comms instead of tracking. The aircraft would need to keep a "contact" list of friendlies in the area and hand off comms works to the different transceivers around the aircraft as it maneuvered.

Not really sure how they'd add new aircraft to the network though, satellite?
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Unread post08 Apr 2011, 13:45

Thanks for the guesses. :D
Score one for OPSEC.
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Unread post08 Apr 2011, 16:57

Just using common sense here, but the AESA comms (just using that term for simplicity) could scan the sky in 360 mode with a 'hello' ping that would contain a GPS coordinate. Any other F-22s in the area would answer back and establish tight-beam comms.

Since the signals are LPI in themselves, the original 'hello' would be hard to detect by the enemy.
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Unread post19 Apr 2011, 14:29

A simpler answer would be, the F-22`s use VERY LOW power levels when sending data by discreet Link. Who else outside of the flight is going to be able to detect it.
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Unread post19 Apr 2011, 14:55

Ok, according to Av week....."Both the F-22 and F-35 use RF intra-flight data link systems, which generate steered, stabilized, pencil beams on a handshake arrangement, so that the beams lock on to the receiver aircraft."

"The Harris Multifunction Advanced Data Link (MADL) on the F-35 uses six phased array antennas to provide spherical coverage around the aircraft. The signals cannot be intercepted unless the listener is on the beam, which is constantly moving."

The USAF is supposed to be adding MADL to the F-22.

There is a rumour that the F-22 isn`t participating in ops over Libya because it only has a one way Link-16 and its IFDL (Inflight Data Link) cannot "talk" to other platforms and other NATO jets. That and nothing "enemy" ever gets into the air :)

http://www.aviationweek.com/aw/generic/ ... ork%20Gaps
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Unread post19 Apr 2011, 15:46

SpudmanWP wrote:Just using common sense here, but the AESA comms (just using that term for simplicity) could scan the sky in 360 mode with a 'hello' ping that would contain a GPS coordinate. Any other F-22s in the area would answer back and establish tight-beam comms.

Since the signals are LPI in themselves, the original 'hello' would be hard to detect by the enemy.


That seems to be as plausible a method as anything I've come across so far.. maybe one day we'll know how. " .. one ping please Vasili... one ping.."
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Unread post19 Apr 2011, 17:17

SpudmanWP wrote:Just using common sense here, but the AESA comms (just using that term for simplicity) could scan the sky in 360 mode with a 'hello' ping that would contain a GPS coordinate. Any other F-22s in the area would answer back and establish tight-beam comms.

Since the signals are LPI in themselves, the original 'hello' would be hard to detect by the enemy.


Seems an Apt description of he F-35 and B-2 MADL system, which the F-22 doesnt have, (see my above post) and won`t have until congress stops blocking funding until the air force comes up with a cost efficient method of solving the comms difficulties between platforms.

The BAC-N Battlefield Airborne Comms Node can apparently take data from the Raptors IFDL or say a Link-16, Link-11 and MADL and ship it to any end user in a format their black boxes understand. Global Hawks with BAC-N do this in Afghanistan now.
In answer to the original question, a phased array antenna does the "pointing". if you know exactly where your wingies are, you know exactly where to point.
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Unread post20 Apr 2011, 00:48

popcorn wrote:Thanks for the guesses. :D
Score one for OPSEC.

no problemo, happy to help :D

popcorn wrote:
SpudmanWP wrote:Just using common sense here, but the AESA comms (just using that term for simplicity) could scan the sky in 360 mode with a 'hello' ping that would contain a GPS coordinate. Any other F-22s in the area would answer back and establish tight-beam comms.

Since the signals are LPI in themselves, the original 'hello' would be hard to detect by the enemy.


That seems to be as plausible a method as anything I've come across so far.. maybe one day we'll know how. " .. one ping please Vasili... one ping.."


Except that lpi means frequency and pulse width variable so what frequency do you listen on? All of them? And it doesn't need gps data, as soon as it's received you've got a bearing and then signal strength from the handshake will give you range. 360 degree pings are problematic too as they have to reach a hypothetical jet on the horizon so they have to be very "loud".

My guess (and it's only a guess) was that AWACs or ground or satellite informs f-22#1 that flight "blah" is at your eleven o'clock range 84km while informing flight "blah" that f-22#1 is at your four o'clock range 84km. That way both ends can fire a direct beam straight at the other formation at the proper power level to ensure that any signal splash is too small to cause a problem.
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Unread post20 Apr 2011, 01:52

jeffb wrote:
Except that lpi means frequency and pulse width variable so what frequency do you listen on? All of them? And it doesn't need gps data, as soon as it's received you've got a bearing and then signal strength from the handshake will give you range. 360 degree pings are problematic too as they have to reach a hypothetical jet on the horizon so they have to be very "loud".

My guess (and it's only a guess) was that AWACs or ground or satellite informs f-22#1 that flight "blah" is at your eleven o'clock range 84km while informing flight "blah" that f-22#1 is at your four o'clock range 84km. That way both ends can fire a direct beam straight at the other formation at the proper power level to ensure that any signal splash is too small to cause a problem.


I'm thinking that those flying antenna farms have the sensitivity to detect those pings and geolocate the source of transmissions so maybe GPS may not even be needed.

I'm of the belief that an AWACS can't detect a F-22 so it won't be able to assist in establishing any link. It s been proven in combat that AWACS can't detect F-117s and the F-22 and F-35 are stealthier than the Nighthawk.
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