Forum: F-16 versus XYZ

Hansundfranz, I noticed it was a typo and I apologize, it was the first thing that I caught. Still, it doesn’t make a difference since such a sensor is better off in the enemy’s hand. In this scenario, nobody in their right mind would rely on such a basic algorithm. IMO this is not a realistic sensor for any plane. Also, the F-22 probably uses novel techniques to find targets

I’m not sure what your knowledge of interferogram interpretation is. I use interferometric instruments for physical research and the article you linked lacks detail and applications. Interferometers are only a small part of the system you would use to find an emitter.

This is of course in principle, one of the main complication I would find be to build a system robust enough. Interferometers I use are very sensitive even to building vibrations, but then again, we measure chemical bond lengths and is considerably different to a ranging interferometer such as a 3-port system. I’ve also heard there are several other convoluted setups involving more complex algorithms than Fourier-Transforms that we use. When I get back to Ames I’ll find out more. By the way, this is one possibility.

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Oh and of course 2 raptors trying to trinagualate together, won´t be decetable by sending dataink information?

The link will no doubt be very low powered. It would probably be like trying to detect a garage door opener or a wifi signal at those distances. It can be done with specialized equipment, but that probably wouldn't fit (especially the antenna) in an enemy aircraft. Any ground station that transmits to aircraft would probably be destroyed early on in the campaign and therefore wouldn't be a player in the Raptor passive detection game Wink

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ESA = Electronically Steered Array. ESA radars do not "steer" in the traditional sense, there is no mechanical gimbal system to steer or point the radar beam. Instead the beam can be redirected, steered, electronically and almost instantaneously to any point within its envelope. An ESA 'scan pattern' consists of a series of discrete vectors, these vectors can be very close together and in a regular pattern to emulate a traditional scan pattern or they can alternate rapidly between already detected targets, thus "the track many while scan" mode.

I think this was just a matter of semantics, nothing make "rediculous" statements about, nor typos to apologize for. In this forum a "humble pie" response will get a better reception than an arrogant one.

(Over 2000 flame-free posts and counting!!!)

hansundfranz wrote:

Runningman,
Aesa radars don´t have to steer the radar beam over the sky tio detect contacts?
This statement is simply redicolus.

Apologies, but I was not trying to imply that aesa radars don't have to scan the sky to find targets. What I was trying to say was that once a target is detected, a radar beam can be directed to stay on the target without having to scan the empty space around the target. my original chioce of words was misleading. if I am wrong about this, please tell me.

also if anyone has any info on aesa, I would like to know more.

Another note about interferometry, knowing the mirror positions and velocity will allow you to deconvolve the interferogram by means of Fourier transformation to construct an emission spectrum with higher resolution than conventional techniques. Also, current algorithms and a regular pentium computer will allow you to obtain precise spectra in a matter of seconds. If emission spectra of different aircraft are compiled in libraries for the computer to compare, it will allow you to identify the aircraft and possibly determine friend or foe.

Sorry for continuous postings. I just wanted to state that ranging interferometry is PASSIVE and, in principle, has no frequency limitation (in practice, most frequencies are useless due to background noise, permeability and mechanical limitations of interferometers)

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What I was trying to say was that once a target is detected, a radar beam can be directed to stay on the target without having to scan the empty space around the target.

This is called STT and can be done with conventional antennas just as easily.

BTW I don´ t think any modern radar would do this to avoid alerting the emenys RWR

Habu, you are right esa has some advanatges however it is possible with convetional radars to create irregular scan patterns (not the old 4 bar 120° coverage), too. Of course you also want to look at all pieces of the sky in regular short time distances to make sure nothing is missed.
With an aesa you can get more creative and its an advanatge but not a silver bullet that makes every convetional radar automatically grossly inferiour.

Pat1

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Another note about interferometry, knowing the mirror positions and velocity will allow you to deconvolve the interferogram by means of Fourier transformation to construct an emission spectrum with higher resolution than conventional techniques. Also, current algorithms and a regular pentium computer will allow you to obtain precise spectra in a matter of seconds. If emission spectra of different aircraft are compiled in libraries for the computer to compare, it will allow you to identify the aircraft and possibly determine friend or foe.

I did not say it is impossible to detect the type of emitter I said its impossibe to detect its range.
if the emtting requency is known (of course its not, you might know the bands but you do not know the operating frequenc right now) it would also be possible to get closure information, simply by using the doppler effect.
Anyway how would you determine distance to an electomagnetic emitter, using one ore more antenas close together, so close that triangulation brings no useful results?

Parrothead, the data link signal must be at least strong enough to be recived and understood by the other plane.
The reciverer will have a very small antenna.
As you say with specialized hardware such as the Ukrainina Colchuga it will be possible to detect such datalink emssions at much greater range.

BTW, with the sucess in scud hunting during GW1 and the general ineffectivity of western airpower over the balkans, I really wonder where you take your confidence from that such passive systems would be found and destroyed early during the war.
Kind a hard to find these things as they don´t emi strong signals, and nothing to prevent the enemy from rigging old run down trucks with fake antennas all over the country side, giving even the US airforce to many targets to destroy them all.

A more general remark; It also seems very likely that more capable nations will build additional long wave radars, which easily detect "stealthy" airplanes. Unfortunately with less precission due to the long wave but if you know where to look you can find everything.
I find it doubtful that stealth will still be a major advantge 15 to 20 years from now, I think the improvements in sensor integration and signal processing that will be made, due to the faster CPUs available will beat stealth and that the money might have been better used in another area.
Imagine what performance and electronic capablities the F22 would have if less monemy would have been put into stealth and if areodynamic efficiency would have got higher priortity then stealth.
A well the future will show, and enjoying a a nice advantge for 10 years until the detector side has catched up is also nice.
And probably the next few US war will also be again some 3rd world countries with russian hardware at best from the early 90s.

What I do realll not like is the amount of admiration for the USA, willingly swallowing every claim, and at the same time the assumtion that the enemy is stupid.

To get back to the original toppic, as already said, the F22 pilot will shoot one or two F-16, create some spacing, reevaluate the situation and then continue to kill some more if the situation is good for him. If it looks to risky he always has the option to leave and kill some more f16 the next day.

Enthusiast Joined: Oct 27, 2004 - 10:49 AM Posts: 70

hansundfranz, how about using a maser for a high bandwith, narrow beam raptor to raptor datalink? If you choose the wavelenght wisely, clouds wouldn't be a problem at all.

I feel we are being laughed at by the people "in the know" Laughing

hansundfranz wrote:

I did not say it is impossible to detect the type of emitter I said its impossibe to detect its range.
if the emtting requency is known (of course its not, you might know the bands but you do not know the operating frequenc right now) it would also be possible to get closure information, simply by using the doppler effect.

In the first sentence you accept the possibility of constructing the emission sepctrum of a target. In second sentence you say you can't, what will it be? Do you know what this is about?

hansundfranz wrote:

Anyway how would you determine distance to an electomagnetic emitter, using one ore more antenas close together, so close that triangulation brings no useful results?.

You accuse people of living in fantasy land. I know this will come as a shock to you, but reality also exist outside your realm of knowledge and understanding. If you like to learn more I suggest a higher education in physics. PhD's spend lifetimes to learn and apply interferometric principles. Interferometric instruments in all fields have unprecedented accuracy, speed and flexibility over those they substitute. Please note that the presicion of a ranging interferometer will probably be in the milimeter to decimeter range. One enormous complication is to have a system robust enough. I can't think of any object harder than an F-22 to mount such a system on.

You can measure the spectrum the frequencys, you recive. Since the emmited frequency is unknown you can not calculate range.

Again, in principle how do you get range information by using interferometire? Please note that in our example, you do not emit any energy yourself. You can only measure the energy emitted from your target. and these electromagnetic waves are of unknown energy and frequency.

hansundfranz, ok you win... the world is flat

I'm not familiar with the technical expressions used in this thread (I guess I'm not the only one either) but my guess is that what it means in practice is that the receiver locks on a given frequency and is able to tell where on the wave form it is locking. With the high frequency in use the measurement is down to centimeters. What you still don't know, however, is how many wavelengths away is the emitter, although you know where on the wavelength he is. If you then have a minimum of 4 measurements, where the larger angel between them the better to analyze you may soon be able to determine a pretty accurate distance and range. In my days as a navigator in the North Sea oilfield we had to do this calculation almost by hand, and it took us just a couple of minutes to tune the receivers to a position (our own) that had an acceptable standard deviation and error ellipse. One’s the initial solution is calculated it is no problem tracking it.

More or less the same principal is used in GPS attitude derivations by suing 3 or more antennas depending on how many axis' you want to determine, and then we're taking distances much larger than what we're talking about in this thread.

So having thought about it I think it is possible to launch an AMRAAM in the right direction for it to find its target when it goes live. However, without guiding the AMRAAM will not know which target to engage, so if there are multiple targets and multiple missiles, one target may get more that its share of incoming AMRAAM’s.

I found a link from a Scottish University
http://www.st-andrews.ac.uk/~www_pa/Sco ... page4.html
I'm currently going over it right now

Sorry guys, too much attitude in this thread. I'll ignore this one from now on.

hansundfranz, what I meant was that even if the passive site could detect the Raptors, it would still have to transmit to someone to tell them where they are. Those transmissions would be used to target the site.

Forum: F-16 versus XYZ

Four F-16s vs one F/A-22