On Wed, 6 Aug 2003 02:31:28 +0100, (phil hunt)
wrote:

On Fri, 01 Aug 2003 20:34:07 -0700, matt weber wrote:

That makes sense. How easy would it be for the UAV to listen to thre
incoming signal, and match its response to it?

The Self Projection jammer pods often represent more than the
available lift capacity of the UAV unless you are talking about
something the size of a Predator or a Global Hawk...

Why would it need to be so big? Is it the receiving equipment, the
transmitting equipment, or the electronics in between that takes up
the space?
All of the above, you need a receiver that can receive almost
anything, and enough electronics to be able to analyse the
transmission in real time (which requires very FAST A/D, identify the
characteristics of the emitter so they can be matched against the
threat library, and then you need a transmitter of sufficient power
and ability to generate an appropriate rep rate and modulation scheme
to be able to jam the threat, if it is a threat. All up, if you are
lucky, perhaps only a few hundred Kg...

(Of course, an adversary could build lots of cheap boxes that give
off signals that appear the same as a real radar, to soak up lots of
anti-radiation missiles).

While it could be done, it isn't all that cost effective, to build an
emitter that would look enough like a real radar to be attacked would
probably cost 15-20% of the price of the real thing.

How much do real radars cost?
Depend upon how fancy you want to make them. The military is famous
for 'gold plating', and what you have now is a computer that happens
to have a radar attached. Some of them have 8 figure price tags, the
problem is in producing an emitter that will be identified as a
potential threat, it really has to produce an output that looks like a
threat, which means you probably need just about the entire transmit
package.

Certainly there are some radio transmitting equipments that are
cheap -- for example mobile phones and wi-fi stations -- and I'd
imagine that scaling up the transmitting powrer on such a device
would be too expensive either.
Those however are very simple emitter that don't depend upon complex
modulation schemes, fast frequency hopping, or monopulse designs...
The bind is that todays ADF and Fire Control Radars control radars are
depend upon complex modulation schemes to extract a great deal of
information. For example they can tell the difference between a
737-200 and a 737-300, a helicopter and similar weight jet fighter,
and it isn't based upon the strength of the radar reflection, it is
based upon the assortment of doppler shifts they see in the return,
they really can see the fan on the engine, the rotor on the
helicopter, and propeller...

How good are passive sensors compared to radar? I would imagine that
visual light and infra-red would be quite good ways of detecting
aircraft (and if you have 2 detectors some distance away you can use
triangulation to get the exact position), at least when there are no
clouds.

Depends upon what you are looking for.
[...]
If you are looking for an F4 or a B52, it won't be very hard,

That's exactly the sort of thing I had in mind (or an F-16 or
Tornado or F-22, etc, bascially any modern supersonic aircraft)
Passive detections at this point is in two parts. At the moment only a
limited amount is done via EO, as a friend who in the business put it,
it is very limited because our heart really isn't in it. Otherwise it
is mostly based upon EMI that is generated on the other end. So if the
other aircraft is electrically quiet, and doesn't have a big visual
image, or create massive air flow disruptions, passive sensing won't
see very much.

Light the burners, or engage in some fancy maneuvers, or turn on the
search radar, and that is another story...

Passive detection is very useful if you have enough information, i.e.
if your threat library says that is a model XX-YY radar, and you know
those are only carried on a single type of airframe...