Defense against UAV's

In article ,
says...
Jack Linthicum wrote:
[snip]


I think that a spread spectrum burst type transmission can be
intercepted and given a rough bearing. The money to do this is
miniscule in comparison with making Trident missiles into hand
grenades.

The command post does not move between transmissions. Spread
spectrum/frequency hopping systems return to previous frequencies every
few seconds. Just use several bursts to home in on the transmitter.


Why are you assuming that the command post does not move? I see no
reason that a mobile command post and multiple mobile transmitters
could not be used.

Spread spectrum and frequency hopping systems do use a finite number
of frequencies---but the sequence of freqencies used may not repeat for
many hours. That leaves you with a broadband collection problem
and having to sort out multiple emitters on the same bandwidth with
different hopping schedules. I suspect that is a problem handled
offline and after-the-fact, and not in real time. However, the
technology has probably advanced a bit in the 30 years I've been
out of the sigint world. ;-)


Mark Borgerson

Mark Borgerson wrote:
In article ,
says...
Jack Linthicum wrote:
[snip]

I think that a spread spectrum burst type transmission can be
intercepted and given a rough bearing. The money to do this is
miniscule in comparison with making Trident missiles into hand
grenades.
The command post does not move between transmissions. Spread
spectrum/frequency hopping systems return to previous frequencies every
few seconds. Just use several bursts to home in on the transmitter.


Why are you assuming that the command post does not move? I see no
reason that a mobile command post and multiple mobile transmitters
could not be used.


This comes down to the definition of mobile. If the command post stays
in the same place for half an hour it is static. A constantly moving
command post would need a vehicle the size of a bus to hold the
operators and long range transmitters, possible but hard to camouflage.

Spread spectrum and frequency hopping systems do use a finite number
of frequencies---but the sequence of freqencies used may not repeat for
many hours. That leaves you with a broadband collection problem
and having to sort out multiple emitters on the same bandwidth with
different hopping schedules. I suspect that is a problem handled
offline and after-the-fact, and not in real time. However, the
technology has probably advanced a bit in the 30 years I've been
out of the sigint world. ;-)

If we are trying to destroy the command post we do not need to receive
the entire message we can simply wait until that frequency is reused by
that transmitter. If the equipment is hopping over 100 frequencies it
should be back within the next 200 transmissions.

The computers will need programming to treat transmissions from two
widely separated locations as two targets. Home in on them one at a time.

Andrew Swallow

In article ,
says...
Mark Borgerson wrote:
In article ,
says...
Jack Linthicum wrote:
[snip]

I think that a spread spectrum burst type transmission can be
intercepted and given a rough bearing. The money to do this is
miniscule in comparison with making Trident missiles into hand
grenades.
The command post does not move between transmissions. Spread
spectrum/frequency hopping systems return to previous frequencies every
few seconds. Just use several bursts to home in on the transmitter.


Why are you assuming that the command post does not move? I see no
reason that a mobile command post and multiple mobile transmitters
could not be used.


This comes down to the definition of mobile. If the command post stays
in the same place for half an hour it is static. A constantly moving
command post would need a vehicle the size of a bus to hold the
operators and long range transmitters, possible but hard to camouflage.

So you don't think the Iranians have buses or semi-trailers? Suppose
there are 100 semis on the coastal road. Which one do you target?

Spread spectrum and frequency hopping systems do use a finite number
of frequencies---but the sequence of freqencies used may not repeat for
many hours. That leaves you with a broadband collection problem
and having to sort out multiple emitters on the same bandwidth with
different hopping schedules. I suspect that is a problem handled
offline and after-the-fact, and not in real time. However, the
technology has probably advanced a bit in the 30 years I've been
out of the sigint world. ;-)

If we are trying to destroy the command post we do not need to receive
the entire message we can simply wait until that frequency is reused by
that transmitter. If the equipment is hopping over 100 frequencies it
should be back within the next 200 transmissions.

With spread-spectrum transmitters, the time spent at one particular
frequency may be only a millisecond or two. If you can provide a link
to a system that can accurately track a moving spread-spectrum
transmitter, I'd be interested in reviewing its specifications.

The problem with intercepting spread-spectrum signals is that the
receiver KNOWS where the next signal will arrive. It can tune it's
receiver software for that frequency. The intercept receive has to be
able to recieve ALL frequencies---and thus cannot use the same signal
processing techniques as a receiver that knows the sequence.

The computers will need programming to treat transmissions from two
widely separated locations as two targets. Home in on them one at a time.

How do you work with one continuously moving target transmitting on
256 different frequencies? I suppose it could be done with large
enough antennas and enough processing power on a number of different
ships. It's not going to be easy, cheap, or widely available, though.

Mark Borgerson

Mark Borgerson wrote:
In article ,
says...
Mark Borgerson wrote:
In article ,
says...
Jack Linthicum wrote:
[snip]

I think that a spread spectrum burst type transmission can be
intercepted and given a rough bearing. The money to do this is
miniscule in comparison with making Trident missiles into hand
grenades.
The command post does not move between transmissions. Spread
spectrum/frequency hopping systems return to previous frequencies every
few seconds. Just use several bursts to home in on the transmitter.

Why are you assuming that the command post does not move? I see no
reason that a mobile command post and multiple mobile transmitters
could not be used.

This comes down to the definition of mobile. If the command post stays
in the same place for half an hour it is static. A constantly moving
command post would need a vehicle the size of a bus to hold the
operators and long range transmitters, possible but hard to camouflage.

So you don't think the Iranians have buses or semi-trailers? Suppose
there are 100 semis on the coastal road. Which one do you target?

The one with the big aerial.

Small aerial to small aerial on moving objects gives a short range.

Spread spectrum and frequency hopping systems do use a finite number
of frequencies---but the sequence of freqencies used may not repeat for
many hours. That leaves you with a broadband collection problem
and having to sort out multiple emitters on the same bandwidth with
different hopping schedules. I suspect that is a problem handled
offline and after-the-fact, and not in real time. However, the
technology has probably advanced a bit in the 30 years I've been
out of the sigint world. ;-)
If we are trying to destroy the command post we do not need to receive
the entire message we can simply wait until that frequency is reused by
that transmitter. If the equipment is hopping over 100 frequencies it
should be back within the next 200 transmissions.

With spread-spectrum transmitters, the time spent at one particular
frequency may be only a millisecond or two. If you can provide a link
to a system that can accurately track a moving spread-spectrum
transmitter, I'd be interested in reviewing its specifications.


Try
http://klabs.org/richcontent/MAPLDCon98/Papers/d3_haji.pdf


For DFing you do not need to accurately track a spread-spectrum
transmitter's hops. You only need to guess one of the frequencies.
To intercept and decode a signal you need (almost) all the frequencies,
providing it can tell the difference between static and modulated signal
the above machine may be able to reconstruct the signal by listening
on hundreds of frequencies simultaneously.

The problem with intercepting spread-spectrum signals is that the
receiver KNOWS where the next signal will arrive. It can tune it's
receiver software for that frequency. The intercept receive has to be
able to recieve ALL frequencies---and thus cannot use the same signal
processing techniques as a receiver that knows the sequence.
The computers will need programming to treat transmissions from two
widely separated locations as two targets. Home in on them one at a time.

How do you work with one continuously moving target transmitting on
256 different frequencies? I suppose it could be done with large
enough antennas and enough processing power on a number of different
ships. It's not going to be easy, cheap, or widely available, though.

You can deal with frequency hopping by listening on hundreds of
frequencies simultaneously. When one of the frequencies is known very
accurate direction finding equipment can tune to that frequency and wait
for the transmitter.

Where the target is physically moving whilst transmitting something like
a radar display is needed. PCs can be programmed to act in this
fashion. Five years ago the army was working on things like this.

Andrew Swallow

In article ,
says...
Mark Borgerson wrote:
In article ,
says...
Mark Borgerson wrote:
In article ,
says...
Jack Linthicum wrote:
[snip]

I think that a spread spectrum burst type transmission can be
intercepted and given a rough bearing. The money to do this is
miniscule in comparison with making Trident missiles into hand
grenades.
The command post does not move between transmissions. Spread
spectrum/frequency hopping systems return to previous frequencies every
few seconds. Just use several bursts to home in on the transmitter.

Why are you assuming that the command post does not move? I see no
reason that a mobile command post and multiple mobile transmitters
could not be used.

This comes down to the definition of mobile. If the command post stays
in the same place for half an hour it is static. A constantly moving
command post would need a vehicle the size of a bus to hold the
operators and long range transmitters, possible but hard to camouflage.

So you don't think the Iranians have buses or semi-trailers? Suppose
there are 100 semis on the coastal road. Which one do you target?

The one with the big aerial.

Small aerial to small aerial on moving objects gives a short range.

You can put a pretty large antenna (at 900Mhz or higher) inside the
back of a semi trailer. (Probably best to use fiberglass panels
rather than aluminum on the outside, though!)

Spread spectrum and frequency hopping systems do use a finite number
of frequencies---but the sequence of freqencies used may not repeat for
many hours. That leaves you with a broadband collection problem
and having to sort out multiple emitters on the same bandwidth with
different hopping schedules. I suspect that is a problem handled
offline and after-the-fact, and not in real time. However, the
technology has probably advanced a bit in the 30 years I've been
out of the sigint world. ;-)
If we are trying to destroy the command post we do not need to receive
the entire message we can simply wait until that frequency is reused by
that transmitter. If the equipment is hopping over 100 frequencies it
should be back within the next 200 transmissions.

With spread-spectrum transmitters, the time spent at one particular
frequency may be only a millisecond or two. If you can provide a link
to a system that can accurately track a moving spread-spectrum
transmitter, I'd be interested in reviewing its specifications.


Try
http://klabs.org/richcontent/MAPLDCon98/Papers/d3_haji.pdf

Thanks for the link. It looks very interesting. I couldn't find
any data on the angular resolution of the DF, though.


For DFing you do not need to accurately track a spread-spectrum
transmitter's hops. You only need to guess one of the frequencies.
To intercept and decode a signal you need (almost) all the frequencies,
providing it can tell the difference between static and modulated signal
the above machine may be able to reconstruct the signal by listening
on hundreds of frequencies simultaneously.

The problem with intercepting spread-spectrum signals is that the
receiver KNOWS where the next signal will arrive. It can tune it's
receiver software for that frequency. The intercept receive has to be
able to recieve ALL frequencies---and thus cannot use the same signal
processing techniques as a receiver that knows the sequence.
The computers will need programming to treat transmissions from two
widely separated locations as two targets. Home in on them one at a time.

How do you work with one continuously moving target transmitting on
256 different frequencies? I suppose it could be done with large
enough antennas and enough processing power on a number of different
ships. It's not going to be easy, cheap, or widely available, though.

You can deal with frequency hopping by listening on hundreds of
frequencies simultaneously. When one of the frequencies is known very
accurate direction finding equipment can tune to that frequency and wait
for the transmitter.

How accurate is 'very accurate'? Back when I was working with HFDF,
one or two degrees angular resolution was considered reasonable.
The system I worked with is described he

http://www.nrl.navy.mil/NewsRoom/images/75awards.pdf
(look at the award citation for high frequency direction finding)

Where the target is physically moving whilst transmitting something like
a radar display is needed. PCs can be programmed to act in this
fashion. Five years ago the army was working on things like this.


Mark Borgerson

On Wed, 31 May 2006 16:44:09 -0700, Mark Borgerson wrote:

Why are you assuming that the command post does not move? I see no
reason that a mobile command post and multiple mobile transmitters
could not be used.

"I see no reason why all of the problems with my idea can't
be addressed by making my system even more complex."

You already have a large number of Predator-sized UAVs (the
Predator has a wingspan of almost 50 feet and is about 28 feet
long, by the way, for a payload of about 450 pounds), which
are apparently equipped with a sensor suite that can image
ships in visible light and IR (it would kind of suck to not
be able to see your target several miles away in haze, or if
it was dark out, so I'm assuming you've already thrown in
multispectral imaging capability, or hey, why not synthetic
aperture radar) plus a laser rangefinder and sophisticated
ESM receivers that can classify and locate enemy radar emissions,
plus a Mk 1 Electronic Brain that can fuse all the sensor data,
analyze images to reliably identify specific ship types from any
angle and in any lighting conditions, and decide all by itself
to engage targets with the weapons that also somehow have to
fit in that 450 lb payload.

Oops, I almost forgot the swarm of decoy aircraft that match
the radar, IR, visual, and ESM signature of your real attack
UAVs (so the enemy can't easily classify them as decoys and
ignore them), but are just there to make things more confusing.

Now you want to add a mobile command infrastructure, presumably
with a horde of mobile decoy transmitters to make the actual
transmitters harder to target (if the decoys aren't mobile,
after all, they won't be very effective decoys.)

What happens if the ships you're trying to attack are below
the horizon from your coast? Better add a satellite
communication system so you can still order your UAVs
around when they're more than 20 miles offshore.

Or hey, wait a minute, the UAVs are autonomous, so why not make
them submersible too? If they're attacked, they can just dive
into the water and continue the rest of the way to the target
safely. At one stroke, you've just rendered all of the enemy's
sophisticated air defense systems useless!

I think there might be a point somewhere in there when the
leaders of Ashcanistan will tell you and your Asymmetrical
Warefare-O-Matic system to get lost, and go back to their
original idea of using WWI-era naval mines and suicide
speedboats to inconvenience the naval forces of the
Great Satan.


ljd