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Comment: Re:RF? Heat? (Score 1) 218

by bobbied (#49800575) Attached to: Why Detecting Drones Is a Tough Gig

GPS Jamming doesn't work as you seem to think. Your receiver would still see quite a few signals, they'd just be lying about the position. Or, if you go with the cheaper model jammer, the receiver wouldn't see anything because the noise floor would be too high.

Switching to alternate navigation modes is indeed possible, but as I've stated in other posts, I'm suggesting that there be physical obstacles added using largely invisible structures to force the drone to fly a complex route to get where it wants, then concentrating the detection capacity along the forced route. In other words, force the bad guys to do specific things that make them more easily detected.

No system is perfect...You do what you can within the resource constraints you have and consign yourself to living with the risks that are left.

Comment: Re:Just wondering (Score 1) 218

by bobbied (#49799381) Attached to: Why Detecting Drones Is a Tough Gig

Silly me, here I thought we where discussing the lawn of the White House where this would be a fixed installation. In known locations, it's not hard to set up fixed systems and limit the affect you have on the neighbors.

Now you want to expand this into ad-hoc locations that are always moving? Fine, but in those cases you just use jamming and forget the consequences to the surrounding area. You only protect these areas on a temporary basis anyway so any problems with the local's garage doors and WiFi networks will be short lived. By the time the neighbors figure out that it is really your jamming that is keeping things from working, you will be long gone and their stuff will be working again. Most won't care at that point.

Also remember this is the government... They can do what they want, jam whomever they choose, and if they have a good security reason, there isn't much you can do about it.....

Comment: Re:Just wondering (Score 1) 218

by bobbied (#49799293) Attached to: Why Detecting Drones Is a Tough Gig

LOL

But you DO know that the available parts which can be used in building this kind of thing easily are going to force one into pretty predictable spectrum. Yea, the bad people might be smart enough and well enough funded to do the modifications necessary to move out of the commercially available spectrum, but the reality is that it's EASY to build a receiver compared to building a transmitter.

With today's SDR (Software Defined Radio) offerings, especially in the high performance receiver area, monitoring large swaths of RF spectrum quickly is pretty easy. You don't have some guy spinning the dial anymore or have to wait for that channelized scanner to cycle though it's frequency list , but you can monitor a whole range of frequencies all at one time. Once you find something of interest, you can quickly go back into the digital buffers and do the direction finding.

My point is that you START by looking at the WiFi spectrum (and other well known frequencies) and move out from there. Would it be possible for someone to figure out a frequency you don't monitor well and build a device to use that? Sure. But you monitor what you can and make that option VERY expensive for the bad guys. You also don't advertise what these frequencies might be so the bad guys have to guess. It's not like you can externally detect if somebody is listening and what frequencies they are listening into....

Comment: Re:The things pump out plenty of RF. (Score 1) 218

by bobbied (#49799121) Attached to: Why Detecting Drones Is a Tough Gig

Iron dome is not really about short range mortars, but ballistic rockets and other long range ballistic munitions. Where the principle is similar, I don't think Iron Dome would be very effective on short range mortars, especially ones fired at very low angles.

However, as another poster pointed out, there ARE systems used to protect areas from mortar shells which are field ready. I was unaware of them. After looking at pictures of the equipment, I couldn't help but notice that there are similar looking things on top of the White House which I had wondered about in the past. So, at this point, I don't believe a mortar attack would be all that successful.

Comment: Re:Just wondering (Score 1) 218

by bobbied (#49799041) Attached to: Why Detecting Drones Is a Tough Gig
Two things come to mind... 1. If the drone just has a camera and is not emitting, the point of the flight is likely to be reconnaissance and the pilot will want to get the thing back to look at the pictures, OR, the mission is really just one way and they pilot is trying to deliver something or observe the responses to the drone. AND 2. The point here is to disrupt the drone's flight so it doesn't reach the intended destination FIRST and then try to locate the pilot who is very likely within line of sight of the drone. Recognizing that detecting a small airborne platform close to the ground is incredibly difficult you do things to make it harder for the drone to reach sensitive locations undetected. You use RF jamming to disrupt things the drone is likely to need (WiFi, RC Frequencies, GPS etc) and force the drone into more expensive and difficult methods being controlled. You also make the drone navigate in ways that makes it more observable, having to fly over and around obstacles and then concentrate your detection and threat elimination efforts to the probable ways a drone would likely have to approach. You also make it more risky for the pilots and though some may successfully get away, make sure some won't. FINALLY, you routinely evaluate the success of your equipment and procedures and make improvements as the state of the art advances and as you identify weaknesses. You won't eliminate every risk, but you can make it pretty difficult for the bad guys...

Comment: Re:RF? Heat? (Score 1) 218

by bobbied (#49795467) Attached to: Why Detecting Drones Is a Tough Gig

Again, you folks act like RF energy cannot be controlled, it just goes off in all directions no matter what you do and that there is no way to isolate the jamming energy to small areas. This is not true. Would there be some residual affect outside the intended area? Perhaps, but if you do this right it would not be wide spread, nor would it need to extend more than a few hundred feet beyond the desired areas....

Tell me it's not possible to limit where you put the RF and control the signal strength outside the desired area to acceptable levels... I think you can do that, if you are careful and think about where you put the jammers, what antennas you use and what direction you point them.

Also, GPS jammers are neither expensive nor rare. They are off the shelf and have been for decades and well with the budget of the Secret Service (In fact I'd bet they ALREADY have a few). Directional antennas are also inexpensive and off the shelf, even at the frequencies of GPS. None of this is rocket science... Just a bit of engineering.

Comment: Re:It's not about detection... (Score 1) 218

by bobbied (#49795431) Attached to: Why Detecting Drones Is a Tough Gig

1. Sound is ineffective (ibid.). Video is probably not much better. You didn't mention synthetic aperture radar, which would be my first choice. 2. Do your barriers extend all the way over the top of the object you intend to protect? How about walls and roofs, would they work?

No, they extend as high as you can manage w/o making them obvious. The purpose is to entangle, snare or disrupt the drone in flight by providing obstacles that the distant pilot cannot observe and don't expect. Of course you *could* just build a structure over the whole thing.... But my working assumption is they don't want to change the ascetics of the thing.

3. GPS jamming is illegal. WiFi jamming is illegal if it exceeds a maximum ISM band transmission power.

Yes, it is illegal for you and I, but the government *can* legally do it anytime and any place it wants.

4. Probably a good idea to find the person responsible. 5. Can you? Would you like to share any of them? Even one?

My primary idea is to use nets similar to the way birds are sometimes captured for scientific study. Tie a couple of bean bags to a net, fire it out of a cannon making sure it's rotating. Rotation spreads out the net, snares the drone and the weight of the bean bags disrupts it's flight. There are a couple of variations on this you could try, even a shot gun might be effective but pretty safe to bystanders if the drone is low enough and close enough to the shooter.

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