The hunt for red demon or the radar jamming satellite navigation

Don't think I'm some kind of criminal element, or paranoid cheating husband, but once I decided to buy a GPS jammer. First, it was interesting in the process. After all, it's kind of illegal, the seller like risk. I wanted to be part of it, not just listen or read. Second, technically, economically and cleanly was wondering — how made and how much it costs.

What it led to read on.

Epigraph

we lost the robot. Work stopped, and should be, until we
discover.
A. Asimov, "As was lost robot"

the birthday of a friend
I. Tsarik, "take the opportunity"

Why do we need GPS jammers and GPS spoofer particularly do not need to tell. Today everyone knows that even the "new aristocracy" uses them for greater security. This is especially know the people of Moscow. What to speak about ordinary people. Well, when we had who cares about a little inconvenience of a neighbor? "If "They" do not care, I especially. If I need turned and left."

But the world is seriously stuck in the technique. Today Navigator is a continuation of the brain are a considerable number of drivers, especially the "blonde" of their representatives. You can smile and mourn, but the process is ongoing. And what if they all cut off the navigation?

Now imagine a Robo-driver of the future...

Not that I personally urged not to use jammers. On the contrary, without them I personally would be less interested in doing the technique, described below. Who war, and who...

Summary — the enemy must know in person. I know that jammer — thing is fine and that there is the work of Professor Ebinuma for more "fine tuning" satellite navigation, but the simplest method the enemy is also interesting to me.

The cheapest way to take out the NAV cost me 2,500 rubles.

A simple thing, but in the package, which gives diseases of the brain. I, at least, once infected. Here, I think, a good sarcophagus for a pet mouse (soon!). And it is, perhaps, as much as the device itself inside.

And what he's got range (video)!

Further, this infection in me has progressed in destructive actions and I broke it:

It's very simple and tasteful, almost rustic. And now you all know why the demon ryzhyi. (Although "History of red demon" I like it too.)

But what is it in action!

Smashing the flames of the Inquisition! Now every kid, saving on beer 30 times, can "burn" all the navigation in the area. Here I want to note that I ran this thing outside the city. Neither motorist was injured.

And, obeying destiny, I'm smitten with the desire to trap this devil. Finder I started using my favorite augmented reality and wonderful chips NT1065.

NT1065 contains four radio path, which can be configured to use a single local oscillator. This is evident in the block diagram:

Then all four channels will be in phase with the precision neodenticula radio paths. The figure below shows the range of phase differences.

It is seen that the phase difference is stable, thus, it is possible to create on the basis of NT1065 a four-phase direction finder.

Take charge of previous article, add to it four antennas with low noise amplifiers (LNA). It was possible and without LNA, but I wanted to pick up the signal in bands where the antenna is consistent bad.

High-pass filters recommended to be installed on the entrance NT1065, for simplicity and for the flexibility of the finder, drop. Antenna configured only on the top navigation band (L1), but closing our eyes to the sensitivity, you can try to use the finder and on the lower bands (L2, L3, L5, etc.). Later we'll see what happens.

So here is the piece:

Had to Tinker. to put everything on one side because the other side only of the antenna. Without ignoring the recommendations on the wiring of the circuits is not done. Lick you will later.

And now — soft (video).

Source — here.

Briefly, the software works like this: take the number of continuous counts, making them FFT (with window, natch), the averaged frequency counts FFT (Bina) in a user-selected band, and calculated bearing. All these operations are standard that are boring to describe the educated public, except for calculation of the bearing.

Here, everything is done in a simple way: the algorithm can be called "beamforming", in English probably beamformer will — find the direction of the main lobe of the radiation pattern that most closely matches the adopted antenna array signal. The formula is this:

Specific code, see github, anyone interested.

Further from the maximum of the directional diagram lay off 1 percent and make the cut. The resulting angular field, a "cloud" angle, which is most likely the source of the signal. This area of the shaded corners on real video from the camera of the tablet. Overall, the piece looks like (as usual mounted on the rear of the tablet):

And works like this: (video).

You can still choose the position and width of the treated band and set the threshold for the signal level. There is also an indicator of total power in the band that allows you to roughly find the sector.

If we compare this phase direction finder with my previous amplitude for WiFi, this is fundamentally more sensitive. Well, he's already not manual, but automatic. That is, in principle, they have to rotate is not required. But still it is desirable to do, as the accuracy is best in focus. And on the reverse side it's not working too. There is less than any internal antenna distortion.

But, as the video shows, the interference has not been canceled. If there is no direct beam distortion can be significant. And the polarization dependence is also have some.

Now, I want to send on their efforts.

PS: On the lower range, in the navigation wording L2, L3, L5, etc., while working not. You need to smoke a calibration.

Article based on information from habrahabr.ru