The topic of satellite navigation radio interference has recently become so hot that the situation resembles a war. Indeed, if you yourself βget under fireβ or read about peopleβs problems, there is a feeling of helplessness in the face of the elements of this βFirst Civil Radio-Electronic Warβ. She spares neither the elderly, nor women, nor children (just kidding, of course). But a light of hope has appeared - now the civilian population can somehow cope with this "radio-napalm" with the help of the latest technological advances.
Dedication, personal
Vovka, happy birthday! With the start of work!
Almost by chance, a useful feature of the u-blox F9P dual-frequency receiver was noticed. It was a field test of a two-frequency antenna. The antenna has separate outputs for different ranges L1 and L2/L5. By mistake, the range output L1 was disabled during operation. And, lo and behold, synchronization with satellites and the solution of the navigation problem (3D fix) remained.
There is a short for two minutes without details.
And long, uncut minutes on .
The nuance of the receiver's operation is as follows: if the L1 range is available when the receiver is turned on, then even if you turn it off later, synchronization with satellites on L2 / L5 and receiving a position remains. If the L1 antenna arm is turned off before the receiver is turned on, then there is synchronization with the L2 satellites, but the navigation task is not solved, there is no position. In this case, it should be noted that synchronization with satellites on L5 does not appear.
It is not known whether this is a bug or a feature of the F9P receiver. It is not known whether this feature will remain in future versions of the device and / or firmware.
But it's a sin not to use this feature now. Therefore, βcombatβ tests were immediately carried out using the βradio-napalmβ of a potential enemy in the form of an L1 navigation suppressor. Fortunately, it has been available since the time of my work on .
The experience was as follows. First, the receiver was switched on in clear air, without suppression. After synchronization and the solution of the navigation task by the receiver, our little friend, the suppressor, turned on. The results were recorded. After the receiver was reset and the results of its work were recorded again. Then the source of interference was turned off and it was checked that the situation returned to the original one - the presence of all satellites and positioning.
Since the tests are very simple, they were simply recorded on video.
Here is a short for one and a half minutes.
And long for .
As you can see, the receiver is jammed!
The long video shows the same puzzle with the disappearance of the L5 satellites as in the first experiments with an antenna with two outputs. I think this riddle will be solved by experts in satellite navigation who will read the article.
There is the following positive conclusion: you can start moving (take off with a drone or an airplane (!), start a run or a walk, move off in a car) in a place where there is no interference, and then even the appearance of interference will not spoil navigation.
This, of course, provided that the interference will be only on L1. But I think that dual-frequency "ammunition" is not yet very popular.
And I hope that even the distortion of the navigation field, which, as we know, can be avoided in . This must be checked.
Work plan:
- Checking the operation of the receiver under the influence of the navigation . Kremlin (is he still working?) or on SDR.
- Checking positioning under obstacles in motion.
- Checking the solution of high-precision navigation problems (RTK) under the influence of interference.
Here, I know for sure, there are people more experienced than me. Please suggest more items.
Thanks to u-blox for giving us hope!
Thanks to my friends who helped make the experiments.
Source: habr.com