Kremlin Demon Pill

    The topic of radio interference from satellite navigation has recently become so hot that the situation resembles a war. Indeed, if you yourself “come under fire” or read about people's problems, there is a feeling of helplessness before the elements of this “First Civil Radio-Electronic War”. She spares neither old people, nor women, nor children (a joke, of course). But the light of hope appeared - now somehow the civilian population can cope with this "radio napalm" with the help of the latest technological advances.

    Dedication, personal

    Vovka, happy birthday! With the beginning of work!

    Almost by accident, a useful feature of the u-blox F9P dual-frequency receiver was noticed. It was a field test of a dual-frequency antenna. The antenna has separate outputs of different ranges L1 and L2 / L5. By mistake, the output of the L1 range was disabled during operation. And, lo and behold, synchronization with satellites and solving a navigation problem (3D fix) remained.

    There is a short video for two minutes without details.
    And a long, uncut nine minutes .

    The nuance of the receiver is this: if, when the receiver is turned on, the L1 range is available, then even if you later turn it off, synchronization with satellites on L2 / L5 and receiving the position remains. If the arm of the antenna L1 is turned off before turning on the receiver, then there is synchronization with the satellites L2, but the navigation problem is not solved, there is no position. It should be noted that there is no synchronization with satellites on L5.

    It is not known whether this is a bug or a feature of the F9P receiver. It is not known whether this feature will work in future versions of the device and / or firmware.

    But it’s a sin not to use this feature now. Therefore, "combat" tests were immediately carried out using the "radio napalm" of a potential enemy in the form of an L1 navigation suppressor. Fortunately, it has been available since the time of my work on direction finding of navigation interference .

    The experience was as follows. At first, the receiver turned on in live broadcast without suppression. After synchronizing and solving the navigation problem by the receiver, our little friend jammer 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 was returning 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 video for a minute and a half.
    And a long three and a half .

    As you can see, the receiver is operating under interference!

    The long video shows the same mystery with the disappearance of L5 satellites, as in the first experiments with an antenna with two outputs. I think this puzzle will be able to solve by experts in satellite navigation, who will read the article.

    The following positive conclusion is evident: you can start moving (take off with an unmanned aerial vehicle or an airplane (!), Start a run or walk, get off the car) in a place where there is no interference, and then even the appearance of interference will not spoil the navigation.

    This, of course, provided that the interference will be only on L1. But I think that dual-frequency "ammunition" is not yet in full swing.

    And I hope that we can even avoid the distortion of the navigation field, which, as we know, happens in quite interesting places in our capital . This must be checked.

    Work plan:

    1. Checking the operation of the receiver under the influence of the navigation spoofer . Kremlin (and it still works?) Or on SDR.
    2. Checking positioning under interference in movement.
    3. Checking the solution of high-precision navigation tasks (RTK) under the influence of interference.

    Here, I know for sure that there are people more experienced than me. Please offer more points.

    Thanks to u-blox for hope!

    Thanks to my friends who helped me conduct the experiments.

    In motion, too, works !

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