Warflying (Wi-Fi scanning) in an airplane up to 450 km

Recently I was traveling by plane over Europe. Of course, I could not resist to check what could be received on 5 GHz there, at an altitude of over ten kilometers…

I took the following equipment for Wi-Fi scanning onboard:

  • Mikrotik Routerboard SXT 5HPnD (AR9280),
  • Raspberry PI 3B with GNSS receiver, RTC and 10 V PoE output – see more: Wardriving @ 5 GHz,
  • USB power bank (5V/2.1A),
  • Nexus 7 tablet.

I was scanning using MikroTik SXT antenna with a built-in radio module. This device is as small as 14×14 cm. The dual-polarization antenna rated at 16 dBi is even smaller, at just 11×11 cm. It was connected to Raspberry PI single board computer.

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Pomiary stacji UKF-FM (MPX power)

Poniższa tabela przedstawia przykładowe pomiary lokalnych stacji UKF-FM w Płocku, wykonane 1 maja 2019 r. (popołudnie i wieczór) przy użyciu FM MPX power monitor z odbiornikiem SDR Airspy HF+. Każdy pomiar odbywał się na kierunkowej antenie (Körner 19.3 lub 2×9-el Yagi) i trwał 31 minut (w tym 60 sekund do uzyskania poprawnej wartości MPX power). Przygotowałem również skrypty generujące histogram dewiacji oraz wykres mocy modulacji multipleksu (gnuplot). 

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FM MPX power monitor

I created a simple MPX power meter using GNU Radio software. It was a quite enjoyable task to create a block diagram of a stereo WFM receiver together with a bit more advanced deviation meter with GNU Radio Companion environment. In order to obtain reasonable results, the measured signal must be perfectly clear and strong.

ITU-R SM.1268 provides detailed information about required conditions for measurements. The signal level should be at least −47 dBm (73 dBf) together with SINR (signal to interference and noise ratio) of 50 dB or more. Also, there should be no multipath interference, so a directional antenna is probably the only option.

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Lato i jesień 2018: nowe rekordy Wi-Fi DX 5 GHz

Jest to kontynuacja wpisu Wiosna 2018: nowe rekordy Wi-Fi DX 5 GHz.

Lato 2018 roku zapisało się jako najcieplejsze w historii obserwacji meteorologicznych, zarówno w całej Europie, jak i Polsce. Rekordowa pogoda, trwająca od wczesnego początku wiosny, przynosiła znakomite warunki propagacyjne na pasmach mikrofalowych rozszerzając standardowy zasięg nadajników poprzez zakrzywianie ścieżek sygnałów lub formując dukty troposferyczne.

Korzystając z mojego zestawu odbiorczego, składającego się z masztu o wysokości 18 metrów wraz z rotorem i dwupolaryzacyjną anteną paraboliczną o zysku 31 dBi na pasmo 5 GHz, mogłem prowadzić dalsze obserwacje propagacji mikrofalowych w troposferze w okolicy Płocka. Dzięki integracji programu z obsługą rotora możliwe jest automatyczne skanowanie sieci w wybranym zakresie azymutów i zapisywanie wszystkich danych, bez mojej ingerencji.

Podczas wiosny uzyskałem nowy rekord odbioru sygnału Wi-Fi w paśmie 5 GHz (i to dwukrotnie) w odległości 370 km. Ale to był przecież dopiero początek sezonu na tropo. Jak powszechnie wiadomo, najciekawsze, najsilniejsze i najbardziej spektakularne propagacje troposferyczne występują w Polsce na jesieni. Tak też było i tym razem…

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Review: Airspy HF+

Airspy HF+ is a software defined radio receiver (SDR), which has been widely available since 2017. Unlike most of other devices, it has some cutting edge features like very high dynamic range sigma-delta ADCs and a polyphase harmonic rejection mixer. This receiver supports multiple frequency ranges: 9 kHz – 31 MHz, 60 – 260 MHz and 1.2 – 1.67 GHz (undocumented).

HF+ uses STA709 front-end tuner IC with two Σ∆ ADCs at 36 Msps, which are an equivalent to direct sampling at 72 Msps. The digital signal is decimated, scaled down and streamed via USB. The output I/Q stream provides 16-bit samples at 768 Ksps rate, but the usable bandwidth is a bit narrower though, up to 660 kHz. Actually, this is not much, but seems to be enough for HF, and some purposes at VHF band. More information about this receiver, including a detailed block diagram, is available on Airspy website. This review concerns VHF reception only (i.e. 87.5 – 108 MHz FM broadcast band).

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October 2018: Wi-Fi DX record at 460+ km (UKR/LTU)

Out of the four seasons, autumn is well known among radio enthusiasts as the best period for spectacular propagation of radio waves. The tropospheric ducting is a propagation mode based on temperature inversion in the vicinity of the Earth’s surface. Such an enhancement extends the regular line-of-sight distribution of electromagnetic waves to the areas out of their general, daily service. During special conditions, air layers may form some kind of a guide for the radio signals. This phenomenon usually happens during periods of stable anticyclonic weather and affects radio frequencies in VHF, UHF and microwave bands. While it is possible to watch distant TV channel or listen to a foreign FM station, one can also check other, less explored radio frequencies… like the 5 GHz band widely used for the wireless LAN communication.

This year was really extraordinary in Poland. The spring was very amazing, as both April and May smashed through all previous temperature records. We have also experienced the warmest summer, at least since the beginning of measurements in 1781. Such weather allowed often occurrence of radiation inversions that produced good tropospheric propagation throughout nights and mornings. I set my previous personal Wi-Fi DX reception record in May twice in a row from Wolin, Poland during unattended scanning on 2018-05-28 and 2018-05-29 mornings, at a distance of 370 km.

In the first half of October 2018, a high pressure system settled down over Eastern Europe and brought excellent propagation conditions in Poland. Again, the summer-like weather brought sunny days and 20-25 °C temperatures. This time I logged some networks from Ukraine, Lithuania and almost… 3600 other from Poland.

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