Arduino Uno R3 failure

Recently I’ve got a genuine Arduino Uno R3 from my friend to repair. The problem with his board was actually very generic – it has just stopped working. Personally, I don’t buy such boards, because  they are extremely overpriced. I have been using several Chinese clones around for years and I have not encountered any problems so far.

At first sight, the USB interface was working fine and the board was detected by the system without any problems.

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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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June 2019: London, Manchester and Cardiff via tropo in Poland

Ten wpis jest dostępny także w języku polskim: Tropo: Londyn, Manchester i Cardiff w Polsce

The early morning of June, 27th 2019 brought one of the biggest tropospheric propagation from Western Europe we have ever observed from Poland. Looking at the results, it can be stated that it was the strongest tropo on the VHF FM band 87.5-108 MHz from the territories of England, the Netherlands and Belgium for at least 15 years (probably since ever), with many transmitters and areas received for the first time. The received signals reached the stereo and even RDS quality on many frequencies, and the maximum distances exceeded 1500 km.

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Tajemniczy sygnał DRM na 3267 kHz

Dziś wieczorem (19 maja po godzinie 22) w trakcie przeglądania zakresów fal krótkich natrafiłem na sygnał przypominający typowy sygnał DRM. Zajętość pasma wynosi około 10 kHz, a po falowaniu sygnału można przypuszczać, że jest to jeden sygnał pochodzący z określonego kierunku. Postanowiłem przekierować wyjście audio z programu gqrx na DReaM i uzyskałem następujący wynik.

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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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