Characterizing Yagi Antenna Directionality via ADS-B Reception

Over on his blog Alex Krotz has been investigating whether adding more passive director elements actually affects the directionality of his home made Yagi-Uda antenna. Instead of using modelling software, Alex wanted a more accurate result that took into account all the imperfections of his antenna.

His idea was to receive ADS-B signals with his Yagi and a dipole antenna, then compare the data received in order to determine in which directions the Yagi receives better than the dipole. To do this he first creates a standard 2D map of plane tracks collected over a 24hr period for both the dipole and Yagi. A gaussian blur is applied to the two maps in order to fill in blank space and the data is normalized. Then he simply subtracts the dipole plot from the Yagi-Uda plot. The resulting difference plot reveals a mapping of where the Yagi receives better or worse compared to the dipole in a 2D plane.

Directivity of the Yagi revealed by comparing against a dipole
Directivity of the Yagi revealed by comparing against a dipole


  1. Ladislav OK1UNL

    OK, that is true, at original topic is a noticed coaxial cable RG-58. This one cable is not usefull for 1090MHz for his high attenuation. Exist much better low loss coaxial cables with impedance 50R originally made for WiFi nets.
    Like H155 or RGC54 etc….. and prices are quite good.

  2. dietrich

    Nice idea!
    But the measurement should be done in a more open space. The setup on the picture with balcony railing and the walls looks somehow useless for antenna measurements.

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