403 MHz Antennas

Last Update Jan 2nd 2015

Radio Sonde hunting and tracking

Weather ballons carrying small transmitters are called Radio Sondes. These weather ballon payloads transmit air temperature, pressure and humidity along the way the ballons drives during it is airborne. The data are transmitted using radio telemetry. A frequented band for these kind of services is 403 MHz. Output power of the small transmitters is around 50 to 500 mW.

Due to the immense height a weather ballon can climb such a weak signal can be monitored over a distance of several hundered of kilometers with a good directive antenna and most SDR or FunCube receiving frontends. With free licenses software the flight data can be tracked all along the ballons journey.
Some builders of my Yagi designs have tracked Sondes over 500 to 600 k easily with full telemetry reading.

Because the transmitters antenna is a 1/4 λ wire hanging down form the load only on most ballons, polaristion during flight period is vertical. After the ballon hull bursts high up in the atmosphere this becomes random polarisation during the sinking phase.

For further information I can not deliver much, I only do these antenna designs, but here are some links
i) French Yahoo Group "radiosonde-monitoring@yahoogroupes.fr"
ii) http://www.radiosonde.eu/RS04/RS04C.html
iii) http://www.rtl-sdr.com/receiving-weather-balloon-data-with-rtl-sdr/
All in French, but plenty of details
iv) http://www.radiosonde.eu/RS08/RS08A.html#08

Yagi identifier notation:

YBN = with standard Dipole (Straight Split or Folded), GTV = with bent Dipole
n = narrow-band version; m = of medium band width, w = wide-band version, z is for low impedance Z,
an added LT (in tribute to the EF0210LT by YU7EF) stands for exceptionally low Antenna Temperature

Yagis with conventional Dipole - direct 50 ohms

14 ele. YBN RS-14w 16.1 dBi / 3.1 m

Low Impedance Yagis with Straight Dipole - 28 ohms / 50 ohms via DK7ZB Match

8 ele. YBN RS-8wz 13.1 dBi / 1.3 m

GTV Long Yagis with bent DE - direct 50 ohms

19 ele. GTV RS-19m 17.8 dBi / 4.5 m

73, Hartmut, DG7YBN