70 meters high tower carries 8 5-element 15m yagis as pairs separated horizontally by 12 meter distance and vertical stacking is 14 meters. The heights of the antenna pairs are 64, 50, 36 and 22 meters.
Antennas are Optibeam OB5-15:
www.optibeam.info/index.php?ar...
Tower is produced by 4O3A/YT3M:
www.4o3a.com/index.php?option=...
Antenna has ca 16 dbd free space gain and over 24 dbi gain at 4 degrees over real ground. Beamwidth is less than 30 degrees. Testing confirms exactly the modelling results. Pattern measured with signal generator and SDR was almost identical to what the computer suggests and signal levels drop ca 12 db when antenna is 20 degrees off and already 20 db when 25 degrees off the correct direction. There is huge -50db+ null at 90 degrees confirmed with real measurements (!) and ca -20-30 db signal drop on the other directions.
The stack has phase switching capability which allows any pair of the 4 to be switched out of phase to change the radiation angle. Pre-configured steps are 4, 7, 10, 15, 30 degrees while maintaining most of the gain as all antennas are always connected
Photo gallery from the tower erection is here: pontu.eenet.ee/es5tv
73
Tonno
ES5TV
4 фев 2013
