Evaluation of the two-band WEBSDR using the RigExpert AA-55 ZOOM antenna analyzer. Part 2


The hardware part of FAIRS WEBSDR that was described in the first part of this article required a two-band low-noise antenna for effective reception. 

There are many different antenna systems used by amateurs for these purposes.

Mainly it is random wires, small coaxial loops, flags of different shapes, and sometimes more sophisticated beverage antennas and arrays of short verticals. Recently, the so-called “on-ground antennas” are becoming popular. These are “beverage on ground” or BOG and “loop on ground” or LoG, designed by KK5JY http://www.kk5jy.net/LoG/. 

These antennas have good Signal/Noise ratio but signal pick-up levels are very low due to their low efficiency which requires high gain pre-amplifiers. We decided then to use the full-size 160m loop mounted 4 to 6 meters above ground. This allowed us to preserve the excellent Signal/Noise ratio and at the same time to receive strong signals both on 160 and 80 meters.

This antenna has a perimeter of approximately 160 meters and is made of twisted military telephone wire. It is supported by wooden 6m poles.

The antenna is fed by high-quality RG-6 coaxial cable and was tuned to resonance at 160 meters with the help of RigExpert AA-55 ZOOM antenna analyzer.

This antenna is resonating on both bands as predicted with SWR =1.11 on 160 meters and 3.1 on 3520kHz which is acceptable for receiving applications.

FAIRS WEBSDR is listed in the worldwide directory and is up and running.