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FRANKLIN BEAM ANTENNA

Notes:

The Beam antennas were a notable piece of engineering and while electronics has changed beyond recognition, antenna theory remains much the same. (Excluding quack designs like Cross Field Antenna!)
Franklin developed a uniformly excited broadside phased array. The antenna, which became known as the ‘Franklin Beam’ used a number of co-linear vertical radiating wires with a screen of vertical wires placed behind to form a reflector. (The number of vertical wires depended upon the wave length but could vary from a minimum of 8 upto 24 for a high gain HF array)
For most services, where frequencies for day and night operation were required, two antenna arrays were required and a typical Beam Antenna System was suspended between of 5, 85 metre masts.
Feeding the transmitter output to the antenna was achieved by the invention of a coaxial feeder, implemented by the use of concentric copper pipes separated by porcelain insulators. A number of junction boxes were used to divide the energy between the various elements of the antenna array.
It is difficult to imagine tuning and phasing multiple antenna elements without the modern day convenience of a network analyzer.

(Beam antenna cheese graphs)