I’ve been doing some antenna modelling and comparisons for John, W2VP comparing some phased and parasitic arrays. One of the phased arrays I modelled was an End-Fed-Half-Wave (EFHW) phased vertical array for the 40m band. It’s got such a nice radiation pattern that I thought I’d add it to my antenna pages here on the website for others to read too.
The EFHW Vertical Phased Array is as simple as two vertical half wave wires both of which are fed via their own 49:1 Unun. Wire 1 (radiator) is exactly 20m tall and wire 2 (reflector) is 21m tall. The space between them is exactly 10.5m.
This simple antenna arrangement gives a surprisingly good radiation pattern with a reasonable forward gain and front-to-back (FB) ratio.
The antenna has quite a wide beam width which is to be expected from a pair of phased verticals. The nice thing about this array is that it has very little in the way of high angle radiation. This makes this antenna ideal for long distance communications. This isn’t an antenna for local chatter!
The 2D Far Field Plot shows that the antenna has a forward gain of 3.16dBi at 19 degrees. This is some 8 degrees lower than a typical 1/4 wave vertical phased array. The array also has a very respectable front-to-back (FB) ratio of 20.53dB.
Both elements in the array will need to be fed via individual 49:1 Ununs with the reflector requiring a feed phase angle of 100 degrees. A 100 degree phase angle gives better performance than the typical 90 degree phase angle that is typically used for 1/4 wave arrays.
For such a simple design this antenna should give great DX results as long as you have the necessary supports for the two vertical wires and the space for the guy lines. If only my garden was much bigger and I had some large trees to hand!
Summary:
Radiator (Element 1): 20m
Reflector (Element 2): 21m
Reflector Feed Phase Angle: 100 Deg
Wire Dia: 4mm
Feed Type: 49:1 Unun on each vertical element and a phasing harness
Impedance: 50 Ohm
SWR: <1.5:1 across whole band