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Do end fed antennas need a counterpoise?
5 Answers. No, it is not needed, but it can improve the antenna system. An EFHW is simply a half-wave length of wire and a matching device, and that’s it. Counterpoises are commonly added to shunt common mode reflections when operating outside of the wire’s resonant frequency to avoid RFI issues (“RF in the shack”).
How long does it take to counterpoise an end fed antenna?
A standard recommendation (see QST, March 1936, p. 32, “An Unorthodox Antenna”) is an 84′ long end fed and a 17′ long counterpoise (6.5′ for 20m)….Wire Lengths for Various Band Combinations.
| Group | USA Bands |
|---|---|
| d | 80-40-30-20-17-15-12-10 |
| e | 160-80-40-30-20-17-15-12-10 |
| f | 160-80-60-40-30-20-17-15-12-10-6 |
What is the behaviour of an antenna counterpoise?
The wire length must therefore be less than 1/4-wavelength. The behaviour of an antenna counterpoise, being located at a low height above ground, is quite complex and is aggravated by the uncertainties in the ground resistivity and permittivity. As a consequence, all program output data is approximate.
How thick should counterpoise wires be in an antenna?
As I understand using three 1/4 wavelength wires just laying on the ground in all directions with 120° between them is considered a good practice, or a starting point at least. What I don’t know is whether counterpoise can conduct a large current and thus I don’t know how thick these wires should be.
Can a ground radial be used as a counterpoise?
Ground radials are also not a practical solution for portable operations. A simple and portable alternative to this problem is a RESONANT COUNTERPOISE. As implied above, you need a low impedance ground connection for the outer shield of the coax right at the feedpoint of the antenna.
What kind of dipole is a vertical counterpoise?
If you elevate your antenna and leave the counterpoise hanging down in a straight line, you will effective create a vertical 1/2-wavelength dipole.