A coil-loaded counterpoise at a low height above ground is used to provide an artificial ground for an antenna when, for some reason, a true ground connection is not possible or there is not enough space to erect a full 1/4-wavelength horizontal wire.
The principal effects of low height are a loss resistance induced in the wire from the ground, and a reduction in propagation velocity along the wire.
A counterpoise can be considered to be an artificial ground. Its input resistance at resonance is equivalent to the input resistance of a true ground connection but its resistance will never be as low as a good ground.
To provide a lower input resistance three or four counterpoises can be used in parallel. Or they can be resonant on different bands.
New program C_POISE estimates the performance of a single coil-loaded counterpoise. The number of turns on a coil of given length and diameter needed to resonate a low wire to 1/4-wave resonance is calculated. The input resistance at resonance is also estimated..
All program output data is approximate due to the very low height of the wire above ground and uncertainty in the characteristics of the soil or whatever other materials may be under the wire. The wire may be allowed to rest on the ground surface but uncertainty will be at a maximum. It will nearly always be needed to prune the wire length for resonance. Or when the wire length is fixed the coil turns may need adjustment.
When wire height exceeds wire length accuracy is much improved. Input resistance at resonance will be fairly small. Working Q will be high and the counterpoise will behave as a short antenna. For precise resonance the wire will still need pruning.
Download program C_POISE in a few seconds from website below and run immediately.
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