One practice which seems common when operating temporary or portable QRP, SOTA, etc., is to throw a counterpoise wire out on the park lawn or shrubbery, mountaintop or hillside or parking lot ground, etc., not buried or wetted, connected to either the (ungrounded) transmitter or an antenna tuner.

So, continuing on with the subject raised about voltages in dipoles, and voltages in beam/Yagi-Uda directors/reflectors, assume an insulated or near-ground counterpoise wire that is roughly a quarter wavelength in length, and a transmitter power in the range of 5 to 10 Watts.

What kind of voltages might appear on such a counterpoise wire?

Does it make a difference whether the antenna is a lambda/4 resonant or non-resonant vertical or a balun-end-fed half wave?

Do these voltages raise any safety concerns?


There are a lot of variables involved in calculating the voltage on an antenna. If you require an accurate answer, the solution is to model or empirically measure the particular antenna in question.

But for a very rough estimate, a 1/4 wave "counterpoise wire" is effectively one leg of a half-wave dipole, so you can treat it as such to get some number. In practice voltage will probably be less due to ground losses.

Generally, it's very difficult to create any kind of shock or RF hazard with a transmitter of only 10 watts. I wouldn't worry.

  • 2
    $\begingroup$ Agreed. OTOH, I nearly caused a forest fire when the open end of a wire antenna driven by a 1500W transmitter rubbed against a dead tree! $\endgroup$
    – Brian K1LI
    Oct 1 '19 at 0:41
  • $\begingroup$ Could we generalize the answer by suggesting that the High Voltge Point may be the square of the B+ in the final am $\endgroup$ Oct 1 '19 at 21:35
  • $\begingroup$ My guess is that in the worst case scenario --where the radial was elevated several feet above ground-- one could get a small RF burn from the very end. Insulated wire and a wire nut over the end of the wire should prevent that. $\endgroup$
    – Mike Waters
    Oct 1 '19 at 22:22

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