Topband: Strange behaviour of radial systems

[Tom W8JI]

Kees,

What else is around your verticals? Just the fact something is not resonant 
does not mean it isn't a problem.

> To my ashtonishment, vertical 1: 28-j328 Ohm and vertical 2: 12-j320 Ohm 
> both on 1825 kHz.
> The vertical with the smallest radial system has the lowest earth 
> resistance (around 5 Ohms, estimating 7 Ohms radiation resistance for a 
> 21m high vertical).
> The oldest vertical (nr1) with 50 radials seems to have more than 20 
> Ohms.....
>

Since it is a system with standing waves, even on the radials, impedance at 
the base might not represent true ohmic losses.

> I measured the earth conductivity with the 2-conductor method and I found 
> that the soil under vertical nr 2 has better conductivity (maximum found: 
> 25 mS/m) compared to vertical nr
> 1 (maximum: 21,5 mS/m).

If that is a low frequency measurement, I have never seen a measurement like 
that mean very much on HF or higher. Typically you are measuring rod contact 
and 50/60 Hz more than RF behavior.

If it is an RF measurement, like rod centered on a large screen and measured 
against the screen, it is much more useful but still not always accurate.

I have little faith in two rods, and no faith in something done on power 
line frequencies.

What you measure might not mean anything for performance.

73 Tom