[Lf] Re.Ground Loss

[Andre' Kesteloot]

Hans-Joachim Brandt wrote:

> Dear Lawrence,
>
> remembering the few results on ground resistance measurements published on this
> server I would regard your 120 ohms somewhat above average for 136 kHz. My own
> value is in the order of 80 ohms when using the house ground, and also when
> using an insulated radial system consisting of 28 wires of 10 m to 30 m in
> length, depending on the space in the relevant direction. Someone who had used
> his 160 meters ground system with several long buried radials also for LF had
> reported a value of 50 ohms at 136 kHz.
>
> I have just heard of two reports of house grounds of about 25 ohms; in this
> cases a tube 12 meters deep into the ground is employed, or an extended wire
> ground system also deep in the ground.
>
> Paralleling different grounds may be a special problem. Direct paralleling often
> results in an INCREASE in ground resistance. Therefore some stations use link or
> transformer coupling between feeder cable (connected to the house ground) and
> the antenna ground, to avoid the bad effect of direct paralleling.
>
> But if both ground systems are tuned against each other the resulting resistance
> may be the same as one ground system alone, or luckily somewhat lower, but never
> the value that is expected due to the paralleling of two resistances.
>
> >From next spring onward I will do further experiments with bare radials buried
>
> flat into the ground, before settling on a final solution.
>
> 73 Ha-Jo, DJ1ZB
>
> LAWRENCE MAYHEAD schrieb:
> > I have just measured my TX ant impedance(R term) and it is 120 ohm! much
> >  higher than I originally thought.It is of course all ground loss,I am using
> >  3 ground rods close to the TX and the house water/mains system.I wonder
> >  wether anyone can  offer me comparitive figs for impedance and details of
> >  ground systems?
> > To improve I will have to put in an awful lot of radials! or consider
> >  counterpoises.
> > 73s Laurie.
> >