Topband: Another DXpedition 160 Vertical Idea

[Larry Higgins]

> Larry Higgins said:
> > However, it is also true that vertical dipoles do induce current in the
> > ground, and the energy transferred to ground comes from the transmitter.
>
> I've seen this warning many times, but when I actually compared a half
> wave vertical with no radials to a quarter wave vertical with
> 32 radials, the difference was too close to measure (ie less
> than 3 dB).  This comparison was done on 20 meters, so we can't
> be certain that the results would hold on 160 meters.  Still, it
> does suggest that the losses aren't all that high.
>
> Rick N6RK

Thanks for that info, Rick.  Measurements are hard to argue with.  And your
results make sense.

>From what I can remember from my basic physics class (50 years ago), for
small points the current induced by the E field diminishes as the square of
the distance between the charges.  I don't know if that holds true for an
antenna element near lossy ground, but I'm sure the induced current would
fall off pretty quickly as the antenna is moved higher.  How high was the
bottom of the dipole? And what kind of soil?

Maybe one of our list subscribers with EZNEC can run a series of heights and
shed further light on how much loss to expect.

73

Larry, N9DX




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