R: [TowerTalk] COUNTERPOISE for Dipoles

[Maurizio Panicara]

A loop is composed by two half wave bend dipoles and not by two quarter wave
dipoles.
True that the radiating portion is almost confined in the quarter wave
sections before bends but the parts after bends don't contribute to
radiation because side to side opposite in phase (and small in current) and
not because of beeing effectively a sort of end loading devices.
It's easy to see that current distribuition in the parts after bends is
linerly distributed like in a straight half wave dipole and not constant as
it would happen in the capacitive loading sections of a shortened dipole.

73,
Mauri I4JMY.

----- Original Message -----
From: Tom Rauch <w8ji@contesting.com>
To: <towertalk@contesting.com>; Tom K Osborne <w7why@juno.com>
Sent: Sunday, August 13, 2000 4:29 PM
Subject: Re: [TowerTalk] COUNTERPOISE for Dipoles


>
> > > Consider a loop. It is really two bent 1/4 wl long dipoles, one is
> > > center fed and the other is fed from the ends by the "bent" loading
> > > sections. These loading sections have phase reversal at the 1/2 way
> > > point, and oppose each other, so they contribute nothing to far- field
> > > radiation.
> >
> > Now I'm really confused.  I thought a full wave loop was 2 half wave
> > sections stacked a quarter wave apart.  What am I missing here??
> > Tom W7WHY
>
> I edited that wrong. The quad element is two 1/4 wl long dipoles
> spaced 1/4 wl apart. Take the "bent" out ahead of the 1/4wl
> dipoles, and it will be better.
>
> The 1/4 wl dipoles aren't bent, they are simply end-loaded by the
> sections beyond the "bend" that contribute nothing to far-field
> pattern.
>
> So what you have is two stacked 1/4 wl long end-loaded dipoles.
> You have the gain of two end-loaded 1/4 wl dipoles stacked 1/4 wl
> apart.
> 73, Tom W8JI
> w8ji@contesting.com



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