In message , Szczepan
Bialek writes

"Ian Jackson" napisal w wiadomosci
...
In message , Rob
writes
Szczepan Bialek wrote:

napisa³ w wiadomo¶ci
...
Szczepan Bialek wrote:

"Ian Jackson" napisal w
wiadomosci
...

In the past, many amateurs did connect coax directly to a dipole.

And what they do if they have the monopole?

Connect it with coaxial transmission line, idiot.

If the monopole has only one radial it is exactly as the your dipole.
Right?

No. A monopole needs many radials, not one. if it has only one radial
the voltage at the end of the radial is the same as on the monopole,
and the whole thing becomes a dipole.

I think we need to avoid Szczepan's black and white (and usually
completely wrong) way of thinking about things. We need to consider "When
does a monopole become a dipole" (or vice versa).

With no actually ground connection, you could have a nominal monopole with
(say) only one radial (eg an extremely badly radiating quarterwave radial
running horizontally at ground level, and a quarterwave radiating element
going vertically (or semi-vertically) upwards. If you then raise the
radial so that it starts to radiate better - or if you raise the whole
antenna system away from the ground - it will then increasingly become a
dipole.

Real dipole has symmetric voltages not in phase (180).

But what happens if the voltages are not quite absolutely symmetrical?
When does it cease to be a dipole?

Of course, while a monopole with a single ground-level radial (and no
ground connection) would work quite well, it would not be as good as if
you added more (preferably spread out) radials. And the more radials you
add - especially if any overall radiation from the radials is negligible -
makes the antenna system more definitely a monopole than a dipole.

I have found that in Polish description the dipole used by radio-amateurs
consists of the radiator and the counterpoise.

If that is true, then that description is essentially wrong. Maybe it is
a translation problem?

It is explained that it is geometrically symmetric.

That is essentially true. However, what happens if the symmetry is not
quite absolutely perfect? When does it cease to be a dipole?

Does anybody use the real dipole?

I doubt if many who use an antenna which has a radiator and a
counterpoise would think of it as a dipole. However, as I have
suggested, it is all a matter of degree, ie how much radiation comes
from the 'counterpoise'. A counterpoise is really intended to provide an
artificial ground - especially in conditions where it difficult to get a
good ground connection, or where the conductivity of the ground is poor.
Usually, the intention is that a counterpoise does not (or does not need
to) radiate. Multiple counterpoises are effectively radials, which are
definitely not intended to radiate.

If a dipole is fed directly using coax - but without a balun, the
'counterpoise' side of the dipole (the side connected to the coax
screen) radiates considerably. Also, a lot of the current in the
'counterpoise' side flows on the outside of the coax. This means that
the coax itself radiates (even if it perfectly grounded at the
transmitter end). Depending on the particular situation, this may - or
may not - cause problems. To prevent the possibility of problems caused
by radiation from the coax, a balun should be used.
--
Ian