Introduction to Roomcap
The Roomcap is a very different
Yet are nearly all constructions are made by wire,
where the wire mostly is
leading up (vertical)or a horizontal wire going to both
sides (at dipole),
or a long wire let to one side.
My new antenna is a plane (or surface), which
works as radiator.
In the beginning I was working with aluminium foil (and
copper foils), but
the wind resistance was very high, therefore now I work
with wire grid, which
behaves like metallic foil, but have nearly no wind
An antenna has the purpose to radiate the transmitter
power as EM wave
in efficient way into space - and to capture wave from the
One wants to produce wind from mechanical power, you can
a knittle needle (20 cm to 150 cm long), or you waggle
with a cardboard
(10cm x 10cm size). You see cleary, that with a cardboard
a stronger wind that with a knittle needle.
The same applies for electric use:
If you bring an electric oscillation to a plane, you will
obtain a stronger
EM radiation, than when you bring oscillation to a wire.
From the transmitter you obtain power as current and
voltage (in phase).
The antenna should radiate the power as a EM wave. The
consists of two components: E field and H field.
(electric field and magnetic field).
In order to radiate real power, both fields have their
strength at the same location. Both components have to be
See your wire antenna, you note, that the current want to
fly to the end of
the wire. There, the current stops, and therefore the
current flow comes
to 0 at the end.
Therefore, the voltage reaches a maximum at the end of the
the current has to "reverse" of the direction, and there
we have a jam
of the charge carriers, where we have a current flow of 0.
The speed of the wave will cause, that at 1/4 wave length
distance from the
end of the wire we obtain a current maximum. At this point
we have a null
of the voltage.
Correspondingly we have a null of the E field, where we
have a null
of the voltage; therefore we have a maximum of the H field
at this point.
1/4 wave longth beside we have a null of the H field, and
there we have
a maximum of the E field.
(See the current/voltage diagram of the half wave dipole).
A real power occurs, when the product of the both fields
is not null.
However, there is always one factor is 0 ...
Therefore, this field is NOT radiating. This applies to
Only on distance, a far-field emerges, where the E field
und H field
are in phase, then this field is radiating.
This range, where the near-field converts to the
far-field, this range
is called transition zone.
Here the new idea:
Use of a plane instead of a wire.
The length of the plane have to be short in relation to
the wave length,
otherwise, the same would occur as wrote above, because at
of the plane we would get a voltage drop, and we would
no radiating near-field.
A short length of the plane, in order that the voltage
over the length
of the plane remains nearly at the voltage maximum
to the cos function for
The current flows at the beginning of the plane, and flows
over the full length into the space, according to the
as I describe it in the theory part, you can see it in the
(A plane forms a open
Through this new constellation of the planes we obtain:
At the same location the both E field and H field consist
from the beginning,
and therefore results the high efficiency of the antenna.
Correspondingly, the far-field begins at the antenna !