Thread: Antenna Theory
View Single Post
  #8   Report Post  
Old September 12th 06, 09:46 PM
Felix Felix is offline
Junior Member
 
First recorded activity by RadioBanter: May 2006
Posts: 15
Default

Quote:
Originally Posted by Cecil Moore
Richard Fry wrote:
If in both cases the matching network has a 2 ohm loss, there is a 10
ohm loss in the r-f ground connection, ...


Thanks, I should have said the problem is getting the
RF energy into the radiation resistance.
--
73, Cecil http://www.qsl.net/w5dxp

Thanks to all,

for your comments and opinions.
I expected this type of arguments!

Let me comment them:
N3OX, Dan, wrote his confession in antennas...
The fundamentel part :"We believe in the fundemental difficulty of
delivering power efficiently to physically small radiating structures,
and we understand the limitations it places on such structures as
compared to their full-size counterparts."
The difficulty is here, and most antennas of traditional design are suffering
under this, and therefore are inefficient, if the relation l/lamdba is small.
That's different in my design:
The Varylink is part of the antenna and permits to feed the available
input power with over 90% efficiency into the radiation resistance Rr of
the antenna. Furthermore, the relation Rr / Rloss is very high, which
ensures that the power is radiated, and not burned.

Wim, PA3DJS, is addressing a very similar problem.
He calculates an overall efficiency of 5% (-13db) under his assumptions.
He is also basing his calculation on data available from traditional
constructions. Im my design X/r is between 28 and 50, depending
upon frequency and version, and at the same time the total series
loss resistance is about 10 times smaller than the radiation resistance.
These characterists ensure, that the efficiency (radiated power/accepted power)
is in the order of 90 percent.

Cecil, W5DXP, is referring to EZNEC, calculating that the small antenna might
achieve practically the same radiation as 1/4 lambda monopole.
His problem again is, how to get the power into the radiation resistance of
the antenna. This is done as said above.

RF, Richard Fry, is addressing the losses in the matching, and most important,
in the ground loss.
The efficient matching is answered above.
The ground loss is very important for efficient radiation of the energy into
space and not into the ground!
This ground loss is not addressed in the IEEE formula for calculation of antenna
efficiency, as it says: efficency = radiated-power/antenna-accepted-power.
This does not take care of the fact, that in most real antennas, a large amount
of the radiated power is lost in the ground as induced ground currents!

To minimise these losses I am using a special grounding concept, based on
a differential, floating feeding system, ensuring that ground losses are minimal, and that
the radiated RF energy reaches the space towards the ionosphere.
All this ensures the high efficiency of the small antenna, so far not
reached by other designs.

Felix Meyer, HB9ABX