Antenna Theory:

There are many textbooks telling that an antenna
to be effcient needs "much wire in the air".
Now the time has come to correct this view.

This new view is based on many practical tests
on all HF bands over a year.
As en example read the email below.

The antenna used for this contact was 3 meters
long and 1.5 m above ground. (= RoomCap Antenna)
The contact was on the 160m band over a
distance of 600 Km.

Date: Thu, 31 Aug 2006 22:57:42 +0200
From: Heino Held
To: hb9abx (at) tiscali.ch
Subject: Mobilantenne oder Festantenne

Hallo Felix,

nach unserem tollen QSO auf 160m waren
Peter (DL1BLD) und ich (Heino, DJ5ER) total
erstaunt mit welch einer tollen Feldstaerke Du
in Bremen angekommen bist.
Wie man eine solche Antenne bauen kann
moechten wir gerne wissen (auch fuer die
anderen KW-Baender).

73 aus Bremen von Peter (DL1BLD) und Heino -
DJ5ER

--- ---

Translation of text:

Hello Felix,

after our fantastic QSO on 160m we (Peter,DL1BLD)
and I (Heino, DJ5ER) we were completely surprised
with what a strong field strength you arrived in Bremen.
We would like to know how such an antenna can
be built (also for the other HF bands).

73 from Bremen ....

--- ---

Heino will receive the construction guide.

Best regards

Felix HB9ABX

On Fri, 1 Sep 2006 22:01:21 +0000, Felix
wrote:

There are many textbooks telling that an antenna
to be effcient needs "much wire in the air".

Were they written by Joe Miller?

Felix, dude, repeat after me:

"We believe in the one way, the addition of fields, radiated from
wires, combined spatially in phase to give gain, or loss, or fire in
the case of too much loss. 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. We believe in the QSO, and
that any antenna can provide many enjoyable ones. We believe in your
puny 160m signal, that we dug from the noise with our phased Beverages,
and replied in kind with our legal limit and transmitting four-square,
and you received us well, yea and verily, despite your use of a
dummy-load. We believe in the gain, 20dB or more, that an antenna may
exhibit when it or its plans are meant to be sold. We believe in the
measurement, scientific and clear, showing clear quantitative
comparisons to a suitable reference aerial; let it now be done, or may
you fall silent."

73,
Dan

Hello Felix,

Regarding antennas that are very small with respect to wavelength.

With regards to your example, no correction to antenna theory is
necessary. Small antennas can be efficient radiators, but the smaller
the antenna, the more difficult to achieve reasonable efficiency.

Antenna theory is well established. When you know the current
distribution in a structure, one can calculate (mathematically or
numerically) how much power is radiated (and also how much power is
dissipated in the structure). This approach is used by virtually all
Antenna Design software packages.

All electrically small antennas have one thing in common, the usable
bandwidth is small. The Q-factor of a lossless electrically small
structure is proportional to
about 0.05*lambda^3/Volume.

For example a small loop of thin material with infinite conductivity
has higher Q-factor than a loop of same diameter, but made of very wide
strip (with infinite conductivity). The last one occupies more volume
and therefore has lower natural Q. The Q-factor of practically small
antennas can be that high that the bandwidth may by just a few kHz.

The problem is in the matching. Matching, for example 0.8 Ohms in
series with a reactance of 2800 Ohm (Q=3500), to 50 ohms is not easy.
The Q-factor of the components is not high enough, some or most power
is dissipated in the additional components, or even the antenna wire
itself. So in the end your antenna may have an overall efficiency of
5% (-13 dB). Also voltages can be that high that power is lost by
corona effects. Often, due to the high local E- and H-fields, power is
lost in nearby constructions.

About the practical use of small antennas. In many cases received
signal levels are in the S9+20 dB range. As the noise level is far
below this, loosing 13 dB (so your signal level will be S9+7 dB), is
acceptable. If not, you may increase the input power. In the end, the
small inefficient antenna is at least better then no antenna.

So in my believe, a nice QSO over 600 km with a small antenna, doesn't
prove that antenna theory has to be revised.

I'm very curious to see the construction details.

Best regards,


Wim
PA3DJS.

Felix wrote:
Antenna Theory:

There are many textbooks telling that an antenna
to be effcient needs "much wire in the air".
Now the time has come to correct this view.

What textbooks say that? EZNEC says that a 3 meter
tall monopole has a maximum gain of 1.5 dBi on 160m
while a 38 meter 1/4WL monopole has a maximum gain
of 1.36 dBi. In other words, they radiate approximately
equally well both with high radiation efficiencies.

The problem is not with the antenna's ability to
radiate. The problem is in getting the RF energy
into the antenna.

The problem is not with losses in the antenna. The
problem is finding an efficient j2250 inductor for
the matching network.

If we knew what your matching network looks like, we
could estimate its efficiency.
--
73, Cecil http://www.qsl.net/w5dxp

"Cecil Moore"
What textbooks say that? EZNEC says that a 3 meter
tall monopole has a maximum gain of 1.5 dBi on 160m
while a 38 meter 1/4WL monopole has a maximum gain
of 1.36 dBi. In other words, they radiate approximately
equally well both with high radiation efficiencies.

The problem is not with the antenna's ability to
radiate. The problem is in getting the RF energy
into the antenna.

The problem is not with losses in the antenna. The
problem is finding an efficient j2250 inductor for
the matching network.
_____________

Radiation resistance, and the r-f resistance in the path for induced ground
currents back into a practical antenna system have a larger effect, though.
Here are some numbers for two vertical monopoles of about the same scale of
height to width.

If in both cases the matching network has a 2 ohm loss, there is a 10 ohm
loss in the r-f ground connection, and both antenna systems present a 1:1
match to the tx, then with equal tx power output the peak power actually
radiated by a 1/4-wave monopole will be about 65X (18 dB) greater than by a
3-meter monopole on 160 meters.

RF

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

Felix,

I call Bull****. Show us REAL data on the efficiency of this antenna.
Show us field strength vs. a full size 1/4 wave vertical with a good
ground system. If you've invented something new and innovative,
awesome, but the world will never know about it. Why? Because you
won't do real tests.

You want people to buy your plans. You make outrageous claims of
efficiency with no data to back it up other than signal reports from
closeby EU stations on 160m. As far as I'm concerned, at best, you're
a optimist blinded by excitement who's built a pretty good low band
mobile antenna and doesn't want to let himself down by measuring
anything. At worst, you're an outright scammer.

Actually, you know what, how much do you want for the plan again?
Maybe we can take up a collection so we can build one and prove that
you're wrong. But you know , I bet if we build it and it doesn't work
as advertised, you'll make some claim about construction tolerances or
sensitivity to nearby objects, or some such and still claim that YOUR
antenna is 90% efficient. Such is the way of a good pseudoscientist.

Dan

Dan, N3OX, please no flames. That is not the correct style here ...

You are criticising by error, or by ignorance.
I did the measuring of the efficiency by feeding the RoomCap antenna with 1 KW HF,
havinga VSWR below 1,1 and the result: Less than 70 W heat is produced by the
antenna, and, as energy can not be destroyed, 930 W was radiated by the antenna.

The definition of efficiency by the IEEE is:
"The radiation efficiency of an antenna is the ratio of the total power radiated by
the antenna to the net power accepted by the antenna at its terminals."

You can measure these data your own, using your instruments in your laboratory.
The construction plan is available. You get it a a very moderate cost, for 30 Euros,
as contribuiton to the development costs.
This is less than you pay here in a restaurant for dining with a drink.
And you call that "business". Please keep realistic and study before
you accuse me of what you did.

Regarding the tests on 160m you commented:
I was testing between 22h and 24h local time, during the last weeks.
At this time no oversea stations were reachable due to the present conditions.
Even the biggest european stations were calling CQ DX, using Kilowatts, without
any reply from DX.
When calling on 1933 Khz, a pile-up of UK stations appeared. They all wanted to
contact me - and gave very good reports. Ask John, G3WWM and Eric, G3IMX
who are very familiar with the 160m band with decades of experience.

73s

Felix HB9ABX