15th July 2007 / Corr.17th Sept 07
to critics of RoomCap
Since I am publishing the
RoomCap antenna (June 2005) critics came from many
They call me a liar, an unserious product seller,
they tell that I am violating the licence rules,
and I would be fooling the HAM community.
Recently, massive critics was made by German HAMs, who
are writing that my antenna would not
work as described, and some of them have quite a high
They base their judgement on their education and
ever having seen
or measured this
They simply can't imagine, that their are better ways to
produce radio waves with small radiators,
than found in all antenna textbooks.
They are standing still on the level of the "old
If you want to critic a product, then you should know at
least this product, and you should
not base your ideas just on hot air.
Without having a real knowledge of it, they better would
remain silent, or they should evaluate
and study the subject, to be able to have a correct
Below you will find a few commented points of critics:
DC7GB, Prof. Dr. Ing. Thomas Schiller
(Correction 17.9.07: Title corrected)
Tom is objecting my anternna comparisons, as the S meters of the
comparing stations are
not calibrated ...
Calibration of the instruments is not required in this
case, as the receivers are just comparing
two signals, where only the difference is of interest, and not the absolute value.
On one receiver, an S point is 5db, on the other 6db,
and the next one 7db, but in the
average, assuming 6 db per S point is not a bad
I any case, a higher S point level reflects a higher
wave or sky wave is used, is unimportant. Important
is, to use the same polarisation
at both sides ..."
This statement is definitely wrong.
In the reflection free
ground wave, the polarisation of the wave
and it is very important,
that both sides use the same polarisation. At reverse
polarisation, signal strength difference of 40 db
may appear (adjusting in 3 axis). -
Arriving sky waves
may have any
polarisation, permanently changing, independent
of the original polarisation.
Here it is is important to average the signal strength in QSB (as
was done in the tests).
Finally, Tom reached the following conclusion:
"This is an antenna with top loading
capacity, which may have an advantage to
short antennas of the same length."
Here he is mistaken completely!
In all published comparison tests (except on 160m) the
version without top
loading capacity was used,
as can be seen in the picture .
Of course, I have versions with top capacities. However,
the additional gain of the top capacity is very small.
The highest impact of the top capacity is in the bandwitdth of the
antenna as described here.
The signal gain
of 0.4db, respectively 1.7db is practically not noticed
on sky wave. That means, that the cause of
the good signal reports is coming from anything else ...
Furthermore, reference to DF6SJ (Prof. Dr.-Ing.
Gerd Janzen, FH Kempten) was made.
Gerd Janzen is consultant for computer simulation of
antennas at the University of Applied Sciences.
He evaluated the SUPER C antenna, and wrote textbooks
about short antennas.
He published a writing
in DARC on that subject.
He does not know the differential,
Therefore, his results of the EZNEC computer simulation
does not apply, as this program does not allow
the definition of the RoomCap antenna, even so the
external shape of the antenna is very similar.
Read more abot that here: Experience
with computer simulation of antennas.
strong promoter of NEC programs, wrote on July 12th 2007 in
antennex.com very clear,
that NEC programs have a considerable set of of
limitations, and that models outside these limitations
are not reliable.
Critics from DJ5IL (Karl Heinz
Fischer, Pforzheim, Consultant of DARC for EMR and
"It is obvious,
that Felix, HB9ABX, refers with the name "RoomCap" to
the concept of Landstorfer / Meinke."
He is mistaken completely. If you study this report (translated
by DJ5IL) you will recognize, that a traditional
feeding system is used, and the authors are not aware of
feeding system .
Measurements have shown, that the difference between the
"System Landstorfer" and my system is
between 5db to 9db, depending on the exact setup and the
type of ground. -
This has been verified by direct
comparisons of 2 antennas, one fed with "System
Landstorfer" and the other
with "System RoomCap", both antennas using an identical
radiator. The field strength was compared,
using a constant carrier, at a distance of 3 wavelength
and at 4 Km.
I think, that they could still learn a lot.
Critics from HB9PJT (Peter Sidler, Affoltern am
Peter also wanted to add his critics, even so he never
has seen, or measured the antenna.
He was using the program EZNEC and began the simulation
... without knowing the construction.
He did not notice that he was not able to define the
antenna correctly, as the Varylink can not be defined
by any NEC program.
The well known expert W4RNL, L.B.Cebik
confirmed, that the present NEC programs do not permit
simulation of this type of feeding.
Disregarding this fact, Peter entered some data in the
program and published his result as proof, that my
comparison with the Titanex
GP would not be correct.
- Furthermore, he specified in his simulation a top
capacity, which did not exist in this comparison.
- In addition, he added a loss of 4db for the tuner,
knowing that the RoomCap antenna works without antenna
I think, that these examples show sufficiently, how
serious they are ...
An other point is very
Peter, DL5GBP, who wrote about his experience with the RoomCap
antenna, is receiving since then
many phone calls, where he is accused of making
false statements in support to me.
I think, this is not HAM-like. Or you think so ?