Reply to critics of RoomCap        
  15th July 2007 / Corr.17th Sept 07   / 2.12.16                                


Since I am publishing the RoomCap antenna (June 2005) critics came from many people.
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 technical background.
They base their judgement on their education and experience, without ever having seen
or measured this new antenna.
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 technology".

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 opinion.

Below you will find a few commented points of critics:



Critics from DC7GB,   Prof. Dr. Ing. Thomas Schiller    (Berlin, Telekom/Post)
 
(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 assumption.
I any case, a higher S point level reflects a higher signal strength.

Tom wrote:
"Whether ground 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 remains unchanged, 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 other
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, floating feeding system.
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.

W4RNL, the 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 antenna questions)

Karl wrote:
"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 the
differential, floating 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 Albis)

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 the
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 tuner.


I think, that these examples show sufficiently, how serious they are ...



An other point is very sad.
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 ?


Felix  HB9ABX

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