Before I finish up with a comparison between a rotating combo dipole and
the weel known beverage antenna for 160M there are a few loose ends to tie
up and ofcourse I will not be describing
the clustered array types.
Moxons book came at the right time for me as I wanted an antenna to reflect
somewhat a transceiver where the antenna design reflected a moveable
bandwidth of a consistant Q and not one where a radio "scans" frequency
response as in a spectrum analyser. The Moxon book gave the answer that I
wanted to read to give me further encouragement, It refered to where ZUKOV
stated that radiation theoretically could emanate from a point and thus one
could read in to that statement that length (wavelength) should not be the
focal point for antenna design after all it would be very difficult to find
anything in a book that focussed around
length. If a point radiation can be realised then length was not a primary
factor instead it was the passive loads that was carried by 'Length". When
Moxon chose the twenty metre length for his
resonator or combo dipole this blurred the impact with respect to what
lengthand constituent passive loads meant,so he chose a random length of
random diameter for his arrangement, after all to factor in the many
resistances involved in radiation without a computor in reverse complex
circuitry aproach would have taken a hundred years. Fortunately he hit on a
suitable size radiator and he was able to procede even tho he made poor
choices later.
The initial arrange ment is shon in his book plus interesting longhand
formula with respect to coupling and corresponding
antenna performance data. Members of the attack group also found an old page
of mine which descibes my interpretations and they also have referred to a
couple of write ups that I did in patent form that clearly shows the
arrangement as did many drawing I made for this newsgroup. Nobody was able
to duplicate Moxons work hich led to the formation of a attack group, I
theorise that the reason that no one could do it was because of a
fascination for the EZNEC program which tho one time a leader in computor
analysis was quickly outpaced by present day modern designs.
The EZNEC program really revolves around providing characteristics around a
previously designed antenna only and not the best arrangement that can be
obtained. For best antenna available one needs the option of assigning
variable values for a design together with large point of moments
assignments so that not only close coupling could be performed with accuracy
but length could be of secondary importance to lumped and distributed
passive components both of which can now be variable. To accomplish what
Moxon did is impossible to duplicate if one ignores distributed loads in a
parallel configuration. Another thing that escaped the naysayers was that
talk of lumped loads in a radiating array placed them in a fixed mind
position where they still hung on to a wavelength design and put these
lumped loads at the feed point to represent an external matching system
which defeats the total intent of a parallel circuit
radiating antenna which provided high Q signal passage which does not
require an external matching system which is known to be lossy for large
size antennas.
The next post will be the last post for the moment because clusterred
antenna design is still ongoing. I have chosen the 160 mtre rotatable dipole
as a base as the initial designs of parallel circuitry revolved around bands
that have now declined. I have chosen to compare it with a simple beverage
antenna even tho this
\beverage is not used as a transmitting antenna but for its listenning
abilities. I might add at this point that when I rotated my
loop/dipole antenna from the horizontal position to the vertical position I
did not get the expected ground noise addition that I expected. This I
attributed to the coupling function of the antenna
which I believe has the ability to remove extranious noise.
Have at it 'experts" you should now be able to portray what Moxon achieved
by the correct use of computorised antenna
programs now knowing the truth of prior efforts that substantiated the
saying of "Garbage in equals garbage out" especially in the attack mode when
one is inclined to listen only to that he wants to hear or substitute for
what he thinks he should have heard.
Art Unwin KB9MZ....XG