This
was a regular and popular monthly column by L.B. Cebik, W4RNL (SK)Because
computerized antenna modeling has become widespread, and its popularity as a design tool
continues to increase, this series is devoted to helping readers get the most from the
design software used. The articles focus upon the use of NEC and MININEC, along with
useful adjunct software as well.
This column is primarily for "Guest
Editorials" to provide a podium for our readers to voice their opinions to the rest
of the world too. This is a chance for readers to get on their "soapbox" and
speak about antenna and radio-related subjects. Don't miss these interesting views about
anything and everything about radio and antenna systems! Now, what have YOU to say??
Ham WorkShop, is also another
regular monthly column filled with a variety of "RADIO-STUFF" of value to
almost everyone in amateur radio from Novice to Extra and those just beginning to take up
this special hobby. This includes subjects, but not limited to: VHF, choosing the right
antenna, coax cable, small to mid-scale construction projects in a practical manner, use of test
equipment, etc. It is also meant to help readers become more familiar with the technical
jargon and the fun side of radio.
Stone' Throw! a
monthly column by antenneX publisher,
Jack L. Stone, among other things, is to keep
the readers informed about our progress, new developments, plans for the future, and to
introduce the authors and their subjects each month. Also, our main slogan around here is
"we aim to please", so this serves as a place for the readers to tell the
publisher what is wanted or at least make suggestions. Just remember, the publisher is
only a Stone's Throw away! Go in for a visit and read this month's column.
Propagation
another monthly column by Marcel H. De Canck, ON5AU of Belgium. Signal propagation
is a subject that is one of the most basic ingredients of radio and is something everyone
in radio should know about in order to maximize communications in the most effective way.
It’s not enough to have the best equipment and the best antenna if you are trying to
send out a signal against a brick wall. Conversely, one may possess a very crude rig,
running low power, but yet transmit/receive a signal to great distances with ease, simply
by making use of a thorough knowledge about how signal propagation works within the
environment. Follow this column and learn more about propagation!
The
author of the monthly column Antenna Design & Use
is Justin Johnson, G0KSC who does in fact design and install antennas in
many parts of the world. He�s a real hands-on expert with years of
experience in this field. Following this column will be helpful
especially to those pondering a new antenna project. Examples of how to
model the designs will appear at times as well. There is something here
for just about everyone wishing to know more about how antennas are
created, tested and used.
FEATURE ARTICLES THIS MONTH IN THE LIBRARY Subscription Required to View Click to
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A Power
divider / splitter by Chris Gare
As an alternative to a phasing
harness, it's possible to build a 2-way splitter which is a more
precise way of matching two 50-Ohm antennas. Also, they can be
bought commercially. Justin, G0KSC identified the sizes of box
section and tubing to use but I thought it worthwhile checking
the size suggestions and this article explains the details of
that and construction.
Practical Antennas: Part 5.03 By
Marcel H. De Canck, ON5AU
Every
transmission line will have some inherent loss, partly of the
resistance of the conductors, partly because power is consumed
in the dielectric used for insulating the conductors and partly
because in many cases a small amount of power escapes from the
line by radiation. As transmission lines are made larger by
using thicker conductors, the resistance is reduced and as the
dielectric material gets closer to low-loss air, the losses are
reduced. The skin effect causes current to travel nearer to the
surface of the conductors at higher frequencies. Therefore, the
effective loss increases as the frequency is increased.
NewcomerNotes ~ It's a New Year! By Robert Gulley, AK3Q
2011 was an interesting, fun, and frustrating year for me and
radio. Interesting because I had the opportunity to experiment
with some new antennas, radios, and modes. Fun because (see
above!) and because I passed a personal milestone of 100+ DX
amateur radio countries. Frustrating because I didn’t get to
spend as much time on the air as I wanted (do we ever?!), and
because I had some storm damage to antennas which were working
quite well before Mother Nature got involved.
Maybe I
have equally described your 2011 experiences too (hopefully
without the damage!), and like me you are looking forward to
2012. I have a number of projects in mind (always more than I
can get to), all of them poised to enhance my enjoyment of this
wonderful hobby. I frankly don’t understand people who get bored
with radio considering the massive number of things one can hear
and do with even a modest setup. No insult intended to those who
are finding their interest in radio dwindling; it’s just that I
always seem to find new things to challenge me and “old” things
to re-discover and thus, new to me.
What is the
Role of the Arms of a Linear Broadcast Antenna? By Kirk T. McDonald, PhD
Professor of Physics Joseph Henry Laboratories, Princeton
University
A broadcast antenna is a transducer of energy from a voltage
source into the energy of distanct electromagnetic fields. In
its simplest form the antenna should consist of a compact
voltage source located in the gap between two linear conductors
(the "arms") as shown in a sketch within this paper. We go on to
discuss the configuration is substantial detail.
The Self- Resonant Ferrite Rod
Antenna - Part 2 By Alan Payne, G3RBJ
A reduction in the length
of resonant wire antennas has previously been achieved by
placing ferrite beads over the wire. However it is shown here
that the ferrite is used more effectively if the wire is wound
around the ferrite
HF antennas are normally resonant
because their input impedance is then resistive and this easies
a potentially difficult matching problem. However resonant HF
antennas can be very long and efforts have been made in the past
to reduce their length by placing ferrite beads over the wire.
For instance Polydoroff (ref 1 p183) measured a 2:1 reduction in
the resonant length, using beads with an outside diameter of 3
times that of the wire. A similar experiment was carried out by
Grimes (ref 2). However for a given volume of ferrite a much
greater reduction in size is possible if the wire is wound
around the ferrite, because of the much reduced phase velocity.
The antenna envisaged here is perhaps 2 meters in length
with a diameter of 10-15mm, and suitable for HF portable or
mobile use. It is self resonant and is therefore unlike
conventional ferrite rod antennas, which are tuned with an
external capacitor. The design of such an antenna will need to
consider a number of parameters, including radiation resistance,
bandwidth and efficiency, but it is the ability to self resonate
which is covered here.
This is the first part of a two
part article appeared last
month, and we continue now in this
second part We
started
by considering the resonant frequencies of straight wires, and
then consider the effects of adding the ferrite.
The DK7ZB-Match for Yagis
By Martin Steyer, DK7ZB
It is a well
known phenomenon that the radiators resistance in a
Yagi-structure drops down by adding parasitic elements to a
dipole as a radiating element. For the VHF-Bands (50-50.5MHz,
144-146MHz, 430-440MHz) a radiation resistance of 25-35Ohm has
the best balance for gain, back and side-lobes, bandwidth and
SWR at tenable losses in a Yagi.
The classic match for
that resistance/impedance is the Gamma-Match. The Beta-Match is
a good choice as well, but realisation on VHF is difficult for a
homebrew. For that reason a new simple, easy to build match was
developed in 1995 for Yagis with resistive loads of 12.5, 18 and
28 Ohms. We present my version in this article.
?need a compact
antenna
?have
signal problems either transmitting or receiving ? can't choose between a vertical or horizontal antenna
? want
to learn about antenna modeling
? just
want to know more about propagation
? want to design an antenna, but don't
want to redo the wheel
? need
a program for antenna design and antenna plotting
? don't
know what antenna is best for hamsats or others
? have
a busy mobile signal on all bands
? need
an inexpensive directional antenna for 10 meters
? need
a low-noise antenna for 160 meters
? want
to know if someone else has solved your problem
? need
a disguised mobile antenna for the vehicle
? just
want to know more about antennas
This
was a regular and popular monthly column by L.B. Cebik, W4RNL (SK)Because
computerized antenna modeling has become widespread, and its popularity as a design tool
continues to increase, this series is devoted to helping readers get the most from the
design software used. The articles focus upon the use of NEC and MININEC, along with
useful adjunct software as well.
This column is primarily for "Guest
Editorials" to provide a podium for our readers to voice their opinions to the rest
of the world too. This is a chance for readers to get on their "soapbox" and
speak about antenna and radio-related subjects. Don't miss these interesting views about
anything and everything about radio and antenna systems! Now, what have YOU to say??
Stone' Throw! a
monthly column by antenneX publisher,
Jack L. Stone, among other things, is to keep
the readers informed about our progress, new developments, plans for the future, and to
introduce the authors and their subjects each month. Also, our main slogan around here is
"we aim to please", so this serves as a place for the readers to tell the
publisher what is wanted or at least make suggestions. Just remember, the publisher is
only a Stone's Throw away! Go in for a visit and read this month's column.
Propagation
another monthly column by Marcel H. De Canck, ON5AU of Belgium. Signal propagation
is a subject that is one of the most basic ingredients of radio and is something everyone
in radio should know about in order to maximize communications in the most effective way.
It’s not enough to have the best equipment and the best antenna if you are trying to
send out a signal against a brick wall. Conversely, one may possess a very crude rig,
running low power, but yet transmit/receive a signal to great distances with ease, simply
by making use of a thorough knowledge about how signal propagation works within the
environment. Follow this column and learn more about propagation!
