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| Antenna Modeling |
From The Shack |
 This
is a regular and popular monthly column by L.B. Cebik, W4RNL 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 |
Stone's
Throw! |
|
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 |
 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! |
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|
The Dual-Element Wideband
Dipole:
Some Preliminary Notes
By L. B. Cebik, W4RNL
(A Posthumous
Publication) |
|
Occasionally, one finds an
antenna design with fascinating potentials. Such is the case with
the dual-element wideband dipole (DEWD), the first sample of which
comes from Nikolay Kudryavchenko, UR0GT. He developed a relatively
simple wire antenna that would cover the entire 80-meter band with a
50-Ω SWR of less than 2:1 without the need for special matching
systems. How or why the antenna works as it does is subject to some
discussion. Our interest will be in better describing the behavior
patterns as it works. It is only a dipole, with a typical
bi-directional pattern when set horizontally over ground. Still, it
has some very unique features. |
|
What Does an AC Voltmeter Measure?
By Kirk T. McDonald, PhD
Joseph Henry
Laboratories, Princeton University |
|
An AC voltmeter is
a device that measures the oscillating I0 across a
large resistor R0 that is attached to leads whose
tips, 1 and 2 may be connected to some other circuit. The reading of
the voltmeter is Vmeter = I0R0.
AC voltmeters typically report the root-mean-square voltage Vrms
= I0R0/√2 rather than the I0R0.
Then, discuss the
relation of the meter reading to the different V1
- V2 in the scalar potential V between
points 1 and 2 in the absence of the voltmeter. |
|
Inverted Amos Antenna as Linear Feed
for Cylindrical Parabolic Reflector
By
Dragoslav Dobričić, YU1AW |
In this paper I will try to
examine the parameters which are leading to the optimum efficiency
of a cylindrical parabolic antenna illuminated by collinear dipole
array in front of plane reflector. In the article of October 2007
issue of antenneX, there are explanations about different
types of parabolic reflectors which are produced by different
slicing of surface created by rotation of parabolic curve around its
axis.
Another type of parabolic surface reflector can be created by
extruding (drawing) parabolic curve along the line which is
perpendicular to the plane in which parabolic curve lies in. Because
the focus point is also drawing along the line, focus line is
created instead of focus point.
As a result we have cylindrical parabolic surface with focus line.
This type of reflector surface needs specific linear feed for good
illumination efficiency. |
|
Taking AIM: Part III
By Bob Cerreto, WA1FXT |
|
So
far, we have discussed hardware descriptions, initial setup, basic
scan features, advanced scan features and some of the antenna
related Functions available for the AIM 4170. This part of the paper
will discuss the remaining antenna and non-antenna related utility
functions.
My test antenna continues to be a simple 2M dipole. The test feed
line is a 6-foot length of RG58A.
We will show you a crystal filter design application to demonstrate
the Measure Crystal function. If you want to design your own crystal
filter with us, you will need some crystals (all the same marked
frequency), small inductors, capacitors, and a test fixture similar
to this one. |
|
Frequency Division and Dividers
By David Jefferies |
|
Most are
happy with the idea of harmonic distortion in non-linear circuits,
in which multiples of the original frequencies are generated. Fewer
people are happy with the idea of subharmonic generation, where the
non-linearities produce lower frequencies than those originally
applied.
In a system which is sufficiently non-linear there is frequently a
route to chaos involving successive period doublings in the response
to a sinusoidal drive, as the amplitude of the drive is increased in
relation to the non-linearity.
In this article, examples are described, and proposals to exploit
this process for the provision of phase locked frequency division
are presented, various systems are considered, and it is suggested
that a diode having charge storage time of 10 picoseconds an
injection voltage of about a volt, and a charge storage capacity of
about 10^5 electrons would provide an ideal device to divide a 50GHz
signal at a power level of around 10mW.
Experiments are presented which demonstrate, for modulated signals
with 100 MHz carriers, phase locked division in which the amplitude
and frequency excursions of a carrier are faithfully followed at
speeds representing a fractional bandwidth of at least 10%. |
|
Designing a 50-Ohm 2-Element Beam the
Hard Way
By Morris Jones, AD6ZH |
|
I was taught to
design a beam by picking a constraint such as boom length, front to
back ratio, forward gain or number of elements; and then use a table
or chart in a reference such as the National Bureau of Standards
(NBS) 688 or an antenna engineering handbook to select a compromise
configuration that best meets design goals. This often results in an
antenna with a feed line impedance mismatch at the end of the design
process. A matching network such as a gamma, hairpin, “T”, coax
transformer, or L/C network is then attached to the antenna. This
experiment's goal was to find a set of design charts where the
impedance is picked first, and then the “best” beam is selected
within a 50 ohm constraint. |
|
|
ARCHIVES Volume I, II, III, IV, V, VI,
VII, VIII & IX available!
Go
Here to See List of Articles
|
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Last modified:
December 29, 2007
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