EMCOMM III Base Antenna
Operator’s Manual
Nevada - USA
WWW.CHAMELEONANTENNA.COM
VERSATILE – DEPENDABLE – STEALTH – BUILT TO LAST
EMCOMM III Base Page 2
Table of Contents
Introduction .............................................................................................................................................. 3
HF Propagation ......................................................................................................................................... 3
Parts of the Antenna ................................................................................................................................. 4
Antenna Configurations ............................................................................................................................ 7
Inverted “L” Configuration .................................................................................................................... 8
End-Fed Inverted “V” Configuration ..................................................................................................... 8
Half Square Configuration ..................................................................................................................... 9
End-Fed Sloper .................................................................................................................................... 10
Installation .............................................................................................................................................. 10
Troubleshooting ...................................................................................................................................... 11
Accessories .............................................................................................................................................. 11
Specifications .......................................................................................................................................... 12
Chameleon AntennaTM Products ............................................................................................................ 15
References .............................................................................................................................................. 16
WARNING! Never mount this, or any other antenna near power lines or utility wires! Any materials:
ladders, ropes, or feedlines that contact power lines can conduct voltages that kill. Never trust insulation to protect
you. Stay away from all power lines.
WARNING! Never operate this antenna where people could be subjected to high levels of RF exposure,
especially above 10 watts or above 14 MHz. Never use this antenna near RF sensitive medical devices, such as
pacemakers.
All information on this product and the product itself is the property of and is proprietary to Chameleon
AntennaTM. Specifications are subject to change without prior notice.
!
!
EMCOMM III Base Page 3
Introduction
Thank you for purchasing and using the Chameleon Antenna
TM
EMCOMM III Base antenna. The EMCOMM III Base
antenna, see plate (1), is an effective multi-band High Frequency (HF) antenna specially designed for short to long
range base station HF communications. Due to configuration and installation flexibility and low visibility design, it is
ideal for home use even in developments with a Home Owners Association (HOA) and Covenants, Conditions, and
Restrictions (CCRs). It is also highly suitable for military, government agencies, non-governmental organizations
(NGOs), Military Affiliate Radio System (MARS), Civil Air Patrol (CAP), Amateur Radio Emergency Service (ARES) /
Radio Amateur Civil Emergency Service (RACES), Salvation Army Team Emergency Radio Network (SATERN), and
shortwave listening.
The EMCOMM III Base antenna is configurable to
facilitate both long distance (DX) and Near-Vertical
Incident Sky wave (NVIS) communication and using an
automatic antenna tuner or coupler with memory
settings will support most Automatic Link
Establishment (ALE), frequency-hopping, and spreadspectrum modes and operations. The EMCOMM III
Base antenna can be installed by the operator in less
than 30 minutes. It should be installed as high and
straight as possible, but almost any available
supports, such as an existing antenna tower, trees, a
flag pole, the eaves of a house, or a non-conductive
fence can be used with satisfactory results.
The EMCOMM III Base antenna is comprised of a
matching transformer and a 130 foot antenna wire on
a line winder - making an effective HF base station
antenna system for permanent installation as a
primary or backup HF base station antenna.
Antennas built by Chameleon Antenna
TM
are
versatile, dependable, stealthy, and built to last.
Please read this operator’s manual so that you may
maximize the utility you obtain from your EMCOMM
III Base antenna.
Plate (1). EMCOMM III Base Antenna.
HF Propagation
HF radio provides relatively inexpensive and reliable local, regional, national, and international voice and data
communication capability. It is especially suitable for undeveloped areas where normal telecommunications are not
available, too costly or scarce, or where the commercial telecommunications infrastructure has been damaged by a
natural disaster or military conflict.
Although HF radio is a reasonably reliable method of communication, HF radio waves propagate through a complex
and constantly changing environment and are affected by weather, terrain, latitude, time of day, season, and the
11-year solar cycle. A detailed explanation of the theory of HF radio wave propagation is beyond the scope of this
operator’s manual, but an understanding of the basic principles will help the operator decide what frequency and
which of the EMCOMM III Base’s configurations will support their communication requirements.
EMCOMM III Base Page 4
HF radio waves propagate from the transmitting antenna to the receiving antenna using two methods: ground waves
and sky waves.
Ground waves are composed of direct waves and surface waves. Direct waves travel directly from the transmitting
antenna to the receiving antenna when they are within the radio line-of-sight. Typically, this distance is 8 to 14 miles
for field stations. Surface waves follow the curvature of the Earth beyond the radio horizon. They are usable, during
the day and under optimal conditions, up to around 90 miles, see table (1).
Low power, horizontal antenna polarization, rugged or urban terrain, dense foliage, or dry soil conditions can reduce
the range very significantly. The U.S. Army found that in the dense jungles of Vietnam, the range for ground waves
was sometimes less than one mile.
Sky waves are the primary method of HF radio wave
propagation. HF radio waves on a frequency below
the critical frequency (found by an ionosonde) are
reflected off one of the layers of the ionosphere and
back to Earth between 300 and 2,500 miles,
depending upon the frequency and ionospheric
conditions.
Frequency
Distance
Frequency
Distance
2 MHz
88 miles
14 MHz
33 miles
4 MHz
62 miles
18MHz
29 miles
7 MHz
47 miles
24 MHz
25 miles
10 MHz
39 miles
30 MHz
23 miles
Table 1. Maximum Surface Wave Range by Frequency.
HF radio waves can then be reflected from the Earth to the ionosphere again during multihop propagation for longer
range communication. The most important thing for the operator to understand about HF radio wave propagation
is the concept of Maximum Usable Frequency (MUF), Lowest Usable Frequency (LUF), and Optimal Working
Frequency (OWF). The MUF is the frequency for which successful communications between two points is predicted
on 50% of the days of in a month. The LUF is the frequency below which successful communications are lost due to
ionospheric loses. The OWF, which is somewhere between the LUF and around 80% of the MUF, is the range of
frequencies which can be used for reliable communication. If the LUF is above the MUF, HF sky wave propagation
is unlikely to occur.
The HF part of the Radio Frequency (RF) spectrum is usually filled with communications activity and an experienced
operator can often determine where the MUF is, and with less certainty, the LUF by listening to where activity ends.
The operator can then pick a frequency in the OWF and attempt to establish contact. Another method is using HF
propagation prediction software, such as the Voice of America Coverage Analysis Program (VOACAP), which is
available at no cost to download or use online at www.voacap.com. The operator enters the location of the two
stations and the program show a wheel with the predicted percentage of success based on frequency and time. ALE,
which is the standard for interoperable HF communications, is an automated method of finding a frequency in the
OWF and establishing and maintaining a communications link.
Even under optimal conditions, there is a gap between where ground waves end (around 40 to 90 miles) and the sky
wave returns to Earth on the first hop (around 300 miles). NVIS propagation can be used to fill this gap. The
frequency selected must be below the critical frequency, so NVIS is can normally only be used on frequencies from
around 2 to 10 MHz. Frequencies of 2 – 4 MHz are typical at night and 4 – 8 MHz during the day.
Parts of the Antenna
The EMCOMM III Base antenna is comprised of the following components:
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a. Matching Transformer
The Matching Transformer, see plate (2), provides impedance matching for the EMCOMM III Base antenna.
Do not open the Matching Transformer, you may damage the weather seal or internal components.
b. Line Winder
The Line Winder is used to store the Antenna Wire (g) and enabling easy installation of the EMCOMM III Base
antenna.
Plate 2. EMCOMM III Base Top View.
c. Antenna Connection
The Antenna Connection is the red colored wing nut on the top of the Matching Transformer (a). When
viewing the Matching Transformer from the front, it is the wing nut on the rind side of the top. It is used to
connect the Antenna Wire (g) to the Matching Transformer.
d. Counterpoise Connection
The Counterpoise Connection is the wing nut on the top of the Matching Transformer (a) that is not colored
red. When viewing the matching transformer from the front, it is the wing nut on the left side of the top. It is
used to connect the Counterpoise Wire (m). The wing nut on the bottom of the Matching Transformer is an
additional Counterpoise Connection and can be used to connect a ground.
e. UHF Socket
The UHF Socket, SO-239, is located on the bottom of the Matching Transformer (a).
f. Eye Bolt
The Eye Bold is located on top of the Matching Transformer (a) and is used to suspend the Matching
Transformer and provide strain relief.
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