CHA HYBRID - MINI / MICRO
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table, decide which distance column (Ground = 0 to 90 miles, Short = 0 - 300 miles, Medium = 300
–
1500 miles,
Long > 1500 miles) best matches the distance to the station with whom you need to communicate. Then,
determine if the OWF is in the lower (↓ = 1.8 –
10 MHz) or upper (↑ = 10 –
30 MHz) frequency range. Finally,
select the antenna configuration with the corresponding symbol in the appropriate distance column. All CHA
HYBRID - MINI / MICRO configurations provide some capability in each distance category, so depending upon the
complexity of your communications network, you may need to select the best overall configuration. The
directionality column indicates the directionality characteristic of the antenna configuration. When using NVIS, all
the configurations are omnidirectional. Most configuration and frequency combinations will require a wide range
antenna tuner or coupler.
Horizontal NVIS
The CHA HYBRID - MINI / MICRO Horizontal NVIS configuration, see figure (1), is a special configuration designed to
provide good NVIS propagation on lower frequencies. It is predominately omnidirectional and also provides
medium range sky wave propagation on frequencies above 10 MHz. It requires two supports that will enable the
ends of the antenna to be raised to a height of 10
–
12 feet and 60 feet apart. A counterpoise wire, with a length
of 50 to 55 feet, is recommended. If a counterpoise wire is not used, the coaxial cable must be 25 to 100 feet in
length, as the shield of the coaxial cable provides the counterpoise. Use the following procedure to install the
Horizontal NVIS configuration.
Figure 1. Horizontal NVIS Configuration.
Site Selection and Preparation.
1.
Select a site to deploy the CHA HYBRID - MINI /
MICRO Horizontal NVIS
configuration. The site
must have two supports that will position the
Hybrid Base and the end of the Antenna Wire to
be at a height of between 10 and 12 feet and 60
feet apart. Higher or lower heights may be
used, but may reduce NVIS performance.
Refer to plates (1) through (3) for the following steps.
2.
If not already attached, connect a Carabiner (d)
to the Isolation Loop (c) at the Wire Connector
(f) end of the Antenna Wire.
Connect the Hybrid Base.
3.
Temporarily remove the Antenna Shackle (k)
from the Antenna Connection (h).
4.
Place the Wire Connector from the Antenna
Wire over the Antenna Connection and replace
the Antenna Shackle. Tighten the nut snugly.
5.
Connect the Carabiner from the Antenna Wire
to the Antenna Shackle.
6.
If using a counterpoise wire, connect it to the
Counterpoise Connection (i). Tighten the nut
(not supplied)
snugly.
