this distance and should be at least a quarter-wave high.
Usable
frequencies fall between 3 to 14 MHz.
Reliability may fall below
ninety percent.
f. Communication between 800 to 1500 miles. Communications over
this distance require antennas with a low take-off angle. A doublet
a half-wave high will work reasonably well.
Reliability may fall
below ninety percent. Frequencies can be from 4 to 25 MHz .
g. Communication over 1500 miles.
There may be times when a
tactical facility may be required to communicate to a station over
1500 miles away.
The only antenna available to the tactical
communicator is the doublet.
The percent of reliability will fall
significantly. To communicate effectively over 1500 miles you need a
more powerful transmitter and a better antenna system than what is
available.
We must accept less than desirable performance when
communicating long distances during tactical situations.
TACTICAL RADIO SYSTEM ANALYSIS
During and after an exercise, an analysis of the communications
needs to be accomplished. Copies of logs, if necessary, need to be
forwarded to indicate time of and reason for outages.
Careful
evaluation of the facts will determine if the assigned frequencies
are too high or too low.
If interference is a factor, report the
interference, and if you have to, change to another frequency.
Unfortunately, it is very seldom that we evaluate our HF net
effectiveness.
From time to time over the sunspot cycle, different
frequencies need to be assigned.
The same frequencies will seldom
work over a sunspot cycle (a sunspot cycle is just over 11 years).
Communication is always better during a maximum sunspot cycle.
Higher frequencies are more useable, because ionization by the sun
increases the density of the layers which will support higher
frequencies.
A higher FOT daytime frequency will be needed in a
sunspot maximum cycle.
The FOT does increase at night, but not
significantly.
Most of our communication outages can be traced to incorrect
In most cases the assignment is too low, in
the 2 to 3 MHz band.
Severe interference should be expected.
In
most cases the LUF for a doublet is used, whereas the LUF for a whip
should have been used, because some of the outages are usually when
we are mobile or mobile-at-a-halt.
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