Barrett PRC-4090 - Page 220

208
BARRETT PRC-4090 TACTICAL HF SDR TRANSCEIVER - APPENDICES
Radio Wave Propagation
The following illustrations show the characteristics of ground-wave and sky-
wave propagation during day and night time. In each illustration the height of
the ionosphere above the ground is shown.
In both illustrations Station A communicates with Stations B, C and D. Propa-
gation from Station A to B is by ground-wave. The diagrams illustrate that the
ground-wave is not affected by the time of day and the height of the iono-
sphere above the ground.
Propagation from Station A to C and D, is by sky-wave and as the diagrams illus-
trate, the sky-wave is signicantly affected by the time of day and the height of
the ionosphere above the ground.
Under each diagram there are recommended working frequencies listed. Please
note that these will vary according to time of year and other factors. They are
intended only as a guide and are subject to change.
Day Night
A
B
20 km
800 km
2000 km
EARTH
IONOSPHERE
C
D
A
B
20 km
800 km
2000 km
EARTH
IONOSPHERE
C
D
The sun is higher
The ionosphere is higher
The best frequency to use is higher.
A to B - Possible optimum working
frequency is 3 MHz
A to C - Possible optimum working
frequency is between
7 - 9 MHz
A to D - Possible optimum working
frequency is between
13 - 16 MHz
The sun is lower
The ionosphere is lower
The best frequency to use is lower.
A to B - Possible optimum working
frequency is 3 MHz
A to C - Possible optimum working
frequency is between
5 - 7 MHz
A to D - Possible optimum working
frequency is between
9 - 12 MHz