One feature that will be particularly useful when a trial and error method
is used to find an HF frequency which is working well. This is the sys-
tem’s capability to be programmed by the pilot with 100 channels using
the PS440 Control Display Unit. Rather than having to select the four to
six digits each time you want to try another frequency, you can prepro-
gram the frequencies you need to contact a particular ground station.
Then if you call and fail to get through, you just change to another chan-
nel.
NOTE: It is advisable to program at least three frequencies for each sta-
tion you plan to contact, in case one frequency suddenly becomes unus-
able. During times of solar disturbances, a useable frequency can fade
out in less than a minute. And the “window” of useable frequencies can
shift rapidly during solar disturbances or during sunset and sunrise when
the level of ionization in the ionosphere is changing rapidly.
Tables 1A and 2A show typical propagation distances due to reflection
from the ionosphere for various frequencies during different hours of the
day and for different seasons of the year. It may prove helpful in select-
ing the optimum HF frequency for the communications distance your
operation requires.
Revision 0 Mar/2003 KHF 1050/PS440 Pilot’s Guide
19
Table 1A - Typical Frequency Propagation Spring And Summer
Frequency (kHz)
4000 8000 12000 16000
Propagation (Miles)
Min Max Min Max Min Max Min Max
Hours After Sunset
1 50 250 200 1000 500 3500 750 6000
2 100 600 250 1500 500 3500 750 6000
3 100 600 250 2000 500 3500
4 100 800 250 2500
5 100 1000 250 2500
6 100 1500 400 3000
7 100 1500 500 3500
8 250 2000 750 4000
9 250 2500 750 4000
10 250 2500 750 4000
11 100 1000 500 2500
Hours After Sunrise
1 100 500 400 2000
2 0 100 400 2000
3 0 100 250 1500
4 0 100 250 1500 500 1000
5 0 100 250 1500 500 1500
6 0 100 250 1500 500 2500 750 4000
7 0 100 250 1500 500 3500 750 4000
8 0 100 250 1500 500 3500 750 4000
9 0 100 250 1500 500 3500 750 4000
10 0 100 250 1500 500 3500 750 4000
11 0 100 150 500 500 3500 750 6000
12 0 200 150 500 500 3500 750 6000
13 50 250 150 750 500 3500 750 6000
KHF1050 PG R0 3/21/03 3:22 PM Page 19
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