Honeywell KHF 1050 Pilot's Manual page 23

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.
Frequency (kHz)
4000
Propagation (Miles)
Min
Hours After Sunset
1 50
2 100
3 100
4 100
5 100
6 100
7 100
8 250
9 250
10 250
11 100
Hours After Sunrise
1 100
2 0
3 0
4 0
5 0
6 0
7 0
8 0
9 0
10 0
11 0
12 0
13 50
Table 1A - Typical Frequency Propagation Spring And Summer
Revision 0 Mar/2003
8000
Max Min Max
250 200 1000
600 250 1500
600 250 2000
800 250 2500
1000 250 2500
1500 400 3000
1500 500 3500
2000 750 4000
2500 750 4000
2500 750 4000
1000 500 2500
500 400 2000
100 400 2000
100 250 1500
100 250 1500
100 250 1500
100 250 1500
100 250 1500
100 250 1500
100 250 1500
100 250 1500
100 150
200 150
250 150
19
12000
Min Max
500 3500
500 3500
500 3500
500 1000
500 1500
500 2500
500 3500
500 3500
500 3500
500 3500
500 500 3500
500 500 3500
750 500 3500
KHF 1050/PS440 Pilot's Guide
16000
Min Max
750 6000
750 6000
750 4000
750 4000
750 4000
750 4000
750 4000
750 6000
750 6000
750 6000