Calculating Maximum Usable Frequency
To determine the maximum usable frequency between two points, it is
necessary to calculate the maximum frequency which each layer will return to earth
at the required distance from the Transmitter, and then select the maximum
frequency obtained by these calculations as the MUF.
Example
Suppose the
distance between the Transmitter and Receiver is 800 Kilometres, and the time
is 12 non on a winter's day.
The maximum
frequency that each layer will return to earth at this distance from the
Transmitter is as set out in the following table:
Layer
Layer
Critical Angle
of Cosine of Maximum
Height Frequency Incidence Angle of Frequency
Incidence
_________________________________________________________________________________
E 100 Kms 2500 Khz 73 Degs 0.29 3700 Khz
F 240 Kms 3700 Khz 53 Degs 0.60 6200 Khz
F2
300 Kms 6000 Khz 49 Degs 0.49 9100 Khz
________________________________________________________________________________
The above table
shows that the maximum frequency which will be received at the receiving point
is the maximum frequency returned by the F2 layer. Therefore, the MUF under
these conditions is 9100 Khz.
For more
information read ANARTS next broadcast 1403 2nd July 2006.