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FREE SPACE
ATTENUATION
Decibel
free space attenuation calculation for line of a site signal path.
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Most RF comparisons and measurements are
performed in decibels. This gives an easy and consistent method to
compare the signal levels present at various points. Accordingly it
is very convenient to express the free space path loss formula, FSPL,
in terms of decibels.
Calculation
to determine the free space path loss in dB for a given frequency
and distance.
Example
Calculation
to determine the free space path loss in dB for a frequency of
146MHz at a distance of 10km
FSPL
= Free Space Path Loss in dB
f
= Frequency in MHz
d
= Distance in km
Fig 1 The
chart shows free space path loss for five amateur band for distances
from 1 to 10000km.
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last revised 05 May, 2025
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