Goto Section: 80.765 | 80.769 | Table of Contents
FCC 80.767
Revised as of October 1, 2006
Goto Year:2005 |
2007
Sec. 80.767 Propagation curve.
The propagation graph, Sec. 80.767 Graph 1, must be used in computing the
service area contour. The graph provides data for field strengths in dBu for
an effective radiated power of 1 kW, over sea water, fresh water or land
(smooth earth); transmitting antena heights of 4,800, 3,200, 1,600, 800,
400, 200, and 100 feet; based on a receiving antenna height of 9 meters (30
feet), for the 156–162 MHz band. The use of this is described in this
section.
(a) Calculate the effective radiated power of the coast station, Ps in dB
referred to 1 kW (dBk), as follows:
[MATH: :MATH]
where,
Pt=Transmitter output power in dB referred to 1 kW: Transmitter output power
in watts is converted to dBk by Pt=10 [log10 (Power in watts)]−30. Also see
Sec. 80.761 Graph 1 for a conversion graph.
G=Antenna gain in dB referred to a standard half-wave dipole, in the
direction of each plotted radial, and
L=Line losses between the transmitter and the antenna, in dB.
Notes: 1. To determine field strengths where the distance is known, for
effective radiated powers other than 1kW (0 dBk): Enter the graph from the
“statute miles” scale at the known distance, read up to intersection with
the curve for the antenna height, read left to the “dBu for 1 kW radiated”
scale and note the referenced field strength (Fe). The value of the actual
field strength (F) in dBu will be F=Fe+Ps where Ps is the effective radiated
power calculated above.
2. To determine distance, where the actual field strength is specified, for
effective radiated powers other than 0 dBk: The value of the field
referenced strength will be Fe=F−Ps in dBu. Enter the graph, from the “dBu
for 1 kW radiated” scale at the corrected value of Fe, read right to
intersection with the antenna height, read down to “statute miles” scale.
(b) Determine the antenna height. For antenna heights between the heights
for which this graph is drawn, use linear interpolation; assume linear
height-gain for antennas higher than 4,800 feet.
(c) For receiver antenna heights lower than 9 meters (30 feet), assume that
the field strength is the same as at 9 meters (30 feet).
(d) Assume that propagation over fresh water or over land is the same as
that over sea water.
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Goto Section: 80.765 | 80.769
Goto Year: 2005 |
2007
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