FCC 80.767
Revised as of September 1, 2021
Goto Year:2020 | 2022
```  §  80.767   Propagation curve.

The propagation graph, § 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:
eCFR graphic ec02ap91.005.gif

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 § 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.
eCFR graphic ec02ap91.006.gif

```

Goto Section: 80.765 | 80.769

Goto Year: 2020 | 2022
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