[Lf] ERP measurements & definitions

[Andre' Kesteloot]

"DEFINITIONS OF RADIATION IN LF, MF AND HF BROADCASTING
BANDS
(1978-1982-1986)
Rec. 561-2

The CCIR UNANIMOUSLY RECOMMENDS
that the following terminology should be used to define and
determine the
radiation from sound-broadcasting
transmitters:

1. Cymomotive force (c.m.f.) (in a given direction)

The product formed by multiplying the electric field
strength at a given
point in space, due to a transmitting
station, by the distance of the point from the antenna. This
distance must
be sufficient for the reactive components of the
field to be negligible; moreover, the finite conductivity of
the ground is
supposed to have no effect on propagation.
The cymomotive force (c.m.f.) is a vector; when necessary it
may be
expressed in terms of components along
axes perpendicular to the direction of propagation.
The c.m.f. is expressed in volts; it corresponds numerically
to the field
strength in mV/m at a distance of 1 km.

2. Effective monopole-radiated power (e.m.r.p.) (in a given
direction)

The product of the power supplied to the antenna and its
gain relative to a
short vertical antenna in the given
direction. (Radio Regulations, No. 157.)
Radio Regulations No. 154 (c) defines the gain of an antenna
in a given
direction relative to a short vertical
antenna G v as the gain relative to a loss-free reference
antenna
consisting of a linear conductor, much shorter than one
quarter of a wavelength, normal to the surface of a
perfectly conducting
plane which contains the given direction.
The reference antenna, when fed with a power of 1 kW, is
considered to
radiate an e.m.r.p. of 1 kW in any
direction in the perfectly conducting plane and produces a
field strength
of 300 mV/m at 1 km distance (equivalent to a
c.m.f. of 300 V).
An e.m.r.p. of 1 kW is assumed in the derivation of the
ground-wave
propagation curves of Recommen-dation
368. An e.m.r.p. of 1 kW at all angles of elevation is
assumed in the
presentation of the sky-wave curves of
Recommendation 435.
Note 1 - Definitions 1 and 2 are mainly used in LF and MF
broadcasting.


3. Equivalent isotropically radiated power (e.i.r.p.)

The product of the power supplied to the antenna and the
antenna gain G i
in a given direction relative to an
isotropic antenna (absolute or isotropic gain) (Radio
Regulations, No.
155).
The idealized reference antenna, when fed with a power of 1
kW, is
considered to provide an e.i.r.p. of 1 kW
in all directions and to produce a field strength of 173
mV/m at 1 km
distance.


4. Effective radiated power (e.r.p.) (in a given direction)

The product of the power supplied to the antenna and its
gain relative to a
half-wave dipole in a given direction
(Radio Regulations, No. 156).
Radio Regulations No. 154 (b) defines the gain of an antenna
in a given
direction relative to a half-wave
dipole G d , as the gain relative to a loss-free reference
antenna isolated
in space whose equatorial plane contains the
given direction.
The reference antenna, when fed with a power of 1 kW, is
considered to
radiate an e.r.p. of 1 kW in any
direction in the equatorial plane and produces a field
strength of 222 mV/m
at 1 km distance."

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