To All from PA0SE
Geri, DK8KW wrote:
Please see below the relevant definitions as they are recommended by the
ITU.
Many thanks Geri. Very useful info.
73, Dick, PA0SE
"DEFINITIONS OF RADIATION IN LF, MF AND HF BROADCASTING BANDS
(197819821986)
Rec. 5612
The CCIR UNANIMOUSLY RECOMMENDS
that the following terminology should be used to define and determine the
radiation from soundbroadcasting
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 monopoleradiated 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 lossfree 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 groundwave
propagation curves of Recommendation
368. An e.m.r.p. of 1 kW at all angles of elevation is assumed in the
presentation of the skywave 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
halfwave 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 halfwave
dipole G d , as the gain relative to a lossfree 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."


