1、CCIR VOLUME*X-1 90 4855232 0503883 3 Rec. 561-2 3 RECOMMENDATION 561-2 * DEFINITIONS OF RADIATION IN LF, MF AND HF BROADCASTING BANDS (1978- 1982- 1986) The CCIR UNANIMOUSLY RECOMMENDS that the following terminology should be used to define and determine the radiation from sound-broad- casting trans
2、mitters: i. 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 fiel
3、d 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
4、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,
5、 No. 157.) Radio Regulations No. 154 (c) defines the gain of an antenna in a given direction relative to a short vertical antenna G, 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 perfe
6、ctly 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)
7、 An e.m.r.p. of 1 kW is assumed in the derivation of the ground-wave propagation curves of Recommenda- tion 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 43 5. Note I - Definitions 1 and 2 are mainly used in LF and MF bro
8、adcasting. 3. Equivalent isotropically radiated power (e.i.r.p.) The product of the power supplied to the antenna and the antenna gain Ci in a given direction relative to The idealized reference antenna, when fed with a power of 1 kW, is considered to provide an e.i.r.p. of an isotropic antenna (abs
9、olute or isotropic gain) (Radio Regulations, No. 155). 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 gi
10、ven 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 Gd, as the gain relative to a loss-free reference antenna isolated in space whose equatorial plane contains the given direction. The reference
11、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. Note i - Definitions 3 and 4 are mainly used in HF broadcasting. Note 2 - The relationship between the radiated powe
12、r expressed in the different units is given in Annex I. Note 3 - For information, some guidance on the determination of the radiated power is given in Annex II. Note 4 - For information, radiated power standards for propagation curves are discussed in Annex III. * This Recommendation should be broug
13、ht to the attention of the CMV. I CCIR VOLUNEKX-L yo rn 4855232 05038a2 3 rnm 4 Rec. 561-2 l ANNEX I i RELATIONSHIP BETWEEN RADIATED POWERS EXPRESSED IN DIFFERENT UNITS 1. Relationship between e.m.r.p. and c.m.f. The value of the e.m.r.p. is related to the c.m.f. (V) by the expression: e.m.r.p. = (.
14、m.f./300) kW I Table I gives some practical examples of c.m.f. and e.m.r.p. in the absence of losses. l TABLE I Gain relative to a short vertical c.m.f. c.m.f. e.m.1.p. (dB) Transmitter power Antenna (kw) antenna (VI (dB (300 V) (kW O 30 - 20 0.01 0.1 O 95 - 10 o. 1 1 1 short vertical O 300 O 1 10 O
15、 950 4- 10 10 2 3 800 4. 22 160 h/2 vertical 2 6 600 4.21 415 2 12 O00 i t32 1600 100 300 1000 2. Relationship between e.r.p. and e.i.r.p. The value of the e.r.p. is related to the e.i.r.p. by the expression: e.r.p. = 0.61 e.i.r.p. (linear scale) e.r.p. = e.i.r.p. - 2.2 dB (logarithmic scale) ANNEX
16、II DETERMINATION OF THE RADIATED POWER 1. Vertical antennas For vertical antenna systems which are actually in operation, the radiation in a horizontal direction is obtainable by measurements of field strength on a radial line over the range, 2h to 15h, from the antenna system. Here, h is taken to b
17、e either the wavelength or the maximum dimensions of the antenna, whichever is the greater, in order to avoid the effect of reactive fields. If E is the field strength at distance, d, the product, Ed, is plotted graphically against d. The line is extrapolated to d = O, and the product ( F, : c.m.f.
18、in the horizontal direction 0; G, : gain of antenna relative to a short vertical antenna. More generally, the total power radiated into space (in other words, the power to be supplied to the antenna if losses are neglected) is related to the c.m.f. by: sphere where F, (cp, 0) is the c.m.f. as a func
19、tion of the azimuth cp and the angle of elevation O, (W is in watts and F, is in volts). REFERENCES SURUTKA, J. V. and GAVRILOV, T. S. i9831 Experimental determination of the cymomotive force of ground-based vertically polarized antennas. Telecomm. J., Vol. 50, IX, 482-486. ANNEX III RADIATED POWER
20、STANDARDS FOR PROPAGATION CURVES The ground-wave propagation curves of Recommendation 368 and the sky-wave propagation curves given in Recommendation 435 are drawn nominally for a field strength of 300 mV/m at 1 km and thus apply to a c.m.f. of 300 V. However, the sky-wave curves were established fr
21、om measurements to which a correction was applied in each case for the vertical radiation pattern (over good ground) of the transmitting antenna: but no correction was applied for the effect of finite ground conductivity on the sky-wave field strength. These curves therefore, include the effect of a
22、verage ground conductivity, which (as compared with a perfectly conducting ground) can cause significant reduction of sky-wave at low angles. This effect is discussed in Report 401. It can be shown that for all types of vertical antenna systems of interest for applications in bands 5 (LF) and 6 (MF)
23、 the ground effect is substantially independent of the type of antenna, and correction for the antenna gain and vertical radiation pattern may be made with good accuracy by correcting the calculated pattern for a perfectly conducting flat earth. The practice is already established for propagation curves at LF and MF to apply for an e.m.r.p. of 1 kW from a short vertical antenna and this corresponds to a c.m.f. in the horizontal direction of O dB relative to 300 V. An e.i.r.p. of 1 kW at all angles of elevation is generally used in HF propagation prediction methods.
