1、CCIR VOLUME*X-1 90 W YB55212 050395b b 78 Rec. 80-3 RECOMMENDATION 80-3 * TRANSMITTING ANTENNAS IN HF BROADCASTING The CCIR, (Question 44/10, Study Programme 44H/10) (1951 -1 978-1986-1990) CONSIDERING (a) that a directional transmitting antenna should be used whenever appropriate, both to obtain ad
2、equate coverage of an intended service area and to minimize unwanted radiation, and potential interference, elsewhere; (6) that the design and installation of a wide variety of directional HF antenna types of improved performance are feasible using current technology; (c) (d) given in Part 1 of Anne
3、x I to Recommendation 705;- (e) antennas is given in Part 2 of Annex I to Recommendation 705, that directional transmitting antennas can radiate significant power in unwanted directions; that comprehensive and detailed information on the theoretical radiation characteristics of HF antennas is that i
4、nformation regarding the differences between the theoretical and practical performance of HF UNANIMOUSLY RECOMMENDS 1. antenna; that Annex I and Annex II should be used to give guidance on the choice of a suitable HF transmitting 2. that side-lobe radiation should be maintained at the lowest practic
5、al value; 3. that in practical operating conditions, for purposes of calculating interference, the field strength in other azimuths at angles of elevation corresponding. to those of the main lobe, cannot be assumed to be less than 222.mV/m at a distance of 1 km for 1 kW of power supplied to the ante
6、nna, in the case of high gain antennas. A lower value of interfering field strength may need to be considered in the case of low gain antennas. 4. that Annex I to Recommendation 705 should be used as a source for more detailed information. Note - The World Administrative Radio Conference for the Pla
7、nning of HF Bands Allocated to the Broad- casting Service (WARC HFBC(l), Geneva, 1987 has adopted for use, calculated values of minimum radiation which in some cases are lower than that given above (see Annex II). ANNEX I* 1. The use of non-directional and directional antennas In HF broadcasting the
8、 antenna is the means by which the radio-frequency energy is directed towards the required service area. The selection of the right type of antenna will enhance the signal in this area, while reducing radiation in unwanted directions. This will protect other users of the radio-frequency spectrum ope
9、rating on the same channel or adjacent channels in another service area. The use of directional antennas with well defined radiation patterns is thus recommended as far as possible. * Since the content of Reports 32-5 and 1062 have been modified and annexed to this Recommendation as Annexes I and II
10、, respectively, Reports 32-5 (Dubrovnik, 1986) and 1062 (Dubrovnik, 1986) are hereby deleted. Nomenclature is explained in Annex I to Recommendation 705 and in Annex II to the present Recommendation. * COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Ha
11、ndling ServicesRec. 80-3 79 Non-directional antennas can be used when the transmitter is located within the required service area. In this case the required service area as seen by the transmitter extends over an azimuthal angle greater than 180“. Directional antennas serve a double purpose. The fir
12、st is to prevent interference to other users of the spectrum by means of their directivity. The second is to provide sufficient field-strength for satisfactory reception by means of their power gains. A chart in Fig. 1 gives some. general guidelines for the choice of optimum antennas for a given typ
13、e of service according to the required distance range. Two different categories are considered: short distance and medium/long-distance services. A short distance service is understood here to have a range of up to about 2000 km. The corresponding area can be covered with either a non-directional or
14、 a directional antenna whose beamwidth can be selected according to, the sector to be served. In the case of directional antennas, both horizontal dipole curtain and logarithmic-periodic antennas can be employed. Medium and long distance services can be considered to reach distances greater than app
15、roximately 2000 km. Such coverage can be provided by antennas whose main lobe elevation angle is small (6“-13“) and whose horizontal beamwidth - depending on the area to be served - is either wide between 65“ and 95“ (generally 70“) or narrow between 30“ and 45“ (generally 35“). The value of the fie
16、ld strength in the reception area is influenced by the radiation characteristics of the antenna, which depends upon the type of array. Antennas of extremely narrow horizontal and vertical beamwidth should nor be used because variations of the ionosphere could change the location of the coverage area
17、. Although rhombic antennas are used for broadcasting, their use should be discouraged because of the size and number of their sidelobes, which could create unnecessary interference. 2. Reduction of subsidiary lobes For the purpose of avoiding interference in frequency sharing, the reduction of subs
18、idiary lobes in high-frequency broadcasting directional antenna systems is of utmost importance. This interference is generally caused by the radiation pattern of the transmitting antenna having subsidiary lobes in unwanted directions, or by scatter of the energy of the main lobe, due to propagation
19、 anomalies. Reduction in intensity of the subsidiary lobes is possible by correct antenna design, while the propagation scatter in unwanted directions presents a complex problem, and its effect should be treated statistically. HF curtain antennas constructed of horizontal dipole elements are made un
20、idirectional by the addition of a reflector screen. This screen can be comprised of either: - an identical array of dipoles tuned to provide an optimum front-to-back ratio over the range of operating frequencies. In general no power is applied to this type of reflector, which is known as either a “t
21、uned dipole“ or a “parasitic“ reflector; or - a screen consisting of horizontal wires which act as an untuned.reflector. This type of reflector is known as an “aperiodic screen“. The maximum slew values obtained in practice for different antenna types are given in Table I of - Annex II. While slewin
22、g does not appreciably affect the horizontal width of the main lobe of radiation, it does increase its asymmetry and at the same time produces a principal subsidiary lobe of considerable intensity. In slewing, the gain of main lobe decreases with the increase of the slewing angle and side lobe radia
23、tion increases. As a consequence the field strength created by the side lobes will substantially increase. . Practical experience in the Peoples Republic of China has confirmed the possibility of obtaining satisfactory slewing by using the value of current phase differences determined by a successiv
24、e approximation method of calculation CCIR, 1986-9Oal. COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling ServicesCCIR VOLUIE*X-II 90 W 4855232 0503758 T W 80 Rec. 80-3 I I I I antenna Narrow I Log. periodic antenna single plane 0.65 Q 7 0.8 17“
25、Q Q 50“ 80“ Q BW Q 130 8 Q Ci Q 14dB Curtain array HR inliifh in = 1 or 2 n =lor2 0.25 a It a 0.6 15 Q Q 50 70“ 6 BW a 180“ 9 Ci 16dB Curtain array HR 4/1/h HR 4/2/h 0.25 Q It 0.6 15“ a e Q 50“ BW 35“ 13 Q Gj Q 19dB Wide . / Horizontal Narrow beamwidth I V I Curtain array i HR2/3/h HR 2/4/h 0.4 12 1
26、.2 6“ a a 13 BW * 70“ 16 Q Cj 19dB Curtain array HR 4/3/12 HR 4/4/h 0.4 h Q 1.5 6“ 4 a 13“ BW E 35“ 19 a Ci 6 22dB Rhombic antenna not recommended FIGURE 1 - Antenna selection chart 8: elevation angie Gi: gain (dB) relative to an isotropic antenna isolated in space Gd: gain (dB) relative to a half-w
27、ave dipole isolated in space (Ci = Gdf 2.2 dB) BW: total horizontal beamwidth (-6 dB relative to maximum) HR: horizontal dipole curtain antenna with reflector curtain rn: number of half-wave elements in each row n: number of half-wave elements in each stack (one above the other) h: height above grou
28、nd in full wavelengths of the bottom row of elements c: taper ratio of log. periodic antenna of maximum radiation of the main beam COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling ServicesCCIR VOLUME*X-I 90 m 4855232 0503959 I M Rec. 80-3 81 Te
29、sts in Italy CCIR, 1963-66a have shown that with an antenna of the type HRS 5/4/1.5 it is possible to reduce the amplitude of subsidiary lobes significantly when feeding the five stacks of dipoles separately. This property is maintained when the main beam is slewed. A special feature of some type HR
30、 4/4 antennas manufactured in France is that the reflector is fed, an arrangement which makes it possible to adjust accurately the current amplitudes and phases in the back and front of the arrays. Measurements of the pattern, using a helicopter, showed that it resembled the theoretical patterns ver
31、y closely (nulls about 40 dB). Compared with systems with passive reflectors, the new arrays have a larger bandwidth and are more easily adjusted. Calculations in France have also shown that, for multiband antennas of .the type HR 2/n/h extension of the frequency ratio to a value of fmaJ fmin close
32、to 3 would result in satisfactory theoretical radiation patterns without significant development of subsidiary lobes. Although it is possible to achieve a substantial degree of suppression of side lobes for curtain arrays, the methods so far employed introduce mechanical difficulties and increase th
33、e cost. 3. Verification of radiation patterns The RAI in Italy and the Vatican City State CCIR, 1982-86aY 1986-90b have made a series of field-strength measurements to investigate and verify the effective radiation pattern of a variety of types of HF antennas. The measurements have been performed by
34、 using airborne equipment. The results of these measure- ments on non-obstructed antennas confirm that the radiation patterns of the main beam are in good agreement with the theoretical values given by the CCIR special publication on Antenna Diagrams, 1984. Detailed studies by several administration
35、s confirm the validity of these theoretical values. Details on these studies may be found in for example CCIR, 1986- OC. Furthermore it is shown that in the case of a practical horizontal dipole antenna with an aperiodic screen reflector the back radiation and that in the principal minimum in the fo
36、rward direction is about 20 dB below the maximum of the main lobe. It can be concluded that the methodology of measuring antenna patterns by helicopter described in Part 2 of Annex I to Recommendation 705 is a reliable and valuable means of evaluating the performance of transmitting antennas. 4. Dis
37、crimination obtained in practice by directional antennas Extensive measurement campaigns have been carried out in different countries, to evaluate the field strength of Co-located transmitters and of transmitters on different transmitting sites using directional antennas directed to geographically s
38、eparated service areas. These results were used to derive antenna discrimination values, that is, the reduction in field strength, relative to the main beam value, at angles of azimuth and elevation other than those of the main beam. The discrimination obtained in practice was consistent with the li
39、miting value given in this Recommendation. The discrimination deduced from theoretical antenna considerations (see Part 1 of Annex I to Recommendation 705 would in most cases have been much higher than that actually measured. These measurement campaigns are reported by the United Kingdom in CCIR, 19
40、62, 1963, 1963-66b, 1970-741 and India CCIR, 1974-781. REFERENCES CCIR Documents 1962: (Bad Kreuznach).X/15 (United Kingdom). 1963: (Geneva). X/221 (United Kingdom). 1963-661: a. X/49 (Italy); b. X/124 (United Kingdom). 1970-741: 10/180 (United Kingdom). 1974-781: 10/57 (India). 1982-861: a. 10/254
41、(Italy and Vatican City State). 1986-901: a. 10/92 (China (Peoples Republic of); b. 10/47 (Italy and Vatican City State); c. IWP 10A-7 (Italy). COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Servicesa2 CCIR 1978 Antenna Diagrams. CCIR 1984 An
42、tenna Diagrams. CCIR VOLUME*X-3 90 4855232 05039b0 8 Rec, 80-3 BIBLIOGRAPHY LACHARNAY, S. August, 19661 LACHARNAY S. 1983 Antennes pour la radiodiffiion, 1st edition. Information Promotion Franaise, Paris, France. MAGENTA, A. and GIUDICI, P. V. September-October, 19851 Diagrammi di Antenne. Poste e
43、Telecornunicazioni, anno LIII, 5. MAGENTA, A. and GIUDICI, P. V. July-August, 19871 Diagrammi di irradiazione di antenna per onde medie verifica e misura con elicottero. (MF antenna radiation patterns: control and measurement by helicopter). Poste e Telecomzrtiicazioni, anno LV, 4. Juvelles antennes
44、 rideaux en ondes dcamtriques au Centre dIssoudun (France). (New HF curtain antennae at Issoudun (France).) EBU Rev., 98-A. PARMEGGIANI, C. 1963 Progetto e realizzazione delle nuove cortine a larga banda del Centro onde corte di Prato Smeraldo PARMEGGIANI, C. 1964 Antenne a pi dipoli con particolari
45、 leggi di distribuzione delle correnti di alimentazione (Plan and implementation of new wide-band arrays at the Prato Smeraldo short-wave centre). Elettroiiica, 3. (Multi-dipole antennae with feeder currents following different distribution laws). Elettronica, 1 and 2. ANNEX II HF ANTENNA PATTERNS F
46、OR SYSTEM DESIGN AND PLANNING 1. A set of reference antenna characteristics The formulae and the associated software for the calculation of antenna patterns and values of maximum gain are given in Recommendation 705 for a wide range of HF antenna types. A limited set of reference HF antenna characte
47、ristics using the patterns of horizontal dipole antennas was adopted by WARC HFBC-87, Patterns of horizontal dipoles were used because it was found that these were the most commonly used antenna type. An examination of the variation in performance of this set of antennas forms a useful introduction
48、to the range of antenna characteristics found in practice. The principal characteristics of this reference set of patterns are summarized in Table I, containing 24 types of directional antenna together with a simplified pattern of a non-directional antenna (type 25). This set of -antennas was select
49、ed so that a relatively wide range of characteristics is represented with only small changes between types. It also includes multiband operation and slewing. The characteristics given in Table I apply to a design frequency of 10 MHz and ground of average conductivity. The characteristics for dual band and multiband antennas are frequency dependent. Information regarding typical expected changes in performance with frequency is given in 0 3. Information is given regarding: - - - - the maximum directivity gain of the main lobe of radia
