1、Rec. 704 1RECOMMENDATION 704*CHARACTERISTICS OF FM SOUND BROADCASTING REFERENCERECEIVERS FOR PLANNING PURPOSES(1990)Rec. 704The CCIR,CONSIDERINGa) that frequency assignment plans must of necessity take into account the characteristics of receivers;b) that the range of performance of receivers used b
2、y the public is very large;c) that a reference receiver with characteristics based on currently available receivers may be useful in a planningcontext;d) that standards for reference receivers should therefore be defined, which can be taken as a basis for frequencyplanning purposes;e) that these sta
3、ndards need to be taken into account by receiver manufacturers,UNANIMOUSLY RECOMMENDSthat the receiver characteristics contained in Annex I should be used for FM sound broadcasting planningpurposes.ANNEX IMONOPHONIC AND STEREOPHONIC RECEPTION USING THEPILOT-TONE SYSTEM ( 75 kHz FREQUENCY DEVIATION)
4、OR THEPOLAR-MODULATION SYSTEM ( 50 kHz FREQUENCY DEVIATION)In deriving the recommended characteristics, the parameters contained in Annex II and Annex III were alsoconsidered.1. AntennaRecommendation 599 gives the directivity of an external antenna which is applicable for fixed installationsonly. Po
5、rtable or car receivers normally have rod antennas; however, for portable or mobile reception of soundbroadcasts, no directivity of the reception antenna should be applied in planning.2. SensitivityFor planning purposes, “sensitivity” is understood to mean “noise-limited sensitivity”, given in terms
6、 of fieldstrength or power level, required to achieve a specified signal-to-noise ratio at the audio output. Sensitivity should bepresented as a single mean figure. The following values are suggested for the sensitivity of an average receiver: with an external antenna input (car receivers included):
7、5 dB(pW) for monophonic reception,15 dB(pW) for stereophonic reception; with a built-in antenna (oriented for optimum reception in the actual field in which the receiver is placed, forconditions of measurement see CCIR, 1986-90a and b:30 dB(V/m) for monophonic reception,50 dB(V/m) for stereophonic r
8、eception.These values are based upon an AF signal-to-noise ratio of 40 dB. The AF signal-to-noise measurement ismade according to IEC Publication 315-4 in conjunction with CCIR Recommendation 468; reference frequencydeviation: 75 kHz for the pilot-tone system, and 50 kHz for the polar-modulation sys
9、tem. If higher AFsignal-to-noise ratios are to be applied in a planning context, the corresponding sensitivity can be calculated by linearextrapolation up to at least 56 dB (see Annex II, 5)._*This Recommendation should be brought to the attention of the IEC.2 Rec. 7043. SelectivitySelectivity of a
10、receiver is a measure of its ability to discriminate between a wanted signal to which thereceiver is tuned and unwanted signals entering through the antenna circuit.The selectivity is understood as an effective selectivity comprising RF selectivity, IF selectivity, limiter,discriminator, stereophoni
11、c decoder characteristics and AF frequency response.3.1 Selectivity with carrier frequency separations 400 kHzThe selectivity should be sufficient to meet the RF protection ratios given in Recommendation 412. Protectionratio measurements are made in accordance with Recommendation 641. It is assumed
12、that test signals are fed via thebuilt-in antenna for receivers without an external antenna input.3.2 Selectivity with carrier frequency separations 400 kHzRF protection ratios substantially lower than 25 dB should be met. At the critical carrier frequency separationof 10.7 MHz (assumed nominal inte
13、rmediate frequency), RF protection ratios lower than 20 dB should be met.4. Performance in the presence of strong signals*FM broadcasting receivers overloading by strong input signals may result in: desensitization or comparable effects, intermodulation.Such overloading may e.g. occur in the followi
14、ng cases:(a) a (very) strong wanted signal;(b) the wanted signal and one strong unwanted signal;(c) the wanted signal and two strong unwanted signals;(d) the wanted signal and more than two strong unwanted signals.With reference to (b), the RF protection ratios should not be seriously affected ( 3 d
15、B) if the input power ofthe wanted signal is increased to 50 dB(pW). Further information may be found in CCIR, 1986-90c.5. Automatic frequency control (AFC)The AFC should be switchable (see Annex II, 4).6. Stereo/mono operationStereo portable and car receivers should preferably be equipped with a ma
16、nual stereo/mono switch that willmake possible satisfactory monophonic reception in case of insufficient field strength or in the presence of stronginterfering signals.7. Intermediate frequency10.7 MHz is assumed even though some receivers use higher frequencies for different reasons (e.g. frequency
17、diversity reception).7.1 Image rejection ratioThe single signal image rejection ratio, when measured according to IEC Publication 315-4, should be at least50 dB.For the assumed intermediate frequency of 10.7 MHz the image rejection ratio can be disregarded with respectto in-band interference. Howeve
18、r, interference from other services has to be taken into account._*Administrations are requested to contribute on this subject to the CCIR under Study Programme 46N/10.Rec. 704 37.2 Interference generated within the receiver related to the intermediate frequency (see Report 946)The AF signal-to-nois
19、e ratio should be at least 50 dB at the critical frequencies which are integer multiples ofthe intermediate frequency (e.g. 96.3 MHz, 107 MHz); RF input level 40 dB(pW), stereophonic reception. The signal-to-noise ratio is measured according to IEC Publication 315-4 in conjunction with CCIR Recommen
20、dation 468; referencefrequency deviation: 75 kHz for the pilot-tone system, and 50 kHz for the polar-modulation system.8. Local oscillator radiationAmendment No. 1 to CISPR Publication 13 and Draft European Standard EN 55013 indicate a measurementmethod and specify the following values:Local oscilla
21、tor fundamental frequency: 60 dB(V/m)Harmonics below 300 MHz: 52 dB(V/m)Harmonics above 300 MHz: 56 dB(V/m)However, some administrations apply the International Standard of the Council for Mutual EconomicAssistance (CMEA) 784-77; 3894-82 and the National Standards of the USSR (GOST) 16842-82; 2205-8
22、3. In thesestandards the following values are specified:Local oscillator fundamental frequency: 43.5 dB(V/m)Harmonics below 300 MHz: 43.5 dB(V/m)Harmonics above 300 MHz: 43.5 dB(V/m)ANNEX IIIn defining the recommended characteristics given in Annex I for receivers related to the pilot-tone system, t
23、hepossible influence of the following receiver parameters was taken into account:1. Overall audio-frequency responseAn overall audio-frequency response with maximum 3 dB attenuation at 40 Hz and 15 kHz has been assumed.2. Overall total harmonic distortionIt is assumed that the overall total harmonic
24、 distortion is less than 1%, measured in accordance withIEC Publication 315-4.3. Linear and nonlinear crosstalkIn stereophonic reception the crosstalk has an influence on the protection ratio curves. It is assumed that thelinear crosstalk between A and B is less than 35 dB at frequencies between 100
25、 Hz to 3 kHz, and less than 20 dBbetween 50 Hz to 100 Hz and 3 kHz to 15 kHz. Nonlinear crosstalk is assumed to be less than 40 dB.These values are measured according to IEC Publication 315-4 and should not depend on the receiver inputsignal level, provided it is high enough to maintain adequate ste
26、reophonic operation.4. Tuning facilitiesVarious receiver tuning facilities may be considered in a planning context, including: adequate mechanical and/or electrical means for continuous or step tuning; switchable automatic frequency control which avoid detuning in the case of strong adjacent channel
27、 signals and alsofor testing purposes; the features offered by RDS (see Recommendation 643) or other supplementary information systems (seeReport 463).4 Rec. 7045. AF signal-to-noise ratio at higher input signal levelsTaking into account Recommendation 641, the AF signal-to-noise ratio for monophoni
28、c and stereophonicreception is assumed to be at least 56 dB for an input signal level of 40 dB(pW). The AF signal-to-noise ratiomeasurement is made according to IEC Publication 315-4 in conjunction with Recommendation 468; referencefrequency deviation: 75 kHz (see also Annex I, 7.2).6. Compatibility
29、 between the main programme and additional information signalsWhen additional signals are added on supplementary sub-carrier frequencies (see Recommendation 643 andReport 463), account must be taken of certain interference effects. Receiver designers should consider these in order toavoid interferen
30、ce to the main programme channel.6.1 RDS (see Recommendation 643)Spurious components due to RDS may appear in the AF band. In the presence of an RDS test signal whichcauses a deviation of 2 kHz on the main carrier, the power sum of these spurious components should be at least 76 dBbelow an audio sig
31、nal level corresponding to a deviation of 75 kHz using a sinusoidal tone of 500 Hz. Formeasurements, an RDS test signal with only two sideband components symmetrically located with respect to 57 kHz isused by modulating with an “all zeroes” data stream. In order to eliminate the effects of uncorrela
32、ted broadband noise,the spurious components in the AF band are measured selectively.ANNEX IIIThe definition of the recommended characteristics given in Annex I for receivers related to the polar-modulation system is based on the following values: an irregularity of 3 dB in the frequency band from 30
33、 Hz to 15 kHz for the overall AF amplitude-frequencyresponse; a distortion factor less than 1%; linear crosstalk between channels A and B less than 30 dB at the frequency 1000 Hz and less than 24 dB at thefrequencies 250 and 5000 Hz.REFERENCESCCIR DocumentsCCIR 1986-90: a. IWP 10/7-14 (France); b. IWP 10/7-46 (Switzerland); c. 10/308 (Germany (Federal Republic of)._
