FM receiver study chosen such that no third order inter-modulation products occur in the pass-band of the receiver tuned to the low level signal. If this is not possible either the power of the low power transmission should be increased or a gap-filler should be installed to achieve the required protection ratio.

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Summary
Introduction The Expertengruppe UKW 2001 has recommended to optimize FM-networks because FM will remain the main modulation technique for radio for the coming fifteen to twenty years. FM networks could be optimized by revising the protection ratios used for frequency planning. The goal of this study is twofold. First, the technical characteristics of a representative group of present day FM receivers should be assessed. Second, the protection ratios for the network configurations conventional, same programme and HF-synchro should be determined using a reference receiver. Approach From a set of thirty present day FM receivers, consisting of ten car radio, ten portables and ten handhelds, the technical characteristics were determined as follows. First, the characteristics of the individual receivers were measured according to Recommendation ITU-R BS.641. Based on these measurements a good, a reference and a bad receiver was selected from the total group of receivers. Next, the protection ratios for frequency planning for three different network configurations based on subjective assessment of sound samples recorded with the good, the reference and the bad receiver were determined. Finally, the high signal performance and the RDS switching behaviour of a select group of receivers was investigated. This summary will present the results and the conclusions for each of these steps. Results and conclusions For this study the radio-frequency protection ratio curve was used to characterize a receiver. This protection curve is determined according to Recommendation ITU BS 641. Initial measurements showed however that some of the car radios and most of the portables and handhelds were not able to meet the minimal audio-frequency signal-to-interference ratio of 56 dB. With a audio-frequency signal-to-interference ratio of 46 dB it was possible to measure about eighty percent of the receivers. The rest was discarded. The results of these measurements are presented in the figure below.
KENWOOD KDC-3024A [C] P NASONIC CQ-RDP162N [C] A P NASONIC CQ-RDP003N [C] A BECKE MEXICO PRO CD 4627 [C] R BLAUPUNKT WOODSTOCK DAB 52 [C] SUP ERTECH AR-921 CD [C] JVC KD- SX997R [C] JVC KS- FX480REX [C] VDO DA YTON CD 2200 [C]

FM receiver study higher. Also an increase in protection ratio with delay times was expected. The results show, in particular for the 0 s case, a relatively high value. Compared to the Zero-Base study the protection ratios for synchronized transmitters are higher for frequency difference of 0 and 100 kHz. The reason for this could be the different synchronisation used. Since a synchronized network is more complicated to operate an the results are not significantly better than those of same programme it is advised to use same programme in stead of HF-synchro between transmitters carrying the same programme. High signal performance tests have shown that interference from third order inter-modulation products may occur around FM transmission sites where many frequencies are used. There the reception of signals from either a station with much lower power than the others, or from other more distant sites could lead to problems. In these situations frequencies should be chosen such that no third order inter-modulation products occur in the pass-band of the receiver tuned to the low level signal. If this is not possible either the power of the low power transmission should be increased or a gap-filler should be installed to achieve the required protection ratio.

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1 Introduction
This report describes the results of the FM receiver study according to the request for tender from SRG/SSR/ide Suisse from 25 June 2002 and the conclusions reached at the meeting between representatives of the Swiss Companies and Nozema on 26 May 2003 in Lopik.

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2 Measuring protection ratio curves
The first step in this receiver study is to determine the radio-frequency protection ratio curves of thirty receiver. This should be done according to Recommendation ITU-R BS.641. Based upon the radio-frequency protection ratio curves a reference receiver will be selected. The following paragraphs describe the selection procedure. 2.1 Receiver selection Thirty receivers were used in this study: ten car radios, ten portables and ten handhelds. SRG/SSR provided a list with the make and type of the radio. Per category a high and a low end type, based on price, was selected. The tables 2.1 to 2.3 give an overview of the selected receivers. Also the Zero-Base reference receiver, the NAD 1600, was included in the tests. 2.2 Method Recommendation ITU-R BS.641 is used to the determine the radio-frequency protection ratio curves of the receivers. This recommendation indicates that the audio-frequency signal-tointerference ratio should be at least 56 dB. Initial tests with only a few receivers indicated that the 56 dB audio-frequency signal-to-interference ratio could not always be reached. To be able to objectively compare receivers it is important that all receivers use the same minimal audio-frequency signal-to-interference ratio as starting point for the determination of the radio-frequency protection ratio curve. Receivers which are not able to reach the minimal can not be taken into account. Therefore, it was decided to determine the maximum attainable audio-frequency signal-to-interference ratio per receiver first. During this test the audio distortion per receiver is also measured. The audio distortion also gives an indication of the quality of the receiver. The results of this test are given in tables below. #

Car radios

Kenwood KDC-3024A Panasonic CQ-RDP162N Panasonic CQ-RDP003N Becker Mexico Pro CD 4627 Blaupunkt Woodstock DAB 52 Supertech AR-921 CD Jvc KD-SX997R Jvc KS-FX480REX Sony CDX-M850MP Vdo Dayton CD 2200

afstir max [dB]

-52,5 -57,5 -56,6 -51,0 -57,0 -55,3 -52,0 52,0 -55,6 -47,0
Table 2.1: Overview of the maximum audio-frequency signal-to-interference ratio (afstir) for car radios.

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Portables
Sanyo DTA-300M Grundig Luna RP 9200 PLL Grundig Ocean Boy 350 Panasonic RX-EX1 Philips AZ3012 Sanyo DC-DA1000 Sony CFD-S550L/SC Sony ICF-C743L Thomson AM1180 Thomson RR 600CD
-47,5 -45,5 -51,5 -44,0 -54,0 -52,0 -47,0 -49,7 -45,5 -49,0
Table 2.2: Overview of the maximum audio-frequency signal-to-interference ratio (afstir) for portables.

Handhelds

Sony ICF-M33RDS Grundig City Boy 52 Digitalway FD100 Nokia 8310 Philips AZT9500 Samsung YP-90S Sony ICF-C1200 United DM2595-2 Aiwa HS-RM539 Sony WM-FX491
-47,0 -43,0 -46,0 -40,0 -46,5 -44,0 -47,0 -47,0 -47,4 -45,6
Table 2.3: Overview of the maximum audio-frequency signal-to-interference ratio (afstir) for handhelds.
The results of this test show that only three of thirty receiver are able to reach the minimal audio-frequency signal-to-interference ratio of 56 dB. Since it is important to use the same the start value for the audio-frequency signal-tointerference ratio for all receiver it was decided to lower this start value from 56 dB to 46 dB. The start value is now lower than the original stop value for the audio-frequency signal-tointerference ratio. Therefore the stop value was lowered to 40 dB. With this adaptation it was possible to measure the protection ration of twenty fore of the thirty receivers. 2.3 Measurement arrangement The protection ratios have been measured in accordance with Recommendation ITU-R BS.641. Figure 2.1 shows a diagram of the measuring arrangement. This arrangement is a practical realisation of the schematic measuring arrangement from Recommendation ITU-R BS.461.

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Signal Generator
(A+B) (V1) Relais Matrix Port 4

Matching Amplifier

Stereo coder
(J+K+L+M+N) CHA-in (R) CHA-out + CHB-out

Low-pass Filter

(V2) Relais Matrix Port 5

Multisource Generator

CHA-out

Matching network

CHB-in
CHB-out (V3) Relais Matrix Port 3 (S)

Noise Generator

(C+D+E)

Receiver under test

Modulation Analyzer
(V4) Relais Matrix Port 6
Figure 2.1: Practical measuring arrangement. Each apparatus in this arrangement has been given a reference an letter printed in italics and placed between brackets - to the function blocks used in schematic diagram of Recommendation ITU-R BS.461.
The stereo coder in the lower branch of figure 2.1 is set up in such a way that only the preemphasis network is used. This is realised by setting the operation mode of the stereo coder to mono and by switching the four dip switch on the circuit board to the off position. The matching amplifiers in the upper and lower branch are used to go from unbalanced (output of the signal and noise generator) to balanced (input of the stereo coder) and back from balanced (output of the stereo coder) to unbalanced (input of the multi-source generator). Details of the equipment used in the measuring arrangement depicted in figure 2.1 are listed in the table below. Equipment

2.4.1 Radio-frequency protection ratio curves Most receivers were not able to meet the required start value of 56dB for the audio-frequency signal-to-interference ratio dictated by Recommendation ITU-R BS.461. Therefore, this start value has been lowered to 46 dB. Since this start value is lower than the original stop value for the audio-frequency signal-to-interference ratio this value was lowered to 40 dB. With this adaptation it was possible to measure the radio-frequency protection ratio curve of twenty receivers. The results are depicted in figure 2.2. The frequency difference is defined as the frequency of the unwanted transmitter minus the frequency of the wanted transmitter.

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KENWOOD KDC-3024A [C] PANASONIC CQ-RDP162N [C] PANASONIC CQ-RDP003N [C] BECKER MEXICO PRO CD 4627 [C] BLAUPUNKT WOODSTOCK DAB 52 [C] SUPE RTE AR-921 CD [C] CH JVC KD-SX997R [C] JVC KS-FX480REX [C] VDO DAYTON CD 2200 [C]
SANYO DTA-300M [P] PHILIP AZ3012 [P] S SANYO DC-DA1000 [P] SONY CFD-S550L/SC [P] THOM SON RR 600CD [P ] DIGITALWAY FD100 [H] PHILIP AZT9500 [H] S SONY ICF-C1200 [H] UNITE DM2595-2 [H] D AIWA HS-RM 539 [H] SONY WM-FX491[H]
Figure 2.1: Radio-frequency wanted-to-interfering signal ratio (wtisr) for twenty receivers recorded according to ITU Recommendation BS.641. The category to which the receivers belongs is indicated between brackets. The letters C, P and H are used for respectively the category car radios, portables and handhelds.
Details of the measurements can be found in Appendix A. About half of the receiver did not have an antenna input. This meant the signal from the multi-source generator had to be transmitted via the fixed or wire antenna of the receiver under test. Disadvantage of this method is that the input level at the input of the receiver is not known. This, however, is not necessary for the determination of the radio-frequency protection ratio if it is assumed that ratio between the output level of the transmitter and the input level of the receiver is the same for both the wanted signal and the unwanted signal. 2.4.2 Sensitivity Besides the radio-frequency protection ratio curve, the sensitivity of each receiver was also measured. The sensitivity is the signal level, in dBV, that is needed for an audio-frequency signal-to-interference ratio of 20dB. The 20 dB audio-frequency signal-to-interference ratio was chosen so that the sensitivity of all receiver could be measured. Not all receivers can be compared based on sensitivity since sensitivity depends on the way the signal is fed to the receiver. For this study three different feeds are used. The first one is a direct feed. This type of feed can be used for receivers that are equipped with an RF-input connector. All receivers from the category car radios have such a feed. Advantage of this type of feed is that the signal level at the input of the receiver is equal to the signal level at the output of the transmitter. The second type of feed uses a alligator clip to transmit the signal onto the fixed antenna. For the third type of feed the receive antenna, a wire, is wrapped around the transmit antenna. In both cases it is not possible to determine the exact input level. This means that only the sensitivity of receivers that use the same type of feed can be compared. Page 15

FM receiver study To get an indication of the actual input level of the receivers that use an indirect feed, two of such receivers are modified. The fixed antenna of the Sanyo DC-DA1000 and the wire antenna of the Sony WM-FX491 were replaced by a BNC connector. The table below lists the sensitivity before and after the modification. Sanyo DC-DA1000
Sensitivity before modification [dBV] Type of feed Sensitivity after modification [dBV] Type of feed 19,30 Indirect via fixed antenna 7,90 Direct via BNC connector

Sony WM-FX491

35,40 Indirect via wire 29,20 Direct via BNC connector
Table 2.1: Indication of actual sensitivity for receivers which are fed indirectly.
Table 2.1 indicates that the loss due to the indirect coupling is 11,40 dB in case the signal is transmitted to the fixed antenna via an alligator clip and 6,20 dB in case the transmitted by wrapping the wire antenna of the receiver around the wire antenna of the transmitter. 2.5 Selection of the reference receiver The radio-frequency wanted-to-interfering signal ratios are used to select a reference receiver. This is done in two steps. The first step is to determine and average and mean radio-frequency protection ratio curve. The second step is to select the receiver which radio-frequency protection ratio curves is closest to the mean and median radio-frequency protection ratio curve. Before the mean and median radio-frequency protection ratio can be determined, the following question needs to be answered: How many receivers from each category are used for determining the average protection ratio curve? With the adjusted minimal value for the audio-frequency signal-to-noise ratio it is possible to determine the protection ratio curves for nine car radios, five portables receivers and six walkmans. In principle the are two options for the determination of the mean and median audio-frequency protection ratio curves. In the first option the mean and median curve will be based on an equal number of receivers per category. The category with the lowest number of receivers determines the total number of receivers. Consequently, in the other two categories receivers have to be dropped. The problem then is which receiver is, and which receiver is not, taken into account. In the second option the mean and median will be based on all receivers. Although this means that the three categories are not equally represented it was decided to determine the mean and median protection ratio curve based on all receivers. This decision is (primarily) based on the fact that the difference between the portable and the walkman category is arbitrary. A division into two categories is more logical since the car radios perform significantly better than the remaining receivers. In that perspective the two categories are more or less equally represented: nine car receivers and eleven other receivers. Based on the mean and median protection ratio curve a reference receiver will be selected. This receiver is used to record the sound samples which will be used in the subjective tests. Page 16

CN, SP, SN CN, SP SN CN, SP SP, SN CN, SP, SN CN, SP, SN SN CN, SP, SN CN, SP CN, SP, SN
Musicam1,2 and 3 0202,0206 8011895-001, -
Table 3.1: Equipment used for the recording of the sound samples. The column network configuration (nc) indicates for which network operation mode the equipment was used.

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RDS ENCODER

CHANNEL SIMULATOR

RECEIVER UNDER TEST

LOCAL OSCILLATOR

AUDIO SPLITTER

FREQUENCY REFERENCE

(B) Figure 3.1: Measuring arrangement for the recording of sound samples. (A) measuring arrangement for the conventional network configuration. (B): measuring arrangement for the network configurations same programme and synchro.
The frequency of the wanted transmitter is set to 100 MHz, the frequency of the interfering transmitter is equal to the frequency of the wanted transmitter plus the frequency difference. The situation where the interfering frequency is higher than the wanted frequency corresponds to the right-hand side of the protection ratio curves. The wanted and interfering transmitter are modulated in accordance with Swiss regulation. The requirement that maximum 10% of the Page 21
FM receiver study instantaneous frequency deviations must lie in the interval from 75 to 85 kHz turned out to be leading. 3.2 Source sound samples Source sound samples are the sound samples that are used to frequency modulate the transmitters. Three different types of source sound samples are used. The first type is speech. For this type a fragment from the Dutch radio station Radio 1 is taken. The second and third type are respectively pop/rock and classical music. For Pop/rock a fragment of Need you tonight by INXS is taken. For classical music a fragment of Der Nussbaum by Vesselina Kassarova is used. All fragment are about one minute in length. 3.3 Sound sampled recorded with the reference receiver The reference receiver is used to record sound samples with speech and classical music as wanted signal. This is done for all three network configurations. The different conditions per network mode - frequency difference, delay and signal to noise ratio - that are used are listed in tables 3.2 to3.4. Network configuration: conventional f[kHz] 100 200
12;18;4;30;36;42;48 -12;-6;0;6;12

The participants took part in both tests and always started with the pairwise comparison test. In the PWC test, ten younger and ten older participants were presented with the speech samples, and the other ten younger and ten older participants with the classical music samples. In the MOS test, all 40 participants were presented with the speech and classical music samples. The samples, stored on a PC, were played back through high-quality headsets, the sound was set at a comfortable listening level (speech at 68 dBA, classical music at 66 dBA). 4.2.1 Pairwise comparison The participants listened to the samples presented in pairs. Their task was to compare the two stimuli in each pair and to indicate what stimulus had a higher sound quality. Thus, participants gave relative judgments. With 4 PWC runs (containing 25 different conditions), each participant judged 246 pairs of samples, as explained earlier. Each pair was presented only once. During the presentation of a sample pair, the participants could hear the samples by mouse clicking on the buttons labelled fragment 1 or fragment 2 on a computer display. They could repeat the samples as often as they wanted. After hearing both samples, the participants made their judgments by mouse clicking on the buttons labelled fragment 1 is better or fragment 2 is better on the display. After they made their selection, a new pair of samples was presented. For the presentation of the 4 PWC runs, ten different orders were created, resulting in 2 participants (a younger and an older) receiving the same order of runs. The order of the sample pairs within each run was different for each participant (randomized). Prior to the first PWC run, the participants were presented with 10 practice sample pairs, to familiarize them with the experimental procedure and with the sample quality range to be expected in the experiment. In total, the PWC test (4 runs) took approximately 2 hours, including short breaks. 4.2.2 Mean Opinion Score In this test, the participants rated the quality of the individually presented samples using a five-point scale from bad (1) to excellent (5) and entered their ratings on a computer Page 24
FM receiver study display using a keyboard. The presentation of the sample was followed by a warning signal to warn the participants that they should enter their ratings (there was a 2-sec interval between samples). Each sample was presented only once. The participants were tested in groups of 3 or 4, in separate testing booths with individual headphones. For each group of participants, the order of the speech samples (MOS run 1) and of the classical music samples (MOS run 2) was different. About twenty (half) of the participants started with the speech samples and the other participants with the classical music samples. Prior to each MOS run, the participants were presented with eight practice trials to familiarize them with the experimental procedure and with the quality range for both the speech and classical music samples to be expected in the experiment. In total, the MOS test (2 runs) took approximately 25 minutes, including a short break. 4.3 Analysis and results of the pairwise comparison For each participant, the preference matrix of the samples was determined. Table 4.1 illustrates an artificial comparison between five samples. A cell value of 1 indicates that the column variable is preferred over the row variable, a cell value of 0 indicates that the row variable is preferred. The sum of the column reflects the number of times the column variable is preferred over all row variables. Sample A B C D E Column total A 3 B 0 Preference C 4

5.3.1 Comparison The results from the protection ratio measurements for the same programme case and for the selected reference receiver are compared with the ITU values in the Table 5.1. f [kHz]

-3 -13

-9 -17
Table 5.1: Comparison between the protection rations from recommendation ITU-R BS.412-9 and those based on the subjective tests for same programme networks.
Conclusions regarding same programme networks
The following conclusions can be drawn: The results of the subjective tests for the network condition same programme show a considerable improvement compared to the ITU values which are for wanted and interfering signals having different programmes, also taking into account that the test conditions (wanted signal speech, unwanted signal pop/rock) are much more unfavourable than the conditions assumed for the ITU results. No reliable result could be found for 0 kHz, grade 3. Extrapolation of the results in the table above would lead to about 19 dB. Page 34
FM receiver study For frequency planning of transmitters carrying the same programme it is advised to use the protection ratios based on MOS score3,5 in case of steady interference. Furthermore the considerations of section 5.2.2 should be taken into account. For frequency planning of transmitters carrying the same programme it is advised to use the protection ratios based on MOS score3,0 in case of tropospheric interference. Furthermore the considerations of section 5.2.2 should be taken into account. Considerations on protection ratios for HF-synchro networks
5.4.1 Comparison The preliminary results from the protection ratio measurements for the synchronised case and for the selected reference receiver are compared with the ITU values in the table 7.4 in case of a frequency difference of 0 kHz. For reference also the values for same programme measured with a delay of 50 s are indicated between brackets. Delay [s]

26 (19)

Table 5.1: Comparison between the protection rations from recommendation ITU-R BS.412-9 and those based on the subjective tests for HF-synchro for f=0kHz. The values between brackets represent the values for network configuration same programme under the same conditions.
Conclusions regarding HF-synchro networks
The following conclusions can be drawn: The results of the subjective tests for the network condition hf-synchro show a considerable improvement compared to the ITU values which are for wanted and interfering signals having different programmes, also taking into account that the test conditions (wanted signal speech, unwanted signal pop/rock) are much more unfavourable than the conditions assumed for the ITU results. Although it was expected that the results for synchronised transmissions with a delay of 50 s would be similar as those for same programme, the protection ratio in the synchronised case appears to be higher. Although an increase in protection ratio with delay time had been expected, the results show in particular for the 0 s case an relative high value. The results for the delays 0, 20 and 50 s are relatively close to each other, statistical analysis has shown that there is no significant difference. As synchronised transmitters are more complicated to operate and the results are not significantly better than same programme it is advised not to use synchronised transmitters for achieving a higher frequency efficiency, but in stead same programme. Page 35

FM receiver study 5.5 Planning considerations
5.5.1 Usable field strength calculations For calculating usable field strength, the nuisance fields of relevant interfering transmitters should be calculated. Transmitters carrying the same programme should be identified. This may require a special code in the transmitter database. The nuisance field of these transmitters should be calculated with the reduced protection ratios (see section 7.3). The nuisance field of the other relevant transmitters should be calculated with the protection ratios for conventional networks (see section 7.2). All relevant nuisance fields should be combined using the agreed method (e.g power sum). 5.5.2 Optimised networks The use of protection ratios for same programme networks may lead to higher frequency efficiency in case coverage areas are interference limited. However flexibility in network operation is reduced. If a transmitter that is part of the network for which the reduced protection ratios are applied, needs to carry another programme, either a regional opt-out or a completely different programme, a new network planning is required; the reduced protection ratios are not applicable any more. The application of transmitters with frequencies N 200 or 300 kHz with the same programme is particularly useful for coverage optimisation in the periphery of a coverage area of a transmitter with frequency N. As there is a negative protection ratio, either the transmitter with frequency N or the one with N 200 or 300 kHz (having the same programme) can always be received. Another application could be made in case of a more or less full replanning. A network carrying the same programme could consist of several transmitters having frequency differences of 0 or 100 kHz. The interference zones between these transmitters should be covered by transmitters on other frequencies. It may also be possible by careful planning to situate the interference zones in areas of low population densities. Also in this case coverage areas can be optimised by transmitters with frequency differences of 200 or 300 kHz as described above. An example of a network that has been planned on the basis of reduced protection ratios for transmitters carrying the same programme is shown in annex [7.1]. This network shows the combination of cases indicated above. The network consists mainly of two sets of frequencies, around 103.1 MHz and around 97.7 MHz respectively. Although the example shows the way planning could be done, it should be noted that the protection ratios in this example are different than those advised in this report. Furthermore also other criteria and methods in the example are different than those recommended by ITU. 5.5.3 International frequency coordination Reduced protection ratios for networks carrying the same programme are not contained in GE84 plan and are not recommended by ITU. Also the GE84 transmitter databases do not contain provisions for indicating that transmitters are working in networks carrying the same programme. Calculations done in the framework of GE84 frequency co-ordinations can therefore not take into account the reduced protection ratios. The usable field strength at test points in the coverage area of transmitters with the same programme, in these circumstances may therefore be much higher than calculated for national frequency planning purposes. Page 36

FM receiver study Consequently more interference may need to be accepted from neighbouring countries, unless specific bi-lateral agreements have been made. It is advisable to make such bi-lateral agreements before national planning starts in order to take into account possible limitations resulting from interference to neighbouring countries in a proper way. 5.5.4 General observations The three tested categories of receivers show clearly different results. In general portable receivers have an average performance, car radios show a better audio signal-to-noise ratio and are more selective. Walkman radios are worse in audio performance and selectivity. It could be considered to create two sets of planning criteria (as is proposed for T-DAB in relation to the RRC). One set for portable reception and one set for mobile reception. Coverage areas could, as far as possible, be optimised for portable reception in urban areas and mobile reception on motorways and major roads. Planning criteria suitable for walkman radios would result in very spectrum demanding frequency plans. The more pragmatic approach is not to plan for reception by walkman radios and leave it to the user if and where to use these kind of receivers. However, if more dense FM networks are planned reception on walkman radios may become more limited than at present.

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6 Comparison with zero-base results in The Netherlands
6.1 General The results from this study show somewhat different results than those from the zero-base FM study in The Netherlands. It should be noted that the starting points for both studies were different. The main differences are given in the table below. Item Receivers Reference receiver S/N in objective tests Frequency deviation Zero-Base study Tuners, portables and car radios NAD 1600 tuner 50 dB ITU-R SM.1268, annex 1 This study Portables, car radios, walkmantype radios Sanyo DC-DA1000 portable 40 dB ITU-R SM.1268, annex 2
Table 6.1: Differences between the starting point for this study and the Zero-Base study.
6.2 Conventional network The tables below show a comparison between the values used for FM planning in The Netherlands. For this study it was concluded to use the ITU values for conventional networks. f [kHz] Steady interference NL values This study [dB] [dB] -2 -15 Troposferic interference NL values This study [dB] [dB] --15 -7
Table 6.1: Comparison between this study and the Zero-Base study for the network configuration conventional.
The 3 to 8 dB reduction in protection ratios, compared to ITU, as used in The Netherlands for conventional networks have not been confirmed by this study. 6.3 Same programme network In the Zero-Base project the MPX synchronisation has been used. Although it is not exactly the same as the network operation a comparison between the two is possible. Only protection ratios for steady interference were used in the Zero-Base project because it assumed that synchronised transmitters are spaced relatively closely.

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Steady interference NL values This study (MPX synchro) (same programme) [dB] [dB] -2 -3 -15 -13
Troposferic interference NL values This study (MPX synchro) (same programme) [dB] [dB] -9 -17
Table 6.1: Comparison between this study and the Zero-Base study for the network configuration same programme.
The values for same programme and steady interference do not differ that much from the Zero-Base values for MPX synchronisation, except for 100 kHz frequency difference. It should be noted however, that the Zero-Base protection ratio at 100 kHz difference is very optimistic. 6.4 Synchronised network As indicated above the synchronised conditions in the Zero-Base project were different than for this study. The table below only shows the protection ratios for synchronised transmitters with a delay of 50 sec. In the Zero-Base study a delay of 50 sec has not been measured. The table show the interpolated value between 20 and 100 sec. Only protection ratios for steady interference are used in the Zero-Base project because it assumed that synchronised transmitters are spaced relatively closely. f [kHz] Steady interference Troposferic interference NL values This study NL values This study (MPX synchro) (HF-synchro) (MPX synchro) (HF-synchro) [dB] [dB] [dB] [dB] --9 -15 -11 -15
Table 6.1: Comparison between this study and the Zero-Base study for the network configuration HF-synchro.
The results from this study show reasonably high for 0 kHz and 100 kHz. The reason for this could be the different synchronisation used.

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7 High signal performance
High signal performance can be defined as the tendency of a receiver to inter-modulate in the presence of strong signals. Recommendation ITU-R BS412 describes a method for determining a receivers performance in the presence of strong signals. This measurement uses three RF signals: one wanted signal and two interfering signals. The performance is expressed as a protection ratio. Details of the high signal performance test can be found in the next paragraphs. 7.1 Approach The frequencies of the two interfering signals of equal levels are positioned above or below the frequency of the wanted signal at equal differences of frequencies. The frequency difference is defined as: f=fi2-f w=f i1-f i2 The interfering signal f i2 is unmodulated and the interfering signal f i1 is modulated with coloured noise according to Recommendation ITU-R BS.461. The RF protection ratio is measured according to the same recommendation, the only difference being that two interfering signals are used. The procedure for determining the interference caused by inter-modulation of strong RF be can be split up in the following three steps: 1 Setting up the wanted transmitter (Determination of the reference level). Source A of the multi-source generator, which represents the wanted transmitter, is frequency modulated with a 500 Hz sinusoidal tone. The output level of the tone generator is adjusted to obtain a frequency deviation of 75kHz, including the pilot tone in stereophonic operation. The QUASI-PEAK reading of the modulation analyzer, with the weighting network switched off (i.e. CCIR UNWEIGHTED) indicates the reference level. This reference level corresponds to 0 dB. 2 - Setting up the unwanted transmitters. Source B of the multi-source generator, which represents the first unwanted transmitter, is modulated with a 500 Hz sinusoidal tone obtained from tone generator. The output level of source B is adjusted to obtain a deviation of 32 kHz. The audio-frequency level at the input of the unwanted transmitter before pre-emphasis is measured by means of the modulation analyzer (noise meter U). The noise-weighting network is switched off (i.e. CCIR UNWEIGHTED). Next a noise signal obtained from the noise generator replaces the sinusoidal tone and its output level is adjusted to obtain the same QUASI-PEAK reading as before at the noise meter. Source C of the multi-source generator, which represents the second unwanted transmitters, is unmodulated. The output level of source C is made equal to the output level of source B. (1)

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FM receiver study 3 - Measuring the radio-frequency protection ratio curve. The following procedure is repeated for frequency differences ranging from 500 kHz to 5 MHz in steps of 500 kHz: The output levels of the unwanted transmitters are kept equal and are simultaneously adjusted to obtain an audio-frequency signal-to-interference ratio of 40 dB at the audio-frequency output of the receiver. In this case, the weighting network of the modulation analyzer must be switched in (i.e. CCIR WEIGHTED) and the QUASI-PEAK detector must be selected. The ratio between the radio-frequency levels of the wanted and unwanted transmitters is the required radio-frequency wanted-to-interfering signal ratio. 7.2 Results The high signal performance tests are executed for two receivers from the category portables a handhelds. For the first category the Sanyo DC-DA1000 and the Sony CFD-S550L are tested, for the second category the Philips AZT9500 and the Sony WM-FX491.

Sanyo DC-DA1000

0 -1 --10 -15 -20 -25 -30 -35 f [MHz]

wtisr [dB]

30dBpW 50dBpW 70dBpW
Figure 7.1: Radio-frequency wanted-to-interfering signal ratio as a function of frequency difference for the Sanyo receiver.

Sony CFD-S550L

wtisr [dB] -5 -4 -3 -2 -1 --10 -15 -20 f [MHz] 5 30dBpW 50dBpW 70dBpW
Figure 7.2: Radio-frequency wanted-to-interfering signal ratio as a function of frequency difference for the Sony receiver.

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Philips AZT9500
Figure 7.3: Radio-frequency wanted-to-interfering signal ratio as a function of frequency difference for the Philips receiver.
wtisr [dB] -5 -4 -3 -2 -1 -5 50dBpW 70dBpW

-10 f [MHz]

Figure 7.4: Radio-frequency wanted-to-interfering signal ratio as a function of frequency difference for the Philips receiver.
The results clearly indicate that inter-modulation products significantly deteriorate the performance of the receiver under test. The frequencies of the second and third order intermodulation product, expressed in in fw and f, can found in table below. Order of the IM products Second Third Frequencies of the IM-products f, 2f, 2fw, 2f w+f, 2fw+2f, 2f w+3f ,2fw+4f fw-2f, f w-f, fw, f w+f, f w+2f, fw+3f, f w+4f, 3fw, 3f w+f, 3fw+2f, 3fw+3f, 3f w+4f, 3fw+5f, 3f w+6f
Table 7.1: Frequencies of the first, second and third order inter-modulation products for the choice of frequencies in accordance with (1).

From this table it can be seen that the inter-modulation effects are caused by third order intermodulation products. The effect of these third order inter-modulation products is most noticeable when they are located in the pass-band of the receiver.

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FM receiver study Experience in The Netherlands has shown that interference from third order inter-modulation products may take place if reception is near an FM transmission site where many frequencies are used and: a) at least one with much lower power (for instance a local station) than the others b) reception of signals from another, more distant, site is required In these situations frequencies should as far as possible be chosen in such a way that no third order inter-modulation products occur in the pass-band of the receiver tuned to the low level signal. If it is not possible to avoid third order inter-modulation products in case a) the power of the low power transmission may need to be increased in order to achieve the required protection ratio for this situation. In case b) a fill-in transmitter may be required that fulfils the conditions indicated for case a). An example of case b) in the Netherlands is shown in Appendix C

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8 RDS Switching
This receiver study focuses on two aspects of RDS switching behavior. The first one investigates the RDS switching behavior due to differences in radio frequency levels of two different sources transmitting the same program on different frequencies. The second one investigates the RDS switching behavior due to multipath. The approach followed in both cases will be explained in the next paragraph. 8.1 8.1.1 Approach RDS switching behavior due to differences in radio frequency levels
This test represents the situation when traveling from the coverage area of one transmitter to the coverage area of another transmitter belonging to the same program chain and thus transmitting the same program on a different frequency. This test investigates the behavior of a receiver under such conditions and can be split up in the following two steps: 1 - Setting up the transmitters. Sources A and B of the multi source generator are frequency modulated with a 500 Hz sinusoidal tone and RDS. For both sources the frequency deviation due to RDS is set to 2 kHz. The combined output of sources A and B is fed to the receiver under test. 2 - Measuring the radio frequency switching level The following procedure is repeated for the following combinations of carrier frequencies: Combination Source A, f (MHz) Source B, f (MHz) 1 90,0 105,90,0 90,105,0 90,90,0 89,9

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