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Research White Paper

WHP 174

18th February 2009

The Plymouth Digital Radio Mondiale (Drm) Trial Long-term Reception Results

Andrew Murphy

BRITISH BROADCASTING CORPORATION

The Plymouth Digital Radio Mondiale (Drm) Trial: Long-term Reception Results

Andrew Murphy

Abstract

The Plymouth (‘Mayflower’) trial was a trial of Digital Radio Mondiale (Drm) [1] that ran from 1st April 2007 for the period of one year. The trial took the existing analogue AM service of BBC Radio Devon on medium-wave (MW) and converted it to Drm operation. Primarily audience-research led, around 100 volunteers were given a consumer Drm radio and asked to give regular feedback on their listening experience.

To support this process, BBC Research put in place a network of monitoring receivers to make objective measurements of the quality of reception at various locations both inside and outside the predicted service area.

The data collected from the monitoring receivers shows that the performance of the Drm broadly matched the initial coverage predictions. There was a significant benefit seen from switching from 64-QAM to 16-QAM during hours of darkness which helped to make the daytime and night-time coverage areas more similar in size.

The addition of a second transmitter to form a single frequency network showed that additional coverage can be gained without adversely affecting existing reception in the mush zone.

Additional key words: Theseus

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The BBC grants permission to individuals and organisations to make copies of the entire document (including this copyright notice) for their own internal use. No copies of this document may be published, distributed or made available to third parties whether by paper, electronic or other means without the BBC's prior written permission. Where necessary, third parties should be directed to the relevant page on BBC's website at http://www.bbc.co.uk/rd/pubs/whp for a copy of this document.

White Papers are distributed freely on request.

Authorisation of the Head of Research is required for publication.


Andrew Murphy

Contents

1 Introduction............................................................................................................................ 1 2 Trial Schedule ....................................................................................................................... 2 3 Transmission Sites ................................................................................................................ 4 3.1 Crown Hill (PYZ) ................................................................................................................. 4 3.2 North Hessary Tor (NHT) .................................................................................................... 4

4 Propagation ........................................................................................................................... 4 4.1 Local sunset and sunrise times........................................................................................... 5

5 Measurement Sites ............................................................................................................... 6 5.1 Predicted Coverage ............................................................................................................ 6 5.2 Reception Monitoring .......................................................................................................... 7

6 Data Collection and Analysis................................................................................................. 8 6.1 Drm audio reliability as a percentage.................................................................................. 8 6.2 Signal strength .................................................................................................................... 8 6.3 Modulation Error Ratio (MER)............................................................................................. 8 6.4 Slots and Slices................................................................................................................... 9 6.5 Transmitter Availability ........................................................................................................ 9 6.6 Renaming of Logging stations........................................................................................... 10 6.7 Audio decoder bug............................................................................................................ 10

7 Analysis methodology ......................................................................................................... 10 7.1 AM transmissions and quiet week..................................................................................... 12 7.2 Drm transmissions ............................................................................................................ 12

8 Results and Discussion ....................................................................................................... 13 8.1 AM transmissions.............................................................................................................. 13 8.2 Quiet week ........................................................................................................................ 15 8.3 Drm: Overall results .......................................................................................................... 18 8.4 Drm: Individual Reception Sites ........................................................................................ 18 8.4.1 Plymouth Studios (PY) ................................................................................................. 19 8.4.2 Newton Ferrers (NFR).................................................................................................. 21 8.4.3 Oreston (ORS) ............................................................................................................. 22 8.4.4 Caradon Hill (CNH) ...................................................................................................... 23

8.5 Drm: Transmitter Performance.......................................................................................... 25 8.5.1 Crown Hill (PYZ)........................................................................................................... 25 8.5.2 North Hessary Tor (NHT) ............................................................................................. 25

8.6 Drm: Diurnal Variation....................................................................................................... 26 8.7 Drm: AM field strength comparison................................................................................... 26

8.8 Drm: Night time reception ................................................................................................. 26 8.9 Drm: 64-QAM vs 16-QAM................................................................................................. 27 8.10 Drm: Single Frequency Network ....................................................................................... 30

9 Conclusions......................................................................................................................... 32 10 REFERENCES.................................................................................................................... 33 Appendix A – Table of local sunrise and sunset times for 2007 and 2008 ..................................... 35

1


Andrew Murphy

1 Introduction The Plymouth (‘Mayflower’) trial was an audience-research led trial of Digital Radio Mondiale (Drm) [1] that ran from 1st April 2007 for the period of one year.

The trial took the existing analogue AM service of BBC Radio Devon on medium-wave (MW) and converted it to Drm operation with the aim of investigating the resulting coverage and reliability of reception. BBC Radio Devon was chosen for the trial as it had recently benefited from an increase in both its FM and DAB coverage. As a result it was felt that the vast majority of the listeners who lost their AM service would be able to receive BBC Radio Devon by other means.

Outside of the urban centre, the coverage area is characterized as rural and hilly. Medium-wave frequencies are ideally suited to this sort of environment and, when used with Drm, have the potential to provide audiences with a good quality of sound at a potentially lower transmission cost than FM or DAB for which a denser network of transmitters might be required.

A panel of around 100 listeners was recruited and given consumer Drm receivers to take home. They were then asked to fill out questionnaires and attend panel interviews, organised by an audience research company, at various points throughout the year to record their listening experience.

To complement this consumer assessment, BBC Research designed a monitoring system, Theseus [2], to examine the technical quality of reception at various sites both inside and outside the predicted coverage area, with the aim of providing the data to enable a comparison to be made between objective measurements and people’s real-life experience of Drm.

Initially the trial was based on a single set of Drm transmission parameters from the single transmitting station that had been used for the AM service. It was later extended to include a second transmission site enabling Single Frequency Network (SFN) operation to be investigated. The parameters of the Drm transmission were also changed during the trial to see the effect on the quality of reception.

The trial was organised by BBC Distribution in partnership with BBC Audio & Music, BBC Radio Devon and National Grid Wireless (NGW) who provided the transmissions. The Drm content server was written and provided by Julian Cable of the BBC World Service and is based on that used for the BBC’s existing Drm transmissions. The audience research was provided by Leapfrog.

2

2 Trial Schedule The basic Drm transmission parameters chosen for most of the trial are shown in Table 1.

Item Value

Transmission Frequency 855 kHz

Drm mode ‘A’

Occupied bandwidth 9 kHz

Code rate 0.6

MSC Constellation 64-QAM

SDC Constellation 16-QAM

Net bitrate ≈ 23 kbit/s

Audio coding AAC+SBR (parametric stereo)

Table 1 – Drm trial transmission parameters

The net bit rate of around 23 kbit/s was enough to allow the use of parametric stereo audio as well as allocating 500 kbit/s for an Electronic Programme Guide (EPG).

Between the switch-off of the AM transmissions and the start of the Drm service, a so-called ‘quiet week’ was accommodated during which no transmissions took place. This was to allow the background noise on the channel to be measured and characterised. Unfortunately, teething problems with the monitoring equipment meant that only data for one day of this week was recorded.

In addition to the basic Drm transmission parameters described above, a switch was made from 64-QAM to 16-QAM for a short period to assess the impact of switching to a more rugged constellation on the quality of reception, particularly at the edge of the predicted coverage area. This resulted in a lower net bit-rate of around 16.5 kbit/s, still enough to provide acceptable audio quality.

The different phases of the trial are shown in Table 2 below.

Dates Description

until 19/03/2007 AM

02/04/2007 – 09/04/2007 No transmissions (‘quiet week’)

01/05/2007 – 21/06/20081 except 22/12/2007 – 15/01/2008

Drm (64-QAM) Drm (16-QAM)

Table 2 – Schedule of transmissions from the Crown Hill transmitting station

________________________________________________________________________________________________ 1 Although the official trial lasted a year, the transmitter stayed on for somewhat longer and reception quality could therefore still be measured.

3

Partway through the trial, a second transmitter was added at North Hessary Tor (Figure 2) so that Single Frequency Network (SFN) operation could be explored. This was a relatively low-power site which meant that reception sites within the core coverage area of Crown Hill were largely unaffected by its operation. Additional reception sites were added, however, to enable a number of additional experiments to be carried out as summarised in Table 3 below:

Dates Transmission from North Hessary Tor

14/08/2007 – 02/09/2007 Co-channel Drm (SFN with Crown Hill)

04/09/2007 – 23/09/2007 Adjacent channel AM

25/09/2007 – 14/10/2007 Adjacent channel Drm

Table 3 – Schedule of transmissions from North Hessary Tor

As shown in the table, a number of adjacent channel transmissions were carried out from North Hessary Tor and used to investigate protection ratios between Drm and AM services. However, these measurements are beyond the scope of the long-term reception monitoring results presented here.

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3 Transmission Sites

3.1 Crown Hill (PYZ) The main transmission site for the trial was based at Crown Hill to the north of central Plymouth. Table 4 below shows the radiated power for both AM and Drm operation. For Drm transmission, 8 dB of attenuation was required to meet the requirements of the Drm spectrum mask from what was a particularly challenging antenna system [ 3]. Whilst this is a fairly large amount of attenuation, it was important not to disrupt the existing AM services being transmitted from the same antenna and as this was a short-term trial this was deemed acceptable.

AM Drm

Transmitter power 1 kW (carrier) 1.26 kW

Attenuation 0 dB 8 dB

Power to antenna 1 kW 200 W

EMRP2 400 W 80 W

Table 4 - AM and Drm transmission powers from Crown Hill (PYZ)

3.2 North Hessary Tor (NHT) On the 2nd July 2007, North Hessary Tor (NHT) also began transmitting on 855 kHz to form a synchronised SFN. The transmitted power was relatively low however, at around 12W EMRP. As a result, it did not make a significant contribution to the majority of measuring locations and an additional site was added to enable measurements of the SFN to be carried out.

4 Propagation Medium-wave propagation is characterised by two mechanisms; sky-wave leading to a diurnal variation determined by the sun’s interaction with the ionosphere and ground-wave which is influenced by the conductivity of the ground between the transmitter and the receiving location.

The diurnal variation is controlled by the presence or otherwise of the ionospheric D-layer. During daylight hours there is enough energy from the sun to ionise the D-Layer which acts to attenuate medium-wave signals before they are can be refracted by the upper layers of the ionosphere. As a result, only the ground-wave signal will be received.

At night time, when there is no incident radiation from the sun, only residual ionisation occurs in the D-layer and medium-wave frequencies are no longer attenuated. This results in sky-wave propagation and the low losses in the ionosphere can produce significant field strengths many hundreds of kilometres from the transmitter causing interference to local transmissions. This is illustrated in Figure 1.

The higher the ground conductivity, the lower the attenuation and hence the further a medium-wave signal will travel. The sea has a particularly high conductivity meaning that, in a coastal location such as Plymouth, it is often possible to hear broadcasts from distant transmitters even during the daytime.

________________________________________________________________________________________________ 2 Effective Monopole Radiated Power

5

Figure 1 - Daytime and Nighttime medium-wave propagation

The main co-channel interferer on 855 kHz is “Radio Nacional 1” broadcasting in a SFN across Spain with transmitters ranging in power from 5 to 300 kW.

4.1 Local sunset and sunrise times Since the medium-wave propagation mechanism is so different between day and night, the local sunset and sunrise times were obtained from the website of the Astronomical Applications Department of the US Naval Observatory. These were then used to take into account the influence of the sun during the analysis of the reception data.

The full tables for 2007 and 2008 are shown in Appendix A. For the purposes of the online calculator, the latitude and longitude of Plymouth was taken to be W04:07, N50:23.

Tx (wanted)

Tx (interferer)

Rx Tx

(wanted) Tx

(interferer)

Rx

6

5 Measurement Sites The measurement site locations were chosen with reference to the predicted Drm and AM coverage areas. The aim was to have a good spread of receiving locations inside and outside the daytime and night time service areas of the AM and the Drm. In practice, the choice of receiving sites was a compromise between having the ideal locations and the availability of people willing to accept the inconvenience of hosting a monitoring receiver and antenna for the duration of the trial.

The resulting locations are shown in Figure 2 along with the transmission sites. Monitoring receivers were also connected directly to a low-power output of the transmitter so that their performance could be monitored. In any trial there will inevitably be breaks in transmission and it is important that these are recorded and taken into account when assessing the overall system performance. The difference between the predicted daytime and night-time coverage areas for both the AM and the Drm service is clearly evident caused by the different medium-wave propagation mechanisms. The effect of night-time interference from “Radio Nacional 1” in Spain is to reduce both the AM and Drm coverage areas at night.

Figure 2 - Transmitter and reception site locations

5.1 Predicted Coverage The coverage contours of Figure 2 were calculated using the method set down in ITU R P.435 7 which is supplemented by ITU R BS.1615 for Drm. This quotes a minimum usable field strength of 40 dBµV/m for the particular Drm parameters used in the trial (Table 1) and a co-channel wanted Drm to AM interferer protection ratio of 7.3 dB for 64-QAM operation and 2.7 dB for 16-QAM.

AM, 400W EMRP: 60 dBµV/m daytime, interference-limited night time

Drm, 80W EMRP: 40 dBµV/m daytime, interference-limited night timeni

ght

day

Mary Tavy(MTY)

Newton Ferrers (NFR)

Plymouth Studios (PY)

Oreston(ORS)

Crown Hill(PYZ)

North HessaryTor (NHT)

Caradon Hill (CNH)

day

nigh

t

Map image © Crown copyright. All rights reserved. BBC licence number 100019855, 2008.

Monitoring site Transmitting station (with monitoring receiver)

AM, 400W EMRP: 60 dBµV/m daytime, interference-limited night time

Drm, 80W EMRP: 40 dBµV/m daytime, interference-limited night timeni

ght

day

Mary Tavy(MTY)

Newton Ferrers (NFR)

Plymouth Studios (PY)

Oreston(ORS)

Crown Hill(PYZ)

North HessaryTor (NHT)

Caradon Hill (CNH)

day

nigh

t


Monitoring site Transmitting station (with monitoring receiver)

7

5.2 Reception Monitoring The reception data was collected using the Theseus monitoring system [ 2] supplemented by the Long-term Test (LTT) System originally developed by the Drm System Evaluation Group. Scripts running at the reception site constantly record the quality of reception of each 400 ms Drm frame. Data for each frame is then aggregated into a minute summary that is stored to disk and sent by email to a central server at BBC Research where the results are stored in an Oracle database.

To perform the analysis, further scripts are run which interrogate the database, extract the information of interest and perform the appropriate statistical analysis.

The site-based scripts currently require some time when they are not recording in order to process and email the data back to base. As a result, no data is recorded between 2300 and 0000 UTC.

The receivers were based on PCs fitted with a WinRadio G313 HP receiver card. Each site was connected to the Internet by whatever means was available, usually ADSL but in one instance a GPRS mobile phone. The receiving antenna was a Wellbrook AL5030 which was oriented to give the maximum signal from the trial transmission. This antenna has a calibration factor of 15 dB/m at the 855 kHz frequency used for the trial and this figure must added to the signal level seen at the receiver (dBµV) to give the actual field strength measured in dBµV /m

The setup of a typical receiving site can be seen in Figure 3 below.

Figure 3 - Typical monitoring receiver setup

The open-source Dream [ 4] software performs the AM and Drm decoding as shown in Figure 4.

Figure 4 – A screenshot of the Dream receiver software

8

6 Data Collection and Analysis A number of different reception parameters are collected by the LTT system for each minute of the day:

6.1 Drm audio reliability as a percentage For each minute, the percentage of Drm (40 ms) audio frames received without error is recorded. Each audio frame carriers a Cyclic Redundancy Check (CRC) word which can be used to detect errors in the received data. It is then up to the audio decoder to decide what the best strategy is for dealing with this. If only a single audio frame is in error between a run of correct ones it is often possible for the audio decoder’s error concealment strategy to hide this from the listener. A long run of errors would, however, force the audio decoder to mute the output.

A recorded value of 100% means that every audio frame was received correctly in the minute. It is very difficult to determine a precise percentage below which reception becomes unacceptable since so much depends on the distribution of the frames in error. In practice, however, values close to 100 % mean that reliable reception is achieved.

6.2 Signal strength Statistics regarding the input voltage to the receiver are collected over the minute. The median, 10th and 90th percentiles are stored. When the receiver is locked and demodulating Drm, the signal strength is measured over the bandwidth of the Drm transmission which may vary depending on the frequency band in use3. When the receiver is unlocked or receiving AM, a default channel bandwidth is used and this was fixed at 9 kHz for the trial.

To convert the signal strength seen at the receiver input (in volts) to a field strength (in volts/m) it is necessary to add the calibration factor of the antenna (in dB/m) (see 5.2)

6.3 Modulation Error Ratio (MER) Since Drm is a multi-carrier system, an average signal to noise ratio is calculated across all of the carriers in use, a so-called Modulation Error Ratio (MER). It is based on the size of the error vector from the currently received point to the closest point on an ideal constellation.

A number of different types of MER have been defined by the Drm Receiver Status and Control Interface (RSCI) [ 5]. In this instance the WMF or “Weighted MER for FAC” has been used. This only makes use of the Drm Fast Access Channel cells which are confined to the 4.5 kHz above the nominal centre frequency.

This measure has the advantage that it is more accurate at low signal to noise ratios. The FAC is always 4-QAM and thus the ideal constellation has only four points. This means that it is less likely that the nearest point chosen on the ideal constellation for the error vector calculation will be for the wrong symbol value.

The disadvantage of this measure is that only the signal to noise ratio in the upper 4.5 kHz of the channel is measured.

The median, 10th and 90th percentiles are recorded as for the signal strength measurements.

________________________________________________________________________________________________ 3 On short-wave the standard channel allocation is 10 kHz where as on medium-wave in Europe it is 9 kHz.

9

6.4 Slots and Slices The data for a complete day is further aggregated before it is stored in the central database. Each day is split into slots; typically one hour or half hour time periods for the given date.

The audio reliability as a percentage over the time period of the slot is calculated whilst the Signal Strength and MER measurements are aggregated and summarised for each slot as:

• the minimum of the per-minute 10th percentile values,

• the median of the per-minute median values and

• the maximum of the per-minute 90th percentile values.

These values are collated into daily reports which were sent by email to interested parties during the trial.

To give a better view of the overall performance of the trial, these slots have been further aggregated across two week periods to give a measurement of the reception conditions at a given time of day, a so-called slice.

As previously explained, medium-wave propagation varies a great deal between day and night and the local sunset and sunrise times vary considerably over the course of the trial. The two week slice period was chosen as a compromise between blurring the effect of the changing local sunset and sunrise times whilst at the same time summarising the data in a manageable way and providing enough slots over which to perform sensible averaging.

For each two-week slice similar calculations to those performed on a slot are repeated. The average audio reliability for a given slice is calculated along with the following measures for MER and signal strength:

• the minimum of the per-slot 10th percentile values,

• the median of the per-slot median values, and

• the maximum of the per-slot 90th percentile values.

6.5 Transmitter Availability The performance of the transmitters was monitored by additional logging receivers connected directly to the transmitter outputs. Inevitably in a trial of this sort there are some glitches in the performance of the modulator which impact on the overall audio reliability figures. In order to negate this, any slots where the audio reliability measured at the transmitter was not 100% are discounted for the purposes of analysis.

An alternative approach would be to divide the audio percentage recorded at a reception site by the measured audio percentage of the monitoring receiver connected directly to the transmitter. This would then have given a measure of the proportion of audio frames received without error of those that were transmitted correctly. This approach was not followed, however, as a loss of audio frames at the transmitter is normally the result of a drop in MER or transmitted signal strength. Whilst this approach makes sense for audio frames, there is no such sensible correction that could be made for the collected MER or RF signal strength statistics.

10

6.6 Renaming of Logging stations Initially the monitoring stations had IDs of BBCpn where n was a number between 1 and 5 approximately representing the chronological order of installation. For the sake of clarity the stations were renamed to indicate their location more clearly. The convention used was to take the abbreviation of the nearest TV or Radio relay station and use it as the receiver ID. Where that was not possible, an abbreviation was invented that was in the same style.

The renaming took place on the 10th May 2007. For reference, the old and new names for the monitoring receivers are shown in Table 5 below. In the presentation of the results, the receivers are referred to by their new ID.

Old Receiver ID New Receiver ID Location

BBCp1 m_PY Plymouth Studios

BBCp2 m_NFR Newton Ferrers

BBCp3 m_CNH Caradon Hill

BBCp4 m_PYZ Crown Hill

N/A m_MTY Mary Tavy

Table 5 - Monitoring receiver IDs

6.7 Audio decoder bug During the early period of the trial, it was noticed that there were quite a few very short audio dropouts occurring on the monitoring receiver at the transmitting station. These were also present simultaneously at all the other monitoring receivers and so it was initially assumed that these dropouts were caused by a brief interruption in the output of the transmitter.

Further investigation revealed, however, that the simultaneous dropouts on all the receivers were caused by a bug in the FAAD audio decoder used by Dream resulting in a single, isolated (40 ms) audio frame error in the presence of certain programme content.

A fix was provided by Nero, the authors of the audio decoder, which solved this problem and was deployed between the 1st and 4th May 2007. This bug would not have affected the overall Drm reception results since any slots where the audio reliability measured at the transmitter was now 100% are not included in the analysis. Fixing the bug did, however, increase the overall number of slots available for analysis. In the event, no Drm data from before 12th May was used in the final analysis and so this bug did not have any impact on the trial results.

7 Analysis methodology The difference between day-time and night-time propagation means that the effect of changing sunrise and sunset times throughout the year must be taken into account. Not all logging stations were available for the whole year of the trial since the network of logging stations was expanded over time. In addition some sites did not record data for certain periods or suffered failures of various components making their results invalid. As a result some care had to be taken to ensure a fair comparison could be made between results collected at different points during the trial. Graph 1 overleaf shows the large variation in the number of hours of daylight over the course of the year.

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00:0001:0002:0003:0004:0005:0006:0007:0008:0009:0010:0011:0012:0013:0014:0015:0016:0017:0018:0019:0020:0021:0022:0023:0000:00

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Date

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e of

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) or D

ay le

ngth

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rs)

sunrise sunset day length

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shor

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, 22/

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est d

ay, 2

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/200

7

PYZ

+ N

HT

(SFN

)

PYZ

only

Graph 1 - Variation of sunrise and sunset times over the year of the trial

12

7.1 AM transmissions and quiet week These measurements were only made over a short period of time and therefore the effect of the changing sunrise and sunset times was small. The only measurement that can be recorded for these is field strength and graphs of this are presented in the following section. Ideally data from more days would have been collected but unfortunately this was not possible given the constraints on time within the trial.

7.2 Drm transmissions The Drm transmissions were monitored over a much longer time frame, including a period during which the transmission parameters were altered to 16-QAM (see Section 2). As a result, the effect of the changing sunrise and sunset times must be taken into account.

For Drm, three measurements are of interest; field strength, MER and percentage audio reliability. Graphs of field strength and MER are presented in the next section showing how these evolve over the various periods for which reception data from the different sites is available.

For the percentage audio reliability scores, an overall figure for each site is of interest in order to answer the question of how well the system performed at a given location. As a result, particular care must be taken over the analysis.

Initially, an attempt was made to pick periods from the data available from different receivers in which the average number of daylight hours was the same. In this way, the same proportion of slices would be affected by night-time sky-wave interference at each location and so a fair comparison between the overall audio reliability percentage obtained from different sites could be made.

For a data collection period lasting a full 12 months, it is possible to start at any point in the year and the average number daylight hours per day will be approximately4 constant. Another measurement period which gives the same average daylight hours is the 6 months beginning at the longest day and ending at the shortest or vice versa. Finding suitable comparison periods of 6 months duration was complicated by the previous designation of fortnight slices but with a careful choice of start date for the analysis this could have been overcome and a fair comparison made between data from different 6 month periods.

Unfortunately, not all the monitoring receivers were available for a suitable 6 month period either because of technical problems or because they were only installed later on in the trial. Furthermore some experiments (such as the SFN tests) were not performed for long enough for this approach to be suitable.

As a result, this approach was not used for the final analysis. Instead, for the presentation of the overall Drm results, the analysis was simplified. The hour slices have been split with those that always have daylight throughout the year (09:00–16:00 UTC) being analysed separately from those which are always dark (21:00–03:00 UTC).

An exception to this was during the change of transmission parameters from a 64-QAM to 16-QAM constellation. The switch was made on the shortest day, around which day lengths are mirrored, meaning that a fair comparison could be made between the two sets of transmissions.

________________________________________________________________________________________________ 4 It is approximate because the time of the solstice changes by around one quarter of a day each year as a year is really around 365¼ days long.

13

8 Results and Discussion In the following section, the results are presented in the order that they were collected.

8.1 AM transmissions PY: 13/03/2007 - 19/03/2007

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RFmed Sunrise Sunset

Graph 2 – AM field strength at Plymouth Studios (PY)

NFR: 13/03/2007 - 19/03/2007

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Graph 3 – AM field strength at Newton Ferrers (NFR)

14

From Graph 2, it is clear that at Plymouth Studios the local AM transmission dominates as the received field strength is at approximately the same high level 24 hours a day.

Further away from the transmitter at Newton Ferrers (Graph 3) however, a variation in field strength can be seen since the wanted signal is so much lower. At night when sky-wave propagation takes place there is a slight increase in the median received field strength caused by the co-channel sky-wave interference from Spanish station ‘Radio Nacional 1’. Not only is there an increase in median field strength but the spread of received values also increases. Deep variations in received field strength are common in sky-wave propagation and this is the likely cause of the increased variability.

Both the NFR and PY receivers show a dip in the minimum field strength in the 13:00 to 14:00 hour slice of around 5 dB. Further investigation showed that this was caused by a dip in signal strength for this slot on 15/03/2007.

Since the dip occurred at both monitoring sites, an abnormality at the transmitter at Crown Hill is suspected. National Grid Wireless have checked their service messages for this date and there is no record of a problem. One explanation for such a dip in power is the replacement of a RF power module. In total there are 8 RF modules in the transmitter, spread across two power supplies. Replacement of one module necessitates switching off one PSU which causes a 6 dB drop in output power. 3 dB is lost because there are half the number of modules operating and a further 3 dB is sent into a balancing load. This cannot, however, be confirmed.

15

8.2 Quiet week

PY: 02/04/2007

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NFR: 02/04/2007

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Graph 5 – Background noise field strength at Newton Ferrers (NFR)

16

The field strength measurements from the quiet week, during which the local transmitter was switched off, allow the level of the local noise floor and interference to be studied.

During the daytime, there is no incoming sky-wave interference and so the field strength measurements would normally be dominated by local sources of noise and indeed this is the case for the PY site. At NFR (Graph 5), however the co-channel Spanish station “Radio Nacional 1” is clearly audible even during the daytime. This is likely to be due to the presence of a 20 kW relay transmitter at Santander on the northern Spanish coast. Newton Ferrers is situated on a creek and there is therefore an almost direct sea path to the transmitter. This allows efficient medium-wave propagation from Spain even during the day time. The true background noise floor at NFR is probably 10-20 dB lower than measured.

Figure 5 below shows the received spectrum at Newton Ferrers during the day. Both the carrier and sidebands of ‘Radio Nacional 1’ are clearly visible above the local noise floor.

Figure 5 – Reception of ‘Radio Nacional 1’ at Newton Ferrers (NFR), 13:30 UTC 02/04/2007

At Plymouth Studios (Graph 4) the quiet week field strength is around 12 dB higher than at Newton Ferrers (Graph 5). This is not surprising since Newton Ferrers is a quiet countryside location whereas Plymouth Studios is an operational building in the city and likely to have many sources of noise and interference. There is also some concern that other equipment installed in the loft space containing the antenna or the links room below may be generating noise.

Unfortunately data is only available for one day of the quiet week due to problems with the logging system. There is also a gap between 14:30 and 17:00. These measurements took place at a very early stage of the monitoring setup and these reliability problems have since been ironed out.

At night, there is a 25 dB increase in field strength at Newton Ferrers. Reception on an AM receiver revealed that the culprit was indeed “Radio Nacional 1” and the increase in interference due to sky-wave propagation.

Listening using an AM receiver at NFR revealed that a very clear number of long (up to 0.5 s) echoes on “Radio Nacional 1” could be head. Since “Radio Nacional 1” is made up of a SFN, the audible echoes are likely to be the result of simultaneous sky-wave reception from a number of transmitters in the network. The length of the echoes cannot be explained by propagation effects alone and the suspicion has to be that the audio feeds to the different transmitters are not synchronised. It is possible that the SFN is only designed to work during the daytime in which case there would be no requirement to synchronise either the audio or carrier frequencies of each transmitter making up the SFN. Alternatively the populations in the mush zones may be very small.

17

At Plymouth Studios, the diurnal variation is significantly less. During the day time, the noise floor is generally much higher (around 56 dBuV/m) than at Newton Ferrers and as a result, the additional power from the interfering signal has much less of a noticeable effect on a graph plotted in decibels. In addition, PY is situated inland so the interfering medium-wave signal is likely to be somewhat attenuated.

The noise floor at Newton Ferrers was not always so low and there was some intermittent wide-band interference which can be seen in Figure 6 below.

Figure 6 – Increase in noise floor at NFR due to intermittent interference, 13:30 UTC 02/04/2007 By comparison, Figure 7 shows the received spectrum at Plymouth Studios during the quiet week. Here the noise floor is much higher and the sidebands of the interfering station are completely obliterated.

Figure 7 – Reception of co-channel 'Radio Nacional 1' at Plymouth Studios, 13:30 UTC 02/04/2007

18

8.3 Drm: Overall results Figure 8 below shows the overall Drm audio reliability results based on the available data for each site. Two results are given for each site: one for slots which were always during the daytime and one for slots that were always dark. Those slots that at some point of the year are twilight were discarded. The predicted coverage contours are also shown.

Figure 8 – Drm reception results

It can be seen that the Drm reception measurements matched the predicted coverage areas well and that where the Drm was predicted to work it did. For example at Newton Ferrers (NFR) which is inside the daytime coverage area but outside the night time contour, the Drm worked during the day but not at night.

8.4 Drm: Individual Reception Sites The evolution of the Drm reception data from the individual monitoring sites over the course of the trial is depicted in the following section. Figure 9 shows how the graph axes should be interpreted.

Figure 9 – Explanation of the Drm evolution graph axes

field strength (RF), MER or audio quality

Fortnight period (slice start date)

Drm, 80W EMRP: 40 dBµV/m daytime, interference-limited night time

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time of day (slice start hour)

19

8.4.1 Plymouth Studios (PY) The holes in the following graphs are due to some data being missing due to a malfunction of the monitoring receiver.

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Graph 6 – Field strength evolution at Plymouth Studios (PY)

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Graph 7 – MER evolution at Plymouth Studios (PY)

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00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 2223/06/2007

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Graph 8 – Audio reliability evolution at Plymouth Studios (PY)

21

8.4.2 Newton Ferrers (NFR)

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Graph 9 – Field strength evolution at Newton Ferrers (NFR)

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Graph 10 – MER evolution at Newton Ferrers (NFR)

22

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Graph 11 – Audio reliability evolution at Newton Ferrers (NFR)

8.4.3 Oreston (ORS) Unfortunately not enough reliable data was collected from this site to produce a meaningful graph.

23

8.4.4 Caradon Hill (CNH) For this site, measurements were extended beyond the official end of trial in order to get a full 6 months of data. This was possible because the transmitter remained on air.

00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 2222/12/2007

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Graph 12 – Field strength evolution at Caradon Hill (CNH)

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Graph 13 – MER evolution at Caradon Hill (CNH)

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Graph 14 – Audio reliability evolution at Caradon Hill (CNH)

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8.5 Drm: Transmitter Performance For the graphs showing transmitter performance, only the audio reliability percentage figures from the logging receivers is presented.

8.5.1 Crown Hill (PYZ)

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Graph 15 – Crown Hill transmitter performance

8.5.2 North Hessary Tor (NHT) The transmitter at North Hessary Tor was switched on and off many times and its parameters changed frequently as part of the SFN and co- and adjacent- channel experiments. As a result, it does not make sense to plot a graph of overall performance. The results from the monitoring receiver at the transmitting station were however used to ensure that the transmitter was operating correctly for the analysis of the SFN data.

26

8.6 Drm: Diurnal Variation It is clear from the evolution graphs that there is a variation in reception quality over the course of the day, determined by the level of the incoming Spanish interferer. The effect of the changing sunrise and sunset can clearly be seen in the MER measurement at Newton Ferrers (Graph 10) for which a complete year of data is available. Starting in spring, the days are long, and the MER is high for a large proportion of the time. As winter approaches, the days get shorter and the MER is low for an increasing number of hours per day. This continues until the shortest day at which point the trend is reversed as the days begin to get longer again and the period of the day that is dark (and hence affected by sky-wave interference) reduces.

At Newton Ferrers there is an unexpected dip in audio reliability during the daytime in the analysis period 02/10/2007 to 15/10/2007.

Further investigation has revealed that this is caused by a number of hour-long slots during this period having 0% audio reliability. These slots also see a drop of 40 dB in reported signal strength (from typically 70 dBuV/m to 30 dBuV/m) and a drop in MER to 1-2 dB. Playback of the RSCI files using Dream reveals that the PSD graph looks normal with the top of the COFDM carriers sitting at around -40 dB relative to full scale, suggesting that the field strength is genuine, the receiver’s AGC having correctly adjusted the IF level to compensate.

This effect is not seen in the graphs of RF or MER because it is only the median that is plotted for these measures.

The sequence of events that precedes these long dropouts is as follows. First the transmitter goes to plain carrier and this is seen as a simultaneous dropout by all of the monitoring stations. The other stations immediately recover, with the exception of Caradon Hill (m_CNH) which had a 7 minute drop out. The Newton Ferrers station, however, continues to report low signal and MER and no audio for a further 2 hours and 57 minutes, affecting the next 3 hour-long slots. It is these subsequent slots which knock down the average audio reliability over the slice as they are included in the analysis because only slots where there was a transmitter dropout are excluded.

The only explanation is some form of bug in the receiving setup that is, as yet, not understood.

8.7 Drm: AM field strength comparison Looking at the field strength results for the NFR receiver (Graph 9) during daylight hours shows that the measured field strength goes from around 77 dBuV/m during the AM transmissions to around 70 dBuV/m for the Drm transmissions, a decrease of 7 dB. This corresponds exactly to the decrease in EMRP from 400 W for the AM transmissions to 80 W for the Drm (see Table 4). A similar differential was also seen at Plymouth Studios.

8.8 Drm: Night time reception The measurements from the quiet week show that the field strength of the co-channel Spanish interferer, ‘Radio Nacional 1’, at night is around 71 dBuV/m at Newton Ferrers (Graph 5). This is almost enough to provide a planned service and indeed the station was clearly audible at night. This is why predictions show Newton Ferrers as outside the night time coverage of Crown Hill.

It is possible to determine what the wanted Drm signal strength is at Newton Ferrers by using a value from daytime reception where only the local, ground-wave signal is received. This gives a wanted field strength of 70 dBuV/m for the Drm (Graph 9). Thus at night-time, the interferer is around 0 dB relative to the Drm and yet the median MER is typically 16 dB (Graph 10).

The Drm is saved by the fact that the vast majority of the power for the AM signal is contained in the carrier at the centre of the channel.

27

For double sideband AM:

( )212mPPPP CCST +=+=

where: PT = Total power PC = Carrier power PS = Sideband power m = modulation index

Equation 1 By contrast Drm, as a multi-carrier system, has power spread evenly across the 9 kHz channel and in fact has a gap in the centre of the channel where nothing is transmitted. It is therefore the sideband power PS of the AM that causes most of the damage.

Looking at the interferer, a field strength of 71 dBuV/m, equates to 55 dBuV at the input to the receiver. With a 50 Ω input impedance, this is -52 dBm or 6.31 nW for the total received power, PT.

Typically the modulation index m is between 30% and 50%. Taking m as 30% gives:

PC = 6.04 nW (-52 dBm)

PS = 0.271 nW (-66 dBm)

Thus, the sideband power is at -66 dBm compared with -52 dBm for the wanted Drm service, a positive signal to noise ratio of 14 dB which is of the same order as the measured MER of 16 dB.

The effect of switching the transmission from 64-QAM to a more robust 16-QAM constellation and the resulting night-time reception quality at Newton Ferrers is shown in the following section.

8.9 Drm: 64-QAM vs 16-QAM For a short period following 22/12/2007, the day of the winter solstice, the main Drm transmission was changed to operate at 16-QAM. For this test, as well as using data from the PY, NFR and ORS sites, data was also analysed from CNH and MTY which were previously well outside the predicted night-time coverage area.

PY: 13/12/2007 - 20/12/2007 64 QAM; 24/12/2007 - 31/12/2007 16 QAM

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Graph 16 – 64-QAM vs 16-QAM at Plymouth Studios (PY)

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NFR: 13/12/2007 - 20/12/2007 64 QAM; 24/12/2007 - 31/12/2007 16 QAM

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Graph 17 – 64-QAM vs 16-QAM at Newton Ferrers (NFR)

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MTY: 13/12/2007 - 20/12/2007 64 QAM; 24/12/2007 - 31/12/2007 16 QAM

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Graph 19 – 64-QAM vs 16-QAM at Mary Tavy (MTY)

ORS: 13/12/2007 - 20/12/2007 64 QAM; 24/12/2007 - 31/12/2007 16 QAM

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Graph 20 – 64-QAM vs 16-QAM at Oreston (ORS)

The biggest effect of the change from 64-QAM to 16-QAM is seen at Caradon Hill (Graph 18), where the change in transmission parameters takes it from being well outside the 64-QAM night-time coverage area (Figure 8) to being on the edge of service.

30

8.10 Drm: Single Frequency Network The second transmitter at North Hessary Tor was used to investigate synchronised SFN operation. It was much lower in power (at 12 W EMRP) than the Crown Hill transmitting site and, given its distance from the centre of Plymouth, had no noticeable impact on most of the monitoring sites to the south. The monitoring station at MTY, however, was specifically located to see the effect of the SFN operation in the mush area. Not only is it much nearer to NHT than PYZ but the directional receiving antenna was oriented so as to make NHT and PYZ be received at equal power (0 dB).

The transmission at NHT was timed to be 0.5 ms behind that emanating from PYZ. This ensured that nowhere in the overlap zone would the signals arrive precisely co-timed, eliminating the occurrence of flat fading.

The received impulse and frequency responses of the received signal at Mary Tavy are shown in Figure 10 below. The reciprocity between the impulse and the frequency responses can clearly be seen; the 0.5 ms path delay giving rise to corresponding dips in the frequency response every 2 kHz.

Figure 10 – The impulse and frequency response at MTY There was some difficulty carrying out the comparison between SFN and non-SFN operation. At first it appeared that the SFN performance was far worse than with the single PYZ transmission alone. On further examination, however, it became clear that the SFN had at points lost synchronisation. Using stored reception data available on Theseus it was possible to see when this had occurred. All that could be done was to discount those dates from the analysis period. The following days were excluded from the comparison: 19/08, 20/08, 25/08, 30/08 and 21/09.

The nature of the comparison period is such that it would not be fair to make a comparison across the day/night boundary as the number of daylight hours changes so much between the periods of SFN and non-SFN operation at this time of year (see Graph 1). As such, these values have been deleted from the graphs that follow.

The results from MTY (Graph 21) confirm that the addition of the North Hessary Tor (NHT) transmitter to give increased coverage to the north of Plymouth has not adversely impacted on reception in the mush zone, even in the presence of a 0 dB echo. Although the job of channel estimation in the receiver is made more difficult with the additional transmitter, the MER stays constant because this difficulty is offset by the gain in field strength seen during SFN operation.

At CNH (Graph 22) the effect of the relatively low power additional transmitter is too small to be seen.

31

MTY: 14/08/2007 - 02/09/2007 PYZ & NHT; 04/09/2007 - 23/09/2007 PYZ Only

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Graph 21 – SFN reception at MTY

CNH: 14/08/2007 - 02/09/2007 PYZ & NHT; 04/09/2007 - 23/09/2007 PYZ only

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Graph 22 – SFN reception at CNH

32

9 Conclusions The overall results for the Digital Radio Mondiale transmissions show that the Drm worked as expected; in the locations where the Drm was predicted to work it did. The 855 kHz frequency used in the trial is heavily affected by strong co-channel interference, making this a particularly challenging test for Drm.

Although the predicted night-time Drm coverage area is smaller than during the day, it is somewhat larger than the AM it replaced and the make-up of the Drm signal is such that it has far greater immunity to co-channel AM.

The switch from 64-QAM to 16-QAM transmissions meant that a site such as Caradon Hill (CNH) which was previously a long way outside the predicted night-time coverage area was now on the edge of service. This suggests there could be some merit in dynamically switching from 64-QAM to 16-QAM at dusk in order to make the daytime and night-time coverage areas more equal. Although there is an inevitable reduction in audio quality with the reduction in bit-rate, the sound quality is still acceptable and is free from the background Spanish interference that dominated reception of the AM service at night.

The SFN results show that additional coverage can be gained through the use of a second transmitter without adversely affecting existing reception in the mush zone, even when the receiver is subject to a 0 dB echo.

33

10 REFERENCES 1. “Digital Radio Mondiale (DRM); System Specification”, ETSI ES 201 980

2. “The Theseus Remote Monitoring System”, Ollie Haffenden, BBC Research Technical Note 3050.

3. “DRM Compatibility of Existing MF Broadcast Antenna Systems”, Kevin Thorley, IBC Conference 2008

4. “The Dream open-source DRM receiver project”, http://drm.sourceforge.net

5. “Digital Radio Mondiale (DRM); Receiver Status and Control Interface (RSCI)”, ETSI TS 102349

6. “Sun or Moon Rise/Set Table for One Year”, Astronomical Applications Department, US Naval Observatory, http://aa.usno.navy.mil/data/docs/RS_OneYear.php

35

Appendix A – Table of local sunrise and sunset times for 2007 and 2008 o , o , PLYMOUTH Astronomical Applications Dept. Location: W004 07, N50 23 Rise and Set for the Sun for 2007 U. S. Naval Observatory Washington, DC 20392-5420 Universal Time Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Day Rise Set Rise Set Rise Set Rise Set Rise Set Rise Set Rise Set Rise Set Rise Set Rise Set Rise Set Rise Set h m h m h m h m h m h m h m h m h m h m h m h m h m h m h m h m h m h m h m h m h m h m h m h m 01 0817 1623 0752 1709 0701 1757 0554 1848 0453 1936 0411 2018 0409 2031 0444 2001 0530 1902 0616 1756 0706 1653 0754 1616 02 0817 1624 0750 1711 0659 1759 0552 1850 0451 1937 0410 2019 0410 2031 0445 1959 0532 1900 0617 1754 0708 1651 0756 1616 03 0817 1625 0749 1712 0657 1801 0550 1851 0449 1939 0409 2020 0411 2030 0447 1958 0533 1858 0619 1751 0710 1650 0757 1615 04 0816 1626 0747 1714 0655 1802 0547 1853 0447 1940 0409 2021 0411 2030 0448 1956 0535 1856 0621 1749 0711 1648 0758 1615 05 0816 1628 0746 1716 0653 1804 0545 1854 0446 1942 0408 2022 0412 2029 0450 1955 0536 1853 0622 1747 0713 1646 0759 1614 06 0816 1629 0744 1718 0651 1806 0543 1856 0444 1943 0408 2023 0413 2029 0451 1953 0538 1851 0624 1745 0715 1645 0801 1614 07 0816 1630 0743 1719 0649 1807 0541 1858 0442 1945 0407 2024 0414 2028 0452 1951 0539 1849 0625 1743 0716 1643 0802 1614 08 0815 1631 0741 1721 0646 1809 0539 1859 0441 1946 0407 2025 0415 2028 0454 1949 0541 1847 0627 1740 0718 1642 0803 1613 09 0815 1633 0739 1723 0644 1811 0537 1901 0439 1948 0406 2025 0416 2027 0455 1948 0542 1845 0628 1738 0720 1640 0804 1613 10 0814 1634 0738 1725 0642 1812 0534 1902 0437 1949 0406 2026 0417 2026 0457 1946 0544 1842 0630 1736 0721 1639 0805 1613 11 0814 1635 0736 1726 0640 1814 0532 1904 0436 1951 0406 2027 0418 2026 0458 1944 0545 1840 0632 1734 0723 1637 0806 1613 12 0813 1637 0734 1728 0638 1816 0530 1906 0434 1952 0405 2027 0419 2025 0500 1942 0547 1838 0633 1732 0725 1636 0807 1613 13 0812 1638 0732 1730 0636 1817 0528 1907 0433 1954 0405 2028 0420 2024 0501 1940 0548 1836 0635 1730 0727 1634 0808 1613 14 0812 1640 0730 1732 0633 1819 0526 1909 0431 1955 0405 2029 0421 2023 0503 1939 0550 1834 0637 1728 0728 1633 0809 1613 15 0811 1641 0729 1733 0631 1821 0524 1910 0430 1957 0405 2029 0422 2022 0504 1937 0551 1831 0638 1726 0730 1632 0810 1613 16 0810 1643 0727 1735 0629 1822 0522 1912 0428 1958 0405 2030 0423 2021 0506 1935 0553 1829 0640 1724 0731 1630 0811 1613 17 0809 1644 0725 1737 0627 1824 0520 1913 0427 2000 0405 2030 0424 2020 0507 1933 0554 1827 0641 1722 0733 1629 0811 1613 18 0808 1646 0723 1739 0625 1826 0518 1915 0426 2001 0405 2030 0425 2019 0509 1931 0556 1825 0643 1720 0735 1628 0812 1614 19 0808 1647 0721 1740 0623 1827 0516 1917 0424 2002 0405 2031 0426 2018 0510 1929 0557 1822 0645 1718 0736 1627 0813 1614 20 0807 1649 0719 1742 0620 1829 0514 1918 0423 2004 0405 2031 0428 2017 0512 1927 0559 1820 0646 1716 0738 1626 0813 1614 21 0806 1650 0717 1744 0618 1830 0512 1920 0422 2005 0405 2031 0429 2016 0513 1925 0601 1818 0648 1714 0740 1625 0814 1615 22 0805 1652 0715 1746 0616 1832 0510 1921 0421 2006 0405 2031 0430 2015 0515 1923 0602 1816 0650 1712 0741 1624 0814 1615 23 0803 1654 0713 1747 0614 1834 0508 1923 0420 2008 0406 2032 0431 2014 0517 1921 0604 1813 0651 1710 0743 1623 0815 1616 24 0802 1655 0711 1749 0612 1835 0506 1925 0418 2009 0406 2032 0433 2012 0518 1919 0605 1811 0653 1708 0744 1622 0815 1616 25 0801 1657 0709 1751 0609 1837 0504 1926 0417 2010 0406 2032 0434 2011 0520 1917 0607 1809 0655 1706 0746 1621 0816 1617 26 0800 1659 0707 1752 0607 1838 0502 1928 0416 2011 0407 2032 0435 2010 0521 1915 0608 1807 0656 1704 0747 1620 0816 1618 27 0759 1700 0705 1754 0605 1840 0500 1929 0415 2013 0407 2032 0437 2008 0523 1913 0610 1805 0658 1702 0749 1619 0816 1619 28 0757 1702 0703 1756 0603 1842 0458 1931 0414 2014 0408 2032 0438 2007 0524 1910 0611 1802 0700 1700 0750 1618 0817 1619 29 0756 1704 0601 1843 0456 1933 0413 2015 0408 2031 0440 2005 0526 1908 0613 1800 0701 1658 0751 1617 0817 1620 30 0755 1705 0558 1845 0454 1934 0413 2016 0409 2031 0441 2004 0527 1906 0614 1758 0703 1657 0753 1617 0817 1621 31 0753 1707 0556 1846 0412 2017 0442 2002 0529 1904 0705 1655 0817 1622

36

o , o , PLYMOUTH Astronomical Applications Dept. Location: W004 07, N50 23 Rise and Set for the Sun for 2008 U. S. Naval Observatory Washington, DC 20392-5420 Universal Time Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Day Rise Set Rise Set Rise Set Rise Set Rise Set Rise Set Rise Set Rise Set Rise Set Rise Set Rise Set Rise Set h m h m h m h m h m h m h m h m h m h m h m h m h m h m h m h m h m h m h m h m h m h m h m h m 01 0817 1623 0752 1708 0700 1759 0552 1849 0451 1937 0410 2019 0410 2031 0445 2000 0531 1900 0617 1754 0708 1652 0755 1616 02 0817 1624 0751 1710 0658 1800 0550 1851 0450 1938 0410 2020 0410 2030 0446 1958 0533 1858 0619 1752 0709 1650 0757 1615 03 0817 1625 0749 1712 0655 1802 0548 1852 0448 1940 0409 2021 0411 2030 0448 1957 0534 1856 0620 1750 0711 1648 0758 1615 04 0816 1626 0748 1714 0653 1804 0546 1854 0446 1941 0408 2022 0412 2030 0449 1955 0536 1854 0622 1748 0713 1647 0759 1614 05 0816 1627 0746 1715 0651 1805 0544 1856 0444 1943 0408 2023 0413 2029 0451 1953 0537 1852 0623 1745 0714 1645 0800 1614 06 0816 1629 0745 1717 0649 1807 0541 1857 0443 1945 0407 2024 0414 2029 0452 1952 0539 1850 0625 1743 0716 1644 0802 1614 07 0816 1630 0743 1719 0647 1809 0539 1859 0441 1946 0407 2024 0414 2028 0454 1950 0540 1847 0627 1741 0718 1642 0803 1613 08 0815 1631 0741 1721 0645 1810 0537 1900 0439 1948 0406 2025 0415 2027 0455 1948 0542 1845 0628 1739 0719 1640 0804 1613 09 0815 1632 0740 1722 0643 1812 0535 1902 0438 1949 0406 2026 0416 2027 0457 1946 0543 1843 0630 1737 0721 1639 0805 1613 10 0814 1634 0738 1724 0641 1814 0533 1904 0436 1951 0406 2027 0417 2026 0458 1945 0545 1841 0631 1735 0723 1638 0806 1613 11 0814 1635 0736 1726 0638 1815 0531 1905 0435 1952 0405 2027 0418 2025 0500 1943 0546 1838 0633 1732 0724 1636 0807 1613 12 0813 1636 0735 1728 0636 1817 0529 1907 0433 1954 0405 2028 0419 2024 0501 1941 0548 1836 0634 1730 0726 1635 0808 1613 13 0813 1638 0733 1729 0634 1819 0527 1908 0432 1955 0405 2029 0420 2023 0503 1939 0550 1834 0636 1728 0728 1633 0809 1613 14 0812 1639 0731 1731 0632 1820 0524 1910 0430 1956 0405 2029 0421 2023 0504 1937 0551 1832 0638 1726 0729 1632 0810 1613 15 0811 1641 0729 1733 0630 1822 0522 1912 0429 1958 0405 2030 0423 2022 0506 1935 0553 1830 0639 1724 0731 1631 0810 1613 16 0810 1642 0727 1735 0627 1824 0520 1913 0427 1959 0405 2030 0424 2021 0507 1933 0554 1827 0641 1722 0733 1629 0811 1613 17 0810 1644 0725 1736 0625 1825 0518 1915 0426 2001 0405 2030 0425 2020 0509 1931 0556 1825 0643 1720 0734 1628 0812 1614 18 0809 1645 0724 1738 0623 1827 0516 1916 0425 2002 0405 2031 0426 2019 0510 1929 0557 1823 0644 1718 0736 1627 0813 1614 19 0808 1647 0722 1740 0621 1828 0514 1918 0423 2003 0405 2031 0427 2017 0512 1927 0559 1821 0646 1716 0738 1626 0813 1614 20 0807 1648 0720 1742 0619 1830 0512 1919 0422 2005 0405 2031 0429 2016 0513 1925 0600 1818 0648 1714 0739 1625 0814 1615 21 0806 1650 0718 1743 0616 1832 0510 1921 0421 2006 0405 2031 0430 2015 0515 1923 0602 1816 0649 1712 0741 1624 0814 1615 22 0805 1652 0716 1745 0614 1833 0508 1923 0420 2007 0405 2032 0431 2014 0516 1921 0603 1814 0651 1710 0742 1623 0815 1616 23 0804 1653 0714 1747 0612 1835 0506 1924 0419 2009 0406 2032 0432 2013 0518 1919 0605 1812 0653 1708 0744 1622 0815 1616 24 0803 1655 0712 1749 0610 1836 0504 1926 0418 2010 0406 2032 0434 2011 0519 1917 0606 1809 0654 1706 0745 1621 0816 1617 25 0801 1657 0710 1750 0608 1838 0502 1927 0417 2011 0407 2032 0435 2010 0521 1915 0608 1807 0656 1704 0747 1620 0816 1618 26 0800 1658 0708 1752 0605 1840 0500 1929 0415 2012 0407 2032 0436 2009 0522 1913 0609 1805 0658 1703 0748 1619 0816 1618 27 0759 1700 0706 1754 0603 1841 0459 1931 0415 2013 0407 2032 0438 2007 0524 1911 0611 1803 0659 1701 0750 1618 0816 1619 28 0758 1702 0704 1755 0601 1843 0457 1932 0414 2015 0408 2031 0439 2006 0525 1909 0612 1801 0701 1659 0751 1618 0817 1620 29 0756 1703 0702 1757 0559 1844 0455 1934 0413 2016 0408 2031 0441 2004 0527 1907 0614 1758 0703 1657 0753 1617 0817 1621 30 0755 1705 0557 1846 0453 1935 0412 2017 0409 2031 0442 2003 0528 1905 0615 1756 0704 1655 0754 1616 0817 1622 31 0754 1707 0554 1848 0411 2018 0443 2001 0530 1902 0706 1654 0817 1623

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