RNK CAMBODIA 918 KHZ TRANSMISSION SYSTEM REPORTdocuments.worldbank.org/curated/en/...RNK CAMBODIA 918 KHZ TRANSMISSION SYSTEM REPORT Prepared by G.R.Smith ARFC Pty Ltd NSW. AUSTRALIA

RNK CAMBODIA

918 KHZ

TRANSMISSION

SYSTEM REPORT

Prepared by G.R.Smith ARFC Pty Ltd NSW. AUSTRALIA

Prepared for Radio AustraliaMelbourneAUSTRALIA

Date December 4, 2007

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© A.R.F.C. Pty Ltd 2007 Document: RECambodia-01.wpd Page 2 of 69

CONTENTSPAGE

INDEX 2Acknowledgment 3

1.0 REPORT SCOPE 41.1 Current RNK Radio System 41.2 Discussion with RNK Staff 41.3 History of the present Harris DX200 transmitter 5

2.0 AM TRANSMITTER PHNOM PEHN 62.1 AM Transmitter Site Location 62.1.1 AM Transmitter Building 7

2.2 Transmitter 8 2.2.1 200 kW Harris Transmitter 82.2.2 25 kW Transmitter 11

2.3 General Transmitter Comments 122.3.1 Transmitter Operating Conditions 122.3.1.1 Power Transformer 132.3.2 RF output Switching 142.3.3 Test Load 142.3.4 Antenna Feed 142.3.5 Antenna and Antenna Tuning Unit 15

2.4 General Transmitter Site Conditions 15

3.0 RADIO COVERAGE 183.1 General Comments 18

3.2 Ways to Improve Reception 233.2.1 Option 1 Single Transmitter Coverage 233.2.2 Option 2 Main Transmitter and Several Rebroadcast Transmitters 253.2.2.1 Land lines 263.2.2.2 Radio links 263.2.2.3 Satellite Distribution 263.2.2.4 Fibre Optic Distribution 283.2.2.5 Off Air reception 28

4.0 RECOMMENDATIONS TO IMPROVE THE PRESENT 30TRANSMISSION SYSTEM

4.1 Transmitter 30

© A.R.F.C. Pty Ltd 2007 Page No. 3 of 69

4.2 Antenna 32

4.3 Spares 32

4.4 Off air rebroadcast 324.4.1 Battambang 334.4.2 Pursat 33

APPENDIXA Recommended Spares 35B Cost Estimates 37C Executive Summary 39D Transmitter Site Condition 45

ILLUSTRATIONS 57Transmission site RNK Cambodia 58 Google Earth General Site Location Phnom Phen-1 59 Google Earth RNK AM Transmitter Site Phnom Phen-2 60

RNK Transmitter 62Rear of DX200 Harris Transmitter Air Inlets 63Top Of DX200 Harris Transmitter Air Outlets 63Monitoring Facilities 64 Power Transformer Showing Exposed Live Terminals On One Side 64Existing 3 Port “U” Link Panel 65Dehydrator 65Harris DX25 Transmitter 66

Antenna 67Antenna Location With Reference To The Old Shortwave 68Transmitter Building.918 khz AM Transmitting Antenna and Tuning Unit 68Antenna Layout (View East) 69Antenna Layout (View North East) 69

ACKNOWLEDGMENTSARFC acknowledges the contributions provided by;

Radio AustraliaRNK Staff, CambodiaJoe Sexton Radio Australia


1.0 REPORT SCOPE

To review the present operational status of the RNK AM broadcast transmitter located in PhnomPenh Cambodia.

To look at the transmitter operation and review the stations signal coverage of Cambodia.

1.1 Current RNK Radio System.

At the present time RNK provides a broadcast signal from its only AM Transmitter located tothe south west of Phom Penh City. Some supplementary coverage for specific programs isprovided by arrangements with FM stations in Battambang and Pursat. The quality of the signalreceived at these locations for rebroadcast is poor, as is the general quality of the signal receivedfrom Phnom Penh throughout the north western area of Cambodia, Pursat, Battambang, Sisphonand Pailin.

Further difficult reception areas were also identified by RNK staff to the north east of Phom Penhincluding the main towns of Kratie, Stung Treng, Ban Lung and Sen Monorom.

1.2 Discussions with RNK

Over the period of time of the visit to Cambodia, a number of discussions took place with RNKstaff in order to provide information as to the operational history of the Harris DX200 broadcasttransmitter and to listen to the expectations of RNK in terms of signal coverage for the whole ofCambodia.

As a brief summary, RNK indicated the transmitter provides the only AM broadcast service forthe whole of Cambodia. Supplementary coverage is provided by low power relay FMtransmitters at or near to Sarrirong OHAM area, near Kampong Thom, Kampong Thumi, Pursatand Battambang. The quality of these relays has been indicated as good except for those atBattambang and Pusat. The problems both at Pusat and Battambang have been described asreception problems of the signal from the Transmitter at Phnom Pehn 918 kHz.

Discussions indicated that RNK would like to be able to provide AM signal coverage on 918 kHzto the whole of Cambodia. However it was recognised that reception problems would beexpected in the following areas;

Koh Kong (west),Palim (northwest)Poipet (north west border)Thma Puok and areas to the north and east including Samraong, Srei SnamBanteay Srei and north to Analong VeaengKrastie and north including Stoeng Treng (north east)


Ban Lung (north east)Sen Monorom (east)

It was desired that Krastie be included in an area of good coverage if possible.

RNK expressed the desire to use a single AM broadcast transmitter and associated antenna toprovide coverage to the whole of the country whether this be with a 200 kW, 300 kW or even a500 kW AM broadcast transmitter. A copy of a proposal put forward from a companyassociated with NAUTEL of Canada using a 300 kW transmitter and a semi-directional antennawas provided.

1.3 History of the Present Harris DX200 Transmitter

In summary, the transmitter has not been operated at the rated power of 200 kW for a long time.This action has been taken in an effort to avoid the transmitter breaking down, as there were nospares to repair it and no stand-by transmitter. The transmitter has been in operation for nearly10 years and has been operating at low power output, approx 100 kW, for some 6 years.

RNK expressed the desire to have a main and standby transmitter. To this end RNK asked if itwas possible to investigate the possibility of returning the Harris DX25, 25 KW transmitter outat the transmitter building to service.

There was then some discussion as to whether or not a 300 kW, 500 kW or the present 200 kWtransmitter was required and the role of a standby transmitter, be it a new 300 kW or 500 kWand the present 200 kW or 25 kW, as the standby.


2.0 AM TRANSMITTER PHNOM PEHN

2.1 AM Broadcast Transmitter Site Location

The transmitter is located to the south west of the central area of Phnom Penh. The transmitteris housed in a building located on the north western edge of an area of wet lands. Thesurrounding area while it would have been of a very low population density a few years ago, nowhas extensive development all around. The current development is to the north and west of theland area where the transmission system is located. It has not been possible to determine theactual transmitter land boundary and there seems to be no drawings in existence showing thebuilding locations and tower locations.

Two prints of the area taken from Google earth are attached for reference in the “Illustrationssection. These images were taken a while ago and do not show the current development, thatwhich has been completed and that which is currently under development around thetransmission site.

The first “Phnom Penh-1". shows the general area with the transmitter’s main transmittingantenna location being in the centre. A scale has been marked to provide an indication of thedistances involved.

The second print “Phnom Penh-2". shows the transmission site in more detail. In particular thebrown areas to the north and north west of the antenna location which are now all three storeyhousing developments. A dotted line shows the current development now under constructionaround the transmission site. The current construction appears to be of the same three storeytypes of buildings as completed on the north and north western areas. See site photos in“Appendix A”

The transmission site has 5 buildings on the site. The Google earth print “Phnom-Penh-2" hasmarked on the following code for each of the buildings and towers on the site.

F FM Transmitter building. Also housed radio Australia’s FM transmitterFT FM and other communication services antenna tower. Guyed mast.T AM Transmitter building RNK 918 kHz.D Diesel Generator plant buildingAT AM Transmitter tower 918 KHz insulated guyed towerATU AM Antenna tuning unit building 918 kHz transmission.GN General buildingSW1 Building that housed a HF short wave transmitter now non operationalGAR General vehicle garageSW2 Building that housed a HF short wave transmitter now non operationalSW1A HF transmitter antenna guyed mast with antenna tuning unit building at the baseSW2A HF Transmitter antenna guyed mast with antenna tuning unit building at the base.LK Guyed mast with microwave link antenna mounted at the top.

The land area bounded to the east of the Diesel generator building “D” down to the east of the


SW2 building just north of the link mast “LK and then just to the north of` the building eastalong the road to the SW2 mast, is all flooded. Towers AT, SW1A and SW2A could not bevisited because of the extent of the water. No inspection was made of the antenna tuning unitbuilding “ATU” or any of the tuning buildings at the base of the short wave masts. SW1A andSW2A.

2.1.1 AM Transmitter Building

The AM Transmitter building has clearly had other transmitters installed there at various times. In the central transmitter hall, the Harris DX200, 200 kW 918 kHz transmitter is installed to theleft, relative to the entrance, while a very old Philips Transmitter (now very much nonoperational) is to the right. Also to the right is located a Harris DX25 25kW transmitter. Thistransmitter is non operational and not connected. See section 2.2.2 re discussion on thistransmitter.

The DX200 Harris transmitter is the transmitter providing the RNK broadcast services at present. The transmitter is installed in an air conditioned room behind a wall, with glass panels at floorlevel. The room has some thirteen air conditioners located around three of the walls, north, westand south walls. Although only eight air conditioners were operational during the time of thevisit, the room temperature was between 26 and 28 Degrees C with the transmitter operatingat 80 kW for most of the time.

The main power transformer for the transmitter is located in a separate room located again to thewest of the transmitter location. Under floor cabling ducts are used to connect the AC power,the output of the main power transformer, control and input signals to and from the transmitterto the respective locations where the connections are required.

The RF output from the transmitter is taken via 4" rigid coaxial cable to a manual “U” linkchange over panel, located in a room to the north of the actual transmitter location. The Ulink panel has rigid coaxial cable feed connections to a air cooled test load (located outside) andto the PVC covered underground coaxial cable interface. The PVC covered coaxial cable goingto the antenna tuning unit. A dehydrator is provided to pressurise the coaxial cable to theAntenna Tuning Unit.

An audio processor and basic off air AM receiver with loud speakers, are provided for transmittermodulation control and the monitoring of the signal output of the transmitter.

A general assessment of the status of the buildings and other infrastructure associated with theRNK transmission system is attached in Appendix D. The report was complied by Joe Sextonof Radio Australia, ABC, Australia.


2.2 TRANSMITTER

2.2.1 200 kW Harris Transmitter

The present transmitter was manufactured by Harris (USA);

Model DX200Part No. 994-9670-102Serial No. S8A001420-00001Manufacture Date 1-6-98Power 200 kWReduced power 50 kWFrequency 918 kHzAC power 380V 50 Hz

On initial inspection the transmitter was operating at about 80 kW output power, the extendedPA cabinet door was open and only eight of the thirteen air conditioners in the room wereoperational. The temperature in the room was quite comfortable with no noticeable hot spots. The exhaustair for the transmitter is being exhausted directly from the top of the transmitter cabinet into theroom. The transmitter takes in cooling air into the transmitter via a series of fan forced intakeson the rear of each of the 6 transmitter cabinets.

After a short time it was seen that the transmitter had two alarm LEDs indicating a fault activeon the transmitter status panel. “Reduced air flow” and “Analogue foldback”. With thesealarms active, the transmitter output power was reduced to 25 kW.

After a short time the transmitter output power returned to 80 kW output and the alarm statuscould be cancelled. Later the same alarms became active again with the transmitter powerreducing and returning to 80 kW output some time later.

On investigating this issue it was found that the fault was due to a “Air flow sensor” indicatinga reduced air flow. Each of the active RF power amplifier cabinets have an Air Flow Sensor.It was found that the air flow sensor in the “Extended PA cabinet” was indicating a fault at thesame time as the “reduced air flow” alarm was activated. This air flow sensor alarm indicatorwas going off after a short period when no intervention was undertaken by any staff. By the airflow sensor alarm status going off, it allowed the transmitters internal reset circuits to activateand return the transmitter’s output to 80 kW under its own control

In order to determine what may be causing the air flow sensor to indicate a fault, a series of testswere undertaken. This involved shutting the door to the cabinet in question normally left open,and noting the time to fault, blocking the air flow past the sensor in question and noting the timeto fault.


An outage was arranged in order to stop the transmitter and inspect the internal section of thecabinet with a view to ensure there was nothing to impede the air flow past the air flow sensorin question. At the same time the air flow sensor was cleaned of dirt and dust to reduce anypossibility of the dirt causing leakage and thus a malfunction of the air flow sensor.

No clear resolution was found as a result of these actions. Discussions with the transmitter staffduring this work revealed that they have had the same fault twice before. In both cases thecomplete printed circuit board on which featured the air flow sensor was replaced. Some checkson one of the printed circuit boards replaced in the past (about 2 years ago) showed that there wasa strong possibility that the reference sensor (two sensors are used, reference and active) wasfaulty. No spare (sensor ANA35) components were available to do an exchange and verify thefindings. In order to try and extend the time between the cycles of the fault, the air flowcalibration control (R213) was adjusted to minimise the effects of the fault.

An e-mail was sent to Harris, the transmitter manufacturer to determine if the air flow sensorproblem was a common fault and to seek assistance in the rectification of the problem. As aresult of their response some further tests were carried out on the air flow sensor with theconclusion that the sensor itself is faulty. It was not possible to stop the transmitter and thenrun it up again to see if all of the fans ran up correctly, but a simple mechanical test indicated thateach fan was running correctly. This will however need to be verified at some point.

The air flow sensor in question is located on the ;

MOD ENCODER PA Extra Cabinet PCB assembly843-5155-011 Rev H

Air flow sensor reference Schematic No 839-7930-011 Sheet 3 of 4.Fault indicator DS7 Air/TempThe assembly in question is located on the right hand wall of the EPA cabinet.

It was concluded that this fault could not be rectified without either;

1. Replacing and re calibrating the whole PCB assembly or 2. Obtaining some of the temperature sensors in question (ANA35) and replaced the actual

components on the PCB assembly and re calibrate the air flow control R213.

A further problem with the transmitter was noted but not investigated as it was considered thatconsiderable off air time was required for it to be traced and also because of time constraints. The fault relates to the ability of the control system to be able to raise and lower the transmitteroutput power.

It would also be a wise time to replace the air filter material. This material removes most of thedust particles from the cooling air before it is passed through the transmitter. The presentmaterial is old, very black and while there is evidence of it having been cleaned, it is quite denseand should be replaced. It is understood that this material is white in colour when new. A


suitable material is Dacron which can be purchased in sheets of various thickness. The sheetsare then cut with a straight edge and Stanley knife, to size. It would be preferable to replacethe filters with the Dacron material say every month unless they get very dirty more quickly.

The transmitter internally is reasonably clean, however there are dirt built ups on components inareas of higher air flow. The dirt or dust is generally dry but should nevertheless, be cleanedaway. This sort of maintenance is perhaps more important if the transmitter was running at fullpower output, just so breakdowns do not occur.

From our discussions it was clear that very little general maintenance had been done on thetransmitter for a very long time. No after hours maintenance had been undertaken and the onlywork done was that necessary for the transmitter to stay on the air. Indeed we were told it wasimperative for the transmitter to stay on the air as it was the only one they had. If it broke down,the AM service including the relay stations were off the air. The transmitter’s processor, an Orban 9200 5 band AM signal processor was operational, butlittle or no AGC action was evident. 4 of the 5 processing bands were gated most of the timewhile the output level indications were showing limiting at -95% for the negative peaks and just+100% for the positive peaks. A visual inspection of the modulation spectrum using a spectrumanalyser, showed little evidence of strong signal processing with what appeared to be a somewhatlower average modulation level than one would expect for a modern day AM transmissionservice. No testing time was available to determine how the processing was set and to see ifimprovements could be made. (Lifting the average modulation level would assist with signalinteligibility in some areas of difficult reception, as it would give an effect of reducing thebackground interference at these receiving locations).

It is usual these days, and the DX200 Harris transmitter has this capability, to positivelymodulate the transmitter to 125% thus providing additional “loudness” and hence the perceptionof a stronger signal to the listener on his or her receiver. It is highly recommended that once theaudio processor is set up it be secured, such that unauthorized access is not possible, to avoid mis- adjustment. The Spectrum Analyser’s display showed that the transmitter was being modulated to 100% fora relatively small percentage of the time, while it was being observed. There also appeared tobe 1 to 2 dB of carrier shift with modulation but this was not determined with any certainty.

The transmitter does NOT have any effective system monitoring or test equipment. As aminimum, a good Modulation monitor should be provided. A suitable product would be anInovonics 520. Such an instrument allows the staff to monitor the transmitter’s operatingperformance as it has indicators for modulation level and carrier level (carrier shift) and canprovide over modulation indications and alarms. It can also be used for proof of performancetesting. The modulation monitor provides a high quality demodulated audio output which canbe used via a suitable audio power amplifier and speakers for listening tests. This instrumentand the associated audio power amplifier should be located at the same location as the audioprocessor.


Other test equipment that is necessary to carry out a basic proof of performance test would bean Audio Oscillator and a Noise and Distortion Measuring Set. Test equipment that is desirableis an Oscilloscope and a portable Multimeter.

2.2.2 25 kW Transmitter

Model DX25Part No. 994-9168-001Serial No. RPS106113-00001Manufacture Date 1-28-93Power 25 kWFrequency 585 kHz

This transmitter clearly had not been in service for some time and is not connected to any ACpower or RF test load. As a result only a visual inspection was possible. Overall the transmitterappears to be in a general good condition with no major items missing that could be seen. Theonly items missing that could be identified were the item(s) associated with TB1 and TB2 locatedin the driver cabinet and some resistors in the power supply cabinet. We were later informedthat the parts associated with TB1 and TB2 were stored for safe keeping.

There was no visual evidence of corrosion but the internal sections of the transmitter were quitedirty. A full clean using pressurised air and suitable cleaning agents would be necessary on allcomponents, both sides of circuits boards and within the wiring ducts etc. At the same time anypossible problems would need to be noted and fixed.

All of the RF amplifier modules were in place and identified as :

2X RF AMP992-7095-001843-4038-200

This model of RF amplifier is different to that used in the DX200 transmitter and therefore notinter-changeable.

In order to fully assess the transmitter’s suitability as a standby, the transmitter would need to beconnected to the AC power supply and have a RF test load connected. To connect the ACpower, major electrical works would need to be undertaken at the transmitter building, with theinstallation of a distribution board and connection of the distribution board to the AC powersupply and transmitter. A test load could be placed along side the transmitter for test purposesas there is no spare connection port to the test load that is used with the 200 kW transmitter.

In effect, a standard commissioning run up would be required to be undertaken to identify anyfaults and rectify them before proceeding to the next stage. This may involve obtaining partsfrom the manufacturer or other sources with the associated delays. At, or near to the end of theprocess, a final determination could be made as to the suitability of the transmitter for a standby


role. During the process a determination could also be made as to the potential reliability of thetransmitter.

It is understood that there are no manuals for the transmitter and no spares in stock.

Given the age of the transmitter, some 14 years, serious consideration needs to be given to thecurrent availability of spare components and complete assemblies from the respective componentsuppliers, as well as to see what the longer term supply situation would be. The manufacturer,Harris, also needs to be approached to see what support could be provided and what their positionwould be on future support.

As a general comment, the component industry is currently undergoing many changes. Somecomponents as are used in the DX25 transmitter currently or their direct equivalentreplacements, may now not be available. This is due to many component manufacturers ceasingproduction of some of the older components altogether because they are old, demand is low andthey can are difficult to produce in a lead free format. (All new components must now beROHS complaint).

While the DX25 is a lower power and earlier model of the DX200, the two are not compatiblein terms of spare parts and or the internal control systems and a separate set of spares needs tobe considered for the DX25.

Based on the visual inspection only, the DX25 transmitter seems to be in a condition where itcould be made operational to act as a standby for the DX200 transmitter after;

1. Major clean, 2. Replacement of parts which are missing 3. Re-tuning of the transmitter from 585 kHz to 918 kHz4. Installation of the AC power supply to the transmitter5. Installation of the AC power distribution and isolation switch board6 Installation of a 4 port “U” link change over panel in place of the present 3 port “U”

panel. This to allow the connection of the 25 KW transmitter to the antenna or test load7. Installation of the rigid feeder cable from the DX25 transmitter to the “U” link panel.

Such a system as outlined above provides a manual change over between the DX200 and DX25transmitter. If automatic change over is required, additional control equipment and motorisedchange over coaxial switches would be required to replace the “U” panel.

2.3 General Transmitter Comments.

2.3.1 Transmitter Operating Conditions

The room in which the DX200 transmitter is located is clean and fully air conditioned, howeveronly eight of the thirteen air conditioners were operational during the visit. While the site visit


was being undertaken, the internal air temperature felt comfortable and was measured at 28degrees. As far as could be determined there was no temperature gradient with height above thefloor. These comments however have to be placed in the context that the transmitter was onlyoperating at 80 kW output and not at the rated 200 kW rated output power.

If the transmitter is to be operated at full power output, then the air conditioners currentlyinstalled need to be fully reconditioned. This to ensure the humidity is reduced and the air intaketo the transmitter is cooled sufficiently to be within the operating temperature range as specifiedby the manufacturer.

The transmitter is specified to operate in ambient temperatures of up to 50 Deg C, but given thelonger term reliability issues, a recommended operating environment of between 22 and 25degrees C is considered normal.

Given that the transmitter exhausts the hot air directly out of the top of the transmitter and drawsin cooling air in the rear of the transmitter, an investigation should be considered to look at theair flow paths, output to input. It may be that a barrier of some type between the air outlet andthe air intake could improve the exhaust air cooling efficiency by having a longer air pathbetween the transmitter air outlets and the air intakes.

2.3.1.1 Power Transformer

The DX200 has a main power transformer located in a room just off the main transmitter room. This room is not air conditioned but has a fan to exhaust air outside with the fan being aboutone metre above floor level. This room therefore is basically at the general outside ambient airtemperature in the shade. The transformer has the top covers off on both its front and back.

A noticeable quantity of heat was being given off by the transformer, even with the transmitteroperating at 80 kW output. No assessment was possible with the transmitter operating at fullpower, 200 kW output. It was suspected that the covers were off to provide better ventilationand hence lower the operating temperature of the transformer.

No warning signs were evident that there were exposed voltages and a potential danger existed.The room however was not readily accessible by the general public or staff. The voltagespresent were 380V three phase AC power at the input to the transformer and the three phase ACoutput at about 250V. All terminals and buss bars were exposed.

Given that ventilation of the transformer is highly desirable from an operational point of view,and that some means of covering up the exposed connections is also desirable, a suitable coverwhich does not impede the air flow but prevents contact (whether intentional or unintentional)with any of the live terminals or buss bars, should be put in place. Some form of perforated steelcover is suggested.

Warning signs of High Dangerous Voltages should also be installed on the front and rear of the


transformer cabinet.

When the transmitter is returned to fully operating output , 200 kW, the room in which the maintransformer is located should be monitored for temperature rise. If the rise is seen to be higherthan desirable, consideration would need to be given to installing further fans to provide an airflow through the transformer cabinet itself.

2.3.2 RF Output Switching

The transmitter’s output is connected to a manual 3 port “U” link switch panel in a small roomoff the room in which the transmitter is installed. The “U” link panel provides facilities toconnect the transmitter to a test load or the antenna. This equipment is in good condition.

2.3.4 Test Load

An air cooled test load is located outside of the transmitter building near to the “U” link paneland power transformer room. Although an internal inspection of the test load was not possible,it appeared to be in excellent physical condition.

A water proofing material, suspected to be a wax impregnated tape of some type, has been usedat the elbow and flange input connection to the test load. This material needs to be checked asto its status, because there are cracks appearing in the covering and it is possible that water mayor could possibly get in and cause a reflected power issue if the test load was to be used to testthe transmitter. No materials were available on our visit to attempt a repair.

2.3.5 Antenna Feed.

From the “U” link panel, connection is made via rigid 4" feeder to the 6" PVC covered Coaxialcable which exits the building underground and goes to the Antenna Tuning Unit.

An Andrews dehydrator with flow indicators is provided to pressurise the PVC covered coaxialcable. The Andrews dehydrator pump is not operational but an external air pump has beenprovided. This pump is located on the floor and connected into the original Andrew Dehydratorair flow system. On arrival it was switched off at the AC power supply and there was nopressure being maintained in the coaxial cable.

It is not known how long it has been since pressure was maintained in the cable and as a result,if there are any air leaks. The dehydrator was run for a period of time and it was seen that airpressure did start to build slightly in the cable, leading to the conclusion that the cable could bepressurised, but whether or not the pressure could be maintained was not determined.

A simple check was undertaken to look for air leaks around the interface between the rigid feeder


and PVC coaxial cable interface but none was evident. To fully verify the integrity of thepressurisation, the system would need to be run for many hours to fully pressurise the full lengthof the cable (some 169 metres) and monitor any flow rate and pressure loss over a 12 hourperiod. If any leaks were evident then it may be necessary to find and repair it, or them.

It is desirable to pressurise the cable in order to keep water and humidity out of the air cavity ofthe coaxial cable and as a result improve the reliability of the operating conditions.

2.3.6 Antenna and Antenna Tuning Unit

It was not possible to get to or inside the antenna tuning unit. This was because the land areacompletely around the Antenna Tuning Units building and the base of the tower was under aconsiderable amount of water. The understanding from the transmitter staff was that no one hadbeen inside the building for 10 years.

Observations made using binoculars showed that there was evidence of long grass around thebase of the antenna and building as well as some deterioration of the building’s outside claddingmaterials.

Access to the building would have required the transmitter to be shut down or reduced to a verylow power level in order to avoid the high levels of Radio Frequency radiation associated withsuch systems.

The evidence is, based on the forward and reflected power readings given on the front of theDX200 transmitter, that there is nothing wrong or that has deteriorated either at the ATU or theantenna. The transmitter’s reflected power is indicating “0" no matter whether the transmitteris set to 25 kW, 80 kW or 180 kW. The initial proof of performance readings were notavailable to verify whether or not the system has changed, or possibly that the reflected powermetering was faulty and hence an assumption has been made at this time that the antenna systemis fully operational.

2.4 General Transmission Site Conditions

As outlined in section 2.1 AM Broadcast Transmitter Site Location and as can be seen in theGoogle Earth print “Phnom PenH-2", there are a number of antenna towers on the land area.The towers marked SW1A and SW2A are towers that have been used in the past for shortwaveservices. These towers are currently unused. Since it was not possible to get to the base ofthe towers, it is not known what type of tower they are, earthed or base insulated. It is also notknown if they are open circuit or if base insulated have been detuned to 918 kHz, or are shortedto ground.

The tower marked LK is a tower which carried the microwave link signal from the RNK studioto the transmitter site for re-broadcast on 918 khz. This tower is earthed to what looks like oneof the ground radial wires. It is not known if the wire in question is associated with the 918 kHz


mast of the near by short wave mast.

The tower marked FT is the newest tower on the transmission site. The tower is earthed at itbase.

No information was available as to the extent of any of the ground radial systems associated withthe towers. Tower KL was clearly only earthed by a single copper wire of about 1.5mm dia asit was clearly visible running into the water right at the edge of the tower foundation. It has not been possible to determine the length of the ground plane radial wires associated withthe 918 kHz mast and how these may or may not have been connected to any ground radial wiresassociated with the shortwave towers, SW1A and SW2A Therefore it is not known how many radial ground wires there are or what length they are,associated with the 918 Khz tower. It is normal practice to provide 1/48 long radial wires and120 of them equally spaced around the base of the tower.

There is no evidence that the earth of the FM tower has been connected to the transmitterbuilding earth or the ground radial system of the 918 kHz tower.

Google Earth has been used to plot the positions of each tower as accurately as is possible in aneffort to look at the relative distances and associated angles that each tower is in relation to the918 kHz tower. Google Earth was used for this analysis as there was no site drawing availableshowing the tower positions. These results are tabulated below.

Antenna Height Distance Bearing 8 @ 918 kHz

AT 92 m 0 0 reference position

SW1A 45 m 90 m 175.1 0.28 8

SW2A 45 m 420 m 125 1.29 8

LK 34 m 170 m 224.45 0.52 8

FT 69 m 240 m 261.79 0.73 8

Notes:

The positions are approximate and therefore indicative onlyThe heights of all of the towers except for the AT tower are estimates only.

The transmission site is currently having extensive development around its perimeter, see GoogleEarth print “Phnom Penh-1".


Housing developments of three storey houses are encroaching to the north, northeast, north west,west, south and south west. The development is along the road running from the northeast to thesouthwest around the corner to the south. Development is on both sides to the road. People arealready living between the SW1A and SW2A towers. RNK staff are working in the buildingsmarked SW1 and SW2,

Concern for the level of RF radiation across the site needs further investigation. While it ispossible to calculate the approximate distances from the main tower that the RF radiationexceeds the generally recognised international limits of 86V/m for the general public, it is notpossible to calculate the effects of re radiation from the guys wires and any other structures thatmay re-radiate. These effects can only be determined by measurement.

Calculations show that from the base of the tower, the level of 86 V/M is reached at a distanceof approximately 15 metres from the tower with the transmitter running at 200 kW. This isbased on 8/4 antenna as set out in reference Evaluating Compliance with FCC Guidelines forHuman Exposure to Radio-frequency Electromagnetic Fields. OET Bulletin 65 (edition 97-01),Figure 2 MININEC AM Model 1 kW 0.25 wavelength.

There is currently NO fence around the antenna and its associated guy anchor blocks, but theantenna is difficult to get access to whilst the water in the surrounding area is present. Since itwas not possible to access the Antenna Tuning Unit, the base of the antenna or indeed the guyblocks due to the water all around the area, no comment can be made as to the state of theseitems. However there was tall grass growing near to the tower base, as well as around theAntenna Tuning Unit building. As soon as access can be gained the grass needs to be cut andinspection of the ATU made.


3.0 RADIO COVERAGE

A radio survey was undertaken with the 200 kW AM Transmitter in Phnom Penh operating at80 kW output power. Field strength readings were undertaken along highway 6 from PhnomPenh via Kampong Thom and Siem Reap north to Sisopon and then back to Phnom Penh alonghighway 5 via Battambang and Pursat. The results have been tabulated below.


No Date Time North East Reading Corrected Bearing Distance Quality Description

1 8 Sept 0945 11 53.66 104 55.38 27mV/m 43.5mV/m 5.26 40 km 5 Located on the side of the road with wet fields

each side flat terrain

2 8 sept 1035 11 12.510 105 07.476 11mV/m 17.4mV/m 18.94 78.8km 5 Good clear signal. No noise. On the side of the

road. Flat fields with crops. Wet fields

3 8 Sept 1112 12 30.298 105 07.318 4.5mV/m 7.1mV/m 13.25 110.3 km 4 Good quality signal to listen to. Built up area.

AC power lines across road. Some evidence of

power line interference while driving mobile.

Flat terrain.

4 8 Sept 1149 12 42.646 104 53.359 3.9 mV/m 6.2 mV/m 0 130.1km 4 Built up area. In town. No noise on signal when

stationary at measuring location (15 metre from

over head power lines). Noise on reception when

mobile.

5 8 Sept 1302 12 48.940 104 41.568 1.2

mV/m*

1.9mV/m 351.44 143.5km 2 Slight noise noticeable in background. Lightning

crackle also present. Possible interference from

another station but it could not be identified or

determined for sure.

6 8 Sept 1345 13 05.684 104 22.264 780uV/m 1.2mV/m 341.97 181.6km 2 Signal subject to lightning crackling. No other

noticeable general background noise

7 8 Sept 1425 13 15.071 104 06.713 520uV/m 830uV/m 336.09 207.9km 2 Lightning noise. Sparsely populated area

Flat wet fields

8 8 Sept 1450 13 21.978 103 51.068 600 uV/m 950uV/m 329.38 221.0km 2 Noise on received signal. Built up main street of

Siem Reap. Suspected local ambient noise

associated with built up commercial area


9 8 Sept 1800 13 36.091 102 59.132 800uV/m 1.3mV/m 315.65 295.0km 2 Lightning noise in received signal. Some

ionospheric interference evident Saw signal vary

up to 200 uV/m due to selective fading but when

interference at minimum reception quality was

good.. Typical sunset and night time propagation

at the boundaries of ground wave and sky wave

propagation. Evidence on station interference

also heard but could not identify.

10 9 Sept 0820 13 31.426 103 01.173 400 uV/m 630uV/m 317.48 299.5 km 1 Very strong interference on adjacent channels

signals of 920 uV, 700 uV/m evident. +/- 100

uv/m beatings with wanted signal.

11 9 Sept 1002 13 06.359 104 10.360 500 uV/m 790uV/m 313.14 255.2km 1-2 Poor signal quality. Beat +/-50 uV, interfering

stations. Can hear another station’s modulation

in the background. Strong adjacent channel

interference.

12 9 Sept 1145 12 48.413 103 25.469 600 uV/m 950uV/m 311.60 212.7km 2 Low frequency beat by interfering station.

Station could not be identified.

13 9 Sept 1300 12 32.623 103 54.813 450 uV/m 710uV/m 316.52 154.1km 1 Unusable. Signal subject to severe interference

from external stations. Very high level of man

made interference which seemed to be coming

from the building area. 7 mV signal level

available at ground anchor for guyed tower. (Re

radiation from guys? +/- 100 uV beat on signal.

Strong adjacent channels evident.

14 9 Sept 1505 12 31.589 104 13.804 550 uV/m 870uV/m 326.88 131.1km 2 Poor quality. Could just hear another signal in

the background. The received signal was not

steady with a +/- 20 uV steady beat.

15 9 Sept 1530 12 27.013 104 27.073 1.7 mV/m 2.7mV/m 334.83 112.0km 4 Good quality. No background noise.

2.1 mV/m at 1 metre above ground level

16 9 Sept 1615 12 12.863 104 40.016 5.1 mV/m 8.1mV/m 342.17 79.0km 5 Very clear signal


17 9 Sept 1650 11 53.083 104 42.597 40 mV/m 63.2mV/m 333.25 43.4km 5 Excellent quality

Notes:

All readings done at ground levelField strength reading done with Potomac FIM-41 serial No. 435Listening tests done using hand held radio Sangeon ATS-909 serial no. 32290All reading carried out with 80 kW transmitter nominal power.Corrected. This is the expected field strength with the transmitter operating at its rated power 200 kW* reading corrected for 80 kW transmitter power as transmitter operating at 25KW at time of reading.All Bearings relative to True North.Quality rating. On a 1 to 5 scale. 5 excellent, no evidence of interference or unwanted noise. No impairments. 1 unlistenable or would be

difficult to listen to.The assessments were made on listening to the signal as present and no attempt was made to guess the qualityhad the impairment not been present at the time. ie lightning interference.

Distance Distance direct from transmitter in Phnom Penh to measuring location.


3.1 General Comments

The signal level and subsequent quality was lower than expected down the western side of LakeBoeng Tonle Sap given the signal levels at comparable latitudes on the west side of the lake. No interference from other stations was evident along Highway 6 from Phnom Penh to SiemReap (along the eastern side of the Lake Boeng Tonle Sap). On the eastern side ofSisophon(measurement 9), slight interference from other stations was noticed but this was notwhat could be considered as objectionable and nothing like the level of station interference notedin measurements 10, 11, 12 and 13 taken the following day.

The signal level and interference noted at measurement location 9 was not unexpected in thisarea, as it can be considered to be on and or beyond the fringe of the ground wave coverage andas such is subject to ionospheric interference at night. However the level of interference notedand when combined with the lower than expected wanted signal levels at measurement locations10 through 13, made the wanted signal generally unusable, especially for rebroadcast purposes.The wanted signal on 918 kHz was being received on a AM receiver and rebroadcast on the localFM service at PURSAT (measurement location 13) and at Battambang (measurement location11)

While increasing the RF power output of the 918 kHz transmitter to 200 kW will increase thesignal strength at all locations (see table above for corrected field strength at 200 kW), it is feltthat perhaps the signal levels at Battambang (measurement 11) and Pursat (measurement 13) willstill not be sufficient to override the interference from other stations.

It must be noted that one of the major sources of interference at Pursat is man made. Theinterference is cyclic, and builds from a low intensity to a high intensity before repeating. Itappears to be coming from within the transmitter/studio building. It was not possible todetermine the source during the time of the visit. The interference reduces rapidly to beinginaudible on the received 918 kHz signal as the receiver and its antenna are moved away fromthe transmitter building. A method of trying to identify the source of the interference was given.This would involve listening to a AM radio receiver at or near to 918 kHz, switching off both theTV and FM stations completely (every item of electrical equipment, lights, computers, airconditioning, Mixer desk, CD players, fans fridges, TV and FM transmitters etc). Then if theinterference is not present, switching each item back on one by one. This procedure then shouldidentify the offending item of equipment and repairs made accordingly.

To improve reception for off air re-broadcasting purposes, it is suggested that a directional AMreceiving antenna be established, direction of pickup being from Phonm Penh. Such an antennawould reduce the pickup of the interfering signals from Thailand and other areas whileoptomising the signal on 918 khz

A high quality off air receiver could then being provided with its output connected to the studiomixer desk. The receivers’s audio output should be of a balanced format to reduce thepossibility of other local noise being introduced on to the signal from 918 kHz - noise such ascomputer noise.

The same arrangement needs to be installed at Battambang. The 918 kHz signal here suffers


from external interference as a result of other stations in Thailand and from the stationscomputer(s). The electrical noise from the computer needs to be reduced and this may beeffected by changing the power supply for one of the newer EMI suppressed types andintroducing some additional filtering. Using a balanced audio signal line from an appropriateAM receiver would then assist with reducing the computer noise. A remotely located directionalreceiving AM antenna would also assist in reducing the susceptibility of the off air 918 kHzsignal to interference as is the current case.

Further work needs to be done in order to access the apparent lower than expected signal levelsfrom Sisophon to Pusat. It is not known at the time of the report preparation if this is apropagation issue or due to other matters.

The propagation path between Phnom Penh and Sisophon, Phnom Penh and Battambang,Phonom Penh and Pursat is lower than expected, given comparable distances on the eastern sideof Lake Boeng Tonle Sap.

Observations using a map of Cambodia that shows the land forms provide information to theeffect that mid way between the AM transmitter location in Phnom Penh and the three mainpopulation areas along the western side of Lake Boeng Tonle Sap, Sisophon, Battambang andPursat, is a rugged, high and heavily forested area. This type of terrain is known to reduce theeffective ground wave propagation and hence would mean that these areas would have to relymore of skywave propagation. The sky-wave propagation is subject to the reflections from theionosphere and therefore has a some what reduced quality of service during the day and is subjectto interference at night form other stations.

It is generally concluded that radio reception of the 918 kHz signal from Phnom Penh would bedifficult on portable and hand held AM radio in the area from west of Siem Reap, throughSisphon, Battambang and Pursat. Reasonable reception would be available from a good qualityAM radio using and outdoor antenna. At all times in the areas indicated, the 918 kHz signalwould be subject to interference from other AM radio stations on an adjacent channel or on thesame channel. The interfering stations were identified as being of Thailand origin with signallevels in the order of 200uV/m to 400uV/m stronger that the wanted 918 khz.(measured andobserved during daylight hours).

3.2 Ways To Improve Reception

There are several possible ways of perhaps improving the radio coverage over Cambodia. Eachoption has its advantages and disadvantages.

3.2.1 Option 1 Single transmitter Coverage

Single transmitter to provide radio coverage to the whole of Cambodia.

Covering the whole of Cambodia with a sufficiently strong signal strength into all of therecognised difficult signal areas indicated in Section 1.1 would require a very powerful


transmitter and an antenna system that optomised the ground wave coverage while minimisingthe potential sky wave interference to other countries. Such a transmission system would have other ramifications in that the health and safety issuesassociated with such a high powered transmitter would need to be assessed. As anapproximation, a transmitter with an output power of some 500,000 watts may be required alongwith a 5/88 antenna. Such a system would require an exclusion zone around the transmittingantenna of some 25 meters from the base of the tower. At 918 kHz the tower height would bein the order of 200 metres high. These considerations alone would require extensive engineeringboth structural and civil to ensure the tower foundations and other factors are all accounted for.

The 25 metre exclusion zone is based on Figure 4 MININEC AM Model for 1 kW 0.625wavelength tower, scaled for a 500,000 watt transmitter. This zone would most likely have tobe extended to account for the radiation from the tower guy wires and any other structures. Inturn, the total system may present issues with the health and safety parameters as far as thepresent and future developments are concerned around the present transmission site in PhnomPenh.

Increasing the transmitter power from 200,000 watts to 500,000 watts represents a signal levelincrease of 3.98 dB. If the 5/88 antenna is used rather then the present 1/48 antenna, a further3.3 dB in in the field strength can be expected. Therefore a total of an additional 7.3 dB in thefield strengths could be expected. Without accessing any additional losses, it is possible that thereceived signal levels in the difficult reception areas identified in the measurement table abovewould increase to;

Measure Point Expected Field Strength

10 1.46 mV.m

11 1.83 mV/m

12 2.19 mV/m

13 1.64 mV/m

14 2.01 mV/m

Even at these signal strength levels, the signal level does not meet the planning targets forsuburban population densities (2.5mV/m). Given that the population in the areas of the abovemeasurements can be considered to be at or above the suburban density, the increased transmitterpower and different antenna is not sufficient to meet the targets and hence the reception wouldhave to be considered marginal. This can only get more marginal as the population increasesand the level of man made noise increases.

Reception in those areas identified in Section 1.1 above, while not specifically measured, wouldstill be expected to be difficult however improvements would be noticed.


Consideration was given to the use of a directional antenna system but given that Phnom Penhis essentially in the centre of Cambodia, any use of a directional antenna array is more likely toprovide improved signal levels in some areas at the expense of others.

Given the mountainous areas to the east, north east, west and north west of Phnom Penh,reception would be difficult within or at the extreme distances in these regions. This is becausethe ground wave propagation is more heavily attenuated in mountainous and heavily forestedareas.

The advantage of a single high powered AM transmitter is that there is only one transmission siteto maintain. The disadvantages are;

1. Very high levels of radiation at the transmitter location.2. The present transmitter location may not be able to have the required tower erected on

the site for space and engineering reasons.2. Coverage would not provide an adequate signal level in all reception areas and as

population increases effective coverage would diminish due to the increase in man madenoise and other factors

3 Coverage to the most distance areas where there are significant population densitieswould still be subject to interference from other stations on adjacent channels or on thesame frequency.

4 It is very costly to implement, maintain and run.5 Possibility that the transmitter infrastructure would need to be upgraded this including

the test load, a new ATU (antenna tuning unit), new emergency Diesel generating plant,improved air conditioning of the building and increased Power supply capacity from theelectrical supply providers.

3.2.2 Option 2 Main Transmitter and Several Rebroadcast Transmitters

The present transmitter, 200 kW, can be maintained and retained at the present location providedthat future development in the surrounding areas takes into account the radiation hazard levelsfrom the antenna. The present mast (SW1A) on the transmission site should be removed or de-tuned, such that it does not have or can not have, any influence on the radiation pattern of thepresent AM 1/48 antenna AT. The SW1A antenna is approximately a 1/48 from the active AMradiating antenna AT and although physically shorter, may be having some mutual effects on theradiation pattern of the AM antenna AT. Removing or de-tuning the tower SW1A, wouldensure that the AM antenna has a true 360 degree of arc coverage pattern.

Since there are potential issues in regards to high levels of radiation at the present transmitter sitein Phnom Penh and the increased transmitter power will only compound the radiation issue,there is a real question mark as to how much the radio coverage would be improved if a very highpowered transmitter was used. Consideration has to be given to alternative ways of providingradio coverage the whole country.

The most practical and efficient way to achieve nation wide coverage for radio is to have a maintransmitter such as the one in Phnom Penh and have a series of rebroadcast transmitters located


in places where the reception would other wise be difficult. As with all rebroadcast locations,the question of how to get the program material to the respective transmitters becomes an issue.

Since the rebroadcast transmitters are usually located in areas of difficult off air reception, thisis usually not a practical way of obtaining an input for the rebroadcast transmitter. The off airsignal from Phnom Penh usually has adjacent channel interference, a higher than desired levelof man made noise and is subject to atmospherics, such as lightning and noise.An alternative way of getting a input program the rebroadcast transmitter locations is to use landlines, radio links and or satellite distribution.

3.2.2.1 Land Lines

For good quality broadcast program, lines would need to be provided by the Telecom service viaits links to the various locations around the country. The land lines usually being used arestandard fixed circuit (leased) telephone lines equalised to provide acceptable broadcast qualityusually up to 10 kHz audio bandwidth, with. one such program circuit to each re-broadcasttransmitter site. These fixed program lines are subject to capacity being available from thetelecommunications authority, the areas where the Telecommunications Authority have suchfacilities, the service reliability of the Telecommunications Authority and operational costs.

3.2.2.2 Radio Links

These comments are made without knowing the regulatory situation in Cambodia. A commonway to link the program to transmitter locations is to use a radio link. The problem with radiolinks is that they usually require a line of sight propagation path, transmitter to receiver andhence for rebroadcast transmitters which can be long distances away from the originating studio,a number of link hops are required. Such a system increases the equipment required, increasesthe service costs and adds complexity.

3.2.2.3 Satellite Distribution

Satellite distribution has the advantage that the satellite can be seen from all locations within thecountry. By using a satellite receiver at each rebroadcast location, the program signal can beobtained with excellent quality. Perhaps the only technical disadvantage of using satellitedistribution is that the signal could be lost during very heavy rain or very heavy cloud cover.

For such a distribution system to be achieved, either the originating station has to have its ownsatellite uplink or it piggy backs its service on another nation wide service. Fixed satellite up linkinstallations tend to be expensive and require a high level of maintenance to run.

It was noted that perhaps the national TV service in Cambodia uses satellite distribution to getits programs to its various transmitters around Cambodia. Most satellite systems for TV thesedays have an allowance for the vision signal and up to 4 separate sound programs. If the TV istransmitted using a single sound (mono), then only 1 of the 4 audio channels would be used.


Stereo TV or dual sound TV would use two channels. This leaves the potential to have 2 or 3sound channels available for other uses. To use such a system, the co-operation of the TVservice would be required to provide the necessary multiplex facilities at their uplink location toadd the additional sound channel to their satellite data stream. NKR would then need to providefacilities to get the program signal from the origination location to the TV uplink facilities.

By using such a system, the rebroadcast transmitters could be located at any location, so long asthe satellite can be seen to receive the signal. Such flexibility allows for AM and FMrebroadcast facilities to be provided. AM rebroadcast transmitters could be used to providewide area coverage (medium power) while FM transmitters could be used to provide wide areacoverage, depending on the transmission sites position in relation to the area to be covered orhave more pocket area coverage (low power).

While this option increases the number of transmitters in service, the operating costs can beminimised by careful planning, low maintenance implementations, using low maintenanceequipment configurations and redundant equipment systems. These systems if implementedsuch that the operating environment of the equipment is not stressed, can be run unattended. Inthis way no additional staff at each transmitter location is required. In order to maintain thetransmitters, a maintenance team of two or three staff, trained in transmitter maintenance couldthen maintain the system on a rotational basis and visit each transmitter on say a 6 monthly visitbasis. Allowance then needs to be made for emergency situations where it is reported that thetransmitter is faulty.

During the visit to Cambodia two older AM transmission sites used in the past were identified.One was only physically seen from distance. The site seen was at Battambang. There are twoAM guyed towers which are not in use. It is suspected that this was a directional antennasystem. Since no information was available on these facilities and as no person could recall itoperating, it was not possible to determine its original function and service area.

Being located at Battambang, which is essentially in the center of the difficult reception areafrom the Phnom Penh transmitter, it is possible that this location could provide a good coveragesignal to Pursat, Sisophon and coverage overlap with Siem Reap. In addition, the transmittercould extend the coverage to the border with Thailand and to the areas north of Sisophon.

The second transmitter location was at Kratie, another area noted above as a difficult AMreception area. This transmitter, now not operational, is understood to have operated on 585Khz. Indeed it is understood that the 25 kW transmitter now at Phnom Penh to be used as astandby for the 200 kW transmitter, came from this location. No details of the service that wasprovided by this transmitter are known. It is not known why the transmitter was withdrawn fromservice.

Using satellite distribution, small local area FM transmitters, possibly located on the sametransmitting site as the TV service, could be used at Sen Monorom, BanLung, StungTreng, KohKong, and possibly Sihanoukville. It is believed that Pailin would possibly get adequate AMradio coverage from an AM rebroadcast transmitter at Battambong if one was activated.

Using satellite program distribution, flexibility is gained in that rebroadcast facilities can be


installed basically where ever they are needed, be it very low power FM services or a more higherpower AM or FM area coverage station. Operational costs can be minimised by usingunattended transmitter site installations, a specalised maintenance team and placing the programsignal to be distributed on to the spare capacity of another satellite distributed service.

3.2.2.4 Fibre Optic Distribution

A fibre Optic cable network could be used to distribute the program signals from the RNK studioto any relay stations. Such a network would need to be installed to all the places where theprogram signal is required, each relay station, along with the terminal equipment required. Sucha network if installed and operated by RNK would have capacity far exceeding RNK’s currentand possibly future capacity. A fibre optic network, if implemented, would have a return pathcapability thus allowing program contributions to be made back to RNK’s studio in Phnom Penh. Spare capacity in the fibre optic system may be able to be leased from other communicationservices, but this would require as the capacity was used, additional terminal equipment andinfrastructure to enable connection to the lessees facilities. This would not be RNK’s corebusiness.

The implementation of such a fibre optic system by RNK would require a large investment ofcapital and require a team of people to implement. Access rights to hang on existing poles orbury the cable underground along the route would need to be sought. Such an undertakingwould take considerable time and be expensive.

3.2.2.5 Off Air Reception

If relay stations are established to provide supplementary coverage in areas where the radioreception of the signal direct from Phnom Penh is difficult, then it is likely that the quality of thereceived off air signal, even with a receiving system that has engineering enhancements toimprove reception, may not be suitable for rebroadcast purposes.

Such systems are prone to interference from other broadcast stations from both on channel andadjacent channel stations. Where the relay station is a long distance from Phnom Penh, thereceived signal can be subject to skywave interference. This interference comes from otherstations located in counties outside of Cambodia. If the main signal is low in signal level, thenthe interference may under some circumstances, cause the main signal to be unusable for rebroadcast purposes.

AM signals are also subject to impulse type interference from man made sources. Such sourcesinclude computers, ignition systems, faulty switches and many other sources. While suchnoise can be suppressed in most cases, it is a very annoying type of noise on a broadcast service.

Because of the interference issues and the fact that off air reception is desirable for backup oremergency broadcast purposes, a receiving antenna which is optomised for the reception of thesignal required should be provided. Such an antenna may be a directional active tuned type.


Another consideration of using Off Air reception for rebroadcast purposes is the fidelity of therecovered signal after the interference issues have been removed. A normal AM broadcastservice’s emissions standards require an audio signal from 20 Hz to 9 or 10 kHz to betransmitted. Most AM receivers have at best, have a recovered audio bandwidth of about100Hz to 6 kHz. This recovered signal after it is re-boadcast by the relay station and againreceived on a listeners AM receiver, would start to sound as if the signal was being sent over astandard telephone line.

Since there are some FM stations in the same areas where the RNK signal would be relayed, thecontrast in signal quality would be very noticeable if a listener tuned between the stations.

It is therefore recommended that OFF air reception be used only as an emergency source and onlyafter the reception system is optomised for a maximum of wanted signal while minimising theinterference issues.


4.0 Recommendations to Improve the Present Transmission System.

4.1 Transmitter

The present Harris Transmitter DX200 is running at 80 kW output most on the time. Thetransmitter occasionally switches down to 25 kW output due to an air flow sensor problem onthe MOD ENCODER PCB assembly located on the right hand wall of the EPA cabinet. Thisfault needs to be rectified and although attempts were made to improve the situation during thevisit, the lack of spare parts and PCB assemblies made this impossible.

As indicated in section 1.3 the transmitter operators were reluctant to operate the 200 kWtransmitter at full power because there are no spares with which to fix the transmitter should itfail and there is currently no standby transmitter to put on air. On this basis the transmitter wasbeing operated at a lower power in an attempt to improve reliability.

Even if the 200 kW transmitter was fully operational, the transmitter room’s air conditioningneeds to be brought up to its full operational capacity to ensure that the transmitters operatingenvironment is conducive to the long term reliability of the transmitter over the full ambienttemperature range. In addition to fixing the existing air conditioners, it is recommended that theair flow distance between the transmitter air outlets and its air inlets be made such that there isas long a path as possible. This to ensure that the hot exhaust air is just not in effect being shortcircuited outlet to inlet. Inserting a baffle would have the effect of making sure the hot exhaustair is adequately cooled before it re-enters the transmitter

Since the 200 kW transmitter would be the main transmitter for the country, it is essential tomake sure it is very reliable. To this end a standby transmitter needs to be provided. While thestandby transmitter could be of a lower power output, it is essential that the 200 kW transmitterbe placed back in service as quickly as possible after a technical problem has occurred. In orderto achieve a fast turn around on any transmitter fault it is necessary to have the spare partsavailable in order to carry out such repairs.

A 25 kW Harris AM transmitter is currently located in the transmitter building at Phnom Penh.The transmitter has been used in the past and is currently set on a frequency of 585 kHz. Thetransmitter looks to be in good condition but requires a very good clean and the replacement ofsome parts which were used as spares for the main 200,000 watt transmitter. The transmitterneeds to be installed in an appropriate environment, frequency changed to 918 kHz, connectedto the AC power and have the RF output connected via a 4 port change over panel to allow it tobe connected to the 918 kHz antenna or test load.

The transmitter should be installed in an area which is close to the present 200 kW transmitter.It would need to have air conditioning such that the exhaust air from the transmitter is cooledsufficiently before it is taken back into the 25 kW transmitter. The air conditioning in the roomwhere the 25 kW transmitter is, then only needs to be turned on when the transmitter is runningwith the air conditioning control being connected to the transmitter ON and OFF functions.

In order for the 25 kW transmitter to be fed with a program signal from the studio, it would need


to be split in three using a Distribution Amplifier (DA), one output of the DA going to thepresent audio processor for the 200 kW transmitter, another going to a new audio processor forthe 25 kW transmitter and a third output from the DA being used for monitoring purposes (noinput program monitoring is currently available).

Currently there is a 3 port “U”link panel which is used to connect the output of the 200 kWtransmitter to either the test load or the Antenna. This “U” link panel would need to be changedto a 4 port panel to allow the 25 kW standby transmitter to be connected to either the test loador the Antenna. The functions would be;

200 kW to antenna 25 kW to the test load, or25 kW to the antenna and 200 kW to the test load.

Control and interlock functions would need to be re arranged to ensure that the transmitters cannot be turned on unless they are connected to an antenna or test load.

In addition to the above facilities additional facilities need to be added;

Program signal monitoring including level monitoring;

Program input from the studioProgram output from the Audio processor for TX1Program output from the Audio processor for TX2 (standby)Demodulated output from a Off air AM demodulator TX1Demodulated output from OFF air AM demodulator TX2

These functions would allow monitoring of the transmitter, main and standby whether they areconnected to the antenna or the test load for live program transmission or test purposes.

In order to test the transmitters the following basic facilities need to be provided.

1. Test Audio Oscillator2. Test Audio measuring set.3. Audio Patch facilities to allow test tones to be connected to the input of the

transmitter and from the measuring set to be connected to the AM demodulatoroutput.

4. An Oscilloscope. 5. Multimeter6 Basic tools7. Field Strength Meter8 Spectrum Analyser

There are other test instruments that would be desirable in the event of a fault with the antennasystem. The main instrument would be an impedance bridge and a set of coaxial cable adaptors.In order for the impedance bridge to be used, the standby transmitter operating at low power (lessthan 5 kW) would need to be used.


4.2 Antenna.

As indicated in section 2.1.1 the transmission site is currently being surrounded by residentialand commercial development. This development raises concerns re occupational Health andsafety issues with regard to the radiation hazard. While at present, (based on theoreticalcalculations), there does not appear to be an issue, the radiation hazard levels should bemeasured at various locations around the transmission site’s perimeter.

Presently the antenna site is difficult to get to and the surrounding land is flooded. Given thatthe antenna has high RF voltages present and there is a potential radiation hazard to humans, theantenna site should be fenced off. The fence being located such that it is located at a distancefrom the antenna where the radiation hazard level is consistent with the world standard of 86V/m. While it is possible to calculate the distance these calculations do not necessarily take intoaccount site specific issues. In order to determine the optimum distance at which the fenceshould be constructed the radiation levels at the site should be measured to take into account sitespecific issues.

Care needs to be taken in the fence’s construction to avoid a metal to metal connection that mayconstitute a short circuit and thus effect the antenna’s operation.

4.3 Spares

A comprehensive set of spares for both transmitters needs to be held at the transmitter location.The spares are to be used to return the transmitter to service as quickly as possible if a faultoccurs. Once a spare has been consumed an assessment needs to be made as to whether the part,in the case of a circuit assembly, can be repaired or if the component is replaced in stock witha new part.

On this basis an stock record system should be established with a standard stock level and aminimum stock level. The minimum stock level would be set by taking into account usage anddelivery time from the supplier. Such a system needs to be integrated with the accounts andordering system.

A recommended set of spares and the holdings is given in appendix.A

4.4 AM Rebroadcast

At the present time the transmission from Phnom Penh is rebroadcast at times during the day,on FM services at Battambang and Pursat. At both locations the quality of the received signalis very poor. Apart from the low signal, (strengths < than 1 mV/m) the output audio signal hassevere interference on it which makes it unsuitable for rebroadcast. The interference is manmade by way of computer noise at Battanmbang and impulse noise made at the station itself atPursat.

In addition, interference from both adjacent and on channel 918 khz stations is evident causing


additional degradation to the quality of the received signal. This was assessed at Battambangwith the computers turned off and at Pursat at locations away from the stations building.

4.4.1 Battanmbang

Improvements can be made to the quality of the program signal by first using low radiation noisecomputers and additional power line filtering. Reductions in the propagation interference couldbe made by using a directional receiving antenna. This may take the form of an active magneticloop antenna system, tuned to 918 khz.

Because of the high levels of man made type interference, the AM receiver used to receive the918 kHz signal should have a balanced audio output in order to avoid earth loops and commonmode interference induction.

4.4.2 Pursat

The essential requirement is to identify and fix the cause of the impulse interference. At the timeof the visit, this interference seemed to be emanating from the station’s building, but the sourcewas not identified during the time available, even though a number of items of equipment wereswitched on and off at the time.

Because of the high levels of man made type interference, the AM receiver used to receive the918 kHz signal should have a balanced audio output in order to avoid earth loops and commonmode interference induction.


APPENDIX A

RECOMMENDED SPARES


Appendix A Recommended Spares

DX200 and DX25 Spares

Extended price

Item Product ID Quantity Description Units AUD

Dollars

1 9928069004 2 PW A Oscillator EA $6 105.47

2 9928196001 1 Buffer4 AMP BD EA $915.07

3 9928193006 1 Mod Encoder Brd EA $3 424.47

4 9928537002 1 Driver Encoder Brd EA $2 690.99

5 9928882003 1 BD, Analog Input EA $2 700.43

6 9928983001 3 Assy, RF Amplifier 3X SP EA $2 415.68

7 9928684005 1 Power Supply Discharge EA $523.58

8 9928536003 1 PW A, Output Monitor EA $3 132.02

9 9929048002 1 PW A, Power Supply Controller EA $1 108.47

10 9929067001 1 BD, LV Power Supply EA $4 193.31

11 5240219000 2 CAP 550uF 200V EA $319.16

12 5240360000 2 CAP 18000uF 200V EA $523.22

13 5240341000 5 CAP 5100 uF 350W VDC EA $886.44

14 5120325000 2 CAP 1000 pF 15KV Test EA $11 094.74

15 5040420000 1 CAP 3900 pF 12 KV 5% (293) EA $966.16

16 3800726000 10 XSTR 2N7000 ESD EA $11.95

17 3800722000 100 XSTR IRFP360 EA $2 134.22

18 3800728000 10 XSTR NMOS IRL250 ESD EA $50.55

19 5420284000 10 RES 3 Ohm 5% 100W EA $721.89

20 3980465000 10 Fuse Fast Cart 2 250V EA $19.06

21 3980458000 10 Fuse 35A 250V CRTG EA $89.31

22 3980407000 10 Fuse Dual 60A 250V EA $439.92

23 3821022222 10 IC 4N33 Opto Coupler EA $2.17

24 3830126000 10 IC MAX705 W atchdog EA $83.49

25 9220922156 4 Transformer EA $160.65

26 5120193000 1 CAP 500pF 30 kV Test EA $5 603.66

27 9927095001 1 RF Amplifier Module EA $667.45

28 9928038001 2 Harris DX50/25U Buffer Module EA $953.26

29 9928077001 1 Analogue input EA $1 622.60

30 9928203003 1 Output Sample EA $1 712.23

31 992864003 1 Power Supply Discharge EA $533.01

32 5420282000 5 RES 1 Ohm 5% 100W EA $377.54

33 542028700 20 RES 10 Ohm 5% 100W EA $913.38

34 5401600201 20 RES 100 Ohm 5% 3W EA $23.87

35 3821048000 20 IC UC3834N ESD EA $1 187.85

36 3820443000 10 IC CD4053BE ESD EA $38.27

37 3820749000 10 IC NE5532A EA $28.75

38 3800681000 50 XSTR IRFP350 ESD EA $928.86

39 3800677000 10 XSTR2N6029 ESD EA $449.28

40 3800083000 10 XSTR 2N2369 ESD EA $26.16

41 5040238000 1 CAP 1000 pF 30 kV 5% EA $1 688.03

42 5140264000 1 CAP VAR 1500 pF 30 kV Test EA $13 120.25

43 8397855184 10 IC TL074 EA $2.49

44 5160208000 2 CAP HV 50 uF 15 kV EA $567.33

45 3980437000 10 Fuse 50A 250V CRTG EA $89.31

46 3980458000 10 Fuse 35A 250V CRTG EA $89.31

47 3980452000 20 Fuse 1 Time Modget 5A 250V EA $160.94

48 4442909124 1 Xtal NE6A 7244 KHz EA $307.38

49 6340297000 1 Meter 0 -30 RFA EA $3 394.40


50 10 ANA35 (Temperature sensor) EA xx

Total $79 198.03

Currency AUD

Price basis US $0.92=AUD$1.00

Transmitter Type Date Serial No Freq

Transmitters Harris DX200 6.1.98 S8A00142000001 918 kHz

Harris DX25 1.28.93 RPS10611300001 585 kHz

Please Note:

1. Exchange rate variations will apply to all items. The exchange rate used to calculatethe Australian Dollar prices above being based on the rate given above.

2. All prices are based on one (1) consolidated shipment of all items. Prices maytherefore vary if only some of the items are ordered as one shipment.

xx This part was not identified by Harris. Searches on the internet for the part have notprovided any information as to the parts specifications or availability


APPENDIX B

COST ESTIMATES


Cost Estimates

Budget

Item Description US Dollars

1 Harris DX200 refurbishment $6,000.00

2 Repair of Air conditioners $8,000.00

3 Power transformer covers $750.00

4 4 port U link Panel Main/Standby Transmitters $9,000.00

5 Spares for Harris DX200 Transmitter $72,863.00

6 Modulation monitoring facilities and test equipment $12,000.00

7 Transmitter ON/OFF Controls $1,500.00

8 Adjustment of modulation processing $500.00

9 De Hydrator Compressor $2,000.00

10 Refurbish Harris DX25 transmitter $8,000.00

11 Install Dx25 transmitter and frequency change $10,000.00

12 Install AC mains power distribution panel for DX25 $5,500.00

13 Instal RF rigid Coaxial line $6,000.00

14 Install remote ON/OFF for DX25 transmitter with interlocks $2,000.00

15 Change over system for main/stand-by monitoring $2,000.00

16 Processor for standby transmitter $8,887.00

17 Spares for DX25 transmitter $50,000.00

18 Safety fence around AM transmitting antenna $25,000.00

19 Travel and expenses. $20,000.00

$250,000.00


APPENDIX C

Executive Summary


CAMBODIA

AM RADIO COVERAGE RNK

Executive Summary

Prepared by.

G R Smith BE (Hons)A.R.F.C. Pty LtdNSWAUSTRALIA

ABN 91 059 951 147

Date September 13, 2007


The contents of this Executive Summary reflect a critique of the findings from the full reporttitled RNK CAMBODIA MF 918 KHZ TRANSMISSION SYSTEM.

General Position

At the present time RNK provides AM broadcasts to Cambodia via a transmitter located in thesouth east of Phnom Penh. The transmitter has the capacity to transmit a signal at a rated poweroutput of 200,000 watts on an operating frequency of 918 kHz. The transmitter operates into a1/48 antenna. There is no operational standby transmitter.

Current Position

The transmitter has been operating at low power output for a number of years. A general decisionseems to have been taken a number of years ago to operate the transmitter at a power output levelof approximately 100,000 watts, in order to reduced the possibility of the transmitter developinga fault which potentially could put them off the air for a long period of time. This is due to therebeing NO spares available and no back up transmitter being available.

The current inspection showed that there are a number of issues in relation to the operation of thetransmitter including a number of faults. The first was that the transmitter output changesbetween 80 kW and 25 kW output from time to time. This has been traced to a faulty air flowsensor within the transmitter itself. On-site work was unable to resolve the issue due to a lackof spare parts and available “off air time”. Another fault is a potential one, which was notpossible to fully investigate. This relates to the ability to raise and lower the power output of thetransmitter from its preset low, medium and high power levels.

Other faults related to faulty RF power amplifier modules with faulty fuse indicators being active.In one of the modules investigated, there were faulty power semiconductor FET devices whichneeded to be replaced. With no spares available this was not able to be repaired.

Eight of the 16 air conditioners in the transmitter room were operational, which under someenvironmental conditions could place the transmitter in an undesired operating environmentespecially if the output power of the transmitter was increased to its full capacity.

There was no way to monitor the modulation and other performance characteristics of thetransmitter available other than a radio that could be listened to. Since it was not possible tomonitor the modulation characteristic of the transmitter, it was not possible to determine if thetransmitter was being modulated to its potential capacity, +125% for positive peaks and -95% forthe negative peaks. The audio processor was showing some times +100% positive and sometimes-95% negative at its output, but there was no AGC action and four of the five processing bandswere in a red gated state for considerable periods. This indicates that perhaps the modulationcharacteristic of the transmitter itself was not optimum.

Another operational aspect that is presently non operational is the pressurisation of the coaxialcable between the transmitter building and the antenna tuning unit (169 metres away). The airpump in the original dehydrator has failed and while a substitute has been installed, it is currentlyswitched off. It is not known if there is a pressurisation in the cable or it has just been left off.


Desired Position

In meetings with RNK, a desire was expressed to be able to provide AM broadcast coverage tothe whole of Cambodia with, if possible, a single high powered AM broadcast transmitter, to havea standby transmitter and spares to fix both transmitters. However a number of problemsassociated with this high power option were recognised and a staged approach was discussed asa possible option

Investigation

As a result of the survey undertaken and reported fully in the report RNK CAMBODIA MF 918KHZ TRANSMISSION SYSTEM, a number of issues were investigated. These included signalquality issues in the north western areas of Cambodia, Occupational Health and Safety issues,transmission site issues and transmission system design issues. The received signal quality inthe north western areas suffers from interference and selective fading. The interference ispredominately coming from other broadcasting stations, some identified as being from Thailand,whilst there was also a small amount of man made noise and selective fading, particularly at night. The selective fading is caused as a result of the ground wave and the reflected sky-wave signalsmixing. The sky-wave propagation is more predominate at sunset, night and sun rise. The areasto the north west also were considered as being on the limits of and even well beyond daytimeground-wave coverage.

Signal level measurements were made throughout the transmitter’s signal listening area with thetransmitter operating at 80 kW. The results including listening tests, were then assessed inrelation to the transmitter being increased to 200 kW. With the corrected signal levels for thetransmitter running at 200 kW, the signal levels expected in the areas of the northwest wereapproximately halfway between that used for planning purposes in relation to rural and suburbanclassifications in terms of population density. Even at these signals levels, interference is stillexpected from the external stations, as well as the selective fading (night time propagation)causing reception problems and as a result, reception will be difficult especially on low cost AMreceivers.

The level of signal that would be required for good reception in the present marginal receptionareas would require a high powered signal if it was to be radiated from a single AM transmissionsite. The high power (greater than 200 kW) is required to overcome the man made interferenceand the interference from the other stations measured and identified in the areas. Such a highpowered transmitter and antenna combination then raises many other issues, such as where tolocate such a transmitter, health and safety issues and what sort of antenna to use. Since a singleAM transmission site solution has a number of long term issues to be resolved, a decision wastaken in consultation with RNK to look at improving RNK’s signal coverage in two stages.

The first stage is to get the present 200 kW transmitter operating at 200 kW output reliably andto refurbish a 25 kW transmitter, currently available, and get this installed as a standby transmitter.Included in this stage, a number of spares for both transmitters would be provided both at themodule level and the individual component level.


The next stage is to devise a plan to provide improved signal coverage on a more general basis. Since the operation of a high powered transmitter and the associated high power antenna could,if installed at the present transmitter location, have radiation levels in excess of thoserecommended in the world standards for the general public, the present transmitter site may NOTbe suitable for such a transmission system.

Extensive residential development is currently taking place all around the present transmissionsite, except for a small area to the southeast. This raises the concern that if the radiation levelsare raised beyond what they currently are, there may possibly be in the long term, health issuesassociated with radiation . It was not possible to look at the present antenna tuning unit at thebase of the present antenna. This antenna may not be suitable for a higher powered transmitter.As a result the present antenna and ATU could possibly have to be upgraded or replaced if indeedthe present 1/48 antenna would not provide the results required.

Two other antenna types could possibly improve the signals at the extremes of the presentcoverage area. These are the use of a directional antenna system or the use of the 1/28 or 5/88height antenna (204 metres high). Both antenna types would be difficult to implement on thepresent transmission site and could have very high radiation levels which may be a health andsafety issue to the public who live near to the present transmission site. Hence as part of stagetwo, an alternative transmission site may have to be taken into account if this option was to beconsidered.

Alternatively, improved coverage could be attained by the use of re broadcast transmitters . Anold AM transmitter site at Battambang has an antenna system already in place, but it would needto be refurbished. This may be an alternative solution to provide supplementary coverage to thenorthwestern area. In other difficult reception areas low powered FM or AM formats could beused. These options are discussed more fully in the RNK CAMBODIA MF 918 KHZTRANSMISSION SYSTEM report.

In both cases the question of how to get the program signal to each of the rebroadcast locationsarises. Several ways of achieving this are possible, off air reception of the main transmitted signalfrom Phnom Penh, using an additional sound channel on the National TV satellite up link anddistribution system, leased program lines (Phone lines) or a fibre optic system. Of these options,the use of an additional sound channel on the existing National TV satellite distribution systemprovides ready access to a high quality signal at any location where a rebroadcast RNK transmittermay be required.

Recommendations

Stage 1

1 Refurbish the present Harris DX200, 200 kW transmitter to allow it to operate at it’s ratedpower output.

2 Repair and make operational the 5 air conditioners that are not currently operational3 Place perforated steel covers and warning signs on the main power transformer to rectify

a safety issue.


4 Replace the 3 port “U” link change over panel with a 4 port “U” panel to allow a standbytransmitter to be connected to the antenna or test load.

5 Provide spares for the DX200 transmitter by way of spare module assemblies including,but not limited to, RF power amplifiers modules and the Modulator Encoder PCBassembly (the two items with a failure history), spares fuses, spare FET semiconductorsas used in the RF amplifiers, temperature sensors and other general items.

6 Improve the modulation monitoring capabilities of the transmission system including amodulation monitor and a suitable audio power amplifier.

7 Place simple ON OFF transmitter control in the same equipment rack as the present inputsignal processor and where the modulation monitoring system would be located.

8 Re adjust the input signal processor to optimise the modulation characteristic of thetransmitter.

9 Replace the air pump in the Dehydrator and check the coaxial cable pressurisation.10 Refurbish the Harris DX25 to be used as a standby transmitter including replacing missing

parts that been identified.11 Install the DX25 Transmitter.12 Install a AC power distribution panel to allow the isolation of the transmitter from the AC

mains power supply.13 Install RF output rigid coaxial line to the 4 port “U” link panel.14 Install a remote ON OFF, with interlocks, in the same location as the remote ON OFF for

the DX200 transmitter.15 Install a change over system to allow the modulation monitoring system to be used with

either transmitter. A flashing light to be provided to indicate the modulation monitoringequipment is not connected to the ON AIR Transmitter.

16 Install a input signal processor for the standby transmitter.17 Provide essential spares for the DX25 transmitter including, but not limited to, spare

module assemblies and spare components.

Estimated cost US$250,000.00

Stage 2

To improve the coverage of the RNK signal throughout Cambodia, for the longer term,consideration of a number of options are available. Since it is unlikely that a single transmissionsite will provide adequate signal level through Cambodia and overcome the present interferencelevels and provide adequate signal levels for the population densities, a number of alternativesneed to be considered.

Among the options are an alternative transmission site for the present AM broadcast transmitter,the re commissioning of an AM transmitter site at Battambang and in other difficult receptionareas, low powered FM or AM formats could be used. These options being discussed more fullyin the RNK CAMBODIA MF 918 KHZ TRANSMISSION SYSTEM report.

No costing can be provided at this time because of the complexity of the issues involved.


APPENDIX D

Transmitter Site Condition

RNK - Phnom Penh - Transmission ReportDocument Template: RA-MW Document File Name: RNK-MW-ReportRelease Date: 09-12-2007 Page 46 of 69 Last Saved: 12 September 2007

MW Transmission Report

for

Radio AustraliaRNK - Phnom Penh

Submitted on12-09-2007


Prepared by Joe Sexton

Radio Australia ABC

Annual Technical ReportMajor Asset Description


Site Name: Radio Australia Site No: RNK - Phnom Penh

Inspecting Officer: Joe Sexton Date: 12-09-2007

Access Road

The Access road is a single sealed road, main entrance from Bid Samdach Monireth number 217. There is a

round about a short distance from the FM studios, The MW site is to the left.

Related Drawings: N/A

Site

Located south of Phnom Penh, the site is surrounded by residential housing and recent developments. There are

five buildings which host the FM studio and transmission services for Radio Australia and 96Mhz. A generator

building and the RNK medium wave TX building. The antenna padlock is mostly flat grass which is flooded.

Typical of Cambodia. There are no sizable trees in antenna padlock. The site is guarded 24 hours


Fencing

There is no fencing. The antennas and ACU hut are not fenced.


Buildings

The medium wave TX building is of brick construction. Typical Cambodian building that has been well

maintained, The interior is clean and well air conditioned.


Building Services

Services include pressure water, three phase power, and septic toilet. There is a microwave and FM link from the

RNK studios.


Air Conditioning & Ventilation

The Transmission room is well air conditioned (24DEG) with thirteen split system air conditioner, eight of which

are working. The rest of the building is not air conditioned.


Fire Fighting & Security

There are two dry powder 8kg fire extinguishers. One located in the tx room and the other in the main entrance.


Mains Power Supply

Three phase transformers located in the back room behind the TX hall supply the transmitter. This room is very

warm with heat being generated by the transformers.


Emergency Power Plant

The Epp is a Stamford 1000kVA water cooled diesel housed in the EPP building.


RF Transmission Systems

One service transmits from the medium wave building

1. 918 KHz – Harris DX200 – 200kW


Antennas & Feeders

The main mast is a 98mtrs tall guyed mast. The mast is not painted in hazard warning colours. There is no

standby mast. 4 1/8 feeder is used.th


Annual Technical ReportMajor Asset Description


Annual Technical ReportSite Inspection




Asset Description * Status See

Notes

Comments/Results

Access Road

Road surface OK Government Site

Gutters & drains N/A

Compound paving OK

Shoulders & verges N/A

Road signs

Site

Gardens OK Lots of vegetation surrounds the

main buildings, typical of tropical

environment

Stormwater drains N/A

General condition

Vegetation/litter control Lots of vegetation surrounds the

main buildings, typical of tropical

environment

PCB storage

Other hazards (see comments)

Water tank/s OK There is one water tank on site, no

leaks

Main fuel tank - condition

Main fuel tank - building

Environment (see comments)

Other (see comments)

Fencing

Perimeter fences A5 The permitter fence at the entrance

to the site is newly constructed,

fencing to the back of the property is

poor

Compound fences None There is no compound fence

Mast/tower fences None There is no mast fence

Stock fences None There is no stock fence

Other fences (see comments)

Gates

Signs All in good condition

Annual Technical ReportBuilding Inspection





Notes

Comments/Results

Buildings (Main)

Structure

Roof

Gutters/Downpipes N/A

Windows/Doors

External Walls

Internal Walls

Ceilings

Floors Very clean

Floor treatment

Vermin/Pest Control

Hoists etc


Building Services

Kitchen/amenities None

Water supply No drinking water

Sewage system

Toilets

Telephone(s) None

Internal lights/GPOs

External lights/GPOs None

Building earth

Earth impedance measured N/A No test equipment to test

Buildings (Other)

Structure Not Inspected Main ACU

Roof Not Inspected A1 Not inspected due to flooding in the

padlock

Gutters/Downpipes Not Inspected

Windows/Doors Not Inspected

External Walls Not Inspected

Internal Walls Not Inspected

Ceilings Not Inspected

Floors Not Inspected

Floor treatment Not Inspected

Vermin/Pest Control Not Inspected


Annual Technical ReportBuilding Inspection





Notes

Comments/Results

Air Conditioning & Ventilation

Wall mounted/plant A2

Air filters

Fluid leaks

Motors

Corrosion

Bleed-off system

Salt build-up

Operation


Fire Fighting & Security

Fire alarm board

Fire alarm log

Fire extinguishers

Hoses & reels

Pumps

Water supply/tanks

Firebreaks

Entry alarms

Movement detectors

VESDA systems


Mains Power Supply

Mains distrib transformer

Main switchboard

Distribution boards

Control (Mains/EPP)

Surge reduction filters

AVR

DC supply


Annual Technical ReportTransmission System and Document Inspection





Notes

Comments/Results

Transmission Systems

Transmitter performance A3 Air Flow alarm with reduced power

Combiners

Antenna switches

Antenna power monitor (PPP)

Tx configuration switches

Off air receivers A4 The off-air receiver is old and in

poor condition

Microwave equipment

Satellite equipment

Audio Processor 9200 Opimod

Test load cooling Not tested

Test load corrosion

Test equipment

Monitoring System

RTU Operation

Monitoring points

Forward control






Notes

Comments/Results

Transmitter Tx A DTX200 Harris

Meters

Voltage regulator

Air filtration

Pumps

Fans

Transformers A6 The transformer room is very warm.

Covers protecting the transformers

are missing

Meter readings

Ant Null 0.3

Net Null 0.4

PA+VDC 255

DC Ampl 250@ 30kW

Forward power A3 30kW – 80kW

Reflected power 0V





Notes

Comments/Results

Antenna/Feeders

Damage/broken elements

Curtain arrays (HF)

Other HF antennas

Dummy load Not tested

Receiving antennas

Satellite dishes

Antenna matching equipment Not inspected


Feeder leaks Dehydrator is turned off !! but

tested OK

Feeder clamps

Feeder earthing

Feeder connectors

Slew & field switches (HF)

Matrix switches

Power dividers & phasing N/A

Dehydrators Dehydrator is turned off !! but

tested OK

Pressurising equipment N/A

Feeder labelling


Towers & Masts

Hazard painting N/A

Protective coatings Not inspected

Corrosion Not inspected

Missing bolts Not inspected

Ladders, cages & anti-fall devices N/A

Aircraft warning lights & beacons

Signs & warnings

Mast verticality

Mast base insulator Not inspected

Mast spark gap Not inspected

Mast top loading/umbrella

Mast sectionalising coils

Guys/insulators

Guy anchor blocks

Bonding/earthing wires

Tower/mast base earthing

Earth mats

Lightning protection

Tower concrete footings



ANNUAL TECHNICAL REPORT

Notes – Infrastructure & Transmission System

Note DetailsA1 We were unable to inspect the ACU hut due to flooding in the Antenna field and

OHS issuesA2 Eight of the thirteen air conditioners in the TX hall are workingA3 The transmitter has an internal fault causing “airflow” alarms. The fault is

intermittent which causes reduced power from Normal Operating power to30kWatts. The fault is likely the air flow sensor located on the mod encoder board.Replacing the board would guarantee fault correction.

A4 The off-air receiver is old and requires replacingA5 No Perimeter fencing at the rear of the siteA6 Covers protecting the transformers are missingA7 A8 A9 A10 A11 A12 A13 A14 A15 A16 A17 A18 A19 A20

© A.R.F.C. Pty Ltd 2007 Page 57 of 69

ILLUSTRATIONS


TRANSMISSION SITE

RNK CAMBODIA

PHNOM PENH


Phnom Penh-1

General Site Location.


Phnom Penh -2

RNK AM Transmitter SiteCambodia

Key

F FM Transmitter building. Also housed radio Australia’s FM transmitterFT FM and other communication services antenna tower. Guyed mast.T AM Transmitter building RNK 918 kHz.D Diesel Generator plant buildingAT AM Transmitter tower 918 KHz insulated guyed towerATU AM Antenna tuning unit building 918 kHz transmission.GN General buildingSW1 Building that housed a HF short wave transmitter now non operationalGAR General vehicle garageSW2 Building that housed a HF short wave transmitter now non operational


SW1A HF transmitter antenna guyed mast with antenna tuning unit building at thebase

SW2A HF Transmitter antenna guyed mast with antenna tuning unit building at thebase.

LK Guyed mast with microwave link antenna mounted at the top.


RNK TRANSMITTER


Rear Of DX200 Harris TransmitterAir inlets

Top Of DX200 Harris Transmitter Air outlets


Monitoring Facilities

Power Transformer Showing Exposed Live Terminals On One Side


Existing 3 Port “U” Link Panel

Dehydrator


HARRIS DX25 TRANSMITTER

Possible standby transmitter. To be installed, frequency changed and refurbished.


ANTENNA

Note.

The notation used on the photos refers to the following antenna and infastructure

AT AM Transmitter tower 918 KHz insulated guyed towerATU AM Antenna tuning unit building 918 kHz transmission.SW2 Building that housed a HF short wave transmitter now non operationalSW1A HF transmitter antenna guyed mast with antenna tuning unit building at the

baseSW2A HF Transmitter antenna guyed mast with antenna tuning unit building at the

base.LK Guyed mast with microwave link antenna mounted at the top.


Antenna Location With Reference To The Old Shortwave Transmitter Building

918 KHZ AM Transmitting Antenna And Tuning Unit


Antenna Layout (View East)

Antenna Layout (View North East)

Documents

RNK CAMBODIA 918 KHZ TRANSMISSION SYSTEM REPORTdocuments.worldbank.org/curated/en/...RNK CAMBODIA 918 KHZ TRANSMISSION SYSTEM REPORT Prepared by G.R.Smith ARFC Pty Ltd NSW. AUSTRALIA