VHF SET (25 WATT) - Indian Railwayrdso.indianrailways.gov.in/works/uploads/File/Handbook on VHF set... · VHF SET 25 WATT December’2002 VHF SET (25 WATT) 1. Introduction It is used

CAMTECH/S/2002/VHF/1.0 1

VHF SET 25 WATT December’2002

VHF SET (25 WATT)1. Introduction

It is used as VHF equipment for base stations andmobile VHF set for Locos of Universal emergencycommunication system in Indian Railway. Theobjective of the universal emergencycommunication system is to install a system forestablishing following communication:

i. Driver and Guard of a train and vice versa.

ii. Driver of a train in section and Stationmaster of nearest station and vice versa.

iii. Guard of a train in section and Station masterof nearest station and vice versa.

iv. Driver and Guard of a train in section andDriver and Guard of another train within thevicinity of 7.5 kms.

v. To extend communication from driver/guardto section controller, when required, with thehelp of interface units at base units.

vi. Driver/ Guard/Station master initiate distresswarning calls to the train/ stations which areequipped with mobile communicationsystems and are with in the vicinity of 7.5kms from the origin of distress signal.



For above communication emergencycommunication system is consist of following subsystems.

a. VHF equipment for base station.

b. Mobile VHF set for Locos.

c. Hand held VHF walkie talkie set.

d. Ground plane antenna for base station.

e. Low profile antenna for Locos.

f. Power supply for mobile VHF set in Locomotive (Electric).

g. Power supply for mobile VHF set in Locomotive (Diesel).

At base stations VHF sets of 25 watt and at locosmobile VHF set of 10 watt are being used. Thishandbook covers operating instructions,installation, testing & maintenance of VHF set 25watt.

2. Description

VHF set 25-watt equipment is installed in eachRailway Station to work as the base station foremergency communication system. The equipment



is fixed permanently in suitable location inside thestation master room. The VHF set is primarilymeant for emergency communication between thestation and the train. However in exceptional casesthe equipment is also used be used forcommunication between two adjacent stations.

An omnidirectional ground plane antenna fixed at asuitable height, mounted on a GI pipe or alightweight mast erected by the side of the stationbuilding. Low loss coaxial VHF cable is connectingthis antenna to the VHF equipment.

The VHF set is mounted on the top of the table orfixed on the wall adjacent to the station master onduty. The VHF set is provided with speaker & handheld microphone with press to talk switch havingflexible connecting cord.

The power supply is provided through a 12-voltbattery bank of minimum 40 AH capacity. There isan interface unit at each base station for manualpatching with control circuit.



2.1 Design Philosophy

The design of the VHF base station equipment isbased on microprocessor controlled frequencysynthesis.

2.2 Channeling Scheme.

VHF set is programmed for two channels minimum.The distributions of these channels are as below:

Channel 1: Frequency F1 allocated forvoice communicationamongst drivers, guards andstation masters.

Channel 2: Frequency F2 allocated fordistress warning ( SOS ).

2.3 Channels

The radio is capable for setting upto 16 channels.These channels can not be programmed through anycontrol switches of the radio panel. Eithermanufacturer or Railway’s authorised staff can doprogramming.



2.4 Frequency Band

The system is operate in 146.2 – 151.25 MHz and159.6 – 169.95 MHz bands. The exact frequenciesare as under:

F1 = 160.400 MHz & F2 = 160.450 MHz

2.5 Modulation : Frequency Modulation

2.6 Channel Spacing : 12.5 KHz

2.7 Mode of Operation : Simplex

2.8 Frequency Stability : + 5 ppm

2.9 Supply Voltage : 12 Volt DC (Nominal)

2.10 Antenna Impedance : 50 ohms

2.11 Receiver

Receiver is equipped with the facility of scanningchannel. The channel frequencies of the receiver areprogrammable.

2.12 Channel Selection

When powered the radio shall automatically selectemergency voice channel-1 with facility of“scanning channel -2” i.e. SOS channel. No separatechannel selection is required.



2.13 SOS channel

Channel 2 is designated as SOS channel fortransmission of distress call. SOS cal is initiated bypressing of two buttons simultaneously for at least 3seconds. The buttons are red colored and the letter‘S’ is engraved on the buttons in luminous paint.The SOS channel is scanned at least once in tenseconds. There is not perceptible cut in the speechwhen the SOS channel is scanned.

2.14 Distress Calls (SOS call)

This system have provision for transmission ofdistress call (SOS) to approaching trains as well asstations within a radius of at least 7.5 Km. Thedistress call is consist of suitable continuousmultifrequency audio tone. The tone is consist oftwo frequencies i.e. 941 Hz and 1633 Hz transmittedfor 3 seconds alternately for a total duration of 30seconds. This cycle of transmission of SOS willrepeat on its own once again after an interval of 30seconds. The stability of these frequencies is betterthan + 1 Hz. The retransmission of the SOS signal isrequired to ensure that all radios in the vicinity ofSOS origin to receive the same.

The distress call can be initiated by station masters.After transmission of SOS, the VHF sets is returnsto normal voice operation. The transmission of SOStone is suitably displayed through LED indicationon the front panel of the equipment to attract



attention of station master/cabin staff. The time anddate of SOS transmission is get recorded on the‘Event Logger’.

2.14.1 SOS Acknowledgement

When SOS is received, suitable audio-visual alarmis operated, which will stop only when thedesignated acknowledgement button ‘A’ is pressed.This arrangement is provided in the equipment itself. The date and time of reception of SOS signal isalso get recorded on the ‘Event Logger’. The buttonA is green colored with ‘A’ engraved in luminouspaint.

2.14.2 Event Logger

It is an integral part of the VHF equipment. Theformat of data to be recorded on Event Logger haveat least three parameters namely date, time andtransmission reception of SOS signals. Thenecessary software and interface for down loadingthe data from the event logger on a PC printer issupplied by the vendor.

2.15 Interfacing with control circuit

It is possible to extend communication from driverguard to section controller, when required. It isachieved by using interface units at base units. Thisunit is provide the interface from 4 wire omnibuscircuit to the radios. Transmission of a DTMF signal



over 4 wire control is executed by pressing PTT(Press to talk) switch of VHF equipment. Theextension of omnibus circuit to the radio at the basestation is achieved by patching the control circuitmanually through the interface unit.

2.16 Transmitter

2.16.1 Power output antenna port : 40 Watt switchable to25 w and 10 watt.

2.16.2 Frequency deviation : ±2.5 Khz (max)

2.16.3 Spurious emission : Better than 60 dbc

2.16.4 Transmitter output impedance : 50 ohms

2.16.5 Modulation sensitivity : Better than 10 mV at ± 1.5KHz frequency deviation.

Modulation distortion: Better than 5% at 1 KHz and± 2.5 KHz frequency deviation.

2.17 Receiver

2.17.1 Sensitivity: Better than 0.25 micro volt for 12 dbSINAD.

2.17.2 Adjacent channel selectivity: not less than 70 dbbelow carrier frequency.

2.17.3 Spurious and image rejection Better than 6 dB.



2.17.4 Audio output : Not less than 5 Watt at full volume.

2.17.5 Volume control : The minimum setting of volumecontrol is adjusted to 1 watt.

2.17.6 AF response: between + 1 dB and –3 dB withreference to 1 KHz over the frequency range 300 Hzto 3000 Hz.

2.17.7 Squelch: Adjustable from 0.5 micro volt to about 2micro volt.

2.17.8 Hum and noise: Level is 40 dB below the ratedaudio output when measured at nominal level ofinput RF signal.

2.17.9 Inter modulation immunity: Better than 70 dB.

2.18 Indications:

Following indications are provided in the equipment:

A) Power ON (Steady) low battery(flashing) -Green LED.

B) Transmitter ON (Steady), SOS transmission(Flashing) – Yellow LED.

C) Receiver ON (Steady), SOS reception(Flashing) – Red LED.



2.19 Power supply

12 V Battery bank of minimum 40 AH capacity ofmaintenance free VRLA batteries with suitablechargers.

Voltage : 12 volt DC nominal.

2.20 Antenna :

The base VHF sets is work with ground planeantenna which is permanently fixed on a GI pipe ora light weight mast of suitable height erected by theside of station building. Connection between theequipment and the antenna is provided with low lossco-axial VHF cable with loss less than 2.5 dB per100 meters.

2.21 Speaker:

VHF sets have a heavy-duty loudspeaker 5-wattoutput, which may be in-built, or external.

2.22 Microphone:

The equipment is provided with high efficiencyhand held microphone with press to talk switch.



2.23 Ground Plane Antenna

Ground plane antenna is used at base stations foremergency VHF communication. Features are asbelow:

2.23.1 Frequency Band 159.6 – 169.95 MHz tuned

for 160.40 & 160.45 MHz.

2.23.2 Power handling capacity 50 Watt (mini)2.23.3 VSWR 1.3:12.23.4 Antenna Impedance 50 ohms2.23.5 Antenna Gain Unity2.23.6 Polarisation Vertical2.23.7 Radiation Pattern Omni Directional2.23.8 Connector N type2.23.9 Height 1.5 m2.23.10 Weight Less than 2.5 Kg.

2.23.11 Mounting Arrangement

Antenna is supplied with suitable arrangementfor mounting it on the mast or pipe.

2.23.12 Maximum Wind Speed 200 KMPH

2.23.13 Environmental condition OperatingTemperatureRange –10 to +650C





3. Installation

3.1 Planning

The base station/control station provides the radiowith a desk microphone and power supply for use ata fixed location. Select a location near to thestationmaster’s chair or it shall be on the table ofstationmasters.

Location shall be as close as possible to where theantenna cable enters the building. Also ensure thatAC power supply available and sufficient air canflow around the radio to permit adequate cooling.

3.2 Tools required

Following tools are required for installing thetransceiver:

Electric drill Drill bits of different sizes Hammer Screw driver

3.3 DC Power Cable connection

I. Check for an existing hole convenientlylocated through which the DC power cablecan be passed.



II. If no hole exists, install a rubber grommet bydrilling a hole.

III. Run the two-power cable leads.

IV. Start routing the power cable while keepingthe plug end of the cable at the transceiver.

V. Connect the red lead to the positive (+)battery terminal or switched power source,and the black lead to the negative (-) batteryterminal.

VI. Always locate the fuses as close to thebattery as possible.

VII. The transceiver operates in 12 V DC withnegative ground systems only. Always checkthe battery polarity before installing thetransceiver.

VIII. Coil up the surplus cable and secure it out ofthe way with the appropriate retaining strap.

IX. Ensure enough slack is available in thecables so that the transceiver for servicingwith the power applied.



3.4 Transceiver Installation

I. Before installing the transceiver using themounting bracket, connect the antenna andthe supplied DC power cable to thetransceiver.

Figure given below shows the various parts of VHFset:

1. Microphone2. Microphone hanger3. DC power cable4. Mounting bracket5. Speaker-jack cap6. Hax headed screw7. Self-tapping screw8. Spring washer9. Flat washer



I. Install the transceiver on the table or nearer tostationmaster in such a way that the controls ofthe front panel are within easy reach of the user.

II. Use the mounting bracket as a template tolocate the holes, then drill the holes andmount the transceiver.

III. Leave sufficient room at the rear of thetransceiver for cable connections.

The diagram given below will guide in makingconnections to the transceiver.



4. Operating instructions

Figure given below is a typical front panel diagramof 16 channel transceiver model GM 300(Motorola).



4.1 To turn the Radio On

Turn ON/OFF Volume knob to the right until itclicks. The LED lights will show the last status ofthe radio and a start-up tone will be heard.

4.2 To Receive

Set the volume by turning the ON/OFF volume knobclockwise.Select the channel by pressing the UP/DOWNbutton.. Continued pressing of the button will scrollthrough the channels.

To monitor a channel, press the Monitor button totake the microphone off hook. When in the monitormode, the amber monitor LED will light steady.

To unsquelch the radio, press and hold the monitorbutton for 2 seconds. To leave the unsquelch mode,press the monitor button again. This will return theradio to the coded squelch mode.

A short beep tone will be heard whenever a validkeypress is made.

4.3 To transmit

When the channel is clear, press and hold down thePTT button on the side of the microphone and speakslowly and clearly. The Transmit/Busy LED will



remain red until the PTT button is released toindicate that you are “on the air”.

.The red Transmit/Busy LED will flash wheneverthere is another carrier on the selected channel.

4.4 Channel Scan

The set may have preprogrammed scan list for eachactive channel and a single user scan list which canbe programmed from the front panel.

4.4 To turn Scan ON or OFF

Press the scan button. The radio will only scan whenthe microphone is on hook.

Green display segments will light to indicate thatscan is functional. Use the select button to advancethrough the various scan types.

When an active channel is detected, the channelnumber will be displayed and you will hear the call.To leave scan, press the SCAN button.

4.5 To respond to scanned channel activity

When the microphone is lifted off hook, the radiowill suspend scanning and return to the channeldisplayed before entering scan. If you wish totransmit on another channel, press the up/downbutton to reach the desired channel. Scan willresume after replacing the microphone on hook.



4.6 To delete a nuisance channel

While receiving an undesired transmission, holddown the select button for 2 seconds and thenuisance channel will be temporarily deleted.Priority channels and the home channel can not bedeleted.

4.7 To create or modify the user list

Hold the Scan button for 2 seconds until you hear asecond chirp tone and the channel number flashes.The displayed channel can be added or deleted fromthe user scan list by pressing the select button.

A vertical segment in the upper left corner of thedisplay will light and flash, alternating with thechannel number, to indicate that the flashing channelhas been added to the scan list. List segment willdisappear when the channel is deleted.

Use the UP/DOWN and select button to add ordelete other desired channels in user list.

4.7 To select Priority for the user list

Go to the desired channel and hold the select buttondown for 2 seconds. The scan LED will flash toindicate that this is the first priority channel. Repeatthe process to select a second priority channel.



Priority two will be indicated by a steady light onthe scan LED.

The priority one channel must be programmed first,followed by the first priority channel. Deletingeither priority channel will delete both channelssimultaneously.

5. Maintenance Schedule

Sr Activity to check TCM/MCM

JE/SESection

SSE/ I/C

1. Status of VHF set checkby test room.

Daily Monthly Quarterly

2. Status of all VHFsimplex / duplex setsinstalled at base stationsby line staff.

Daily Monthly Quarterly

3. Testing for Working ofchannels.

Monthly Quarterly Halfyearly

4. Check of Voltage andSp.Gravity of battery set

Weekly Monthly Quarterly

5. Check of power supply Weekly Monthly Quarterly

6. Check of antenna and it’ssupport and feeder cable.

Weekly Monthly Quarterly

7. Earthing Weekly Monthly Quarterly



5. Joint inspection report of set

Sr.

Des

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Supp

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On

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ain

On

char

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Def

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bas

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Def

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for r

epai

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Lyin

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Bei

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for s

ome

purp

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othe

r tha

n gu

ard/

driv

erco

mm

unic

atio

n

Rem

arks

1 VHF set Make 1. 2.

2 Batteries Make 1. 2.

3 Charger Make 1. 2.

Condition of electric Input AC voltage Output AC voltagewiring = before CVT= from CVT=

( ) ( )

Signature JE/SE/SSE/Tele Signature of Station I/C With date and stamp With date and stamp

Sr.DSTE Sr.DME Sr.DOM



7. Do’s & Don’ts

7.1 Do’s

I Turn off the power immediately if anabnormal odor or smoke is detected comingfrom the transceiver.

II Always check the battery polarity andvoltage before installing the transceiver.

III Radio must be switched off while installingor removing the system.

IV Turns off transceiver in area where blastingis in progress.

7.2 Don’ts

I Do not operate radio while taking on fuel, orwhile parked in gasoline service stations.

II Do not operate radio when anyone istouching the antenna or when anyone isstanding within one meter of antenna toavoid the possibility of radio frequencyburns or related physical injury.

III Do not operate transceiver in area whereblasting is in progress. Transmitting withtransceiver can cause dynamite blasting capsto explode if such operations occur within150 meters of the blasting caps.

IV Do not attempt to configure the transceiverwhile driving because it is simply toodangerous.



V Do not modify the transceiver for anyreason.

VI Do not expose the transceiver to long periodsof direct sunlight.

VII Do not place the transceiver near heatingappliances.

VIII Do not place the transceiver in excessivelydusty areas, humid areas and unstablesurfaces.

IX Do not use any radio having damagedantenna.

Documents

VHF SET (25 WATT) - Indian Railwayrdso.indianrailways.gov.in/works/uploads/File/Handbook on VHF set... · VHF SET 25 WATT December’2002 VHF SET (25 WATT) 1. Introduction It is used