Radio Communication (Analog/Digital VHF) PDF

CHAPTER XI ========== 1. RADIO COMMUNICATION =================== 1. "Communication by Radio" means the transfer of intelligence from one point to another through space using radiated electromagnetic energy (Radio Waves) (in the FREQ spectrum of from about 10KHz to...

CHAPTER XI ========== 1. RADIO COMMUNICATION =================== 1. "Communication by Radio" means the transfer of intelligence from one point to another through space using radiated electromagnetic energy (Radio Waves) (in the FREQ spectrum of from about 10KHz to about 30,000 KHz.) **Class** **Freq. Range** ----------- ----------------- -- VLF LF MF 300-3000 kHz HF 30-300 MHz UHF 300-3000MHz MW 3 to 30 GHZ 2. The objective of any communication is to pass information from one place to another. Radio Communication consists of generation, propagation and reception of electromagnetic waves. Modes used in Indian Railways are- - VHF Communication - UHF Communication - M/W Communication 3. VERY HIGH FREQUENCY (VHF) COMMUNICATION ======================================= Uses of VHF =========== - Traffic Control - Police Duties - Mobile Communication - Point to Point Communication - Point to MultiPoint (Group) Communication - Disaster Management - Communication during Maintenance and Construction Blocks - Yard communication - Communication in the train between Guard & Driver. - Mobile Communication in between moving train/vehicle with fixed location (Station) or another moving train/ vehicle. - Emergency Communication: - ART equipped with hand held and base station VHF sets - Duplex VHF Sets are utilised for - Extension of exchange number to distant place. - Control working.( Train Traffic Control )/Patching. 2. SPECIFICATION & PERFORMANCE PARAMETERS ====================================== 5. **VHF PARAMETERS** 1. Frequency Range - 30 MHz to 300 MHz - Frequency Band used in Railways is 146.2 MHz to 167.95 MHz. - One spot frequency is used for each channel 2. Mode of Propagation: 3. Type of operation: Simplex 4. Channel capacity: - 1/16/128/256 channel - Voice or Low speed Data or both. 5. Type of Equipment: i. Walkie-Talkie (Hand Held) Set- ii. Portable 25W VHF Sets -- iii. Fixed 25W VHF sets (Base Stations) -- Installed at desired locations , mainly at ASM rooms. - Operating on AC Mains or by 12V battery. - External antenna with feeder cable connector mounted on a mast by itself or on Roof top as needed. ( For digital 25W 6. Antennas used - Whip Antenna - Ground Plane (GP) Antenna - Dipole - Low Profile - Yagi Antenna 7. Feeder cable: 8. Expected Communication Range in open area: - Walkie -Talkie to Walkie - Talkie - 1 to 2 Km. - Portable Set can transmit - 12 Km to 15 Km. - Fixed 25W VHF Set to Fixed 25W VHF Set - upto 25 Kms when antenna used are directional & fixed at the height of 15 to 20 metres. 9. License: 10. Frequencies allotment: 6. LIMITATIONS OF VHF COMMUNICATION ================================ - Range limited up to 25 Km maximum due to requirement of line of sight. - Dark Zones occur due to terrain, high rise buildings & other structures. - VHF sets consume more power, hence the set may require more than one battery set for long duration usage. - Interference due to other users operating at the same frequency. - Effect of prevailing noise in the surrounding. 7. Digital radio VHF sets ====================== INSTALLATION OF VHF =================== - For point-to-point communication availability of line of sight is essential. - Antenna height must be decided at both locations by measuring minimum field strength needed for satisfactory communication. This can be measured by putting one trans-receiver at one end and mounting antenna at a suitable height of 15m to 20 m and measuring the field strength by field strength meter at receiving locations. VHF sets of the same power and frequency can also be installed to check the quality of communication. Antenna height and orientation can be adjusted to get a maximum signal strength or voice. - Antenna can be mounted on a tower/Mast of approved design or on a pipe on the roof of a building. Feeder cable must be of 50 Ohm. impedance unbalanced of approved design. Antenna and its feeder cable must be earthed as per earthing arrangement defined in chapter XXIII. - Connectors used must also be of good quality and supplied by an approved supplier. - 230V AC mains operated power supply of rated voltage & current is supplied by the supplier along with VHF set. A 12V/80-120 AH battery must be connected on float to the set to prevent communication failure during mains failure. 4. VHF Walkie/Talkie Sets ====================== 8. VHF Walkie/Talkie sets are used in several departments of the Railways. PCSTE with approval of GM and Sr. DSTE with approval of DRM shall distribute these sets among various departments and units under their jurisdiction in view of safety, train operation, security and maintenance. 9. Procurement of VHF sets and their condemnation shall be done by the S&T department.as per RDSO procedures and Railway Board guidelines. 10. The S&T department of the divisions shall be responsible for obtaining frequency authorization and obtaining license from Wireless Planning Commission. It shall also be responsible for payment of spectrum charges and license renewal of the entire population of the VHF sets being used in the division. Funds for the procurement, initial license fee and its subsequent annual renewals of license shall be provided by the respective user department. 11. Maintenance of VHF sets ======================= a. Maintenance of the VHF sets for the entire population of the division is the responsibility of the S&T department. b. Nodal supervisors of the user department shall inform or handover defective sets to the concerned SSE/Tele. c. SSE/Tele concerned shall then arrange for repair/replacement of these sets for minor defects departmentally and for major defects through authorized agencies/OEM. d. The unserviceable handsets should be expeditiously condemned and payment of license fee for those sets to be stopped. e. VHF set's transmitting power at different frequencies/channels are to be measured once in a year. f. Spurious emission squelch operation current drain frequency stability, frequency deviation, sensitivity of receiver & adjacent channel selectivity are to be checked once in a year in the centralized repair center or during repair through authorized agencies/OEM. g. List of Standard Testing Tools for VHF sets in the centralized repair center include Digital Multimeter, Communication radio test set, Dummy Load, Variable power supply, 0-30V, 0-30 A, Battery analyzer, Digital load for battery test, Channel programming kit etc. 5. INSPECTION ========== FAILURE REPORT ============== - VHF system's failure must be reported to the controlling officer daily in the morning. - Monthly statements of a failure must be reported in the PCDO to Headquarter. - Spare sets must be kept at site or at a suitable location to replace the faulty sets. -x-x-x- =======