Radio Communication VHF Overview

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Questions and Answers

Which department is responsible for the procurement of VHF sets?

Railway Board

User department

S&T department (correct)

DRM office

What must be reported to the controlling officer daily in the morning?

Monthly financial statements

Maintenance schedules

VHF system's failures (correct)

Procurement updates

Who is responsible for obtaining frequency authorization for VHF sets?

The Wireless Planning Commission

The S&T department (correct)

The user department

The DRM office

What action should be taken for unserviceable handsets?

Condemn them and stop license fee payment Signup and view all the answers

What types of checks must be performed on VHF sets annually?

Transmitting power and frequency stability checks Signup and view all the answers

Who is responsible for the maintenance of VHF sets in the division?

S&T department Signup and view all the answers

What should nodal supervisors do with defective VHF sets?

Inform or handover to SSE/Tele Signup and view all the answers

What document must be prepared monthly relating to VHF system failures?

A failure statement for PCDO Signup and view all the answers

What is the frequency range classified under Very High Frequency (VHF) communication?

30 MHz to 300 MHz Signup and view all the answers

Which of the following is NOT a use of VHF communication?

High-Speed Data Transfer Signup and view all the answers

What type of operation does VHF communication primarily use?

Simplex Signup and view all the answers

What is the expected maximum communication range for a fixed 25W VHF set using directional antennas at a height of 15 to 20 meters in an open area?

Up to 25 Kms Signup and view all the answers

Which of the following is NOT a limitation of VHF communication?

Communication is always clear in open areas Signup and view all the answers

In VHF communication parameters, what is the channel capacity mentioned?

All of the above Signup and view all the answers

What type of equipment is typically used in VHF communication?

Walkie-Talkie Sets Signup and view all the answers

What must be ensured when installing VHF antennas for point-to-point communication?

A line of sight is necessary Signup and view all the answers

Which type of antenna is designed to be more compact and often used in space-constrained environments?

Low Profile Antenna Signup and view all the answers

What is the primary mode of propagation used in VHF communication?

Line of Sight Signup and view all the answers

Which VHF communication function is specifically designed to facilitate safety during emergencies?

Emergency Communication Signup and view all the answers

What is the impedance required for feeder cables used in VHF installations?

50 Ohm Signup and view all the answers

What is the primary power source for fixed 25W VHF sets used in communication?

AC Mains or 12V Battery Signup and view all the answers

What factor can lead to 'dark zones' in VHF communication?

High rise buildings and terrain Signup and view all the answers

What type of power supply is generally connected to VHF sets in addition to batteries?

230V AC mains supply Signup and view all the answers

When measuring field strength for satisfactory communication, what is the recommended height for antennas?

15 to 20 meters Signup and view all the answers

Study Notes

Radio Communication (Analog/Digital VHF)

Radio communication transfers intelligence between points using radiated electromagnetic energy.
Radio waves operate in a frequency spectrum from about 10 kHz to 30,000 kHz.
Radio frequency spectrum classes include VLF, LF, MF, HF, VHF, UHF, and MW, each with specific frequency ranges and corresponding wavelengths.
VHF communication operates in the 30 MHz to 300 MHz frequency band.
Indian Railways uses the 146.2 MHz to 167.95 MHz band for VHF communication.
VHF communication relies on line of sight, reflection, and scattering of waves.
VHF applications include traffic control, police duties, mobile communication, point-to-point communication, point-to-multipoint (group) communication, and disaster management.

VHF Frequency Range and Parameters

The frequency range for VHF communication is 30 MHz to 300 MHz.
The frequency band used by Indian Railways is 146.2 MHz to 167.95 MHz.
VHF communication uses one frequency per channel.
The propagation modes are line of sight, reflection, and scattering.
Operation types include simplex and duplex.
Channel capacity options range from 1 to 256-channel voice or low-speed data.

VHF Equipment and Specifications

VHF equipment includes walkie-talkies (handheld), 25W portable sets, and fixed 25W base stations.
Walkie-talkies (handheld) use NiMH/Li-ion batteries with 1W to 5W output.
Portable 25W VHF sets are typically used in locomotives and vehicles powered by 12V batteries.
Fixed 25W VHF base stations are generally installed in designated locations and operate on AC mains or 12V batteries.
Antennas used include whip, ground plane, dipole, low profile, and Yagi.
The feeder cable must be 50-ohm unbalanced coaxial cable.

Communication Range and Limitations

Expected communication range in open areas for walkie-talkies is 1-2 km, portable sets 12-15 km, and fixed sets up to 25 km (with height of 15-20 m).
The range may be reduced by terrain, obstructions, and other factors.
Communication is limited by line of sight and can be affected by buildings and terrain.

Maintenance and Inspection

Maintenance and condemnation of VHF sets is handled by the S&T department.
Defective sets are reported to the respective supervisors and teams for repair.
Monthly and yearly inspections of VHF installations and equipment are required.
Regular maintenance, including frequency verification, ensures reliable communication.

Reporting and Spare Parts

Failure reports of VHF systems should be submitted daily.
Monthly failure summaries must be reported.
Spare units must be stored at a suitable location to replace faulty equipment.

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Description

This quiz explores the principles of radio communication, specifically focusing on VHF (Very High Frequency) technology. It covers frequency ranges, applications in various sectors including Indian Railways, and the operational characteristics of VHF communication. Test your knowledge on the fundamentals of this essential communication medium!