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CONTENTS• INTRODUCTION• Working • application• ADVANTAGES• Conclusion • references

A helical antenna is a specialized that antenna emits and responds to with rotating (circular) polarization. These antennas are commonly used at earth-based stations in satellite communications systems. This type of antenna is designed for use with an unbalanced such asThe center conductor of the cable is connected to the helical element, and the shield of the cable is connected to the reflector.

CONSTRUCTION DIAGRAM

WORKING OF HELICAL ANTENNA

A helical antenna is an antenna consisting of conducting wire wound in the form of a helix.

this antenna can operates in one of two principle modes,

1. NORMAL MODE2. AXIAL MODE

NORMAL MODE In this modes the dimension of helix are small compare with the wavelength this antenna typically used mobile communication

AXIAL MODEIn this modes the helix dimensions are at above the Wavelength of Operation.The antenna the falls under the class of waveguide antenna and produces True circular polarization.These antenna are best suited for space communication

AXIAL MODE

• Model 8617-810 - High Gain UHF High Power Helical Antenna

• For uplinks to UHF satellites, this antenna operates from 236 - 330 MHz with right-hand circular polarization with a gain of 12 to 17 dBic.

• Overall length is 10 feet. A special perforated metal cup reflector increases gain and reduces side lobes.

• The antenna comes complete with an elevation/azimuth pipe mount allowing for elevation adjustments from horizon to 65°. Equipped with a type N connector, this antenna can handle up to 1 KW of RF

EXAMPLE OF HELICAL ANTENNA

Model 8617-800UHF 12 - 17 dBic Gain

APPLICATION• High Gain • RH Circular Polarization • Adjustable Tilt Stainless Steel Bracket • Type N Female Connector • DC Grounded for lightening protection • Rugged, Lightweight and Waterproof

• Greater Bandwidth (range 400MHz to 900MHz,14dB)

• greater gain• more flexibility• Uni-directional antenna• crystal clear transmision

We conclude A Helical antenna is We conclude A Helical antenna is broadband VHF and UHF.broadband VHF and UHF.This antenna are right hand This antenna are right hand circular polarization.circular polarization.

This antenna can operates in one of two principle modes,

REFERENCE:

Electronics Communication System

AuthorGeorge Kennedy & Bernard Davis

Website :-en.wikipedia.org/wiki/helical_antennaen.wikipedia.org/wiki/helical_antennaand google searchand google search