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HF Helical Antennas: Theory and Practice

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ANTENTOP- 01- 2020, # 024

HF Helical Antennas: Theory and Practice

 

 

 

Figure 2 Design of the Helical Antenna of the Broadcasting Radio Station of the 30s of the 20th Century

 

Helical Antennas of the CB and VHF radio

 

Shortened helical antennas born again in CB hand held radio for 27-MHz band. I cannot found information when first time the antennas were used in the CB radio. Military hand held radio (Squad radio, References 5) of the early time- 40- 60 do not use helical antennas. However, the shortened helical antennas began widely used in CB and VHF (144- 430- MHz) hand held radio in the times. Times are gone but helical antennas still are used in hand held radio. You may prove it on practice if you open antenna of the hand held radio. Figure 3 shows view of the typical hand held radio and design of the helical antenna.

 

Helical antennas were more effective compare to usual vertical telescopic antennas thereof the helical antenna begin to be the only one type that is used in CB hand held radio and as well in VHF/UHF hand held radio. VHF/UHF hand held radio now used not only by radio amateurs but by military and for commercial radio communication.

 

The length of standard CB helical antenna (for 27-MHz Band) is near 15- 50- cm. The antenna has resonance on 27-MHz band, or wavelength 11- meter. So shortening factor of the antenna is near 5- to 18.

The length of standard VHF helical antenna is near 5- 15- cm. The antenna has resonance on 145-MHz band, or wavelength 2- meter. So shortening Factor of the antenna is near 3- to 10.

 

MW and LW helical antennas of old broadcasting radio stations and the NikolaTesla helical antenna had almost the same shortening factor. So, we can say that for over a hundred years, shortened helical antennas have been used to work on the Air.

 

Reasons for the Small Number of Publications on Helical Shortened Antennas

 

Take to consideration of the numbers of hand held radio in the world it possible to say that the helical antennas are most widely used for radio communication one. Helical antennas as well used in old wireless phone system, in WI-FI routers, in old cell phones...

 

 

 

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January 30, 2021 14:05

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