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.
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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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