Is CB radio still used in UK?
(CUT OUT & PLACE AT OPERATING POSITION)
Preferred & Designated Channels
Channel 8 Agricultural operations
Channel 9 Emergencies and travel info.
Channel 13 Maritime and RV’s
Channels 16 to 18 Single Sideband only
Channel 19 Trucks/Vehicles in transit*
Channels 31 thru 40 Single Sideband Only
*Note that in many areas there are also 1 or more
additional channels designated and/ or normally used for
in-transit vehicles, often Channels 10 and/or 12. This is
especially true in metro areas and their suburbs where
Interstate Highways are on 19 and secondary roads such as
parkways are on alternate channels. Base stations are
requested to avoid using all area in-transit vehicle channels
in order to permit their full, free, unobstructed and
exclusive use by in-transit vehicles.
Stations using power mikes should be cautious that their
audio levels are set to a level which will not cause voice
distortion, over modulation, or splashover on adjacent
channels.
Single sideband stations now generally operate on
Channels 16, 17, 18, and 31 through 40, although this may
vary in specific areas. Stations using standard AM
transmission are requested to avoid use of local Sideband
channels, likewise Sidebanders are requested to confine
their transmissions to those channs established locally
The antenna on the vehicle
Firstly there is the aesthetic aspect, Le., where will
the antenna not look too conspicuous and what may
be done to avoid boring a hole in the car body. All
antennas for mobile operation must unfortunately
have a direct ground connection to the car body
which itself must be all metal. The Home Office gave
Increased efficiency
The three degrees shown in fig. 2 are optimum for
a physical length of about 1.5 metres but unfortunately they are considered illegal. The design (A) is
tuned, as it must be, to an electrical quarter-wave
length but being centre loaded more current is able
to flow in the straight portion of the radiator beneath
the coil with the result that a little more power will
be radiated. The design (B) is somewhat more complex and electrically tuned to a half-wavelength. The
base coil combination (Lm and c) form a shunt ted
low to high impedance transtormation network so
that the antenna section which includes the centre
coil.(Lc) ;s voltage fed. This design has a high rate of
efficiency although tuning and VSWR adjustment
can be critical unless certain special precautions
are taken.
Lastly we have design (C) which is the helically
wound antenna. The long coil system (Lh) can only
be made to operate electrically as either a quarterwavelength or five-eighths of a wavelength, depending on the total amount of inductance used.
Such antennas are normally series fed and it may be
difficult to get an easy adjustment of VSWR. Some
helical antennas have a small sliding top rod to
facilitate this. The five-eighths wavelength design is
the most efficient and the performance compares
favourably with that of the centre loaded half-wave
design (B). Alas the Home Office will not allow these
types of antennas to be used, at least not yet,
although for some time now they have been carrying
out tests to prove whether or not such antennas are
liable to cause interference to other services due to
radiation of harmonics emanating from the CB transmitter. This is most unlikely anyway but if the results
of the tests are satisfactory the use of such
antennas for 27MHz CB may be permitted but to
date no one knows when.