Specifications

FCS1362 Page 31 of 74 © Nov 2010
Covert type antennas can be either a modification of an existing body mounted antenna (e.g. bee sting)
or an internally fitted unit. Internal, discreet or covert types generally have a reduced performance
compared to conventional antennas due to their design and/or mounting location. Consideration should
be given to their suitability for the customer’s application before fitting this type of antenna. See Appendix
G for information regarding antenna performance of covert antennas.
Active type antennas incorporate a powered amplifier. These are considered as an electronic sub
assembly (ESA) and should carry 'e' or CE mark as per section 2.2.1.
4.1.1.1. Internal antennas
If a vehicle manufacturer states that internally radiating antennas – i.e. an antenna fitted within the interior
of the vehicle – cannot be fitted then this may affect the proposed antenna type for the installation.
4.1.1.2. Antenna bases and whips
It is not advisable to mix and match antenna bases and whips from different manufacturers as this could
lead to poor performance or damage to equipment due to an impedance mismatch.
4.2. Antenna installation
The antenna must be:
• The correct type for the application and frequency used by the radio equipment
• Located in the recommended position and of a suitable type for the vehicle. Refer to the vehicle
and antenna manufacturer’s guidelines.
• Installed correctly and, if exposed to harsh environmental conditions, sealed to prevent ingress of
dirt and water.
Following antenna installation:
• All connections should be electrically tested see section 4.8.1
• Where required ensure that a VSWR test shows a satisfactory match is obtained – see section
4.8.2
Before and after replacing any vehicle trim that may have been removed to install the antenna it is
advisable to carry out the antenna checks to ensure the cabling and installation has not been
compromised.
Additional information on testing antennas is contained in section 4.8 and example radiation patterns
illustrated in Appendix E.
4.2.1. Avoiding interference
EMC issues may occur with an antenna install in two ways:
a) Radiated EMI - Interference may occur to in-car entertainment equipment or other vehicle electrical
equipment. If possible this should be checked before final fixing of the antenna on the vehicle, see
section 5.3.1
b) The antenna may pick up noise received from the vehicle or other fitted role equipment such as light
bars, GPS processors and other digital (computing) equipment and present it to the radio equipment
as interference.
Repositioning, or a different type of antenna, should be considered if either type of interference occurs. It
is good practice to site the antenna at the greatest distance possible from the offending equipment, and
any antennas or cables it has, to minimise these EMC problems.
Also see section 4.2.5.1 regarding the antenna co-axial cable.