Specifications
FCS1362 Page 32 of 74 © Nov 2010
4.2.2. Approximate frequency to wavelength conversion
A simple formula to calculate the wavelength in metres from a given frequency is:
300
Frequency (MHz)
e.g. For 150MHz, 300/150 = 2 metres
and therefore a ¼ wave is 0.5m or 50cms, a ½ wave 1m or 100cms.
Table 2 - Approximate frequency to wavelength conversion
Band Name
Frequency
(MHz)
Wavelength
(cm)
¼ Wavelength
(cm)
Citizens Band (CB) 27 1100 275
Band 1 50 600 150
Low Band 80 375 94
VHF Mid/High 150 200 50
Band 3 200 150 38
TETRA/Public Safety 400 75 19
UHF 1 420 71.5 18
UHF 2 460 65 16
800MHz Band 850 34.5 9
GSM 900 900 33 8
GPS 1545 19.5 5
GSM 1800 1800 16.5 4
UMTS 2100 14 3.5
W-LAN & Bluetooth
devices
2400 12.5 3.2
2.6GHz Band 2600 11.5 2.90
4.2.3. Locating antennas on vehicles
Refer to section 2.3.1 regarding vehicle manufacturers supplying specific information on antenna type
and location. When available this should be used as the prime guide.
The centre of the vehicle’s roof is the ideal position to achieve a good 360 degree omni-directional
radiation pattern from an antenna. Any other location will affect the antenna radiation pattern, see
Appendix F and Appendix G.
On-glass and window clip type antennas will always suffer some distortion to the radiation pattern due to
their mounting positions usually being at the edge of the vehicle ground plane.
The antenna should be located away from any vertical structure, windscreen pillar, or any structure on
the roof etc. which could act as a screen or reflector to RF.
Care should be taken when positioning the new antenna close to an existing aerial. There should be a
separation of at least half wavelength for transmit frequencies below 600 MHz and one wavelength for
transmit frequencies above 600 MHz. With complex multiple antenna installations the presence of other
antennas on the roof, especially if operating in the same frequency band, may:
a) Alter the radiation patterns of each individual antenna.
b) Cause mutual interference between the radio devices that the antennas are connected to.