Specifications

FCS1362 Page 36 of 74 © Nov 2010
check the specification with the supplier. As a guide the cable should have a minimum of 90% braid
coverage
In addition to attenuation, consideration should be given to the impedance – a tolerance of +/-2Ω at 1GHz
and +/-4Ω at 2GHz is acceptable.
It should be noted that some cable types may not be suitable for use in the higher frequency bands (e.g.
above 1800MHz) – if in doubt check the manufacturer or suppliers specification.
Double shielded coax cable has an additional foil shield around the dielectric which often combined with a
different dielectric material, improves the attenuation performance of the cable especially at higher
frequencies.
Table 3 - Coaxial Cable – Typical Loss per Metre for Different Types
Coaxial Cable
–
Typical Loss per Metre for Different Types
Frequency
►
▼Cable Type
80MHz
(Low
Band)
150MHz
(High
Band)
220MHz
(Band 3)
400MHz
(TETRA
Airwave)
900MHz
GSM900
1800MHz
GSM/
PCN
2100MHz
3G UMTS
RG174
2.7mm diameter
0.2dB 0.3dB 0.5dB 0.7dB 1.0dB 1.2dB 1.4dB
3.5mm diameter
Double Screen
0.15dB 0.2dB 0.3dB 0.5dB 0.7dB 0.9dB 1.1dB
RG58/URM76
5mm diameter
0.1dB 0.15dB 0.2dB 0.3dB 0.45dB 0.7dB 0.8dB
5mm diameter
Double Screen
0.07dB 0.1dB 0.15dB 0.22dB 0.3dB 0.45dB 0.55dB
Excess coaxial cable should not be coiled up as this may affect the tuning of the antenna as well as
producing electrical interference. It is best practice to cut the cable to the correct length and then
terminate it accordingly. Some antenna kits are, however, supplied with pre-terminated connectors and it
may be necessary to retain the full cable length that should be “laid out” over a larger area instead of
being coiled.
If the provided cable is too short, where possible, a suitable cable of the correct length should be used to
replace it. Where an extension cable is required the correct method of joining lengths of coaxial cable is
the fitment of quality low loss connectors to each end of the cable maintaining the correct impedance and
loss properties throughout the total length. The consequences of the additional loss should be considered
Jacket Braid Dielectric
Conductor
Foil
Conductor
Standard RG58/URM76 cable
Double shielded 5mm cable