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GFK-2489 Chapter 6 Installation 6-9
6
Feedlines
The choice of feedline used with the antenna should be carefully considered. Poor-quality
coaxial cables should be avoided, as they degrade both transmission and reception. The
cable should be kept as short as possible to minimize signal loss.
For 900 MHz systems with cable runs of less than 20 ft./6m, an inexpensive cable type such
as Type RG-8A/U may be acceptable. For longer runs, or for 2400 MHz systems, we
recommend using a low-loss cable type such as Andrew Corp. HELIAX® cable.
The choice of cable depends on the required length, cost considerations, and the amount of
signal loss that can be tolerated. The table below lists several types of popular feedlines and
indicates the signal losses (in dB) that result when using various lengths of cable at 900 MHz.
10 Feet 50 Feet 100 Feet 500 Feet
Cable Type (3.05 m) (15.24 m) (30.48 m) (152.4 m)
LMR-400 0.39 dB 1.95 dB 3.90 dB Unacceptable Loss
1/2 inch HELIAX 0.23 dB 1.15 dB 2.29 dB 11.45 dB
7/8 inch HELIAX 0.13 dB 0.64 dB 1.28 dB 6.40 dB
1-1/4 inch HELIAX 0.10 dB 0.48 dB 0.95 dB 4.75 dB
1-5/8 inch HELIAX 0.08 dB 0.40 dB 0.80 dB 4.00 dB
. The next table shows the same data for 2400 MHz systems.
10 Feet 50 Feet 100 Feet 500 Feet
Cable Type (3.05 m) (15.24 m) (30.48 m) (152.4 m)
LMR-400 0.70 dB 3.50 dB 6.61 dB Unacceptable Loss
1/2 inch HELIAX 0.35 dB 1.73 dB 3.46 dB 17.3 dB
7/8 inch HELIAX 0.20 dB 0.99 dB 1.97 dB 9.85 dB
1-1/4 inch HELIAX 0.15 dB 0.73 dB 1.45 dB 7.50 dB 1
-5/8 inch HELIAX 0.13 dB 0.63 dB 1.25 dB 6.25 dB