User's Manual

MDS 05-6302A01, Rev. B MDS Mercury 16E Technical Manual 53
Invisible place holder
Figure 36. Typical Yagi Antenna (mounted to mast)
Feedlines
The choice of feedline used with the antenna should be carefully consid-
ered. Poor-quality coaxial cables should be avoided, as they will
degrade system performance for both transmission and reception. The
cable should be kept as short as possible to minimize signal loss. We
recommend using a low-loss cable type suited for the frequency of oper-
ation, such as Heliax
®
.
Table 16 lists several types of popular feedlines and indicates the
approximate signal losses (in dB) that result when using various lengths
of cable at 1800 MHz. Note that losses will be approximately doubled
for 3650 MHz and tripled for 5800 MHz. The choice of cable will
depend on the required length, cost considerations, and the amount of
signal loss that can be tolerated.
NOTE: The authority to operate the transceiver may be void if
antennas other than those approved by the applicable regula-
tory authority are used. Contact your factory representative for
additional antenna information.
Table 16. Length vs. Loss in Coaxial Cables at 1800 MHz
Cable Type
10 Feet
(3.05 m)
50 Feet
(15.24 m)
100 Feet
(30.48 m)
500 Feet
(152.4 m)
RG-214 1.52 dB 7.6 dB Unacceptable
Loss
Unacceptable
Loss
LMR-400 0.78 dB 3.9 dB 7.8 dB Unacceptable
Loss
1/2 inch HELIAX 0.46 dB 2.3 dB 4.58 dB Unacceptable
Loss
7/8 inch HELIAX 0.26 dB 1.28 dB 2.56 dB Unacceptable
Loss
1-1/4 inch HELIAX 0.20 dB 0.96 dB 1.9 dB 9.5 dB
1-5/8 inch HELIAX 0.16 dB 0.8 dB 1.6 dB 8.00 dB