TRAK MODEL 9100 MODULAR FREQUENCY/TIME SYSTEM
TM4400013 E-
8
REV.
D
2-1.1 Calculating Antenna System Gain
As stated in paragraph 1-3, when selecting the coaxial cable type and length it is very important to maintain the
external gain within the limits of the GPS receiver. For the TFS models: 8821, 8900, and 9000 the gain must be
greater than 13 dB and less than 23 dB with an optimum gain of approximately 18 in front of the GPS receiver.
The TFS Model 9100 gain must be greater than 18 dB but less than 36 dB with an optimum goal of
approximately 25 dB in front of the GPS receiver. These values include 3 dB of margin for the minimum and
maximum values. Below is an example of how to calculate antenna system gain. Table 2 provides coaxial cable
attenuation and delay with the minimum and maximum cables lengths for commonly used cables.
Note: TFS 9100 systems sold prior to April 2004 contain a different GPS receiver. The antenna gain for these
systems must gain must be greater than 13 dB but less than 30 dB with an optimum goal of approximately 22
dB in front of the GPS receiver.
Antenna System Component
Gain (dB)
Antenna
∼
35
Cable (50’ RG58)
-12.45
System connectors and internal cables (typ)
- 2
Gain at front end of GPS receiver
20.55
Table 2 Coaxial Cable Delay and Attenuation
Cable Length for 9100 ft (m)
Bold values in MAX & OPTM
Column for units sold after April
2004
Cable for Length for
8821, 8900 & 9000 ft
(m)
Coaxial
Cable
Type
Delay
ns/ft
(m)
Atten
dB/ft
(m)
Min Max
Optm Min
Max
Optm
RG-58
1.54
(5.06)
0.249
(0.817)
12
(4)
80
(24)
68
(20)
52
(16)
40
(12)
28
(9)
80
(24)
68
(21)
RG-213
1.54
(5.06)
0.129
(0.423)
23
(7)
155
(47)
150
(39)
100
(31)
77
(23)
54
(17)
155
(47)
132
(40)
9913
Belden
1.21
(3.97)
0.071
(0.233)
42
(13)
281
(85)
239
(72)
183
(56)
140
(42)
99
(30)
281
(85)
239
(73)
FSJ1-
50A
Andrew
1.21
(3.97)
0.078
(0.256)
38
(12)
256
(78)
217
(66)
166
(51)
128
(39)
90
(27)
256
(78)
218
(66)
FSJ2-
50A
Andrew
1.23
(3.98)
0.054
(0.177)
55
(17)
370
(112)
314
(95)
241
(73)
185
(56)
130
(113)
370
(112)
315
(96)
LDF4-
50A
Andrew
1.15
(3.76)
0.031
(0.101)
97
(30)
645
(196)
548
(167)
419
(128)
322
(98)
226
(69)
645
(196)
548
(167)
Note 1: Delay per cable type is specified in nanoseconds (ns) per unit of length at 1575.42 MHz. Factory default
setting for the antenna cable delay compensation is 65 ns. This value can be changed through the remote
interface or front panel user interface of available.
Note 2: The delay should be calculated for each installation and entered into the GPS receiver.