Model: MTS200 (1U)
Doc. Ref. no. : - m08/om/201
Issue no.: 03
Page 29 of 195
User’s Manual
6.1.5
Technical Details on GPS Antennas and Cables
Antenna Cable
Length and Loss Considerations
Standard Antenna Cable
The standard antenna cable assembly included with
mas
TER
T-Sync
Model MTS200 is constructed using
a 15-meters (50-foot) length of RG-6 type low-loss coaxial cable, terminated with male Type N connector
and BNC male connector. Optional lengths of RG-6 coax are separately available for longer runs; see
Table 4.2, Cable Data and Accessory Information.
Effects of Cable Parameters
To receive GPS signals and properly operate the clock, the type and length of the cable are important.
Due to their effect on specific parameters described in the following paragraphs, any changes to the
length and/or type of antenna cable should be made carefully. Damaged cables may also affect
performance.
Cable Delay
The velocity factor and the physical length of the cable determine cable delay. User has to enter delay
value according to antenna cable length.
For cable options, the delay is tabulated below. The formula for calculating
cable delay is:
Where:
T = Cable delay, in nanoseconds;
ƛ= Cable length, in meters;
C = Speed of light (3 _ 108 meters per second);
Kv = Nominal velocity of propagation (0.85).
One nanosecond is added to the calculated value to account for the length and velocity factor of the short
connecting cable inside of the clock.
Attenuation
Attenuation depends upon the cable length, and the loss per unit length. The total attenuation must be
limited to 30 dB (maximum) at the GPS L1 frequency of 1575.42 MHz
DC Resistance
The cross-sectional area and length of the conductors in the cable determine the dc resistance.Since
power to the RF preamplifier in the antenna is supplied via the antenna cable, excessive dc resistance
will degrade performance. Because of the above factors, changes to the length and/or type of antenna
cable should be made carefully. Damaged cables may also affect performance.
