GE Reason RT430 - Page 98

GPS Grandmaster Clock
98
RT430-TM-EN-5
The antenna cable delays GPS signal. In applications in which the ultimate time accuracy is desired, this
delay should be compensated inside the unit.
Typically, the delay introduced by coaxial cables is in the magnitude of 4 ns/m (1.2 ns/ft) of cable length.
The exact delay can be computed by using:
 



 
Where C =     

m/s is the speed of light, 

    is a constant which depends on the cable
and  is the cable length in meters.
The table below summarizes some typical delays caused by coaxial cables
Tabela D.2: Atenuação de cabos de antena.
Cable length
Tipical delay
m (50 ft)
60 ns
m (82 ft)
100 ns
m (164 ft)
200 ns
m (246 ft)
300 ns
m (328 ft)
400 ns
m (410 ft)
500 ns
m (492 ft)
600 ns