Spectracom - Essential Ingenuity

Troubleshooting a Raven Fiber Transmitter/Receiver System

Tutorial Steps

If the GPS Signal is weak or has no signal on the output of the Model 1201-KIT-FIB1 DUC GPS Fiber Transmitter/Receiver check all connections first. Then review this FAQ and other troubleshooting tips:

Q: Is the signal over the fiber analog or digital?

A: Analog

Q: Would the fiber signal attenuation affect the RF output signal level?

A: Yes it would.  We test satellite lock through 5000’ of fiber cable at the factory with a total attenuation of 5.5dBm.  Fiber attenuation in excess of 6dBm would reduce the RF output signal significantly.  

Q: The LED on the Receiver indicates green = good and red = bad. Does this monitor the Fiber input level only or are there other signals sent from the Transmitter?

A: It monitors the presence of the fiber signal, not the availability of GPS satellites.  A green LED does not necessarily mean you would get satellites, but it does indicate you have a good fiber connection.

Q: Are there any common causes for low output level?

Kinks in the fiber, or a poor optical alignment of fiber is the most common cause. 

Q: How many feet of coax is between the antenna and fiber transmitter? 

If more than 50’, you may need a line amplifier.

Other troubleshooting tips:

  • If you have two systems side by side, try swapping out the components (antennas, transmitters, and/or receivers) to isolate which one is the weakest.  You may find that the weak signal follows a particular piece of equipment, or fiber connection.
  • What color is the LED on the weak and no signal receivers?
  • Make sure there is at least 10’ of cable between the antenna and the fiber transmitter. 
  • There should be at least 10’ of cable between the fiber transmitter and fiber receiver also.

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