Marc, Yuhang

Today we went to check the GPS receiver.

First we went to the roof of the central building.

We have 4 cables going there : 1 for several environmental sigals (wind, rain, pressure, ...), 2 for radio signals and 1 for the GPS (see fig 1).

We powered on the GPS receiver but only the power led turned on.

From the user guide we also expect the led ''GPS lock' to turn on if the receiver reference clock is phase-locked to the gps one.

We monitor few output channels with an oscilloscope and results are shown in fig 2 to 4.

1 pps output delivers a continuous signal with offset of 144 mV (fig 2)

10 MHz output delivers a 10 MHz signal (fig 3)

Irig-B output delivers a modulated signal with especially the signal at 1 KHz together with time-varying sidebands. (fig 4)

We need to  check if the 1 pps signal should be generated by the GPS receiver or by the Irig-b card.

We let the GPS turn on to check if it requires time to phase-lock with GPS satellites.