Measuring RF Amplifier Output

If an oscilloscope is available, there is a test point on the RF amplifier output, inside the Netclock/2 that allows the WWVB carrier signal to be viewed. Viewing the WWVB carrier with an oscilloscope can help define if noise or saturation is present. Connect the oscilloscope probe to TP E1 located just in front of the metal shield on the top board. Connect the probe ground to TP E2 located just to the right of TP E1. The figure below is an example of good reception. The signal is decreased in amplitude once a second for a set duration depending on the data bit being sent.

Indications of good reception:

• A clean sine-wave at an amplitude of about 0.48Vp-p that is reduced in amplitude every second is present.
• No noise spikes above or below the positive and negative lobes are present.

  

  Example of good reception

 

The next figure is an example of poor reception. The peaks are filled in, making the signal look like a ribbon cable.

Indications of noise or saturation at the site:

• If there are noise spikes present above and below the sine wave.
• The positive and negative lobes are filled in, making the sine-wave look more like a ribbon cable instead of a clean sine-wave.
• The sine wave intermittently cuts out (becomes a straight line).

  

  Example of poor reception

 

If no amplitude modulated signal present at TP E1, the Netclock/2, Antenna or preamplifier has failed. Contact Spectracom tech support

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