GatesAir Inc. CZF Manual De Usuario
APEX
™
Exciter Incorporating FLO
™
Technology
Maintenance and Troubleshooting
Exciter Troubleshooting
Page: 5-22
888-2604-001
03/08/07
WARNING: Disconnect primary power prior to servicing.
While performing these tests alternately monitor exciter and FLO w/RTAC on the main
screen chart display (these are selected in the chart source on the display setup screen). The
exciter display is derived from the ADC data output and the FLO w/RTAC display is
derived from the DAC input data.
screen chart display (these are selected in the chart source on the display setup screen). The
exciter display is derived from the ADC data output and the FLO w/RTAC display is
derived from the DAC input data.
1
This method uses the digital loopback feature of the adaptive processing diagnostics
screen. It loops the digital input of the DAC to the digital output of the ADC (J1 to J2
on the Adaptive corrector board), which eliminates the two converters and the entire
analog tray from the test.
screen. It loops the digital input of the DAC to the digital output of the ADC (J1 to J2
on the Adaptive corrector board), which eliminates the two converters and the entire
analog tray from the test.
A
When viewing the digital loopback main screen monitoring displays, the
spectral response should look good.
spectral response should look good.
B
Observing the On-Air Data, the LSB and USB (lower and upper sidebands)
should be better than -38 dB at the shoulders.
should be better than -38 dB at the shoulders.
The SNR and MER readings will show N/A until the Lin HPF of the main
screen RTAC is set to adapt, at which time the SNR should be better then 32
dB and the MER should be 33 dB or better,
screen RTAC is set to adapt, at which time the SNR should be better then 32
dB and the MER should be 33 dB or better,
2
This method uses the analog loopback feature of the adaptive processing diagnostics
screen. It loops the 11.1 MHz analog IF output of the DAC to the analog IF input of
the ADC and bypasses the analog IF input from the down converter. This eliminates
the entire analog tray from the test. The analog loopback is accomplished via cable
W26, which connects J2 of DAC to J2 on ADC.
screen. It loops the 11.1 MHz analog IF output of the DAC to the analog IF input of
the ADC and bypasses the analog IF input from the down converter. This eliminates
the entire analog tray from the test. The analog loopback is accomplished via cable
W26, which connects J2 of DAC to J2 on ADC.
A
When viewing the analog loopback main screen On-Air Data, the SNR
should be better then 32 dB and the LSB and USB (lower and upper side-
bands) should be better than 38 dB.
should be better then 32 dB and the LSB and USB (lower and upper side-
bands) should be better than 38 dB.
The chart source Post HPF, Pre HPF, and Exciter selections all come from the
ADC digital output (as that particular source is being monitored). Since only
the exciter output is being looped back in this test, all of these selections will
display the exciter output.
ADC digital output (as that particular source is being monitored). Since only
the exciter output is being looped back in this test, all of these selections will
display the exciter output.
Faulty DAC and/or ADC boards are indicated if the exciter passed the digital loopback test
and failed the analog loopback test.
and failed the analog loopback test.
5.8.5.2
Checking Operation of the Entire Exciter
It is possible to view the output of the exciter on the main screen to verify its overall correct
operation. This test loops an RF sample from the output of the exciter output amplifier
through the down converter to the ADC board. The output of the ADC is monitored on the
main screen spectral response and On-Air data displays. The procedure is given below.
operation. This test loops an RF sample from the output of the exciter output amplifier
through the down converter to the ADC board. The output of the ADC is monitored on the
main screen spectral response and On-Air data displays. The procedure is given below.
1
In the down converter board diagnostics screen, set the RF sample select from auto-
matic to exciter. This causes the RF sample from exciter output to be the only signal
that is looped back through the down converter.
matic to exciter. This causes the RF sample from exciter output to be the only signal
that is looped back through the down converter.
2
Set the main screen chart source (on the display setup screen) to the Exciter position.
This monitors the output of the ADC.
This monitors the output of the ADC.
Actually, the chart source Post HPF, Pre HPF, and Exciter selections all come from
the ADC digital output (as the particular source is being monitored). Since the exciter
output is the only signal which is looped back during this test, all of the four chart
source selections mentioned above will display the exciter output.
the ADC digital output (as the particular source is being monitored). Since the exciter
output is the only signal which is looped back during this test, all of the four chart
source selections mentioned above will display the exciter output.
3
Set RTAC Lin HPF to adapt.
4
The SNR should be 32 dB, and the upper and lower shoulder sideband attenuation
should be 38 dB or better.
should be 38 dB or better.