Comtech EF Data LTT1450G - Manual (Page 25)

LTT1450G Ku-Band Loop Test Translator Maintenance
TM063 - Rev. 1 Page 4-1
Section 4 - Maintenance
4.0 Confidence Test and Troubleshooting
This section provides two functions. Primarily, this section describes a procedure for performing a
confidence test on the translator. In the process fault identification and isolation can be performed. The
confidence test section is appropriate for incoming inspection of the unit.
4.1 Confidence Test Procedure
The confidence test procedure requires the following test equipment:
Signal Source/Sweep Generator 3-15 GHz +5 dBm leveled output.
Spectrum Analyzer
(alternately a scalar network analyzer can be used for transfer
characteristics testing)
Dumb Terminal (VT100)
Voltmeter
4.1.1 Power-ON Testing
Connect the VT100 configured for 9600 baud, 8 data bits, 1 start, 1 stop bit and no parity to the serial
port connector. This connector is wired as a DCE and should allow for interfacing to a terminal without
the aid of a null-modem cable. Apply power and turn the translator on. The Power On LED should light
and the terminal should print a Radyne Microwave, Inc. banner followed by a carriage return and line
feed followed by the firmware revision number. The LO fault should not be lit at this time.
4.1.2 Transfer Characteristics Testing
Built-in test of the converters is not a function that can be monitored internally on the translator. For this
reason, a manual test must be performed to test the performance of all the converter bands. This test
procedure requires that a CW input signal be applied to the translator input at -5 dBm (nominal). The
spectrum analyzer start and stop frequencies should be set to those that correspond to the band under
test. Prior to performing the test, the operator should calibrate the test setup by connecting the cables
used on the input and output port together. This test allows insertion loss in the cables to be measured,
the actual input power level determined, and the frequency of the sweeper to be determined. The latter
determination is useful when the signal generator is not synthesized.
Next, the signal is presented to the translator at a known power level and frequency. By observing the
frequency and power of the translated output signal, the conversion loss and functionality of the PLO for
the selected band can be determined. With the spectrum analyzer set at the correct stop and start
frequencies, the sweeper can be swept across the required input frequency range. With the attenuation
set to zero, the frequency response of the band can be tested. Conversion loss is nominally -15 to -18
dB. Test data provided with the translator should be consulted to verify that the gain and transfer
characteristics are as tested at the factory.