ITCR Base Radio User's Guide
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9/8/2011
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4.
Attach a 100W 30 dB RF attenuator to the TX/RX N-type antenna connector.
Attach an (e.g., Agilent MXA or PXA) vector spectrum analyzer or similar to the
transmitter port for power and frequency measurements. The VSA should
contain either a precision stability reference oscillator or attach an external
rubidium reference to the VSA external reference input.
4.3
Measure and Calibrate Reference Crystal Oscillator
Parameters
The instructions below allow you to change the factory calibration settings for the
master reference oscillator crystal. The new setting is stored in volatile memory and
will revert to factory settings when the radio is powered off and then on.
To check the master reference crystal oscillator frequency calibration:
1.
Open an XtermW session.
2.
Put the radio into test mode by typing:
i.
dsp,watchdog,off
ii.
dsp_mode,test
3.
Reduce output power to approximately 2W by typing:
i.
cal,set,igain,-1000
ii.
cal,set,qgain,-1000
4.
Begin transmitting a test tone 8kHz from the carrier:
i.
l1_test,stop
ii.
l1_test,set,txmod,cw
iii.
l1_test,set,txfreq,220012500
iv.
l1_test,start,tx
5.
Use the frequency counter or frequency counting marker on the VSA to measure
the output frequency. The measured value is exactly 8 kHz greater than the
actual carrier frequency. The carrier frequency is normally well within 22 Hz (0.1
ppm) of the carrier frequency.
6.
Alternate to the test tone: Substitute the following π/4-DQPSK modulation
command for the second line in step 4.
i.
l1_test,set,txmod,dqpsk
