Chapter 2 47
Making Adjustments
4. 10 MHz Precision Frequency Reference
Procedure
1. Place the analyzer on its side as shown in Figure 2-7 and set the
LINE switch of the analyzer to ON.
2. Allow the analyzer to remain powered ON and undisturbed for at
least 24 hours, so that both the temperature and frequency of the
OCXO can stabilize.
3. Connect the frequency standard to the frequency counter rear-panel
TIMEBASE IN/OUT connector. Refer to Figure 2-7.
4. Disconnect the jumper between the 10 MHz REF OUTPUT and EXT
REF IN jacks on the analyzer rear panel. Connect a BNC cable
between the 10 MHz REF OUTPUT jack and INPUT A on the
frequency counter.
5. Set the frequency counter controls as follows:
FUNCTION/DATA ....................................... FREQA
INPUT A:
x10 ATTN ........................................................ OFF
AC ............................................. OFF(DCcoupled)
50 Ω Z .................... OFF (1 MΩ input impedance)
AUTO TRIG ........................................................... ON
100 kHz FILTER A .............................................. OFF
INT/EXT switch (rear panel) .............................. EXT
6. On the frequency counter select a 1 second gate time and a 10 MHz
offset of the displayed frequency by pressing the following frequency
counter keys.
GATE TIME, 1, GATE TIME
MATH, SELECT/ENTER
CHS/EEX, 10, CHS/EEX, 6, SELECT/ENTER
SELECT/ENTER
The frequency counter should now display the difference between
the frequency of the INPUT A signal and 10.0 MHz with a displayed
resolution of 10 MHz (0.010 Hz).
7. Locate the FREQ ADJ control on the OCXO. See Figure 2-8. Remove
the dust cap screw.
8. Use a nonconductive adjustment tool to adjust the FREQ ADJ
control on the OCXO for a frequency counter indication of 0.00 Hz.
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