20 Chapter 2
Test Descriptions
10 MHz Out Frequency Reference Adjustment
Step 1. Note Counter Reading 1 for the 10 MHz Reference Accuracy Test and
calculate the actual error in Hertz.
Actual Error = 10 MHz - Counter Reading 1
Step 2. With the actual error calculated, determine which DAC setting to adjust
from the table below.
Example 2-1 Standard NFA Actual Error
If a standard NFA Actual Error = 10,000,000 Hz - 10,000,012 Hz
the error is -12 Hz
From Table 2-4, the DAC setting must be decremented by 1 coarse
setting and 5 fine settings giving an approximate -12 Hz adjustment.
Therefore, if the original settings were, for example, Coarse = 127 and
Fine = 136, then the new settings after adjustment are Coarse = 126,
Fine = 131.
NOTE A negative error value decrements [⇓], while a positive error value
increments [⇑].
Step 3. Access the
Service menus Time Base sub-menu and press the System key.
Then press the
More, More and Service menu keys. Enter the service
password -2010, press
Enter, then press Service and Time Base.
Decrement
[⇓] the NFAs DAC settings by pressing Coarse once and Fine
five times.
OR
You can type in the new value on the numeric keypad and then press
Enter.
Table 2-4 DAC setting adjustments
Control Setting Standard Step Size (Hz) Option 1D5 Step Size (Hz)
Coarse ≈ 7 Hz ≈ 0.1 Hz
Fine ≈ 1 Hz ≈ 0.0015 Hz
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