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Reference
3-10 GB1400 User Manual
Generator (TX) Functions
This section defines key functions of the GB1400 Generator and how to set up
these functions using front panel controls.
Clock Source and Frequency
The Generator can operate using its internal clock, or an external clock source.
The CLOCK section of the Generator front panel is used to select clock mode
(internal or external), set internal clock frequency, and store or recall user-
defined frequencies. In addition, the CLOCK section contains an input for an
external clock source. When using the internal clock, you may set frequency
directly, or recall one of 10 previously saved frequencies from memory. The
frequency save/recall feature is especially useful if you often switch back and
forth between a limited number of different frequencies.
External Clock Input
When the Generator is in external clock mode, a clock source must be connected
to the connector labeled INPUT in the CLOCK section of the Generator's front
panel. The operating bit rate of the Generator will then be determined by the
frequency of this source. However, when the Generator is set to internal clock
mode, any signal applied to this input will be ignored.
The EXTERNAL CLOCK input is AC-coupled into 50 Ohms (unless BURST
OPTION is installed).
Clock Source
Generator clock source may be set to internal or external using the EXT key in
the CLOCK section. When the LED in the EXT key is off, then clock source is
internal. If the LED is on, the clock source is external and an external source
must be connected to the external clock input (INPUT).
Press the EXT key to toggle clock source between internal and external.
Step Size and Frequency
The frequency of the Generator internal clock may be set using the
FREQUENCY, STEP, and CLOCK section up/down keys. First select a step size.
Then adjust current frequency using this step size. The complete setup procedure
follows:
1. Select a step size. Do this by pressing the STEP key one or more times until
the underscore in the frequency field is under the desired digit. Note that the
underscore moves right one digit for each key press. The selected digit
indicates step size. For example if the current frequency is 622.950 MHz, and
the underscore is under the "5" , then current step size is 10 kHz. Or, if the
underscore is under the "9" then the current step size is 100 kHz, etc.
2. Press the FREQUENCY key. Verify that the FREQUENCY key LED turns
on.