Tektronix 071-0590-00 Generator TX Functions, Clock Source and Frequency, External Clock Input

Reference

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.

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