BNC 630 - Manual (Page 45)

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5.25 Data Modulation Mode
Introduction
The data modulation mode will digitally modulate a binary message of up to 960 bits (60 words) in length.
The data is digitally modulated using FSK modulation at an adjustable baud rate. The mark and space frequencies may be
independently specified from 0 Hz to 21.5 MHz with .01 Hz resolution. The baud rate is adjustable from 0 Hz to 130 KHz in 1 Hz
steps. By specifying a Mark or Space frequency of 0 Hz, 100% digital AM modulation may also be done.
The Data Modulation mode operates in a triggered burst mode. The Data Modulation mode starts by setting the output frequency to
0 Hz and awaiting a trigger condition.
When a trigger condition occurs, the 630 examines the first data bit of the binary message and sets the output frequency to the
Mark frequency if the bit is a 1 or to the Space frequency if the bit is a 0. The output is held at that frequency for a period of time
specified by the Baud rate field. After that, the next bit of the modulation message is processed and so on until all bits have been
modulated. After the last bit has been modulated, the 630 resets the output frequency to 0 Hz and awaits another trigger condition.
Using the Data Modulation Mode
To use the Data Modulation mode, you must do the following:
1. Switch the 630 to Internal FSK mode by pressing Mode, 5, 1
2. Enter the Baud rate, Mark & Space frequencies and output level on the front panel.
3. Download your data message to the 630 through the serial port. (see below)
4. Trigger the transmission (see below)
5. Optionally store the instrument setup and message to nonvolatile memory.
Each step is described in more detail on the following pages.