BNC 630 - Manual (Page 29)

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5.10 External FSK Mode
Introduction
The External FSK mode generates a frequency shift keyed signal of fixed amplitude. An external digital input signal is used as a
modulating signal to shift the output frequency between the Mark frequency and the Space frequency.
External FSK Mode Parameters
The External FSK mode has the following front panel display:
Figure 5.10-1: External FSK mode display
1. Mark Frequency
In this field enter the Mark frequency, from 0 Hz (DC) to 21.5000000 MHz in .01 Hz steps.
When the voltage on the Ext FSK In connector is high (+3V to +10V), the output frequency will be set to this value.
2. Space Frequency
In this field enter the Space frequency, from 0 Hz (DC) to 21.5000000 MHz in .01 Hz steps.
When the voltage on the Ext FSK In connector is low (0V to -10V), the output frequency will be set to this value.
3. Level
In this field enter the output level, from 4 mVp-p to 10 Vp-p in 1 mV steps or from -44.0 dBm to +24.0 dBm in .1 dBm steps.
NOTE: For wideband FSK (where the difference between Mark and Space frequencies is > 1.0 MHz), the output level may shift
slightly between the mark and space frequencies. The 630 has internal leveling circuitry which is disabled in this mode, in order to
offer faster FSK switching rates.
NOTE: The level specified is a 50 ohm LOADED level. This is the level of the signal which will appear across a 50 ohm load
connected to the SIG Out connector. Into an open circuit, the output swing will be twice the value entered.
Offset
By pressing this key, you may enter an offset voltage for the output waveform. For more information on output offsets refer to
section 4.4.
Ext FSK Input
(rear panel connector)
Apply the digital data to be modulated to this connector. When this input is high, the output frequency is set to the Mark value.
When this input is low, the output frequency is set to the Space value. For more information on this input refer to chapter 2.0.
Ext FSK: Mark: 1,000,000.00 Hz
Space: 2,000,000.00 Hz -10.0 dBm
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