5.10 External FSK Mode
Introduction
External FSK Frequency Shift Key generates a frequency shift keyed signal of fixed amplitude. External signal is used to toggle the output signal frequency between mark frequency and the space frequency. Mark and space frequencies, level and DC offset values could be manually entered from the front panel keypad in this mode.
External signal gating option is available in this mode. External FSK mode could be entered by pressing “Mode”> “FSK” >”2” key at any time.
External FSK Mode Parameters
The External FSK mode has the following front panel display:
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| Ext FSK: | Mark: 1,000,000.00 Hz |
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| Space: 2,000,000.00 Hz |
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Figure 5.10-1: External FSK mode display
1. Mark Frequency
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In this field enter the Mark frequency, from 0 Hz (DC) to 21.5 MHz in 0.01 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 21.5 MHz in 0.01 Hz steps. When the voltage on the Ext FSK In connector is low (0V to
3. Level
In this field enter the output level, from 4 mVp
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 4070A has internal leveling circuitry, which is disabled in this mode, in order to offer faster FSK switching rates.
NOTE: The level specified is a 50O loaded level. This is the level of the signal, which will appear across a 50O 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 signal. For more information on output offsets refer to section 4.4.
Ext FSK Input
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.
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BK Precision 4070A User Manual Rev.2.2
