B&K 4070A - Manual (Page 27)

BK Precision 4070A User Manual Rev.2.2
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5.9 Internal FSK Mode
Introduction
Internal FSK mode generates a frequency shift keyed signal of fixed amplitude. Internal timer is used as
modulating signal to toggle the output signal frequency between mark frequency and space frequency. Mark and
Space frequencies, output level, modulating shift frequency 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. Internal FSK mode
could be entered by pressing “Mode”> “FSK” >”1” key at any time.
Internal FSK Mode Parameters
The Internal FSK mode has the following front panel display:
Figure 5.9-1: Internal FSK mode display
1. Modulating Frequency
In this field enter the frequency at which the output will switch between the Mark and Space frequencies. You may
enter from 0 Hz to 130,000 Hz in 1 Hz steps. The internal modulating frequency is accurate to 1 Hz from 0 Hz to
3900 Hz. It is accurate to within 1% across its full range of 0 Hz to 130,000 Hz.
2. Mark Frequency
In this field enter the Mark frequency, from 0 Hz (DC) to 21.5 MHz in 0.01 Hz steps.
3. Space Frequency
In this field enter the Space frequency, from 0 Hz (DC) to 21.5 MHz in 0.01 Hz steps.
4. 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 4070A has internal leveling circuitry, which is
disabled in this mode, in order to offer higher FSK modulation 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
You can enter an offset voltage for the output signal. For more information on output offsets refer to section 4.4.
Ext Gating Input
This TTL compatible input can be used to gate the output signal on or off. A logic high voltage turns off the
output. For further information on the Ext Gating Input, refer to section 2.0.
Int FSK: 1,000 Hz Mark: 1,000,000.00 Hz
Space: 2,000,000.00 Hz -10.0 dBm
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