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BK Precision 4070A User Manual Rev.2.2
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5.3 External AM Mode
Introduction
External AM mode generates amplitude-modulated signal of fixed carrier frequency, were externally supplied
signal is used as a modulating signal to vary signal modulated frequency and depth. Modulated frequency, output
level, input gain and DC offset values could be manually entered from the front panel keypad in this mode. External
signal gating options is available in this mode. External AM mode could be entered by pressing “Mode”> “AM”
>”2” key at any time.
External AM Mode Parameters
The External AM mode has the following front panel display:
Figure 5.3-1: External AM mode display
1. Input Gain
In this field specify a value used to scale the input signal. With a value of .999, a 1 Vp-p signal on the input will
result in 100% modulation of the carrier amplitude. You may enter a value from 0 to .999. (The gain value is always
less than 1.0).
To enter a value, type 1 to 3 numeric digits. If you type 3 digits, the value is automatically entered. If you only
type 1 or 2 digits, you can press the MHz key or the KHz key or the Hz key (all are equivalent) to enter the gain
value.
2. Carrier Frequency
In this field enter the frequency of the carrier, from 0 Hz (DC) to 21.5 MHz in 0.01 Hz steps.
3. PEP Level
In this field enter the output level, from 4 mVp-p to 10 Vp-p in 1mV steps or from -44.0 dBm to +24.0 dBm
in 0.1 dBm steps.
NOTE: The level specified in External AM mode is the Peak Envelope Power, or PEP. As a peak-to-peak value,
this level represents the maximum peak-to-peak voltage swing that will result from a 100 percent modulated carrier.
If no modulating signal were applied, the unmodulated carrier would have only half the peak-to-peak swing of a
100% modulated carrier.
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.
External AM
Input gain: .999
1,000,000.00 Hz PEP level: -10.0 dBm
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