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BK Precision 4070A User Manual Rev.2.2
17
5.5 External FM Mode
Introduction
External FM mode generates frequency-modulated signal of fixed amplitude were externally supplied signal is
used as a modulating signal to vary frequency of the carrier signal. Modulated frequency, level, peak deviation 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 FM mode could be entered by pressing “Mode”> “FM” >”2” key at any time
External FM Mode Parameters
The External FM mode has the following front panel display:
Figure 5.4-1: External FM mode display
1. Peak Frequency Deviation
In this field specify the degree to which the modulating signal is allowed to change the carrier frequency. You may
enter from 0 Hz (no change) to 5.0 MHz in 1 Hz steps. This parameter is a peak value. If the deviation were 1 KHz
and the carrier frequency were 1 MHz, for example, then the output frequency will swing between a maximum of 1
MHz + 1 KHz and a minimum of 1 MHz - 1 KHz for an input signal level of 1 Vp-p.
NOTE: If values for the deviation and carrier frequencies are entered such that the output frequency exceeds the 0
to 21.5 MHz range, distortion of the output waveform may result.
2. Carrier Frequency
In this field enter the frequency of the carrier. You may enter from 0 Hz (DC) to 21.5 MHz in 0.01 Hz steps.
NOTE: If values for the deviation and carrier frequencies are entered such that the output frequency exceeds the 0
to 21.5 MHz range, distortion of the output waveform may result.
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: 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 FM
Pk dev: 10,000 Hz
1,000,000.00 Hz -10.0 dBm
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