BNC 630 - Manual (Page 23)

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5.5 External FM Mode
Introduction
The External FM mode generates a frequency modulated signal of fixed amplitude. An externally supplied signal on the Ext Mod
In connector is used to vary the frequency of a carrier sinusoid.
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 21.5000000 MHz in .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 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
You can enter an offset voltage for the output waveform. For more information on output offsets refer to section 4.4.
Ext Gating Input
(rear panel connector)
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
20,000,000.00 MHz -10.0 dBm
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