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External Source
When external modulation source is selected, the Frequency and Shape menu in the modulation
menu is grayed out and disabled.The instrument receives the external modulation signal from the
[FSK/Trig/Sync/Extmod] connector on the rear panel.At this point, the AM modulation amplitude
is controlled by the ±4V signal level on this connector.For example,when the modulation depth is
100%, the output amplitude is maximum when the external modulation signal is +4V, and the
output amplitude is the minimum when the external modulation signal is -4V.
OtherChannels
CH1 and CH2 can be used as modulation sources reciprocally. When CH1 is used as the
modulated wave, CH2 can be used as the modulation source. And vice versa.
When selecting another channel as the modulation source, please turn on the output of that
channel.
5.1.5 Modulation Frequency
When internal modulation source is selected,press[Mod] >Frequencysoftkey to set the frequency
of the modulating waveform.
Use the numeric keypad or direction keys and knob to enter the desired frequency values.
The modulating waveform frequency range is 2mHz to 1MHz, and the default value is 100Hz.
Note: This menu will be grayed out and disabled when other modulation sources except the
internal modulation source are selected.
5.1.6 Modulation Depth
The modulation depth is a percentage that represents the amplitude variation.
Press [Mod]>Depthsoftkey to set AM modulation depth.
Modulation depth range: 0% to 120%. The default is 100%.
At 0% depth, the amplitude is one-half of the carrier’s amplitude setting.
At 100% depth, the output amplitude is equal to the specified value.
In >100% modulation, the output amplitude of the instrument would not exceed 10Vpp (50Ω
load).
When external modulation source is select, the output amplitude of the instrument is also
controlled by the ±4V signal level on the [FSK/Trig/Sync/Extmod] connector on the rear
panel.For example, set the modulation depth to 100%, the output amplitude is the maximum when
the modulating signal is +4V and the minimum when the modulating signal is -4V.
5.2 DSB-AM Modulation
In the Double-sideband AM signal, there are only two side frequencies, and there is no carrier
component. Its frequency bandwidth is still twice the frequency of the modulated signal.
User Manual 35
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