OPERATION
3-1-25
Low intermodulation mode
When carrying out intermodulation tests the output signal from two signal generators is
combined using a resistive or hybrid combiner. If the carrier frequencies are relatively close
together each generator will receive an interfering signal from the other source. The RF ALC
system will detect a beat frequency equal to the difference in carrier frequencies and attempt to
apply AM in order to cancel the signal. In so doing the RF ALC system will generate AM
sidebands which are indistinguishable from intermodulation products. By using the low
intermodulation mode the RF ALC system can be disabled to prevent the injection of AM
sidebands.
If pulse modulation is not fitted proceed as follows:
(1) At the Sig Gen menu press [Low Intermod].
(2) This causes either Low Intermodulation Disabled or Low Intermodulation
Enabled to be displayed in the lower panel.
(3) Press the [MOD ON-OFF] key to toggle between the enabled and disabled states.
(4) If an attempt is made to [Set Steps] from the Δ menu, the message Low Intermod:
No Steps Allowed will be displayed.
If pulse modulation (Option 002) is fitted proceed as follows:
(1) Press the [Pulse Mod] key.
(2) This causes the message PULSE ON to be displayed.
(3) Press the [Pulse ON/OFF] key.
(4) This causes PULSE OFF to be displayed together with Low Intermodulation
Disabled or Low Intermodulation Enabled shown in the lower panel.
(5) Press the [MOD ON-OFF] key to toggle between the enabled and disabled states.
(6) If an attempt is made to [Set Steps] from the Δ menu, the message PULSE : No
Steps Allowed will be displayed.
Note...
AM is not available in the Pulse Modulation or Low Intermodulation modes of operation.
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