Connecting an External Amplifier

The Bridge12 SCN has an internal RF power delivering up to 2 W output power. For many (low frequency) experiments this power is sufficient.

If the available power from the internal amplifier is not sufficient, an external high-power RF amplifier can be connected to the system.

To connect an external amplifier the input of the external device must be connected to the AMP OUT connection on the back panel of the SCN. The output of the external amplifier must be connected to the AMP IN connection located on the back panel.

To blank the external amplifier, connect the blanking gate to the AMP BLNK output of the SCN. The blanking gate is active low.

Specifying the Amplifier pre-Blanking Time rof1

To use an external amplifier with blanking, the amplifier needs to be unblanked before sending the RF pulse. Amplifiers typically require a short time unblank. This time can be specified using the OVJ parameter rof1. The value is typically given by the manufacturer in the data sheet of the amplifier.

The value can be set from the OVJ command line:

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rof1=1000

If the required value is larger than the default value, for rof1 can be changed using the setlimit command as shown below.

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setlimit('rof1',MAX_VALUE,MIN_VALUE,STEP)

Enabling the External Amplifier and Setting the Drive Level

OVJ needs to be connected to use the external amplifier. This is done from the OVJ command line:

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B12SCNControl('extamp 1')

The B12SCNControl('state?) command can be used to query the state of the amplifier. If the system returns “extamp” the external amplifier is enabled.

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B12SCNControl('state?')

The drive level (input power) of the external amplifier can be set using the OVJ command line by specifying the value stored by tpwrf.

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tpwrf=1

To disable the internal amplifier from the OVJ command line enter this command:

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B12SCNControl('extamp 0')
B12SCNControl('state?')

If the command B12SCNControl('state?) returns “intamp”, the internal amplifier is used. The tpwrf value is automatically set to 100 (the maximum).