Chapter 3. Wideline Solids Module Operation
49
VNMR 6.1C User Guide: Solid-State NMR
01-999162-00 C0402
Although you should study the AR manual before using the amplifier, an abbreviated set of
operating instructions are given here (words in all capital letters refer to controls on the
front panel).
The gating input to the amplifier is of positive logic, with a 5 V on and 0 V off signal. The
amplifier is class A with noise blanking in the CW mode. In the pulsed mode, the amplifier
operates class AB and the gating input acts as a gating signal. When gated off, the output is
greatly attenuated.
• To operate in the continuous mode, turn on the POWER button, wait for the
STANDBY button to light, then press the OPERATE button. In the continuous mode,
the gating signal input should be disconnected at the AR front panel.
• To operate in the pulsed mode, press the OPERATE button to set the amplifier in the
standby mode. Press the PULSED button, then the OPERATE button once again. The
amplifier is now in the pulsed mode, with pulse gating, not noise blanking. The
maximum rated power output in the pulsed mode is 1 kW (60 dBm). This should not
require adjustment of the amplifier gain.
• To return to the continuous mode, switch back to the standby mode by pressing the
OPERATE button, followed by powering off the amplifier.
The AR amplifier has been calibrated at 100 MHz so that when its front panel gain control
is set to the marked position and the manual attenuators are set to 0, the power output is
equal in dBm to the value of
tpwr
, in other words,
tpwr=60
delivers 1 kW (60 dBm) and
tpwr=50
delivers 100 W (50 dBm). This calibration may not be precise at other
frequencies, but provides a first approximation.
AMT Linear Amplifier
The AMT linear amplifier is gated off whenever the receiver is gated on. A time of at least
8
µ
s is required for the bias to come on fully and thus for the amplifier to provide full output
power. Allowance for this time delay must be made in any pulse sequence programming,
using
rof1.
The maximum pulse width is 20 ms at full output and with a maximum duty cycle of 10%.
The AMT amplifier is fully protected against thermal overload and it indicates excessive
duty cycle and excessive pulse width. Status lights on the front panel and the power switch
are visible inside the front door of the third cabinet as well as on the status panel. The gating
input to the amplifier is of positive logic, with a 5 V on and 0 V off signal.
CAUTION:
Never operate a high-power amplifier unless terminated by an
appropriate 50-ohm load.
Decoupler Amplifier
The three possibilities for the decoupler amplifier in wideline systems are as follows:
• Standard decoupling operation.
• 100 W CP/MAS decoupler—operation of this is the same as for CP/MAS.
• 1 kW decoupler amplifier.
Status Panel
The high power amplifiers are controlled by a status panel.
The HI POWER ENABLE subpanel contains two switches: