Bruker Fourier 300 - Table 5.1 Preamplifiers; Preamplifiers; Lock Switch; Transmitters

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Z31980_00_03
Design and Function
5.3.4.1 Transmitters
There are two transmitters which are identical in build but have a fixed routing so that the
upper one is dedicated to 1H (providing about 50W at 300 MHz) and the other is dedi-
cated to C13 (providing about 150W at 75 MHz). The transmitters receiver their RF and
gating inputs from the main board and have an RF-Output monitor which can be routed
to the main board receiver for diagnostic purposes.
The Transmitters receives only 28Vdc from the central 28V PSU. The gating inputs on
both transmitters are active high TTL.
5.3.4.2 Preamplifiers
There are three dedicated preamplifiers. The 13C (75 MHz) and 2H (46 MHz) Preamp
are of the same type. The 1H (300 MHz) preamp is unique. All preamps have a gain of
ca. 40dB.
Each amp has an RFin, RF out and two logic inputs. “Gate” is used to actively gate the
preamp for low power pulses that don’t have enough voltage to gate themselves. This is
a coaxial input and is driven by one of the service pulses on the main board.
“Tune/Blank” is a dual purpose input. It switches the amplifier to “tune” mode, which
measures the reflective power and is used for the wobble function. Since this mode also
bypasses the 40 dB gain stage, it also blanks the preamp. The software always blanks
the preamp that is not being used for observing, to avoid reflected power from decou-
pling pulses on the other channel getting to the receiver. The tune/gate signal is gener-
ated by the main board and is fed to the lock switch via a ribbon cable. From there it
routes the tune/gate signal to the individual preamps (see wiring schedule in appendix).
LEDs indicate the status of tune/blank mode (see below).
The preamps do not have a separate protection input as they are self-protecting. They
receive +12V as a single supply voltage.
5.3.4.3 Lock Switch
The Lock Switch is required in order to perform gradient shimming on Deuterium for
samples that do not contain water. It reroutes the transmit and receive signals from the
C13 channel to the 2H coil. For diagnostic purposes 2H observe spectroscopy can be
carried out by selecting the 2H observe nucleus.
Function Sub-D9 1H 13C / 2H
Tune/Blank 6 Hi Hi
Gate SMB Low Hi
GND 3;7;8 0V 0V
Vsupply 4;5;9 12V 12V
Table 5.1 Preamplifiers