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Chapter 3. Wideline Solids Module Operation

VNMR 6.1C User Guide: Solid-State NMR

01-999162-00 C0402

• The older Wideline ADC board was shipped with UNITY and VXR-S systems. It

acquires data in a fundamentally different manner. Data is temporarily stored in its on-
board, 2 x 8 Kword buffer (maximum

16384

). After each FID is collected, data

is transferred to the normal acquisition memory and the fast memory is cleared. This
process requires an overhead of about 32

s for each complex point.

Both ADC boards are single VERSAbus boards containing sample-and-hold modules,
ADC chips, memory, and control logic, and each board is capable of digitizing 12 bits in
500 ns. The ADC conversion time is adjustable in 25 ns steps, so there are only a limited
number of actual values that the spectral width can take. The entered value of

automatically adjusted to the nearest valid spectral width.

The standard Observe Receiver board for

UNITY

INOVA and UNITYplus systems has the

correct bandwidth amplifier and is not replaced. For UNITY and VXR-S systems, the
Wideline Receiver and Filter board is a replacement of the standard 100 kHz receiver and
contains filters appropriate for both small and large spectral widths. Improved filters give
better baseline and phase characteristics; however, they may show a 10% reduction in
signal-to-noise as determined by the standard

C test.

For spectral widths above 100 kHz, 6-pole true
Bessel filters are used. The outputs from these
filters are routed to the wideband ADCs. The
permissible values of the parameter

, which are

identical to the 3 dB points of these filters, are
listed in

Table 6

For 100 kHz and below, the signal is routed
through a pair of 8-pole quasi-elliptical filters to
standard ADCs. The characteristics of these filters
provide superior performance for both phase and
amplitude flatness across the full spectral width.

The Wideline NMR Module for the

UNITY

INOVA

system is a board that includes two 5-MHz 12-bit ADCs and 2 MB of onboard memory.

High-Power Amplifier

The wideline high-power (1 kW) amplifier is intended mainly for use in solid-state NMR
studies. The amplifier is housed in a third cabinet, as shown in

Figure 16

, and configured

to permit maximum flexibility. Manual controls permit selection of either the solids
amplifier or the standard liquids amplifier for the observe function.

CAUTION:

Never use probes designed for liquids studies with amplifiers intended
for solid-state studies. The high power from these amplifiers will
destroy liquids probes.

Because the wideline package is for low-band (12 to 200 MHz) nuclei, no

H or

F high-

power amplifier is provided unless the CP/MAS module or CRAMPS/Multipulse module
is also installed. The 1-kW power amplifier is one of the following models:

• The AR Model 1000LPM10 covering the range of 9 MHz to 200 MHz with 60 dB of

gain and a maximum output power exceeding 60 dBm over this range.

• The AMT Model M3201 covering a range of 6 MHz to 220 MHz with 10 dB of gain

and a maximum power output exceeding 60 dBm over this range.

Table 6. Bessel Filter Outputs

(kHz)

100 – 225

256

> 225

1000

300 – 540

300