22 (327) BRUKER BIOSPIN User Manual Version 002
General Hardware Setup
are rather close, >140 dB may be necessary (as in the case
1
H/
19
F). More than
90 dB is usually hard to achieve with one filter.
Using external filters has three principal safety aspects:
1. Make sure you do not pulse into a filter with a frequency that this filter does not
pass.
2. Make sure the pulse power you apply does not exceed the power rating of this
filter. Most modern Bruker filters will survive 1 kW pulses of 5msec, but older fil-
ters (or non-Bruker filters) may not.
3. Remember that filters may attenuate the pulse RF voltage by as much as 1.5
dB (about 20%!)
The following figures illustrate the most common filter combinations.
Figure 3.6. Standard Double Resonance CP Experiment, Bypassing the Proton
Preamp
Figure 3.7. Standard CP Experiment, Proton Preamp in Line