I found something on our DRX 500 machine that doesn't sound logical for
me. When I run an inverse exp (HSQC) H-C correlation and I connect the
cable going through the preamp unit to the BB coil of our inverse,
triple resonance probe (H, BB, C configuration) everything is OK. The
same is true when I attach this cable to the C-coil. But it's not OK
when I connect the free cable bypassing the preamp unit to the C-coil.
Although p90 is not very different from the p90 on BB coil (15 us versus
12 us) signal to noise is much worse. I would expect a worse signal to
noise for the C-coil, no matter which cable is attached to it in
comparison with the BB-coil because of the design of the probe (the
C-coil is further from the sample).
When I attach the pramp cable to the C-coil and the free one to the
BB-coil and set up H-C-N configuration I can not use the full power on
the C channel. When the attenuation is less than 1.7 db I get mismatch.
Has anyone met something similar.
Thanks
Richard Hrabal
-- * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Richard Hrabal email hrabalr@vscht.cz * * * * NMR Laboratory tel. +420-2-3114782 * * Institute of Chemical Technology * * Technicka 5 fax. +420-2-3116109 * * CZ 166 28 Prague 6 * * CZECH REPUBLIC * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *