Several times on our drx300 I have seen a broad and noisy band of
signals appear at left hand side of the 13C spectra and gradually move
to the right hand side and then disappear! I have not been able to
relate that to anything we might have done prior to the experiment.
Wei
-----Original Message-----
> From: Grace, David (GE Healthcare) [mailto:David.Grace_at_ge.com]
> Sent: Wednesday, June 22, 2005 1:53 AM
> To: Hongjun Pan; ammrl_at_chemnmr.colorado.edu
> Subject: RE: Thanks - Strange RF radiation interference
This question reminded me of a similar situation which stared a couple
of years ago:
Running 19F on an Inova 500 we observed intermittant signals in the 19F
spectrum. The signals were rather remarkable in that they initially
appeared as a broad band (500-1000Hz width)of signals of various phases.
This band coalesced over a period of about one hour to one sharp signal.
At the same time as this coalescence process was progressing the band
would move in an apparently exponential manner towards lower frequency
(alomost as if some sort of warming up process was occuring).
Immediately the one sharp signal state was reached, however, the
frequency of the signal would remain stationary and this sharp signal
would persist for a period of time (1-2 hours) and then suddenly
disappear. The time of day when this happened was not constant. The
signal was present also with the probe ouside the magnet.
We never managed to track down the cause nor was I able to ascertain
what could be transmitting in the 470 MHz region. Luckily, the behaviour
was so well defined, we learnt to live with it but if anyone has any
ideas I'd still very much like to know them!
regards
David Grace
Amersham Health,
Oslo
Norway
-----Original Message-----
> From: Hongjun Pan [mailto:hpan_at_utk.edu]
> Sent: 20. juni 2005 17:56
> To: ammrl_at_chemnmr.colorado.edu
> Subject: Thanks - Strange RF radiation interference
Dear Ammrl friends:
About a month ago, I sent an email about strange RF radiation
interference on our Mercury 300 at 75.438 MHz. I received a lot of
responses with good suggestions. Thank you all for the great help and
suggestions. After followed many suggestions and more search, I finally
comfirmed that this intermittent pulses are from out side, not from NMR
instrument itself. I swapped a probe which is better shielded, the
detected intermittent signal is much smaller and does not cause the
receiver overflow. This signal is just outside of normal 13C spectrum
window (20 KHz away from the 13C center), so is not seen in normal 13C
spectrum.
However, I am very confident that this 75.438 MHz pulses is most
likely from the local pager service tower. Hope it will not cause
problems in the future.
Again, thank you all for reponses and suggestions.
Hongjun
Received on Fri Jun 24 2005 - 17:19:36 MST