After having a bad HMC182S14 chip replaced in our dual mixer (which
was preventing signal from passing from J5115 (2H OBS IN) through
J5102 (IF out), we are still not seeing any output from the dual mixer
for 2H OBS in the preamp. In the past, we had tested the functionality
of the J5111 (tune in) pathway by tuning the probe with the digital
display on the magnet leg. Today, I decided to check this signal path
in the dual mixer by using qtune. I was shocked to see that the
tune dip was overlaid with a square wave which was positive on the
left side of the dip and negative on the right side of the dip. The
square waves were narrow but spaced about 1 MHz apart when tuning
H1 at 800 MHz. Has anyone seen this artifact before? I am thinking it
could be related to the reason that we don't see 2H OBS output with
the dual mixer installed in the preamp. This is all in an Inova
system of course.
Jack
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Jack W. Howarth, Ph.D. 231 Albert Sabin Way
NMR Facility Director Cincinnati, Ohio 45267-0524
Dept. of Molecular Genetics phone: (513) 558-4420
Univ. of Cincinnati College of Medicine fax: (513) 558-8474
Received on Wed Nov 05 2008 - 11:03:27 MST