For a "standard" GN 1H decoupler, the output frequency ( in
MHz) is:
( ( SYN+95 ) / 24 ) + X
where, SYN is the synthesizer frequency, in MHz and X is
296 for a GN-300 and 496 for a GN-500.
Now, the internal, 293 synthesizer can put out frequencies
(in MHz) of:
( 10 * i ) / 1048576
where, i is an integer from 0 to 524287. You can see that
this synthesizer's resolution is about 9.5367 Hz. To find
a place where f1 exactly equals f2 (phase coherence), you
just need to find a place where the above conditions will
result in a frequency that is an exact multiple of 0.1 Hz,
which is the settability and resolution of the GN observe unit.
A convenient place is where i = 1048576 / 4 = 262144.
At this value of i, the synthesizer is exactly 2.5 MHz,
and a GN-300 decoupler is at 300.0625 MHz and the GN-500
decoupler is at 500.0625 MHz.
Credits, disclaimers:
Thanks to a persistent, pain-in-the-***, short-lived, never-
take-no-for-an-answer product manager who was at GE NMRI in
the 80's, (and who shall go unnamed [8-) ) this information was
finally put in some of the last GN Hardware Manuals sent to
press as well as the Omega Hardware Manual and you might refer
there for more information.
Tom Early, GE CR&D