In response to my question on where to obtain an RF sweep generator
for tuning NMR probes at 750 MHz, I received a number of suggestions which
may be summarized into these categories:
1. Use a sweep generator which can tune probes at 375 MHz and add a
frequency doubler between the probe and the sweep generator. This will
work, but the insertion loss of the doubler results in a loss of vertical
scale for matching adjustments.
2. Find an old Wavetek 2001 sweep generator capable of going to 750
MHz. Reportedly, Wavetek no longer manufactures these.
3. Buy a (very expensive) digital sweep generator, spectrum
analyzer, or network analyzer from HP. This will also work, but is a huge
overkill for simply tuning probes to 750 MHz.
As far as I can tell, nobody currently manufactures a handheld
antenna tuner for 750 MHz with an LCD display, analogous to the devices
made by Morris Instruments, AEA, and Bird at lower frequencies. With the
increasing number of 750's in the world and the advent of yet
higher-frequency NMR spectrometers, an inexpensive, non-magnetic 750 MHz
sweeper with an LCD display would be an ideal product for an enterprising
designer out there. Any volunteers?
Regards,
Ken Fishbein
Facility Manager, NMR Unit
NIH/NIA/GRC
Ph. (410) 558-8512
FAX (410) 558-8323 or 8173
E-mail: fishbein@vax.grc.nia.nih.gov
Address: Ken Fishbein
NIH/NIA/GRC
4940 Eastern Avenue
Baltimore, MD 21224 USA