Hello, Time-Nutters-- Full disclosure-- I am a complete newbie at understanding the intricacies of generating a really stable, low phase noise, accurate frequency reference for microwave reception up around the 8 GHz DSN (Deep Space Network) band. I have been following the back and forth comments on the Time-Nuts list about improving the Trimble T-bolt's 10 MHz output but confess that most of it is pretty much deeper technical voo-doo than I am comfortable with.
I have been following the exploits of a group of folks around the world who receive the incredibly weak signals from space probes such as Juno. The idea is to detect the signals and then deduce and confirm what probe is being detected by analyzing its doppler and orbital characteristics. This is being done at around 8.4 GHz with relatively small dishes of under 8-ft diameter. Part of the magic that permits identifying signals so far below the noise floor is the ability to use very narrow bandwidth; as little as couple of Hz or even more narrow than that. In order to do this a really accurate/stable/low phase-noise frequency reference is needed. I have been running a Trimble T-bolt 24/7/365 on Lady Heather for around 5 years but have just started to take note of comments on this list that the T-bolt is not really very good as a source to phase-lock to for producing super narrow bandwidths of only one or two Hz at 8 GHz. The comments I hear on the DSN space-probe hunters chat-list is that obtaining a really high quality freq reference is one of the big obstacles to success at this game. My workbench test gear is limited to a pair of spectrum analyzers (Tek 495AP and a Tek 494AP) and an HP 8714ES Vector Network Analyzer. John Miles was the source for the Tek 495 spec-analyzer a few years ago. John-- you might recall the check I sent you for the Tek495AP that got lost...? Did it ever turn up? Accordingly, what possible options might I have open to obtaining a decent 10 MHz frequency reference for working up at the 8 GHz DSN band? Any feedback on this will be much appreciated! Mike Baker Gainesville FL (Micanopy, actually, about 12 miles south of Gainesville) **************************** As a side note, I built a tracking downlink to receive and display the digital imagery from the environmental low-earth polar orbit satellites several years ago. This HRPT data comes down at around 1.7 GHz. The USA, Russia, Japan and China each have 2 to 4 of these low-earth orbit birds (100 minute orbits) and one of them passes overhead every other hour or so. I have a lot of trees around my house and these limit my open-sky area but I can still start to get solid reception when the birds pass over Cuba and drop-off when they are over Tennessee. Photos of my home-brew tracking station can be seen here in the back yard behind my workshop building: *http://tinyurl.com/j676ap2* And some low-res screen-grabs of false-color infrared earth surface images here: http://tinyurl.com/jsv323l *http://tinyurl.com/jvxkc9g **http://tinyurl.com/hbo886y* _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
