Hi If your OCXO is putting out less than 0 dbm, it’s broke. Given the way these parts are treated in the salvage loop, damage is not unusual. There are a *lot* of examples of surplus OCXO’s with low output. Normally it’s a damaged output cap or something like it. I’ve seen roughly half the units in some lots come in that way ….
Bob > On Jan 26, 2016, at 2:52 PM, walter shawlee 2 <walt...@sphere.bc.ca> wrote: > > I have been working on a compact portable 10Mhz bench standard > using both an FE FE5680A Rb oscillator and an Oscilloquartz ovenized > crystal oscillator. I was curious to see how their short and long term > stability > would work out, and I needed something to drive my 6502 amp to pipe the > signal to some bench instruments which could benefit from better master > references. all of these were inexpensive ebay acquisitions, so the total > cost to make the package is maybe $250 plus a few weekends work and a > left-over but nice looking tilt-bail case & Condor 65W switching power supply. > I drove everything from some independently, heavily post-filtered +15VDC > power. > > to try and keep any unexpected interaction to a minimum, the outputs exit > though floating BNCs, so they don't have an unwanted ground loop at the case. > only the FE5680A is physically grounded to the case for heatsinking, so the > connection is a single point. > > while looking at the outputs of the two sources, I saw some surprising 20Mhz > harmonic content on my spectrum analyzer. I expected a bit from the 5680A, > but it was actually much bigger on the OCXO, which had a chinese add-on dual > buffer board attached. I had thought there might be some, so I also scored > some little 10Mhz BP filters at the same time and did some before/after tests. > > here's what I got: > > FE5680A 10Mhz (+5dBm), 20Mhz (-55dBm) (with filter) > > OCXO 10Mhz (-2dBm), 20Mhz (-35dBm) as received > OCXO 10Mhz (-5dBm), 20Mhz (-60dBm) with filter > > I hate to distribute any spurious RF around the lab, so I thought less > harmonic content was the better plan, although I realize that as a counter > time base source, it is probably irrelevant, but might play a role in my > 8656B RF generator as added unwanted spurs. I was a bit disturbed by the low > level and harmonics from the OCXO assembly, so I thought some external > comments about norms were needed at this point before I go further. > > what kind of harmonic content does everyone else see in their 10Mhz > standards? the -5dBm level seems too low to me, I am used to 0 to +5-7dBm > from sources, but I have not tried to run it through the distribution amp > yet, so possibly that's enough. I can try and dig into the totally > undocumented surface mounted chinese add-on board to improve things, and > increase the level, but hard to say what will happen there. > > all comments and data welcome. > all the best, > walter > > > > -- > Walter Shawlee 2, President > Sphere Research Corporation > 3394 Sunnyside Rd., West Kelowna, BC > V1Z 2V4 CANADA Phone: (250) 769-1834 > walt...@sphere.bc.ca > WS2: We're all in one boat, no matter how it looks to you. > Love is all you need. (John Lennon) > But, that doesn't mean other things don't come in handy. (WS2) > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
