I know this is an old thread but I've decided to revamp my GPSDO so I thought I'd get feedback and give some impressions with OCXO's that I've worked with.
A couple of years ago I bought two or three Milliren 260 OCXO's. These go for $1k US a pop so getting them on eBay for ~30 bucks seemed like a good deal. Milliren advertises these as up to Rubidium standards. The ones I got from China (fully tested....Yeah right!) were hit and miss. One couldn't be voltage adjusted and another one had a voltage reference drift, then after a day on the bench the heating element quit for awhile and then came back on and off and on.... This makes sense, at the price they go for nobody wants to change them out more than they have to. The seller sent me a replacement for the first one and after testing for several days I now know I have two good ones. These are 5Mhz, by the way and I double the frequency with a Cypress chip.
The work very well, when they work, but look at the dates if you buy them. I noticed they're mostly past their MBTF dates (about 17 years if I remember Milliren telling me). The date is the bottom line, something like this
99 is the year, 07 is the month and 18 is the day. The "-2" is the number in the line up that day out of the total number made.
Even the best ones still had some ref drift but not enough to make any real freq. difference.
The Morion 89 uses more power, I think it came in around ~380ma at 12V as opposed to 250ma for the 260. I got hotter too (around 125F) but the voltage ref seemed to be more stable, after a couple of days the histogram showed a few uV's drif, much better than the 260. Both had superb frequency stability. I have a Rubidium standard that's calibrated but it's handy to see drift. I turn it on for a day, adjust the OCXO and then shut if off to save it. The uC 12 bit DAC controlled circuit I built (manual adjust using the 260's ref ) was within a few parts in 10 gigs over the few months since I checked. I didn't test the Morion but I would expect, after watching it for a few days on the bench, that it would be pretty close to the 260.
I tested a few more OCXO's, a CMAC for one, but it was no where as good as the two above.
I've decided to build a uC controlled 1 sec GPS GPSDO. Seeing the long term stability of these OCXO's I figure I can go quite a while before freq,. corrections. I know people have done it but I use Atmel mostly with an external 12 bit DAC. I like this arrangement so I'd like to stick with it as much as possible, maybe tweaking a design. I do have a one second timing GPS, I had a Jupiter 10Khz but it died but with these OCXO's I think I don't need the, now scarce, 10Khz outputs.
Thanks for your help,