Electronics > Metrology
OCXO's and friends
Lemonizer:
Hello everybody !!
I'm getting more and more interested by OCXO's, and GPSDO's in particular.
I read multiple threads about a few known brands like Morion, Oscilloquartz, ISO-Temp, etc, and I'm quite interested to know which ones are in the top 3, stability/phase noise/overall quality-wise !
I'm asking the same question for GPSDO's, and GPS modules too !
I know that not all OCXO's even from the same brand/model are equal, some are better than others (its the same for every production product I guess), but I'm sure this is like wine, some years must be better than others ! :P And some very knowledgeable and qualified peeps here must know things that aren't in books !
I was interested by purchasing an Oscilloquartz 8663-XS, a Morion MV89A, and a few others cheaper like Bliley, NDK or ISOTEMP to measure them over days/weeks, and see which one is a good performer. Do you have anything to say on those models ? They seem to be highly regarded here ! (the morion seems to have issues !).
I'm soon getting a BG7TBL GPSDO from 2018-01, his distribution amplifier (to connect the GPSDO to my HP 5345A, and Siglent 1032X) and the FA-2 counter (that I will also use with the GPSDO as his reference).
I'm wondering what people think about that FA-2 counter, compared to high-end counters like Agilent, Pendulum's ones, just accuracy wise (once used with a well stabilized GPSDO, with a good signal ofc). I mean, it seems to be pretty nice, it got a huge resolution, and its mostly the external reference that does all the work accuracy wise, right ?
I thought it would be nice to later replace its OCXO with a better one (once I got my hands on a few that were measured during days, prior to that) and power it with a linear supply, instead of a wall-wart. Am I right ?
If it was in a nicer box, with a big brand sticker slapped on it, would people pay much more for it ? (the 1 million dollar question ! :scared:)
I'm still pretty new to this, I'm trying to read as much as I can to avoid asking redundant questions, I would greatly appreciate if any veteran time-nut could help me out on those ! :-+
Have a nice evening/day ! 8)
Lemon
KE5FX:
A few random thoughts --
- Right now the OCXOs with the best short-term stability are probably the high-end models from Rakon, intended as replacements for the Oscilloquartz BVA models. They are about 5x-10x better than most other high-quality oscillators. You probably don't need one, but if you do, the price will run well into five figures in either Euros or USD.
- In terms of value for money, it's hard to beat a well-aged Morion or C-MAC DOCXO. These are often sold on eBay out of Hong Kong or Shenzhen, having been removed from decommissioned hardware by someone with a blowtorch. So you should plan on buying 2 or 3 to get a working one, and a dozen or more to get an outstanding one. At the prices they sell for, this value proposition is quite reasonable.
- The BG7TBL GPSDO has good overall performance but if you are interested in amateur time and frequency metrology (as opposed to simply wanting a good frequency standard for the ham shack), you will want to make sure he has fixed the bug that was documented earlier.
- No experience with the FA-2 personally, but I've been hearing good things about it. Customers would pay more for it if it were in a nicer box with a Keysight logo, but unless you're being paid for your own work or trying to impress visiting time nuts, a fancy brand name adds little value to a counter. Unlike an OCXO or a GPSDO, a counter maintains the accuracy and stability of its reference, as you've noted. If it's not working properly, it probably won't work at all. There is unlikely to be any benefit to messing with the power supply, in any event.
Lemonizer:
Thanks for your answer, I appreciate that ! :P
Those Rakon's are sure pretty neat, but yeah, out of reach sadly :phew: !
About the C-MAC, those for example ? https://www.ebay.fr/itm/OCXO-Oscillator-C-MAC-STP2187-10-Mhz-Double-Oven-Sine-wave-12V-EFC-Freeshipping/252616346274?hash=item3ad11b8aa2:g:qaAAAOSwSwNbNDIj
And for Morion's, the MV89A is a good option ? Looking at their price, I'd rather directly get a few of the 'best', if I just need to spend a few bucks more.
Thanks for pointing out that bug on the BG7TBL GPSDO, hopefully its fixed by now, we will see !
About the GPS part of a GPSDO, as long as it locks correctly and its getting a strong signal, do I benefit from getting a 'better' one, accuracy wise ? Will those lonnnng string of digits on my FA-2 counter (with the GPSDO as a ref) will be more accurate, to put it simply ?
Lemon
KE5FX:
--- Quote from: Lemonizer on March 29, 2020, 09:45:25 pm ---About the C-MAC, those for example ? https://www.ebay.fr/itm/OCXO-Oscillator-C-MAC-STP2187-10-Mhz-Double-Oven-Sine-wave-12V-EFC-Freeshipping/252616346274?hash=item3ad11b8aa2:g:qaAAAOSwSwNbNDIj
And for Morion's, the MV89A is a good option ? Looking at their price, I'd rather directly get a few of the 'best', if I just need to spend a few bucks more.
--- End quote ---
Yes, but as others have noted you may have to go through several to get a good one. I don't know of anyone selling cherry-picked MV89As. If purchased new from Morion, they will probably cost multiple thousands of dollars, and you still won't have any guarantee of getting an unusually good one.
For C-MAC, I've only bought STP-2055Bs, so can't comment about the others. The best OCXO I have in-house is one of those.
--- Quote ---About the GPS part of a GPSDO, as long as it locks correctly and its getting a strong signal, do I benefit from getting a 'better' one, accuracy wise ? Will those lonnnng string of digits on my FA-2 counter (with the GPSDO as a ref) will be more accurate, to put it simply ?
--- End quote ---
Yes, that's the idea.
Lemonizer:
Ok thanks, I'll be looking for 2055B's, it seems theres none on ebay right now. What is a good price for those ? (non cherry picked, just 'working' :P)
About GPS modules, what are the best ones around ? How are ranked those Ublox that comes in BG7TBL's GPSDO's ?
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