$10 OCXO board - Page 1
Forum section: electronics / rf-microwave

author: tatel
author_rank: Frequent Contributor
timestamp: August 17, 2024, 11:14:26 pm
content: Hi, just stumbled upon a ludicrous, cheap listing on ebay:https://www.ebay.com/sch/i.html?_nkw=314688036939It seems it doesn't have uC, nor antenna input...Any opinions?

author: ataradov
author_rank: Super Contributor
timestamp: August 17, 2024, 11:54:16 pm
content: Your link is broken.

author: tatel
author_rank: Frequent Contributor
timestamp: August 18, 2024, 12:17:27 am
content: ?It works for me: I just checked it againPerhaps an advanced ebay search will give some results? item # is 314688036939Edit: or perhaps this one:https://www.ebay.com/itm/314688036939?

author: ataradov
author_rank: Super Contributor
timestamp: August 18, 2024, 12:23:18 am
content: This one works.It is not a GPSDO, just an OCXO. Why would it need an antenna and a uC?And for an OCXO the price is fine. Those are the boards built from recycled OCXOs. You can see the related listings are for the same OCXOs that are just cut from the PCBs.

author: tatel
author_rank: Frequent Contributor
timestamp: August 18, 2024, 12:31:42 am
content: OK, now I understand. I'll probably get one or two just to play a little...Thank you

author: squadchannel
author_rank: Frequent Contributor
timestamp: August 18, 2024, 12:43:39 am
content: maybe recycled cti's ocxo.

author: tatel
author_rank: Frequent Contributor
timestamp: August 18, 2024, 01:12:05 am
content: Very nice at that price. Very much doubt I could build an OCXO board at that price. I have some blue/black pills and a very old Garmin 12XL with antenna lying around. So I probably can begin to play FrankenGPSDO game on the really really cheap.

author: DaJMasta
author_rank: Super Contributor
timestamp: August 18, 2024, 01:56:33 am
content: AC coupled TTL output... interesting choice. 5x10^-12 is also one hell of a specification for "stability" even in the short term.May be interesting to play with and test, as with many bargain-bin electronics, I wouldn't expect it to meet specification.

author: ataradov
author_rank: Super Contributor
timestamp: August 18, 2024, 02:25:22 am
content: One big concern I would have with any of those recycled TCXOs is potential mechanical damage. They are scrapped from recycled boards and that scrapping is not the most gentle process out there. They heat them with blowtorches for de-soldering and smack them on the floor to separate PCB from the part.

author: fourfathom
author_rank: Super Contributor
timestamp: August 18, 2024, 05:23:27 am
content: I've purchased a few of those boards, for general lab and radio use. One issue you may discover is that the freq-setting pot may no longer be able to pull the OCXO on frequency. This is probably due to xtal ageing. On my boards with this problem I merely changed a few resistor values. In general a well-aged xtal is more stable than a brand new one, so this isn't necessarily a bad problem.There have been some good EEVblog threads about these boards. Here's one:https://www.eevblog.com/forum/projects/cheap-chinese-ocxo-frequency-reference-modules/

author: EggertEnjoyer123
author_rank: Frequent Contributor
timestamp: August 18, 2024, 07:24:04 am
content: You can buy the actual OCXO for much less (~$2-3 each)https://www.aliexpress.us/item/3256806630149942.htmlI have a few of those OCXOs and they're pretty good.

author: tatel
author_rank: Frequent Contributor
timestamp: August 21, 2024, 02:28:17 am
content: For now I rather prefer a board...On ali for €5:https://aliexpress.com/item/1005006400213075.html

author: tatel
author_rank: Frequent Contributor
timestamp: September 23, 2024, 04:22:03 pm
content: Well, it was delivered way faster than said in the listing. I didn't test it until now.It gave 10,000,003 Hz right from the start. Driving the trimpot to the limit, I'm getting 10,000,000 -10.000.001 Hz. Counter has accuracy of +/- 1 count +/- time base accuracy so pretty happy with it.I think it probably woulnd't be worth the hassle to change any resistor so it could be adjusted exactly to 10 MHzOCXO is CTI OSC5A2B02

author: 807
author_rank: Frequent Contributor
timestamp: September 25, 2024, 10:26:44 am
content: Quote from: tatel on September 23, 2024, 04:22:03 pmHave you ever calibrated the internal timebase of your counter with a higher order reference? The spec for that counter is 1ppb (if it has the OCXO fitted), so could be up to 11Hz out at 10MHz.I measured mine on a counter with a GPSDO external reference.

author: tashvikb
author_rank: Newbie
timestamp: September 27, 2024, 03:47:55 am
content: What is OCXO board used for

author: 807
author_rank: Frequent Contributor
timestamp: September 27, 2024, 08:20:35 pm
content: Quote from: tashvikb on September 27, 2024, 03:47:55 amIf you have some test gear that uses a non-OCXO 10MHz reference, you could replace it with this one to make it more stable & accurate.I'm going to replace the 10MHz reference in my Racal Dana frequency counters with OSC5A2B02 oscillators.

author: tatel
author_rank: Frequent Contributor
timestamp: September 27, 2024, 11:03:36 pm
content: Quote from: 807 on September 25, 2024, 10:26:44 amNo, this is literally first time I get into frequency counting. I just wanted to check this OCXO board is or isn't junk. I mean, perhaps the OCXO was damaged while desoldering or something like that.So far I think it couldn't be too bad after getting that result; so in the drawer it goes until the moment I'm ready to play more with it.