$10 OCXO board

[tatel]

Hi, just stumbled upon a ludicrous, cheap listing on ebay:

https://www.ebay.com/sch/i.html?_nkw=314688036939

It seems it doesn't have uC, nor antenna input...

Any opinions?

[ataradov]

Your link is broken.

[tatel]

?

It works for me: I just checked it again

Perhaps an advanced ebay search will give some results? item # is 314688036939

Edit: or perhaps this one: https://www.ebay.com/itm/314688036939?

[ataradov]

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.

[tatel]

OK, now I understand. I'll probably get one or two just to play a little...

Thank you

[squadchannel]

maybe recycled cti's ocxo.

[tatel]

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.

[DaJMasta]

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.

[ataradov]

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.

[fourfathom]

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/

[EggertEnjoyer123]

You can buy the actual OCXO for much less (~$2-3 each)

https://www.aliexpress.us/item/3256806630149942.html

I have a few of those OCXOs and they're pretty good.

[tatel]

For now I rather prefer a board...

On ali for €5:
https://aliexpress.com/item/1005006400213075.html

[tatel]

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 MHz

OCXO is CTI OSC5A2B02

[807]

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 MHz

OCXO is CTI OSC5A2B02

Have 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.

[tashvikb]

What is OCXO board used for