10MHz OCXO Frequency reference 8-ch output not accepting Ext-in - Page 1
Forum section: electronics / testgear

author: ytterligare
author_rank: Regular Contributor
timestamp: April 25, 2021, 09:37:46 pm
content: Hi there, anyone got this 8-ch puppy ? I can't seem to make it work with an external reference.The Hardware :A ZYT GPSDO with a 10 Mhz sine wave and two 10 Mhz square wave outputsAn OCXO Frequency reference with Ext-in input and 8 sine wave outputs.The second box, has an internal OCXO, which theoreticallycan be automatically bypassedwhen connecting an external reference, in my case from the Zyt GPSDO.You can see the red "Ext LED" in the picture which I believe is supposed to light up when connecting the 10 Mhz sine wave deriving from the GPSDO or any other external source.GPSDO out signal and OCXO differs by about 8 Hz : 10.000.000 to 9.999.992 about 30 minutes after power-up.When connecting the signal from the ZYT to the OCXO box "Ext-in", the distributed signal from the 8 channels remains 9.999.992 Hz and the led doesn't light up. Tried also with the square wave signal, no joy.Got the OCXO from a chinese seller on eBay, with no instructions, which I don't think are needed...Any hint or suggestions ? Anyone has the same OCXO and succeeded in make it work only as "distributor" of signal instead of being a source ?Thank youAndreaThe GPSDO :The 8-ch OCXO :

author: bob91343
author_rank: Super Contributor
timestamp: April 25, 2021, 11:13:12 pm
content: It seems to me that you need to command the unit to go into EXT mode. Simply connecting a signal isn't enough.I don't know enough about this unit to help any more than I have. Perhaps the RS-232 connector would be the way to make it work.

author: hpw
author_rank: Frequent Contributor
timestamp: April 26, 2021, 06:58:23 am
content: >> Got the OCXO from a chinese seller on eBay, with no instructions, which I don't think are needed...more than you think, while the seller is may a chica who knows nothing about. As my Ali... experiences..A manual for commands is a must have.Purchased a simple 10MHz Morion MV89a reference... phase noise outside the spec's, may a home made fake gear. Just open your 10MHz ref and thenSo be prepared as you get what you payed for.Hp

author: Ghislain
author_rank: Regular Contributor
timestamp: April 26, 2021, 08:20:40 am
content: There is some good information, including a manual here:https://www.eevblog.com/forum/testgear/zyt_gpsdo/

author: ytterligare
author_rank: Regular Contributor
timestamp: April 26, 2021, 10:21:22 am
content: Thank you gentlemen, but I don't think the problem is the ZYT Gpsdo, which is working quite well : strong signal, from the sine output, could even cascade the REF 10 Mhz through the Fluke signal generator ( which has a REF in and out ) without any problem....It is the 8-ch OCXO which is not acknowledging the 10 Mhz signal "IN" and then switching automatically from the internal REF source ( the crystal) to the signal coming from the GPSDO, distributing it through the 8 ports out....When I said that the manual for the 8-ch OCXO shouldn't be needed it is because there are no ports to communicate with it other than RF ports ( see pic. 4 )EDIT :I think I've found the problem : cracked the 8-ch box open and found that the center contact and the outer contact of the REF-IN BNC are shorted ( note the bad solder job of the armored pigtail to the board).Now, I'll try to fix it, but at this point, the mechanism of auto-switching to external reference remains to be seen....