10 Mhz OCXO , Improvised  - Page 1
Forum section: electronics / general

author: GigaJoe
author_rank: Frequent Contributor
timestamp: June 20, 2019, 11:48:28 pm
content: I found 10M , 5Volt china made crystal, I believe it AT cut; purchased a long time ago, Wrapped in 5cm thick wall Styrofoam box , where the inner size just enough for the ocxo and lt1021-5 for voltage adjustment, linear PSU +5 +12; then tune freq. precisely after a week of running against GPSDO - cant measure phase run , it such stable, just drifting back and forth.the styrofoam box, decrease a power consumption from 190ma (open) to 85ma (in box)now after one week I still cant observe a shift in a frequency, it changing when I tilt the box (visually starting to slow moving on the scope), or change the box position .... but not itself.Does it mean it a good one?How to distinguish crystal to be good or bad for a long run, in overall ? like changing freq to 0.1Hz for a week - bad, but after 4 weeks a good one ....Don't shoot me about the box, was in hurry:

author: testpoint1
author_rank: Frequent Contributor
timestamp: June 21, 2019, 02:56:54 pm
content: Quote from: GigaJoe on June 20, 2019, 11:48:28 pmuse a calibrated Rubidium oscillator as reference, then the CNT-90 to test its 10MHz, you will find the frequency jitter (maximum-minimum of 100 seconds)

author: GigaJoe
author_rank: Frequent Contributor
timestamp: June 22, 2019, 02:47:14 am
content: got it ...Do i calculate it right:I measure time in seconds when one period drifted relatively another to precise one period for 10M base signalthen do calculation 1/[ drift time in sec] = Hz of difference.so when it moving to the right it lower then base , left - higher then basein my case:1/1280 = 0.00078125 Hz drifting right, it means = 9 999 999.99921875 Hz ( assuming 10M precisely)

author: awallin
author_rank: Frequent Contributor
timestamp: June 22, 2019, 05:51:08 am
content: Quote from: GigaJoe on June 22, 2019, 02:47:14 amif you want results in fractional frequency you could calculate this as one period of 10MHz during 1280s i.e. 100ns/1280s = 7.8e-11

author: testpoint1
author_rank: Frequent Contributor
timestamp: June 22, 2019, 11:11:03 am
content: Quote from: GigaJoe on June 22, 2019, 02:47:14 amwhat is your testing tool please? which model is your external frequency reference?

author: GigaJoe
author_rank: Frequent Contributor
timestamp: June 22, 2019, 04:48:15 pm
content: External are Thrimble GPS, I just assume it ideal. frequency started to change, before to measure it probably hours when 1 period shifted, it was like almost a week, but i change the location of the box with ocxo and power it off\on it started to change slowly ...day 21 22:30 1280 sec, to rightday 22 13:30 540 sec , to rightday 22 18:50 540 sec, to rightday 22 23:30 420 sec, ...i don't think it gps drifting ...i purchased rubidium recently seller in this forum claim 5E-11, but I see a large disagreement with GPS 0.02Hz, so the unit need boxed , psu, adjustment, and it really consumed power -- I don't need such precision dailyOCXO I see it as an excellent 10M source for a 9 digit counter , and a generator, that source will be powered on constantly and consuming just a few watt.trying to figure out how fast\bad etc. it drifting ...Nothing more from this project ...