After my post a few days ago I decided to install a TCXO in my SDR1000. Three days since my last cal, I just checked WWV on 10MHz. I'm seeing one rotation on the 'Phase' display every 2 seconds or 1/2 Hz. Hard to tell if it's WWV or me.
I thought this was fantastic until I read Alberto's post. He's not satisfied with 2 to 3 in 10^11. That's 0.0002 to 0.0003 Hz at 10MHz. Whew, Alberto what are you doing that needs that accuracy? The TCXO I'm using is a 10MHz unit from a piece of HP test equipment. I padded the output for 1Vpp and am very happy with the results. Then again, I don't plan to use it for submarine positioning at this time. :) Lots of TCXOs on EBay for < $25. 73, John k2ox Ray J wrote: > with all the talk of frequency stuff lately.... found this on ebay while > looking around.. > don't know if its useful to any of the experimenters out there.... > > Isotemp model OCXO134-10 10.000000MHz OCXO $75 > > http://cgi.ebay.com/New-Isotemp-10MHz-OCXO-1PPB-EFC-For-GPS-Discipline-12V_W0QQitemZ5833990844QQ Hmmm, I bought one of those OCXO three years ago. I paid 25 USD (one third of that price) and used it to build a GPSDO. It works, but you cannot do better than a few parts (2 or 3) over 10^11, which can be a superb result, depending on your goals... The problem with that OCXO is that its oven regulation has a periodic temperature change of about 0.2 degrees Celsius peak-to-peak, with a period of about 6 or 7 minutes. That period is too fast for the PI controller implemented in the Atmel AVR, which, after the initial transient period, has time constants in the order of more than one hour. So the frequency change caused by that variation in temperature goes almost uncorrected, causing that 2 or 3 part over 10^11 of frequency "pendulum" I have graphed it, you can see it here : http://sundry.i2phd.com/Lock3be.gif Of course, it could be that only my specific Isotemp OCXO had this problem, and other units work well. Anyway, my next GPSDO will make use of a double oven 10811... I found one brand new, still in its box...: 73 Alberto I2PHD
