On Dec 1, 2008, at 2:33 PM, Stanley Reynolds wrote: > Message: 6 > Date: Mon, 1 Dec 2008 14:31:33 -0800 (PST) > From: Stanley Reynolds <[EMAIL PROTECTED]> > Subject: Re: [time-nuts] DAC resolution in GPSDO > > The oscillator I think has a manual adjustment. You could be using > the 5 volt provided on board or the 8 volt provided by the OCXO for > the ECC op amp. Note the ECC voltage is dependent on the control > board regulation some what even using an external reference. You > may want to manually adjust the OCXO closer to zero and set the > upper limit lower as well. By?using a external voltage divider on > the ECC voltage or lowering the gain (R7 & R8).
Nope, this Isotemp was made for OFC, labeled OSC092, or maybe OFC/ McCoy sold out to Isotemp. There's no external adjustment available. I used a 78L05 to make the +8V reference supply for the OCXO and it works quite well. I don't use the BertBoard's signal output chip at all, nor the RS-232 chip, so loading hasn't been a problem. Compared to my recently purchased Thunderbolt, running off the same antenna, the Zauhar GPSDO moves around by a few parts in 10E-10 to 10E-11. Using the +8V ref supply to make a larger range of DAC output makes the problem worse, not better. A 16-bit DAC would help, but this project has gotten more complicated than I wanted already -- see my webpage. The best solution now would be a good 10811A... Dick Moore _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.