Ed, I've been playing with a CW12, it basically appears to do what they say but I will not confirm any numbers for the moment, it certainly compares to my VLF derived 10MHz signals. I was looking to build a GPSDO and 10MHz from the GPS Rx seemed a better starting point than 1PPS.
I'm only now near to completing part two of the exercise, phase locking a 10MHz double oven XO to the CW12 10MHz, the phase noise on the CW12 output is rather significant and needs cleaning for most applications. The ssb numbers I see from the CW12 (using an HP8560E) relative to the 10MHz carrier are : 1kHz -80 dBc/Hz 10kHz -102 dBc/Hz 100kHz -109 dBc/Hz 1MHz -126 dBc/Hz The signal is far from a pure line, close in there is a set of sidebands based on harmonics of 132 with the fundamental at -22dBc, there are various synthesis artefacts. This unit clearly needs filtering. The PLL I've built to clean it up is essentially a simple 2nd/3rd order loop with the phase comparison at 78kHz (sigs divided by 128), my model claims the 3dB closed bandwidth will be 0.3 Hz and sideband suppression about 127dB at 1kHz offset in principle. In reality I'll need to play with it to look at the real world limitations of acquisition, loop BW, analogue offsets etc . The OCXO I'm locking is a Temex part, a 'Doc1478-D" which seems to be from their S110 series. It claims to manage -145dBc at 1kHz offset. There were on ebay at low cost a while ago, everything else has largely been built from scrap which has biased the design ever so slightly, the less it costs the more amusing the project if you are not doing it for a customer. The slight disappointment has been the lack of support information about the CW12 on the web, when I spoke to them in March they said their site was going to be updated by the end of that month, clearly they have dropped the ball somewhere but the email support seems responsive. I think I've seen the CW25 appear in a recent GPSDO from Quartzlock, have a look at : http://www.quartzlock.com/cgi-bin/servepage.cgi?usr=61390&page=tech_DS_E8-X. pdf This appears to use a DDS/PLL to clean the reference clock rather than a large and expensive OCXO. Starting afresh I may have gone for the CW25 but I've got the CW12 so not thought much more about it. Regards David Mackenzie (GM4HJQ) _______________________________________________ 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.