[time-nuts] ultra stability ocxo
My company is in China, which has a huge market for Time Frequency products, especially for ultra stability ocxo. We are looking forward to working toghther with you and selling your products in China as an agency .waiting your reply weijiazhen ___ 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.
Re: [time-nuts] DSP WWVB Receiver Idea
Brooke Clarke wrote: On the PICLIST there has been a discussion about the CMAX WWVB front ends and noise. Olin mentioned that you could use a dsPIC to look at the I and Q signals resulting from mixing the WWVB signal with a carrier at 60 kHz. His example case was to use a cheap crystal (+ or - 3 Hz) and so use a 10 Hz low pass filter on the I and Q signals prior to squaring and adding them. I've built such a thing ( http://n1.taur.dk/dcf/ ). The zero-if I/Q approach has a few things that make it less ideal than it sounds. There's the 1/f noise, discovering and compensating for DC offset on each of the channels requires that you remove the input, and it might not be a nice divider from 10MHz. If you choose a small arbitrary offset you can solve these problems in software, only the filters in hardware need to be wider. Having the first filters wide, I found, was a good thing: In the very early morning I get a lot of sferics, and my steep filter rang like a bell with every crackle. A low-Q front end allowed throwing those samples away. Since that was done I have added a narrow bandwidth phase integrator (2mHz) in software, and it will happily pull out ~10ns rms phase with a +60dB carrier 1Hz from center. It even stayed locked when the antenna amplifier broke and output 5Vp-p instead. The real advantage of the I/Q method is that the bandpass filter becomes two lowpass, and two lowpass is easier than a similar width bandpass with enough precision and phase stability to be centered around 60kHz (and if you use crystal resonators in the front end you can't track anything else, and you get a problem with suppressing sferics). You might not be able to get continuous reception no matter how hard you try; I've seen inversions where the carrier just slowly fades and comes back inverted with no apparent phase jumps (it looks like extremely slow bpsk). If I did it today I'd try phk's approach first. Preferably with a somewhat tuned antenna to keep harmonics from PAL horizontal retrace from clipping the converter. The one above was built with what was available in the junkbox at the time. /Kasper Pedersen ___ 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.
[time-nuts] [Fwd: Re: Code Review for NTP upgrade requested.]
In case anyone here is interested in the OpenSolaris project. Brian sent this to me a few minutes ago, and I am forwarding with his permission. Rob KC6OOM/5 Begin forwarded message: From: Brian Utterback brian.utterb...@sun.com Date: April 22, 2009 2:29:22 PM CDT To: Robert Vassar robert.vas...@sun.com Subject: Re: Code Review for NTP upgrade requested. Sure. Great. Robert Vassar wrote: Brian Utterback wrote: I am very pleased to announce that I have just posted the webrev for the upgrade of NTP version in Solaris to cr.opensolaris.org. As members of this mailing list know, I'm upgrading NTP from the currently included version 3 to version 4, specifically version 4.2.5p161. There are two steps to this, since the packages currently reside in the ON consolidation, and afterwards they will reside in the SFW consolidation. I currently have the SFW webrevs available. I will have the ON webrevs soon. Please help to code review the modifications. The webrev is at: http://cr.opensolaris.org/~blu/ntpv4/sfwnv-webrev/ All comments will be gratefully appreciated. May I forward this to the time-nuts? Rob -- blu Mark my words, nanotechnology is going to be huge! -- Brian Utterback - Solaris RPE, Sun Microsystems, Inc. Ph:877-259-7345, Em:brian.utterback-at-ess-you-enn-dot-kom ___ 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.
