On Wed, Mar 14, 2012 at 3:08 PM, Brooke Clarke <bro...@pacific.net> wrote: > Hi: > > I sure would like a WWVB BPSK receiver for the new modulation. The > processing gains described in the paper John Seamons linked describes > processing gains that are tens of dB above what's possible with the old AM > data format. John has also measures the experimental phase modulation > testing, see: http://www.jks.com/wwvb/wwvb.html > The WWB paper "New Improved System for WWVB Broadcast" given at the 43rd > PTTI November 2011 is at: http://jks.com/wwvb.pdf > > Part of the processing gain comes directly from the BPSK modulation and that > amounts to a little over 10 dB improvement, but there's a further 18 dB gain > to be had by accumulating an hours worth of data and processing that. > > I'm sure in time there will be plenty of low cost ICs designed to receive > the new signal, but my guess is that many Time Nuts would like to be in on > the ground floor. Also NIST probably would like to get reports on the new > signal when they do test transmissions. > > How to move forward?
I'd say to go "100% SDR". In other words a simple front and that pushes as much of the functionality into software as possible. The carrier is only 60K. That is low enough that one can directly digitize the RF using an ADC that samples at only 192K/sec. 192K/Sec is a common sample rte for high-end audio and you can buy a 24-bit dual channel interface for under $200. So I'd use an antenna (the best would be a shielded loop with many turns of wire but ferrite "loop stick" could work) Follow that be an RF amp and very narrow filter and then the above 24-bit 192K ADC. With a 24-bit ADC you may not need any automatic gain control. So yo are almost sampling the voltage off the antenna, so that's why I called it "100% SDR" Once the data are inside the computer the very next step might be an FFT. Some good easy to use software is this: http://gnuradio.org/redmine/projects/gnuradio/wiki/GNURadioCompanion Using this you simply drop function blocks on a screen and connect then with lines. It's a visual drag and drop way to build a signal processor As an example to build a spectrum analyzer you drop a block the represents your audio interface, another for the FFT operator and a third for a graph. Connect them together. Then plug in a microphone and point it as something you want to plot. If you do use the simplest possible RF front and that can still work, followed by a common off the shelf audio interface and then a simple graphical programming environment you then will have a wider community of people working on this. You could use more complex technology like an FPGA or a DSP chip but then the number of people who would know how to help will be a number close to zero. The RF front end does not need to be sophisticated because much of the selectivity and gain control is done in software. You just need a hard low pass filter to remove everything above 60KHz > > -- > Have Fun, > > Brooke Clarke, N6GCE > http://www.PRC68.com > http://www.end2partygovernment.com/Brooke4Congress.html > > > _______________________________________________ > 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. -- Chris Albertson Redondo Beach, California _______________________________________________ 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.
