[time-nuts] WWVB Receiver
For those who are looking for a source of WWVB receivers / chips there is a person in the UK who is selling the Symtrik board and antenna on ebay -- item 23099171331. Unfortunately, the chip is embedded in expoy but it does have a 1 pps LED. Here is the link to the data sheet: http://www.pvelectronics.co.uk/rftime/SYM-RFT-XX.pdf I have no connection with this item or listing. ___ 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] WWVB Receiver
To Paul re my receiver thoughts. You are absolutely correct in some regards and for some implementations. The limiter must have very high dynamic range and must not convert changes in input level to changes in transmission phase; i.e. No AM to PM conversions. Thus my specific suggestion of the Analog Devices parts. Normal diode limiters and such simple stuff won't work.The internal configuration of Low AM-PM limiters is 9 or 10 stage of emitter coupled differential pairs. Now conveniently available as ICs. Likewise you need a slow PLL in front of the divide by 2 in order to coast through fast fades. Alternatively you can use the log output of the limiter as an instantaneous level indication and not sample the input during periods of no signal. Some implementations could use a really stable frequency standard as the VCXO in the PLL and freeze the control voltage during fades. I did this once with good success. Using the HP 10544 we could ride through a 2 hour outage and maintain code synchronization. So it is possible. With regard to filter phase, I mentioned BW because it is easier to measure. Wider BW = better phase response for all else being equal. However properly implemented - the suggested configuration should work OK. Once upon a time -1976 - A similar setup was used to extract the carrier for a BPSK demodulator from a spread spectrum IF signal. Good luck with your design. -73 john k6iql ___ 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] WWVB Receiver Comments
For David - re WWVB carrier recovery. On squaring vs absolute values for carrier recovery. Never heard of using absolute value. As I said in my initial remarks - some perusal of the prior art is helpful for this problem. There are 70 years of literature on how to do this for any imaginable purpose. The squaring loop that I described and the Costas loop are classical solutions. Both can be made to work for this problem, though I prefer the former having implemented it previously. Same applies to narrow band tracking of weak signals. It is in the literature. This is not hard stuff nor is getting a GPS signal without the neighbors finding out and repeating the riot scene from Young Frankenstein. -73 john k6iql ___ 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.
