Hi 10 MHz does not divide by an integer to 60 KHz. 15 MHz, 6 and 9 MHz are all more reasonable candidates. The attractiveness of 15 MHz and the value of a tunable OCXO is what makes the current $25 price of the KS boxes pretty attractive. You *might* even be able to dispense with the tear down of the KS box and feed it 1 pps out of your ADC / FPGA / MCU / Bailing wire rig. Instant WWVB disciplined OCXO.
Bob > On Aug 5, 2015, at 6:07 PM, Mike Magin <[email protected]> wrote: > > If one were trying to use it not simply for the time code but also as a > frequency reference, it seems to me that the ideal thing would be a ADC > that can easily use an external clock (derived from a local voltage-tuned > OCXO reference under control of the SDR). Otherwise one is doing (rather > coarse) software compensation for the phase offset between the ADC clock > and the WWVB signal. > > Does that make sense? Anyone know of some reasonably affordable > off-the-shelf ADC board/module that takes 10 MHz external clock? > > On Wed, Aug 05, 2015 at 12:40:10PM -0500, Graham / KE9H wrote: >> There are several high end audio Analog to Digital Data converters that >> will clock at 192 kHz, ~23 bits ENOB, which puts a 60 kHz signal sweetly in >> the first Nyquist zone. Typical NF of the front end of the data converter >> is 20 to 25 dB, so noise floor well below the atmospheric noise level at 60 >> kHz. You would only need a preamp if you were running some negative gain >> antenna. Lots of dynamic range. Won't overload until 2 Volts peak-to-peak >> or so. A very simple, high performance digital receiver front-end. >> >> --- Graham / KE9H >> >> == >> >> On Wed, Aug 5, 2015 at 6:15 AM, Bob Camp <[email protected]> wrote: >> >>> Hi >>> >>> The front end would be “dealers choice”. He who does the >>> project gets to decide what gets used. >>> >>> If you look over some other designs, you can indeed get >>> a device going with a 12 bit converter. The qualifier is that >>> the signal to noise needs to be pretty good. With fades >>> and switcher interference, you probably would notice its >>> limitations. >>> >>> The “other end” of the design spectrum would be with a part >>> designed as a high range font end chip. You can get to a lot >>> of bits at low frequency. Even the prices aren’t all that crazy. >>> >>> Is there one and only one approach here? Not in any way. There >>> are several thousand possible ways to do it. AGC or no AGC would >>> be a pretty major decision. Next decision would be things like clocks. >>> 15 MHz from a ($25) KS box that also puts out 10 MHz looks like a >>> pretty good choice at the moment. >>> >>> Past that it’s decimators / filters and the usual DSP stuff (or any of >>> a dozen alternatives). Given the high noise environment I’d lean towards >>> a DSP approach. >>> >>> Most of the choices run into the easy / quick / cheap tradeoff triangle. >>> I’m >>> sure that the debating process can find a solution that should “cost 10 >>> cents”. I’m >>> also sure that a basement lash up of available parts is quick, but hard to >>> reproduce. >>> I’m not terribly surprised at the lack of 10 cent solutions. I’m a bit >>> surprised >>> that there are no unique lash up designs. The debate process seems to >>> have made this a pretty un-attractive thing to do. >>> >>> Bob >>> >>>> On Aug 4, 2015, at 11:36 PM, Hal Murray <[email protected]> wrote: >>>> >>>> >>>> [email protected] said: >>>>> So far there have not been any home brew design radios show up that will >>>>> demodulate and lock to the new data format. There is plenty of info on >>> the >>>>> transmit format. The demodulation approach is not crazy hard. That said, >>>>> there’s still a lot of work to get a receiver running. >>>> >>>> Has anybody looked into a software approach? What sort of front end >>> would >>>> you want? >>>> >>>> >>>> -- >>>> These are my opinions. I hate spam. >>>> >>>> >>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- [email protected] >>>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>> and follow the instructions there. >>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >>> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
