LPF filter added 2.2mH choke to a .0022uf cap 1K R pretty simple and anttenuators and isolation to drive up to 4 receivers. Have not looked at the power amp and loops stick antenna yet. But it really is time for GPS a neo. Looking very good.
On Tue, Aug 28, 2018 at 7:29 PM, paul swed <[email protected]> wrote: > Ed appreciate the details but no intent to generally run a GPSDO in fact > the 5 V @ 50 ma is a serious power pig. The chronverter draws 5 ma. Clearly > the TTL is a heater. Chuckle. I do want to drive the chronverter with GPS > as its designed for. > Whats pretty interesting is you can adjust its offset. I just jammed time > into it several days and its been fairly good with power ups and down. Its > impressive. Though not in an ultimate time-nuts way. > GPS just assures it is accurate. But there is a lot of flexibility. > Main goal of this whole project is to replace wwvb if it goes away. If it > does the project doesn't even have to run 24/7. Fire up at 10 pm to 3 am > and power down. Thats enough to set my wall clocks for a day. Its just nice > to know it can also set the spectracoms and Truetimes. Icing on the cake. > I am impressed with what Dave did with the 8 pin pic. He has all of the LF > time signals in there. (No wwvb BPSK though) DSTs settings, zone offsets, > half zones, etc. > Just looking at low pass filters for the 60 KHz ttl out right now. Simple > LR or RC. Since this particular output feeds coax to the quality receivers > I don't need to be that careful. Its working great without any filtering. > Reality if it draws little power I will let it run 24/7 but then you just > have to stick a display on at that point. > Regards > Paul > > On Tue, Aug 28, 2018 at 7:11 PM, ed breya <[email protected]> wrote: > >> Paul, >> If you're going to reference it from a GPSDO anyway, why worry about a >> TCXO reference (and power too, for that matter). You can easily make the 60 >> kHz from the 10 MHz. >> >> For example, with two 74HC390s and a 74HC86 you can make 50 kHz and 10 >> kHz and mix them with one EXOR section of the '86 to have 60 kHz available. >> Some fairly simple bandpass filtering should select and clean it up >> sufficiently. Two other sections of the '86 can be set up as inverters and >> self-biased as amplifiers - one to convert the 10 MHz sine reference to >> logic, and the other from the filter output to logic, if needed. And, you'd >> still have a divide by 5 and an EXOR left over to fool around with. >> >> The same parts and process can be done at a higher frequency and then >> divided down afterward. (5+1) MHz/100, and (500+100) kHz/10 would work too. >> It depends on what frequency you prefer for the BPF. If you go high at 6 >> MHz, you then have the option to make a crystal filter from readily >> available parts. >> >> Going the high way also provides for higher logic frequencies that are >> more or less in sync, in case you want to do any I-Q modulation type stuff >> - you can even use synchronous counters instead, to really make sure. >> >> Overall, I think I'd recommend going at 5+1= 6 MHz, filtering with 6 MHz >> crystals, then dividing down to 60 kHz, with 2f and 4f clocks available for >> I-Q use. I sketched out a quickie circuit that's quite simple and I think >> would do. It would take two HC390s for the dividing, as before. Each HC390 >> is two divide by 10 counters, including a 1/2 and 1/5 in each, usable >> separately. So, with two parts, there are four 1/5s and four 1/2s available. >> >> Here's a verbal process description: 10 MHz sine convert to logic with >> HC86, 10 MHz/2=5, 10 MHz/10=1 with first HC390, add 5+1=6 with EXOR, BPF 6 >> MHz, convert to logic with HC86, 6 Mhz/25=240 kHz=4f, 240/2=120 kHz=2f, >> 120/2=60 kHz=f, with second HC390. >> >> Ed >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to http://lists.febo.com/mailman/ >> listinfo/time-nuts_lists.febo.com >> and follow the instructions there. >> > > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
