You could also download the specification :-) Sync is a requirement, IRIG STANDARD 200-04 says, 3.2.10 Amplitude Modulated Carrier. A standard sine wave carrier frequency to be amplitude modulated by a time code is synchronized to have positive-going, zero-axis crossings coincident with the leading edges of the modulating code bits. A mark-to-space ratio of 10:3 is standard with a range of 3:1 to 6:1 . Robert G8RPI.
________________________________ From: Chris Albertson <[email protected]> To: Discussion of precise time and frequency measurement <[email protected]> Sent: Tuesday, 14 May 2013, 23:16 Subject: Re: [time-nuts] Is there any IRIG-B hardware decoders available? Not me, THis was not my idea. I was reacting to the claim that IRIG had to sync the carrier phase. I had not heard of it before but it was not surprising. And what the heck, it sounds like a good idea, and a 4046 chip cost about the same as a 555, We could "cheat" and actually read the IRIG clock reference driver source code and see how it works. The NTP ref clock driver reads u-law sample data at 8096Hz. So it could be 8x sampler the 1KHz carrier, it could be detecting phase. I don't know. On Tue, May 14, 2013 at 1:43 PM, paul swed <[email protected]> wrote: > Boy Chris I don't know what to say here I use IRIG B decoder displays and > they have been happy with my free running xtal oscillator for 12 years. I > do not recall IRIG B making phase lock a requirement. I use gps to get a > time stream then a SXB micro to convert that to IRIG B... > Regards > Paul. > WB8TSL > > > On Tue, May 14, 2013 at 1:35 PM, Chris Albertson > <[email protected]>wrote: > >> OK the 555 timer is not so good of an idea. You need a phase locked >> 1KHz oscillator. >> >> You can also buy IRIG cards for the PCI bus. We used them where I >> used to work. They are not cheap. Almost any company that working in >> timing or telemetry will have these cards. >> >> But still if the goal is to have the computer's system time track >> irig, use NTP. It should be easy to build a phase locked 1KHz >> oscillator. 1K is such a low frequency. I'd thing a 4046 chip would >> do the job. >> >> On Tue, May 14, 2013 at 10:04 AM, Esa Heikkinen <[email protected]> wrote: >> > Chris Albertson kirjoitti: >> > >> >> NTP will so this. There is an IRIG reference clock. You really do >> >> want to use NTP to discipline the PC's clock. Almost every other >> >> method is worse and causes time discontinuities. >> >> If you happen to have TTL level IRIG it s very easy to convert it to >> >> amplitude modulated IRIG. The standard is a 1KHz tone. >> >> Build a cheap 1KHz oscillator. A 555 timer is good enough. Then you >> >> a single transister if IC time switch to modulate the amplitude of the >> >> signal. The details are not critical. >> > >> > >> > That's good idea if the phase of the 1 kHz signal is not critical? >> > >> > I checked the IRIG-B signal with oscilloscope and looks like the 1 kHz >> > signal's phase is locked to the time signal. The bits will always start >> and >> > stop at exactly same phase. That makes sense because with phase detector >> it >> > could be possible to get very accurate timing from the 1 kHz signal - >> much >> > better than following the amplitude only. That's one reason why I was >> > interested about chipsets; if they can follow the phase also. I think if >> I >> > design any hardware for that it should follow the phase also? It may be >> > complex... >> > >> > Does anyone know if the soundcard based IRIG decoder will follow the >> phase >> > also, or only the amplitude (?) >> > >> > -- >> > 73s! >> > Esa >> > OH4KJU >> > _______________________________________________ >> > 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. >> >> >> >> -- >> >> Chris Albertson >> Redondo Beach, California >> _______________________________________________ >> 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. -- Chris Albertson Redondo Beach, California _______________________________________________ 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.
