Hi If you happen to pick 5 or 10 MHz as your target frequency, all sorts of interesting things come into play. The first is that any 5 or 10 MHz local standard distribution may well get into your receiver. That can create all sorts of odd effects as the signal fades. Next is that you aren’t just on a channel for two stations. There are a number of standard broadcasts that pop up. Depending on propagation, they may be strong enough to notice.
*If* you can get WWV to give you sub 1 ms timing accuracy (or even low ms), that’s better accuracy (as opposed to jitter) than NTP can do with a normal home internet connection. Internet modems have some pretty nasty timing asymmetries built into them. On top of that you may have asymmetric routing. Up stream and downstream routing is a “two pipes” process in a lot of head end installations. Again, we’re talking about internet and not some sort of GPS based system. To get the accuracy into the 1 ms range on WWV, you would need a pretty good idea of the path length between you and WWV. If you are looking at ground wave, that is a bit easier than if you are bouncing off the ionosphere. Just as with WWVB, there probably is a “best time of day” to run your comparison. Since you get a lot of ticks, there is no real need to just use one. Feed the audio into a computer and let it sum them up. Monitoring for 10 minutes does not seem to be overly crazy. That’s still a lot of ticks. If you dig into the archives, there are some good posts from PHK about doing this sort of thing with Loran-C. Bob > On Dec 7, 2017, at 4:29 PM, Bill Hawkins <[email protected]> wrote: > > One way to compare any WWV receiver to a local standard is to use the > PPS output of a standard against the PPS tick modulated on WWV. The tick > is five cycles of a one KHz signal derived from the master frequency. > See > https://www.nist.gov/pml/time-and-frequency-division/time-services/wwv-a > nd-wwvh-digital-time-code-and-broadcast-format > > It will be a bit tricky to determine the onset of the first cycle amid > the noise on shortwave radio. A computation that determined that there > were just 5 cycles and worked backwards to determine the timestamp of > the beginning or middle of the tick could then allow calculation of the > offset between the standard PPS and the tick. Limit of accuracy might be > 100 microseconds. > > Years ago, I had a standard calibrator made by Lavoie that had a vacuum > tube WWV receiver. IIRC, the WWV carrier caused a circular sweep on a 2 > inch CRT. The sine wave from a standard modulated the intensity of the > circular trace, so that a bright half moon appeared on the CRT and > rotated at the error rate between the two frequencies. On several > evenings the dominant signal varied between WWV and WWVH (identified by > the voice broadcasts). Here in Minneapolis the phase difference between > the two stations was about 180 degrees, causing the bright arc on the > CRT to change sides. > > So yes, this could be interesting for a hobbyist, but it won't add > anything to Science. > A MASER is overkill. Heck, so are Rubidium and Caesium. > A naked crystal will be rock solid compared to received WWV. > > OTOH, NTP has marvelous mathematical tricks to reduce Internet > propagation delay. > A scheme to reduce varying atmospheric delay would be useful, if there > weren't much better ways to get a standard frequency. > > Bill Hawkins > > > -----Original Message----- > From: time-nuts [mailto:[email protected]] On Behalf Of Patrick > Barthelow > Sent: Thursday, December 07, 2017 7:48 AM > > Hello Friends, > > I am picking up locally a couple of vintage analog Radio Shack SW time > cube radios, 70s vintage, 3 switchable SW frequencies. Two types, the > one pictured and a Radio Shack model also that has WWV and Weather > channel VHF frequencies. > I am interested in an accurate bench test to compare the analog > shortwave radios time reporting hopefully UT-1 against other available > references. For accuracy, and > repeatability. Could eventually add an SDR to the mix, too. > The 5,10,15 mhz radios obviously are subject to the WWV Ft Collins site, > propagation distance delays, somewhat calculable, and the vagaries of > Ionospheric propagation, and, propagation delays between the antenna and > the measured tap point to the seconds ticks of WWV. I have some > friends, > microwave professionals, who are also hams here in Auburn who may enjoy > doing a bench test, with published results, etc. But wonder if anyone > else would be interested in borrowing a RS Timecube radio (and/or use an > SDR) and designing an accurate bench test against available modern > standards? > We are talking probably HUGE UT-1 errors compared to what this group > plays with, and that is OK but I think still a worthwhile test, > especially if the errors using available and cheap equipment are > predictable, and repeatable. > https://forums.qrz.com/index.php?attachments/dscn1187-jpg.400844/ > > ----- %< ----- [snip of microwave stuff] > > Best, 73, Pat Barthelow AA6EG > apol <[email protected]>[email protected] > > _______________________________________________ > 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.
