A great thread by everyone. Oh to make the loran receivers work. But that is indeed the past. Can not hear Europe on east coast. But the question really is, what do you want to accomplish? I don't think its a time stamp. Its just to easy to get it from GPS or the network. But that could be a secondary use. I believe the primary goal would be frequency distribution with perhaps a tick. If this is the goal then I am 100% in agreement that there are far more efficient modulation and recovery methods today. The trick is you need something that does not effect the accuracy of the timing and may improve the various transmission issues at these frequencies. By the way this list has a heck of a brain trust so its very very possible. Someone mentioned spread spectrum. Thats very interesting as it is what GPS uses and could work at these lower frequencies. Like the "Hey this is just telemetry" comment. You know the FCC does indeed give temp authorization for quite long periods of time. Years in fact. So I would be in the keep it simple mode. Great a single carrier with a id every 10 min. Maybe that could be waved to 1 per hour or 24 hours. Unfortunately then we have nothing better then wwvb. The modulation method may be key and then what freq we would use. BPSK at higher frequencies is also impressive. My first contact was in the indian ocean on 5 whats from boston. Regards Paul WB8TSL
On Tue, Oct 5, 2010 at 6:59 AM, Bob Camp <li...@rtty.us> wrote: > Hi > > If you were starting from scratch there are a lot of things you could do. > If the intent is to put out something a Loran receiver will recognize ... > not so much. > > Bob > > > On Oct 5, 2010, at 6:44 AM, Poul-Henning Kamp wrote: > > > In message <b69fdcaf-2b39-4575-b5cd-66a87fa1b...@rtty.us>, Bob Camp > writes: > > > >> Even though it's pule, the RF power is way beyond the sub 1 W > >> outputs currently contemplated on those bands. Signal to noise > >> *does* matter. > > > > You know, there are other ways to skin that cat these days. > > > > Old-time signals had to be grossly inefficient because the receivers > > were inefficient, in particular the "ear-wristwatch" kind of time > > receivers. > > > > These days we have spread-spectrum modulation, and if our only goal > > is to transmit a timestamp, you can spread pretty wide and far and > > need very little power to produce a receiveable signal at long > > distances. > > > > The QRSS hams are playing around with numbers like 17,840,000 miles > > per watt, and all it takes to turn that into a time/frequency > > services is a spreading function with a really good autocorrelation. > > > > Obviously, you will not get second by second measurements, but the > > measurements you do get, say once per hour, will have much higher > > precision because of the averaging that goes into them. > > > > And equally obvious: propagation effects will take their toll, but > > still... > > > > Somebody with a license should try that on 137kHz... > > > > Poul-Henning > > > > -- > > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > > p...@freebsd.org | TCP/IP since RFC 956 > > FreeBSD committer | BSD since 4.3-tahoe > > Never attribute to malice what can adequately be explained by > incompetence. > > > > _______________________________________________ > > 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 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 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.
