Bob Camp wrote: > Hi > > WWVB and WWV (like any radio uncorrected radio system) has fairly predictable > shifts > associated with the day / night ionosphere. One *could* fix that issue with a > table > based on station location. I do not know of any library of code that does > that already. > > The next “layer” of trouble comes from how the low cost receivers are > implemented. The > common issue is local noise. The common solution is a narrowband crystal > filter in front > of the receiver. The bandwidth of that filter (and to some extent it’s > temperature dependance) place > a “best case” limit on performance in the 10’s to 100’s of ms range depending > on the > exact details. There are higher performance receivers (but not a lot of them) > that do get into > the single digit ms range. At that point the propagation issue mentioned > above needs some > work. > > Further complicating things is the distance factor. A user in Denver with > ground wave “view” > of the transmitter will do *much* better than the numbers above. A user in > Miami or Bangor ME > may be very lucky to get close to the numbers above on an intermittent basis.
I'm basically familiar with the ground wave / sky wave problem. Quite some time ago I had found a PDF on the 'net with some explanations, measurements, and a U.S. map showing e.g. which regions were mostly affected by temporary cancellation due to interference of the sky and groundwave with the same amplitude. If I remember correctly this was an old publication from NIST or so. Eventually it's hard to find by search machines since it wasn't a generated PDF with text, but just a scan of an old printed article. Unfortunately I hadn't saved a copy, and now I'm unable to find it. Anybody has a hint what this could have been? Thanks, Martin _______________________________________________ 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.
