[time-nuts] Timing Distribution in Mountainous Terrain
Don Latham
djl at montana.com
Sat Sep 11 05:39:14 UTC 2010
ground wave has variation due to changes in refractive index over the path.
----- Original Message -----
From: "WB6BNQ" <wb6bnq at cox.net>
To: "Discussion of precise time and frequency measurement"
<time-nuts at febo.com>
Sent: Friday, September 10, 2010 6:46 PM
Subject: Re: [time-nuts] Timing Distribution in Mountainous Terrain
> Hal,
>
> The LORAN frequency was picked to have predominately ground wave
> acquisition over
> the less preferred skywave. The only signal worth considering from Fort
> Collins
> is the WWVB signal which is at 60 KHz.
>
> For Ralph's application in Colorado, the WWVB signal would probably do it.
> Particularly considering the short distance between the sites and Fort
> Collins.
>
> LORAN and WWVB are about the same as far as stability goes at the actual
> transmitter site with WWVB having a slight edge. The value is 1x-E11 or
> better.
> For Ralph, the WWVB would be more stable due to his site proximity to the
> transmitter over any LORAN signal (when working) which is much further
> away.
>
> Bill....WB6BNQ
>
>
> Hal Murray wrote:
>
>> ralph at ralphsmith.org said:
>> > There are probably several fatal flaws with this approach. In
>> > particular,
>> > the following are required:
>> > 1) Ability to maintain constant lock to WWV
>> > 2) Common-mode error. Will the propagation from WWV be similar
>> > enough for all stations to it be a practical common reference.
>> > 3) Adequate resolution. Even if, for some reason 1 and 2 are possible,
>> > would the result be good enough to use.
>>
>> My quick guess is that WWV would be worse than LORAN since LORAN got to
>> pick
>> the frequency that would work best.
>>
>> If you want more info, you probably need to contact a radio propagation
>> wizard. Unless you are very close, the signal will be bouncing off the
>> ionosphere and that isn't stable. There are big changes from day to
>> night,
>> and I think you can measure the tiny changes during the day if you have a
>> good clock at the receiver.
>>
>> Didn't one of the recent FMT discussions mention something like this? I
>> think they were measuring a frequency shift which would translate into
>> velocity of the layer.
>>
>> Dave Mills has drivers for NTP that decode WWV/H signals from a short
>> wave
>> radio going into a PC audio chip.
>> http://www.eecis.udel.edu/~mills/ntp/html/drivers/driver36.html
>> In general, he's getting sub ms rather than few ns.
>>
>> --
>> These are my opinions, not necessarily my employer's. I hate spam.
>>
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