[time-nuts] eLORAN in the Antipodes ? (was: Re: eLORAN will be on the air GRI 99600)

[Bob kb8tq]

Hi

The main point is: If you are looking at a VLF system, phase matters a lot. If your
objective is a 100 ns @ 1 second sort of accuracy, you need a very stable phase.
At 100 KHz, you are looking at 3.6 degrees of phase shift. Go down to 60 KHz and
you are right at 2 degrees. Head to Omega sort of frequencies and it just gets worse.

If you are trying to be “as good as” GPS / GNSS, this is still an order of magnitude (or more)
away from the goal ….

Since fairly normal propagation effects can get you into  “which cycle am I on?”, antenna 
effects are *not* the dominant issue. Toss in things like skywave and …. yikes ….

Bob

> On Aug 8, 2020, at 4:15 PM, Hal Murray <hmurray at megapathdsl.net> wrote:
> 
> 
> kb8tq at n1k.org said:
>> Same basic issue, lots of weird interactions and a need to keep the signal
>> very precise. Not as easy as it might seem. 
> 
> What does "precise" mean in that context?
> 
> I'm not an antenna-nut.  Can an antenna miss-match change anything other than 
> the amplitude?
> 
> How do you automatically tune something like that?  The manual way would to 
> twist the knob while watching a meter.  If the meter goes down, you are going 
> the wrong way.  If it goes up, keep going until it starts going down, then 
> back up to the peak you just passed.
> 
> How do you even know that it needs tuning?  Can you measure something 
> accurately enough?  If so, what?
> 
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
> 
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