[time-nuts] Rebroadcasting time signals [WAS: La Crosse Clocks - ]

[Tim Shoppa]

Presumably any "rebroadcast" of WWVB is done in the spirit of near-field
communications where any far-field radiation falls off like 1/r^3 from a
small inductive transmitter loop.

A loop the size of your entire house would be "small" in terms of 60kHz
wavelength.

Unintended coupling of the 60kHz into AC power mains or copper network
wiring could result in the near field extending into places you didn't want
it to go.

Far-field radiation of 10 MHz signals unintentionally, is a helluva lot
easier than radiating 60 kHz intentionally.

Tim N3QE

On Sun, Dec 27, 2020 at 4:33 AM Charles Steinmetz <csteinmetz at yandex.com>
wrote:

> Hal wrote:
>
> > Transmitting on the same frequency you are receiving on seems like
> asking for
> > troubles.
>
> Difficult perhaps, but not impossible.  As /tvb notes, one solution is
> time domain multiplexing; and, as Alex says, phase domain multiplexing
> is another (although the phase discrimination of 60kHz antennas this
> size is problematic).  There are others.
>
> > How far apart would the antennas have to be?  How would you calculate
> that
> > distance?  Or what is the right question?
>
> I've watched discussions of this topic for several years, and have
> always been surprised that nobody has ever once mentioned the potential
> for harmful interference extending beyond one's own property.  (Tom
> mentioned it today, including the possibility of legal implications.)
> This is especially true of people, like some on this list, who
> reportedly run a big loop around their house ("so that all their WWVB
> clocks can hear it").  But really, any scheme with leakage can (and
> likely does) create harmful interference beyond your property.
>
> I can say positively that if anyone who has such a system lived down the
> block from me, I would be most unhappy about it and would be in a very
> foul mood by the time I figured out what was causing the interference I
> was receiving.  (I know whereof I speak -- I spent quite a lot of effort
> a few years ago chasing down a leaking 10MHz reference of very dubious
> quality in use by a local ham nearly a kilometer from me.)
>
> So, please, if you are going to rebroadcast a time signal to your
> receivers, make sure the modulator and RF generator are in
> well-RF-sealed enclosures and that you use good coax (or, preferably,
> triax) to send the signal to each receiver individually.  BTW, this
> applies to *any* such signal, not just LF but HF and GNSS rebroadcasters
> as well.
>
> Best regards,
>
> Charles
>
>
>
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