[time-nuts] Re: local WWVB ?

[Andy Talbot]

To "transmit" on 60kHz and radiate ANY reasonable power needs a very large
antenna.   I used to transmit on 73kHz when we briefly had an amateiur band
there, have  7 metre high antenna with a substantial capacity hat, was
putting 200 Watts into it but was getting an estimated radiated power of
just a few milliwatts.  It was detected at 400km distance, but only in an
ultra narrow bandwidth DSP based receiver, far too narrow for 1s timing
window

The small transmitters you are talking about for relays operate using a
magnetic loop that couples only (well, very nearly only) the magnetic H
field from the source.   The H field falls off not as the square of
distance, as the radiated field normally associated with a radio
transmission does, but as the sixth power of distance.   SO once you get
beyond a few metres of a small loop antenna  with a few milliwatts being
put into it, any signal will have dropped below the noise and cannot be
considered to be "transmitted"



Andy
www.g4jnt.com



On Sat, 11 Dec 2021 at 16:11, <rcbuck at atcelectronics.com> wrote:

> Although not advisable a search of the Internet will turn up several.
> There is a well know Raspberry PI version. The range of the transmitters
> is only a couple of feet so if placed next to your clock it will work.
> Anything that would cover your entire house would certainly not be
> advised.
>
> There is also a smart phone app that does the same thing. It uses the
> phone speaker somehow to generate a harmonic (probably 3rd of 20 kHz).
> The watch or clock has to be placed next to the phone speaker for it to
> work.
>
> Ray, AB7HE
>
>
> On 2021-12-11 06:43, Attila Kinali wrote:
> > On Fri, 10 Dec 2021 15:54:55 -0500
> > "Lawrence Brandt" <lawrence.brandt at gmail.com> wrote:
> >
> >> Has anyone designed and/or sold a "WWVB repeater" device? I can
> >> picture a
> >> Raspberry Pi which had software to get NTP data or GPS-referenced
> >> time, and
> >> a small 60 kHz transmitter, which would send the proper WWVB timecode
> >> data
> >> to the several "atomic clocks" I have around the house.
> >
> > Today, with all the non-licensed wireless stuff we have as
> > gadgets, it doesn't seem to be as obvious as it once was, but:
> > Transmitting on a frequency you don't have the explicit license
> > for is forbidden. And there are some quite hefty fines for that.
> > Especially transmitting on a widely used frequency of an
> > infrastructure service like WWVB might not be looked kindly upon.
> >
> > If you want to lock WWVB clocks that are placed somewhere, where
> > the reception is not good enough. Then you should inject the signal
> > directly into the clock. This way you avoid transmitting.
> >
> > Alternatively, replace the electronics with some 802.15.4 system
> > (e.g., 6LowPan) and distribute time in this network. There are
> > plenty of developer boards available for this kind of stuff,
> > just check adafruit and sparkfun.
> >
> >                       Attila Kinali
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