[time-nuts] lawnmower robots may be the end of VLF timekeeping

[Bob Camp]

Hi

There are dog collar systems that work the same way as well as low speed data over power line systems. 
For what ever reason - they really like to create RFI. My guess is that it’s easy to generate a pulse with logic
gates than it is to properly filter that pulse. 

The first question I’d have about the gizmo is: does it really *need* that awful looking square wave? I’d bet
that the “antenna” in the lawnmower is a tuned loop of some sort. It probably would be happy with a much less
wide band signal. I’ve had good luck with the buried dog fence setups and some pretty basic filtering. 

Of course this all works ok for your system. You have to be on very good terms with the neighbors to fix the 
problem from their system ….

Bob


> On May 9, 2015, at 8:15 AM, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:
> 
> I spent some time capturing some data today.
> 
> The measurements is from my $20 loop-antenna in the attic, which is
> something like 8 meters up and 10 meters besides the lawn-mower loop:
> 
> 	http://phk.freebsd.dk/time/20150509.html
> 
> -- 
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
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