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

[Jim Lux]

On 5/9/15 5:15 AM, Poul-Henning Kamp 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
>

Clearly, you need a better nav system for the robot based on precision 
time of flight measurements from a network of transmitters around the 
property linked to your hydrogen maser.

More practically, what about some sort of canceller.. This is low 
frequency, so if you put a "pickup loop" near the wire, you can collect 
a sample of the transmitted signal, and then adjust the mag and phase to 
cancel at your timing receiver antenna.  I suspect the variation in mag 
and phase will be quite small over time/temperature/weather/volume 
occupancy.