[time-nuts] NIST

[Scott McGrath]

As Brooke notes while low frequency jammers are possible, practicality is another matter,   All it takes to jam a city scale area is a box the size of a pack of cigarettes.    Because the GPS signal is very, very weak.

As an intentional denial put a couple hundred on stray animals.    Now track those jammers down.

I doubt if any agency owns enough DF equipment to find them all in a reasonable amount of time.

Thats why we need backup systems and each backup system will have less and less accuracy as it increases in robustness.   The HF systems could provide adequate syncing for the Market example.



On Aug 30, 2018, at 6:18 PM, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:

--------
In message <96e995c4-5ca2-af02-9738-0a6d87a9f813 at pacific.net>, Brooke Clarke writes:

> But it's extremely hard to make a jammer for WWVB (60 kHz) [...]

You can do it city-scale with a 18-wheeler sized loop-antenna
and a good size diesel-generator.

However pedestrians will very likely note metalic items vibrating
as they pass the "mystery white truck".

Sweden were much more serious about it:

   http://www.antus.org/RT02.html

Tl;drs:

They erected 9 200m tall Loran-C class antennas each driven by
a Loran-C transmitter with an advanced degree which could jam
Loran-C or Chayka.

They even mounted decoy parabolas on the towers them to hide their
true purpose.

The fact that all the transmitters were on the east coast does drop
a hint that swedens much touted neutrality had a bit of a slant.

-- 
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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