[Elecraft] OT: 3Y0Z Bouvet Island DXpedition

[Fred Jensen]

Yep.  The "civilian channel" on GPS was a gift to everyone from the US 
Department of Defense, I suppose they could turn it off if they so wish, 
but it is so ingrained in today's culture that they won't.  Years ago, 
the channel was purposely perturbed to limit the horizontal accuracy to 
something between +/-100 to 200 meters.  It was called "Selective 
Availability."

The US Coast Guard [another branch of the US military] promptly 
installed GPS receivers in very carefully surveyed key locations, and 
published the error between the known position and the GPS reported 
position.  They called it Differential GPS.  If you had a DGPS receiver, 
and were close enough to the DGPS receiver, it would use the broadcast 
error to correct the received position. In the US at least, they're 
still broadcasting from various sites in the 280 – 460 KHz range which 
you can receive if your K3 has the new synthesizer [and you have the 
BPSK decoder and a cheat-sheet for the format].  Over time, commercial 
interests also began doing this too.

Quite awhile back, someone in the guvmint must have realized that SA 
wasn't really working all that well at limiting position precision on 
the civilian channel and gave up.  The DGPS transmissions continue, or 
at least did in 2015.  So much these days depends on GPS, it's hard to 
see the "100 ms channel" going away.

73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County
On 1/24/2018 11:18 AM, Ken Chandler wrote:
> Course, Governments/Military have overall control over civilian use of the Birds!  or certainly use to have, whether that’s still the case I’m unsure!
>
>
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> Ken.. G0ORH
>