[time-nuts] Story in the Economist about GPS jamming

[Magnus Danielson]

On 31/07/13 13:54, Jim Lux wrote:
> Yes.. You put a gain antenna on the space craft, so for the same tx power, you get the same flux density on the ground.   The gps height was chosen for a variety of reasons.  It is out of the debris band, for one.  There's also a tradeoffs on launch costs, etc.  GPS world magazine had a great multipart article on the history and design last year

The GPS birds have a directivity in their antennas to start with, it 
performs a first degree compensation of the distance change to signal 
strength, so the GPS bird transmit stronger in a circular lobe on the 
edge of the earth than straight down.

Doing the same for a GEO sat bird is trivial. The antenna changes the 
geometry just a tiny bit to achieve it, as the distance difference isn't 
all that large.

Those interested should play around with NEC2. :)

Cheers,
Magnus