[time-nuts] GPS Jamming in the UK

Magnus Danielson magnus at rubidium.dyndns.org
Wed Nov 14 05:41:07 EST 2007

From: "Rob Kimberley" <rk at timing-consultants.com>
Subject: Re: [time-nuts] GPS Jamming in the UK
Date: Wed, 14 Nov 2007 10:13:41 -0000


> GPS is a military system. Fact. The C/A code just happens to be available to
> Joe Public, but there are no guarantees of its availability. If the US
> military want to take out C/A at any time during a conflict they can and
> will, because the new Direct Acquisition P/Y technologies allow them to
> continue operations without it.

Agreed. Only old military receivers depend on C/A code. As DSP-power has become
cheap direct acquisition went from a nice but expensive idea to reality.

However, there are more refined methods of disabling navigation than disabling
a signal in the satellite. Each bird views almost half the earth. You can use
deployed GPS jammers in an area of conflict as well as use beamsteared jamming
from sats.

A bird viewing a conflict in say Iraq also provides service to Europe, Africa
and a great part of Asia.

Total disabling of that bird would have far greater concequence than needed.
The US forces have sufficient methods at hand to cause the needed effect on the
ground without disabling or reducing the capabilities of users for the same
hemisphere (conflict centered).

I do disagree about the C/A just happends to be available. It has been actively
promoted into the civilian community. There is awareness of this fact and it
has been increasingly important for policies. Alternative measures than pulling
the plug has been deployed. I don't consider the disabling of C/A as such a
great risk considering the intentional and unintentional jammer risk. The C/A
disabling option is still there thought, but as alternatives have become
available it is less likely.


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