[time-nuts] GPS Jammer

Michael Perrett mkperrett at gmail.com
Wed Oct 3 03:13:57 UTC 2012


John,
Coherent reproduction of the spread PRN standard positioning signal (SPS)
signal gives ~30dB of A/J protection, the GPS signal level, as received at
the GPS receiver is on the order of -160 dBW (L1-CA). If the jammer outputs
half a Watt, and is anywhere nearby, the receiver will not maintain lock on
the civilian code as the jammer would overwhelm the receiver front end. A
commercial GPS receiver has a maximum of 20 dB power bandwidth. If the
jammer is present prior to initial acquisition then the receiver would
certainly never acquire lock.

My experience is that the civil signal (SPS) is very easy to jam, where the
precise positioning signal (PPS), using the P(Y) code adds significantly
more protection.

All values are round numbers and the individual receivers signal strategy
can make some difference, as well as GPS aiding (especially a good clock,
known position, velocity and so forth).

Michael, K7HIL

On Tue, Oct 2, 2012 at 7:33 PM, <johncroos at aol.com> wrote:

> In considering the effect of a simple jammer on a GPS receiver, a simple
> link analysis
> is insufficient.
>
> What must also be considered is the anti-jam capability of the receiver
> which due to spread spectrum processing gain will reject any simple
> jamming signal even though is it 10's of dB stronger than the desired
> signal.
>
> 73 -john k6iql
>
>
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