[time-nuts] How hard is it to detect a GPS Jammer?

[Scott McGrath]

And some of them have considerably higher EIRP,   Like THIS one,   As you
can see they are not sophisticated devices they are intended to swamp the
real GPS signal,

Spoofers would be much harder to detect which is why GNSS systems intended
for military use rely on encrypted signals and fairly sophisticated key
management techniques.

Now for nightmares - the GPS Jammer shown below has an advertised EIRP of
3.4W and the vendor has another with an EIRP of  7.2W

http://hem.passagen.se/communication/gps.html

[image: Inline image 1]


On Mon, Oct 7, 2013 at 9:11 PM, Jim Lux <jimlux at earthlink.net> wrote:

> On 10/7/13 8:31 AM, Chris Albertson wrote:
>
>> OK so let's say you have a receiver and detect a certain about of power at
>> the right frequency.  How do you determine which of three cases you have
>> (1) an actual GPS signal from a satellite. (2) a spoofer (who tries hard
>> to
>> look like #1) or (3) a jammer.
>>
>
>
> The jammers put out many milliwatts and have enormous signals that are
> obvious on a spectrum analyzer.  GPS signals are invisible on a spectrum
> analyzer, normally.  IN fact, most GPS receivers don't work very well if
> there are signals above the noise floor: they depend on the noise to make
> them work with their mighty 1 bit quantizers.
>
>
>
>
>>
>> Spoofers are a real problem.
>>
>
> I doubt anyone is selling spoofers on eBay.
> Sure, one can probably find some  code to run on a USRP from some grad
> student's project.
>
>
>  So the easiest thing to detect would be a cheap, GSP jammer that is
>> moving.
>>    You could use multiple receivers to triangulate the location and then
>> determine it is not in orbit and is not a reflection from a metal roof or
>> something.    The problem is the jammer's very low power.  These things
>> are
>> inteneded to only cover a tiny area
>>
>
> They are not designed with coverage area in mind.  They are basically
> "whatever power the VCO puts out coupled to the antenna"  From a jamming
> standpoint, they're not very sophisticated.
>
> As a result they dump out something like +10dBm.
> So running a quick Friis formula link budget, and assuming you want to
> have a Prec of around -100dBm (10 MHz BW, kTB)
>
> 110 = 32+ 20*log10(1575) + 20*log10(d)
> 110-32 - 25 = 20*log10(d)
> d = 400 km...
>
> This is why they are such a problem
>
>
>
>
> ______________________________**_________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/**
> mailman/listinfo/time-nuts<https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts>
> and follow the instructions there.
>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: GPS-JAMMER.gif
Type: image/gif
Size: 18265 bytes
Desc: not available
URL: <http://febo.com/pipermail/time-nuts_lists.febo.com/attachments/20131008/654cada4/attachment.gif>