Hi It’s back in the FCS archives. I don’t think it’s one of the ones you can hit without going through a paywall. It was a fun paper to attend. The chatter in the room was “interesting” to say the least.
Bob > On Aug 31, 2018, at 1:07 PM, Brooke Clarke <bro...@pacific.net> wrote: > > Hi Bob: > > Do you have and info on that article that would allow me to read it? > > -- > Have Fun, > > Brooke Clarke > https://www.PRC68.com > https://www.end2partygovernment.com/2012Issues.html > axioms: > 1. The extent to which you can fix or improve something will be limited by > how well you understand how it works. > 2. Everybody, with no exceptions, holds false beliefs. > > -------- Original Message -------- >> Hi >> >> The original “we cracked GPS” paper back in the 1980’s (that unlimitedly >> lead to the end of SA) >> used a medium sized dish ( think of the good old C-band antennas) to pick >> out a single sat. >> >> Bob >> >>> On Aug 30, 2018, at 9:54 PM, Brooke Clarke <bro...@pacific.net> wrote: >>> >>> Hi Gregory: >>> >>> I wonder if anyone has tried using a small parabolic dish, like used for >>> Free To Air satellite TV and aimed it at a GPS satellite track or at a WAAS >>> geostationary satellite using a feed antenna with reverse polarization from >>> a normal GPS antenna? >>> http://www.prc68.com/I/FTA.shtml >>> >>> -- >>> Have Fun, >>> >>> Brooke Clarke >>> https://www.PRC68.com >>> https://www.end2partygovernment.com/2012Issues.html >>> axioms: >>> 1. The extent to which you can fix or improve something will be limited by >>> how well you understand how it works. >>> 2. Everybody, with no exceptions, holds false beliefs. >>> >>> -------- Original Message -------- >>>> On Thu, Aug 30, 2018 at 9:43 PM Brooke Clarke <bro...@pacific.net> wrote: >>>>> I would disagree in that ease of jamming/spoofing is strongly related to >>>>> wavelength. That's because antenna efficiency >>>>> goes down as the size of the antenna gets smaller than 1/4 wave. >>>>> So, it's easy to make a GPS jammer (1,100 to 1,600MHz) since a 1/4 >>>>> wavelength is a few inches, something that you can >>>>> hold in your hand. >>>> However, the short wavelengths of GPS make beam forming a reasonable >>>> countermeasure against jamming. >>>> >>>> By having a small array of GPS antennas a receiver can digitally form >>>> beams that both aim directly at the relevant satellites (so even >>>> reducing intersatellite interference) while also steering a deep null >>>> in the direction of the jammer. If the jammer is powerful enough to >>>> overload the front-end then this won't help, but against a >>>> non-targeted area denying jammer it should be fairly effective. >>>> >>>> There are many papers on GNSS beamforming. ( e.g. >>>> https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5134596/ >>>> https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5134483/ ) >>>> >>>> This kind of anti-jamming solution should even be pretty inexpensive >>>> -- really no more than the cost of N receivers. Except that it is >>>> specialized technology and thus very expensive. :) >>>> >>>> Seeing some open source software implementing beam-forming was one of >>>> the things I hoped to see result from the open hardware multi-band >>>> GNSS receivers like the GNSS firehose project ( >>>> http://pmonta.com/blog/2017/05/05/gnss-firehose-update/ ) since once >>>> you're going through the trouble of running three coherent receivers >>>> for three bands, stacking three more of them and locking them to the >>>> same clock doesn't seem like a big engineering challenge... and the >>>> rest is just DSP work. >>>> >>>> Even absent fancy beam forming, for GNSS timing with a surveyed >>>> position except at high latitudes it should be possible to use a >>>> relatively high gain antenna pointed straight up and by doing so blind >>>> yourself to terrestrial jammers at a cost of fewer SVs being >>>> available. But I've never tried it. >>>> >>>> In an urban area I noticed my own GPSDOs losing signal multiple times >>>> per week. Monitoring with an SDR showed what appeared to be jammers. >>>> >>>> As others have noted intermittent jamming is pretty benign to a GPSDO. >>>> Spoofing, OTOH, can trivially mess up the timing. It's my view that >>>> if you need timing for a security critical purpose there isn't really >>>> any GNSS based solution commercially available to the general public >>>> right now, the best bet is a local atomic reference with a GPSDO used >>>> to monitor and initially set it. >>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- time-nuts@lists.febo.com >>>> To unsubscribe, go to >>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>> and follow the instructions there. >>>> >>> >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@lists.febo.com >>> To unsubscribe, go to >>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>> and follow the instructions there. >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@lists.febo.com >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. >> >> > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.