http://www.chronos.co.uk/pdfs/rac/labsat.pdf

Hi, found an interesting unit. I think it is not for the usual pocket money for a time-nuts. have a look... http://www.chronos.co.uk/pdfs/rac/labsat.pdf Rgds Ernie. -----Original Message----- From: John Green <wpxs472@gmail.com> To: time-nuts@febo.com Sent: Mon, Nov 22, 2010 6:43 pm Subject: [time-nuts] GPS jamming susceptibility Given that this is an extremely sensitive topic and completely illegal lso, let me just state at the outset that I have no interest in amming anyone's GPS. A while back, I was looking at one of those hinese discount electronics websites, I'm sure we all have, and oticed a GPS jammer for sale. I had been wanting to do some jamming usceptibility testing for quite some time but had never got around to uilding a generator to test with. The thing was cheap so I ordered t. After it arrived, I opened it up, first thing, to see how it was ade. It has a dual 555 oscillator, a couple of analog switches, a 1.9 Hz VCO, a single amplifier. It doesn't look capable of putting out ore than 50 milliwatts or so into a 2 inch antenna. I was somewhat ubious that it would do anything, so I took it to the bench where the 3801 lives and turned it on. Within 2 seconds, the holdover LED lit. immediately turned it off and within a few more seconds, the oldover LED was back off. The GPS antenna is perhaps 35 feet away ith a cinder block wall, a brick wall, and a metal roof in between. I lso put a 15 Db attenuator between it and the antenna with almost the ame result. I am going to do more testing with it wired into the GPS ownfeed an an adjustable attenuator in line just to see how much ignal it takes. That way, there will be little danger of messing with nyone's reception. It is just a simple sweeper so it must do its job y brute force. I am amazed that it took so little to shut my Z3801 own. Has anyone here had any actual experience testing GPS receivers or susceptibility? _______________________________________________ ime-nuts mailing list -- time-nuts@febo.com o unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts nd follow the instructions there.

   http://www.chronos.co.uk/pdfs/rac/labsat.pdf

Hi One bit serial at 16 MHz isn't all that fancy any more. Sounds like a shift register feeding a couple filters. The money must be in the receive side. Bob On Nov 24, 2010, at 5:14 PM, ernieperes@aol.com wrote: > > > > Hi, > > found an interesting unit. I think it is not for the usual pocket money for a time-nuts. > have a look... > > http://www.chronos.co.uk/pdfs/rac/labsat.pdf > > Rgds Ernie. > > > > > > > > > > -----Original Message----- > From: John Green <wpxs472@gmail.com> > To: time-nuts@febo.com > Sent: Mon, Nov 22, 2010 6:43 pm > Subject: [time-nuts] GPS jamming susceptibility > > > Given that this is an extremely sensitive topic and completely illegal > lso, let me just state at the outset that I have no interest in > amming anyone's GPS. A while back, I was looking at one of those > hinese discount electronics websites, I'm sure we all have, and > oticed a GPS jammer for sale. I had been wanting to do some jamming > usceptibility testing for quite some time but had never got around to > uilding a generator to test with. The thing was cheap so I ordered > t. After it arrived, I opened it up, first thing, to see how it was > ade. It has a dual 555 oscillator, a couple of analog switches, a 1.9 > Hz VCO, a single amplifier. It doesn't look capable of putting out > ore than 50 milliwatts or so into a 2 inch antenna. I was somewhat > ubious that it would do anything, so I took it to the bench where the > 3801 lives and turned it on. Within 2 seconds, the holdover LED lit. > immediately turned it off and within a few more seconds, the > oldover LED was back off. The GPS antenna is perhaps 35 feet away > ith a cinder block wall, a brick wall, and a metal roof in between. I > lso put a 15 Db attenuator between it and the antenna with almost the > ame result. I am going to do more testing with it wired into the GPS > ownfeed an an adjustable attenuator in line just to see how much > ignal it takes. That way, there will be little danger of messing with > nyone's reception. It is just a simple sweeper so it must do its job > y brute force. I am amazed that it took so little to shut my Z3801 > own. Has anyone here had any actual experience testing GPS receivers > or susceptibility? > _______________________________________________ > ime-nuts mailing list -- time-nuts@febo.com > o unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > nd follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.

   http://www.chronos.co.uk/pdfs/rac/labsat.pdf

Agreed. The trick is to properly partition what is done in hardware ane what is done in software. This could eliminate a lot of logic hardware. Clearly, the RF stuff and modulator are hardware. Ditto PR code generation. Everything else in SW, I think. FWIW, -John =============== > Hi > > One bit serial at 16 MHz isn't all that fancy any more. Sounds like a > shift register feeding a couple filters. > > The money must be in the receive side. > > Bob > > On Nov 24, 2010, at 5:14 PM, ernieperes@aol.com wrote: > >> >> >> >> Hi, >> >> found an interesting unit. I think it is not for the usual pocket >> money for a time-nuts. >> have a look... >> >> http://www.chronos.co.uk/pdfs/rac/labsat.pdf >> >> Rgds Ernie. >> >> >> >> >> >> >> >> >> >> -----Original Message----- >> From: John Green <wpxs472@gmail.com> >> To: time-nuts@febo.com >> Sent: Mon, Nov 22, 2010 6:43 pm >> Subject: [time-nuts] GPS jamming susceptibility >> >> >> Given that this is an extremely sensitive topic and completely illegal >> lso, let me just state at the outset that I have no interest in >> amming anyone's GPS. A while back, I was looking at one of those >> hinese discount electronics websites, I'm sure we all have, and >> oticed a GPS jammer for sale. I had been wanting to do some jamming >> usceptibility testing for quite some time but had never got around to >> uilding a generator to test with. The thing was cheap so I ordered >> t. After it arrived, I opened it up, first thing, to see how it was >> ade. It has a dual 555 oscillator, a couple of analog switches, a 1.9 >> Hz VCO, a single amplifier. It doesn't look capable of putting out >> ore than 50 milliwatts or so into a 2 inch antenna. I was somewhat >> ubious that it would do anything, so I took it to the bench where the >> 3801 lives and turned it on. Within 2 seconds, the holdover LED lit. >> immediately turned it off and within a few more seconds, the >> oldover LED was back off. The GPS antenna is perhaps 35 feet away >> ith a cinder block wall, a brick wall, and a metal roof in between. I >> lso put a 15 Db attenuator between it and the antenna with almost the >> ame result. I am going to do more testing with it wired into the GPS >> ownfeed an an adjustable attenuator in line just to see how much >> ignal it takes. That way, there will be little danger of messing with >> nyone's reception. It is just a simple sweeper so it must do its job >> y brute force. I am amazed that it took so little to shut my Z3801 >> own. Has anyone here had any actual experience testing GPS receivers >> or susceptibility? >> _______________________________________________ >> ime-nuts mailing list -- time-nuts@febo.com >> o unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> nd follow the instructions there. >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > >

  http://www.chronos.co.uk/pdfs/rac/labsat.pdf

Hi It's not real clear that they do anything more than sample the RX and play it back for the TX. Bob Sent from my iPhone On Nov 25, 2010, at 9:39 AM, "J. Forster" <jfor@quik.com> wrote: > Agreed. The trick is to properly partition what is done in hardware ane > what is done in software. This could eliminate a lot of logic hardware. > > Clearly, the RF stuff and modulator are hardware. > Ditto PR code generation. > Everything else in SW, I think. > > FWIW, > > -John > > =============== > > >> Hi >> >> One bit serial at 16 MHz isn't all that fancy any more. Sounds like a >> shift register feeding a couple filters. >> >> The money must be in the receive side. >> >> Bob >> >> On Nov 24, 2010, at 5:14 PM, ernieperes@aol.com wrote: >> >>> >>> >>> >>> Hi, >>> >>> found an interesting unit. I think it is not for the usual pocket >>> money for a time-nuts. >>> have a look... >>> >>> http://www.chronos.co.uk/pdfs/rac/labsat.pdf >>> >>> Rgds Ernie. >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> -----Original Message----- >>> From: John Green <wpxs472@gmail.com> >>> To: time-nuts@febo.com >>> Sent: Mon, Nov 22, 2010 6:43 pm >>> Subject: [time-nuts] GPS jamming susceptibility >>> >>> >>> Given that this is an extremely sensitive topic and completely illegal >>> lso, let me just state at the outset that I have no interest in >>> amming anyone's GPS. A while back, I was looking at one of those >>> hinese discount electronics websites, I'm sure we all have, and >>> oticed a GPS jammer for sale. I had been wanting to do some jamming >>> usceptibility testing for quite some time but had never got around to >>> uilding a generator to test with. The thing was cheap so I ordered >>> t. After it arrived, I opened it up, first thing, to see how it was >>> ade. It has a dual 555 oscillator, a couple of analog switches, a 1.9 >>> Hz VCO, a single amplifier. It doesn't look capable of putting out >>> ore than 50 milliwatts or so into a 2 inch antenna. I was somewhat >>> ubious that it would do anything, so I took it to the bench where the >>> 3801 lives and turned it on. Within 2 seconds, the holdover LED lit. >>> immediately turned it off and within a few more seconds, the >>> oldover LED was back off. The GPS antenna is perhaps 35 feet away >>> ith a cinder block wall, a brick wall, and a metal roof in between. I >>> lso put a 15 Db attenuator between it and the antenna with almost the >>> ame result. I am going to do more testing with it wired into the GPS >>> ownfeed an an adjustable attenuator in line just to see how much >>> ignal it takes. That way, there will be little danger of messing with >>> nyone's reception. It is just a simple sweeper so it must do its job >>> y brute force. I am amazed that it took so little to shut my Z3801 >>> own. Has anyone here had any actual experience testing GPS receivers >>> or susceptibility? >>> _______________________________________________ >>> ime-nuts mailing list -- time-nuts@febo.com >>> o unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> nd follow the instructions there. >>> >>> >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.

  http://www.chronos.co.uk/pdfs/rac/labsat.pdf

Hi, The fact they refer that atmospheric s/n degradation and dropouts etc being replayed precisely lead me to think this is just a spectrum rec/play machine (no mod/demod of any kind) like the ham-oriented "time machine" but for GPS. http://www.expandedspectrumsystems.com/prod2.html Luis Cupido. ct1dmk. Bob Camp wrote: > Hi > > It's not real clear that they do anything more than sample the RX and play it back for the TX. > > Bob > > Sent from my iPhone > > On Nov 25, 2010, at 9:39 AM, "J. Forster" <jfor@quik.com> wrote: > >> Agreed. The trick is to properly partition what is done in hardware ane >> what is done in software. This could eliminate a lot of logic hardware. >> >> Clearly, the RF stuff and modulator are hardware. >> Ditto PR code generation. >> Everything else in SW, I think. >> >> FWIW, >> >> -John >> >> =============== >> >> >>> Hi >>> >>> One bit serial at 16 MHz isn't all that fancy any more. Sounds like a >>> shift register feeding a couple filters. >>> >>> The money must be in the receive side. >>> >>> Bob >>> >>> On Nov 24, 2010, at 5:14 PM, ernieperes@aol.com wrote: >>> >>>> >>>> >>>> Hi, >>>> >>>> found an interesting unit. I think it is not for the usual pocket >>>> money for a time-nuts. >>>> have a look... >>>> >>>> http://www.chronos.co.uk/pdfs/rac/labsat.pdf >>>> >>>> Rgds Ernie. >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> -----Original Message----- >>>> From: John Green <wpxs472@gmail.com> >>>> To: time-nuts@febo.com >>>> Sent: Mon, Nov 22, 2010 6:43 pm >>>> Subject: [time-nuts] GPS jamming susceptibility >>>> >>>> >>>> Given that this is an extremely sensitive topic and completely illegal >>>> lso, let me just state at the outset that I have no interest in >>>> amming anyone's GPS. A while back, I was looking at one of those >>>> hinese discount electronics websites, I'm sure we all have, and >>>> oticed a GPS jammer for sale. I had been wanting to do some jamming >>>> usceptibility testing for quite some time but had never got around to >>>> uilding a generator to test with. The thing was cheap so I ordered >>>> t. After it arrived, I opened it up, first thing, to see how it was >>>> ade. It has a dual 555 oscillator, a couple of analog switches, a 1.9 >>>> Hz VCO, a single amplifier. It doesn't look capable of putting out >>>> ore than 50 milliwatts or so into a 2 inch antenna. I was somewhat >>>> ubious that it would do anything, so I took it to the bench where the >>>> 3801 lives and turned it on. Within 2 seconds, the holdover LED lit. >>>> immediately turned it off and within a few more seconds, the >>>> oldover LED was back off. The GPS antenna is perhaps 35 feet away >>>> ith a cinder block wall, a brick wall, and a metal roof in between. I >>>> lso put a 15 Db attenuator between it and the antenna with almost the >>>> ame result. I am going to do more testing with it wired into the GPS >>>> ownfeed an an adjustable attenuator in line just to see how much >>>> ignal it takes. That way, there will be little danger of messing with >>>> nyone's reception. It is just a simple sweeper so it must do its job >>>> y brute force. I am amazed that it took so little to shut my Z3801 >>>> own. Has anyone here had any actual experience testing GPS receivers >>>> or susceptibility? >>>> _______________________________________________ >>>> ime-nuts mailing list -- time-nuts@febo.com >>>> o unsubscribe, go to >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>> nd follow the instructions there. >>>> >>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- time-nuts@febo.com >>>> To unsubscribe, go to >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>> and follow the instructions there. >>> >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >>> >>> >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. >

Luis Cupido wrote: > Hi, > > The fact they refer that atmospheric s/n degradation and dropouts etc > being replayed precisely lead me to think this is just a spectrum > rec/play machine (no mod/demod of any kind) > like the ham-oriented "time machine" but for GPS. > http://www.expandedspectrumsystems.com/prod2.html > > Luis Cupido. > ct1dmk. > But they mention software to generate sequences. It's actually a fairly clever idea. It's easy to stream 16.3xx Mbps from a modern computer, so you could generate an arbitarily complex signal off line.. For a lot of applications this would be great. A nice test source that you could replay on command. The only question I'd have is whether the 1 bit DAC can adequately represent the real-life complex signal. I suppose, intuitively, since your receiver is digitizing it with a 1 bit ADC... And, I have a question whether the 1 bit DAC can produce a high enough fidelity waveform for a higher performance receiver that uses a multibit digitizer. Since the clock you are recording and playing back with isn't necessarily as good as the one on the satellite, you probably couldn't use this for testing your precision receiver. It would be like introducing a random propagation variation or coax length variation in the system. It is intriguing though.. a homebrew version could be quite simple.. you can get the USB interface and a small FPGA pretty easily. One of those 10.23 MHz crystals from Rick might be handy...

> But they mention software to generate sequences. Hummm... right... so I think we need to look inside one to be sure what it is... lc ct1dmk. jimlux wrote: > Luis Cupido wrote: >> Hi, >> >> The fact they refer that atmospheric s/n degradation and dropouts etc >> being replayed precisely lead me to think this is just a spectrum >> rec/play machine (no mod/demod of any kind) >> like the ham-oriented "time machine" but for GPS. >> http://www.expandedspectrumsystems.com/prod2.html >> >> Luis Cupido. >> ct1dmk. >> > > > But they mention software to generate sequences. It's actually a fairly > clever idea. It's easy to stream 16.3xx Mbps from a modern computer, so > you could generate an arbitarily complex signal off line.. > > > For a lot of applications this would be great. A nice test source that > you could replay on command. > > The only question I'd have is whether the 1 bit DAC can adequately > represent the real-life complex signal. I suppose, intuitively, since > your receiver is digitizing it with a 1 bit ADC... > > And, I have a question whether the 1 bit DAC can produce a high enough > fidelity waveform for a higher performance receiver that uses a multibit > digitizer. > > Since the clock you are recording and playing back with isn't > necessarily as good as the one on the satellite, you probably couldn't > use this for testing your precision receiver. It would be like > introducing a random propagation variation or coax length variation in > the system. > > It is intriguing though.. a homebrew version could be quite simple.. you > can get the USB interface and a small FPGA pretty easily. One of those > 10.23 MHz crystals from Rick might be handy... > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. >

Hi My guess is the 1 bit DAC is nothing more than the FPGA output pin. About all you really need is enough of a buffer to stay ahead of the USB bus. That may not be much with a modern USB chip set and a hand made driver on the PC. Bob Sent from my iPhone On Nov 26, 2010, at 10:34 AM, jimlux <jimlux@earthlink.net> wrote: > Luis Cupido wrote: >> Hi, >> The fact they refer that atmospheric s/n degradation and dropouts etc being replayed precisely lead me to think this is just a spectrum rec/play machine (no mod/demod of any kind) >> like the ham-oriented "time machine" but for GPS. >> http://www.expandedspectrumsystems.com/prod2.html >> Luis Cupido. >> ct1dmk. > > > But they mention software to generate sequences. It's actually a fairly clever idea. It's easy to stream 16.3xx Mbps from a modern computer, so you could generate an arbitarily complex signal off line.. > > > For a lot of applications this would be great. A nice test source that you could replay on command. > > The only question I'd have is whether the 1 bit DAC can adequately represent the real-life complex signal. I suppose, intuitively, since your receiver is digitizing it with a 1 bit ADC... > > And, I have a question whether the 1 bit DAC can produce a high enough fidelity waveform for a higher performance receiver that uses a multibit digitizer. > > Since the clock you are recording and playing back with isn't necessarily as good as the one on the satellite, you probably couldn't use this for testing your precision receiver. It would be like introducing a random propagation variation or coax length variation in the system. > > It is intriguing though.. a homebrew version could be quite simple.. you can get the USB interface and a small FPGA pretty easily. One of those 10.23 MHz crystals from Rick might be handy... > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.