[fizzymagic]

John E Cache, on 11 August 2011 - 09:37 PM, said:

You missed my point entirely. Only harmonics can be generated and they do not fall in the adjacent band. So there is no GPS interference.

No, he didn't miss your point. You are incorrect. The interference being discussed here is sideband interference, not harmonic interference. You seem oddly fixated on one and completely ignorant of the other.

Once again, slowly. A high power in one band will always leak into adjacent bands if there is information being transmitted. It's pretty basic physics.

[John E Cache]

fizzymagic, on 12 August 2011 - 02:19 AM, said:

John E Cache, on 11 August 2011 - 09:37 PM, said:

You missed my point entirely. Only harmonics can be generated and they do not fall in the adjacent band. So there is no GPS interference.

No, he didn't miss your point. You are incorrect. The interference being discussed here is sideband interference, not harmonic interference. You seem oddly fixated on one and completely ignorant of the other.

Once again, slowly. A high power in one band will always leak into adjacent bands if there is information being transmitted. It's pretty basic physics.

I guess I don't get what basic physics you are talking about unless you can cite a reference. I learned about frequency domain and Fourier series and Laplace transforms in third or fourth year electrical engineering. The modulation method is designed so the bandwidth of the signal fits in the band. The bandwidth of the signal does not increase when run trough a linear amplifier to increase power. As far as the two sidebands from amplitude modulation(AM) the sidebands and carrier frequencies fit in the band.

In the "band pass filter" link I cited, the slanted sides of the filter in the GPS may be in the adjacent bands and if the Lightspeed signal is towards the GPS end of their band the signal may be in the skirts of the GPS filter. That's all I am saying. If you are listening to radio and drive by a powerful station it appears to be bleeding over, but in fact the signal is stronger than the filter can filter out(even the flat floor on the sides of the filter diagram).

As far as harmonics, I think the oscillator of the transmitter as a spinning wheel with a white dot. If you count how many times the white dot passes the frequency is the count divided by time. If you add a dot you get a harmonic at twice the frequency.

As a side note for listeners: Fizzy and I like to argue. At least on my end it is all in fun if it does not get personal. "You seem oddly fixated" and "slowly" is getting close being personal, but not there, yet.

[ecanderson]

John E Cache, on 11 August 2011 - 09:37 PM, said:

I am glad another EMI guy agrees with me.

Mostly - as long as we agree that although you say "Garmin's problem is that their filters are not sharp enough", we can extrapolate from that to say "None of the GPS manufacturers' filtering is sharp enough, and neither should anyone have thought to attempt to design them to handle a problem like this. Nor is it clear that given the power levels involved, that it is even practical to do so."

This post has been edited by ecanderson: 12 August 2011 - 08:25 AM

[Woodstramp]

John E Cache,

You're an EE with obvious RF experience. Maybe you can explain this for me. This whole Lightsquared thing reminds me of something I recall from years ago.

I used to fiddle around with Citizen's Band radio. I think it was near 29mhz and AM. The FCC suposedly limited transmission to 4 watts. In pre-cell phone days we kept one in the boat and base station at the house just in case we broke down on the lake. We also chatted at night with other locals at times. There was this one guy though. If he fired up his amp (bragged he could crank out 1KW) nobody on any of the adjacent channels could carry on a conversation within a 10 mile radius.

The problem was not that our CB radios were faulty. It was the jerk suddenly cranking out 1000 watts on our lake.

[John E Cache]

ecanderson, on 12 August 2011 - 08:25 AM, said:

John E Cache, on 11 August 2011 - 09:37 PM, said:

I am glad another EMI guy agrees with me.

Mostly - as long as we agree that although you say "Garmin's problem is that their filters are not sharp enough", we can extrapolate from that to say "None of the GPS manufacturers' filtering is sharp enough, and neither should anyone have thought to attempt to design them to handle a problem like this. Nor is it clear that given the power levels involved, that it is even practical to do so."

I used Garmin as an example because they were the one's who's response was posted here. I have since learned that they designed their filters with low power sat signals on adjacent bands in mind. I now see their point and think Garmin has a valid point.

[ecanderson]

Woodstramp, on 12 August 2011 - 09:18 AM, said:

The problem was not that our CB radios were faulty. It was the jerk suddenly cranking out 1000 watts on our lake.

To be fair, some of the cheapo Class B CB linears tended to have poor harmonic distortion specs (zero crossing issues) and really did "splatter" outside of their channel space into adjacent channels - something the prior poster doesn't address on the assumption that gear that passes FCC muster will behave better.

[John E Cache]

John E Cache, on 12 August 2011 - 09:35 AM, said:

ecanderson, on 12 August 2011 - 08:25 AM, said:

John E Cache, on 11 August 2011 - 09:37 PM, said:

I am glad another EMI guy agrees with me.

Mostly - as long as we agree that although you say "Garmin's problem is that their filters are not sharp enough", we can extrapolate from that to say "None of the GPS manufacturers' filtering is sharp enough, and neither should anyone have thought to attempt to design them to handle a problem like this. Nor is it clear that given the power levels involved, that it is even practical to do so."

I used Garmin as an example because they were the one's who's response was posted here. I have since learned that they designed their filters with low power sat signals on adjacent bands in mind. I now see their point and think Garmin has a valid point.

Your CB story is the similar. I should point out EEs argue with each other on occasion. :-) The CB band is 11 meters or 27mhz, I think. Ham amplifiers that work for the ham 10 meter band(28mhz) band work for 11 meters. One difference is you are talking several CB channels in one band, not adjacent bands. My guess is that your old CBs probably were not selective enough to select only the weak channel in the presence of an illegal high power channel. Hams can put filters on their neighbors TV if they are running high power and it gets into their TV. The problem is the ham is perfectly legal, like LightSquared, and a filter is not legally required by the transmitter owner.

I can see several towers on the west hills of Portland. They do not interfere with each other by design and governed by laws founded by Fourier in the 1800s. Just because someone draws a nice picture of the radio spectrum with the bands in a nice order, you can not infer that nearby bands interfere with each other. The math is much more complicated than a simple picture.

[Woodstramp]

ecanderson, on 12 August 2011 - 09:45 AM, said:

Woodstramp, on 12 August 2011 - 09:18 AM, said:

The problem was not that our CB radios were faulty. It was the jerk suddenly cranking out 1000 watts on our lake.

To be fair, some of the cheapo Class B CB linears tended to have poor harmonic distortion specs (zero crossing issues) and really did "splatter" outside of their channel space into adjacent channels - something the prior poster doesn't address on the assumption that gear that passes FCC muster will behave better.

The "splattery" transmission side didn't occur to me. Guess better filtering on transmission side could help. John also mentions Hams having to install recieve filters on the neighbor's TV's. (From what I know of Ham operators they tend to be self policing and upright folk. Not like outlaw CB skip-hounds or truckers running huge sloppy amps). A Ham using his own time and money to keep the neighbors happy still makes me think that if an electonics pro like that can only keep his high power "splatter" controlled to a certain extent. Regardless of of transmission end filtering.

[Woodstramp]

--delete of accidental double post--

This post has been edited by Woodstramp: 16 August 2011 - 09:36 AM

[Woodstramp]

John E Cache, on 15 August 2011 - 10:39 PM, said:

I should point out EEs argue with each other on occasion. :-)

I am out of my pay grade here, admittedly. Just some things don't seem Kosher here judging from what I do know.

Quote

Hams can put filters on their neighbors TV if they are running high power and it gets into their TV.

Like I told Ecanderson...sounds like even if you have transmission filters that were salavaged from the alien spacecraft they keep at Area 51, the transmitter running high enough power will still be like dropping boulders in a pond that is used to gentle sound of rain drops.

Quote

The problem is the ham is perfectly legal, like LightSquared, and a filter is not legally required by the transmitter owner.

"Legal" with the US gubbment doesn't neccessarily mean "right" from time to time . The Trail of Tears, as an example. Which is gonna make me cry if LS makes my current gizmos deaf.

Also, earlier in the thread you mentioned local towers messing with your GPS units now. I've never experienced that with my Garmins. Did experience this with my PN-20 on sporadic occasions near a local array (mix of microwave/TV/cell). This was rare, but in the same location and only within a mile of the towers.

[7rxc]

I still say that the mobile devices the network is supposed to provide coverage to won't be thrilled to lose the GPS function either.

As for filtering. I bet existing GPSrs are better at it than the phones are...

And it pretty much is always a two sided coin... the transmitter and the receiver need to control their signals.
Band pass and band reject filtering should be there to attenuate the undesired signals. However, when the signal is so strong it bypasses the filtering completely no receiver will work properly, since it can no longer hear its intended station(s). That is part of radio in general. I saw something about 'WiFi on Steroids' recently but got the impression that that was not the LS thing.
That could take a brick or two out of the LS wall. Or it could be that the providers are starting to gear up to provide the coverage away from the LS sat frequencies as predicted.

I was glad to see in that report that they have considered external mixing of rf to create stray signals... that can be a problem as well. We used to have problems with paging systems trying to expand their areas (without permit) cheaply and using poor quality components and the odd illegal amp or two hidden in the woodwork. They started mixing with other signals and were wreaking havoc on several repeaters (ham and commercial) until tracked down and lectured sternly.

Doug 7rxc

[7rxc]

John E Cache, on 15 August 2011 - 10:39 PM, said:

Hams can put filters on their neighbors TV if they are running high power and it gets into their TV. The problem is the ham is perfectly legal, like LightSquared, and a filter is not legally required by the transmitter owner.

Hams are required to provide technical assistance to 'neighbours' if there is an interference problem... many offer filters that are external to the device. This does not imply that they are responsible for the interference beyond checking their station is operating within proper specs.. A lot is done for good relations (like CITO for cachers). I think that transmitter filtering depends a lot on whether the transmitter is 'dirty' or not. Fixes run from an alignment through touching up existing filters that are failed or failing to adding say a low pass filter on the transmission line in the case of a tv problem. Same goes for adding a high pass filter on the receiver(s) that experience that. Digital transmission may have mostly eliminated that sort of thing, I don't know since we are a bit behind switching from analog, but it's coming. However, it is held that the Ham should not be responsible if the problem is coming as a result of non existent filtering on the neighbouring device, or poor design. The manufacturers have been told this and that they are responsible for poor design and making it that way to save money. Gray market electronics are bad that way, since their North American offices know better now... but people shop for bargains anyway. End up with a product with no NA warranty, and often sub standard or no compliance with electrical codes. Like the LS project, as long as people try to profit off of others and do so by shortchanging the processes it will happen. From getting the waiver in the first place to changing tactics to bully it through regardless, it will happen. That part has to be stopped... follow the darn rules.
and as you say physics is a set of laws/rules.

Doug 7rxc

[ecanderson]

Woodstramp, on 16 August 2011 - 10:04 AM, said:

Like I told Ecanderson...sounds like even if you have transmission filters that were salavaged from the alien spacecraft they keep at Area 51, the transmitter running high enough power will still be like dropping boulders in a pond that is used to gentle sound of rain drops.

Understanding the various stages of a radio receiver, and that's really what's on the front end of any GPS, will help to understand why even filtering may be insufficient if a unit is close enough to a LS transmitter.

The very first (RF amplifier, AKA "front end") stage of a receiver is designed with a certain amount of gain (amplification) in mind based upon the strength of the desired signal and the signal to noise ratio needed to keep the signal intelligible. The sensitivity of a receiver is in no small part a function of the very first RF stage that grabs the signal from the receiver's antenna and amplifies it. At a distance, any radio signal is surprisingly weak, and it's quite the miracle that receivers can be designed to take those weak signals and do something with them. In the case of a GPS receiver, the signals being received are (relative to other signals) VERY weak, coming from a very low power device half a bazillion miles up there, and with an antenna that has to cover a few degrees of arc and spread its signal around a fair bit of turf, making the result in any one spot on the ground weaker still.

A subsequent stage takes the amplified signal and tries to pick out a particular center frequency from the million different signals that are being received. If the first stage or this stage is being overloaded due to a signal that is far more powerful than the receiver was designed to manage, things can go badly here, even before we reach other stages. Some of the very strong adjacent channel signal will push its way through, and the result will be distorted to boot. In a radio designed to pick up audio, it will just sound lousy. On a GPS receiver, you'll get an unintelligible data signal that can't be used to figure out what satellite is talking, much less compute a position.

Apart from ANY filtering that might or might not be employed downstream, it is possible to simply overload the front end of a receiver to the point where any signal will be distorted beyond use. Using sharper filters really doesn't respond to the problem. Given the spectrum involved, there would always be a problem if you get close enough to a LS facility. The working group showed that under the original plan, "close" wasn't very close at all, and was measured in miles. Attempting to improve on this would have been only to try to reduce by some amount the distance at which the LS equipment was interfering with the GPS signals, not to eliminate the problem.

There's no such animal as an RF filter that has 90 degree slope (square) sides - the perfect bandpass filter. There's always some slope on the sides. To avoid attenuating desirable signals on frequencies that are toward the edge of the band, a certain amount of signal from outside of the band is allowed in as well. The problem occurs when the undesirable signal is orders of magnitude stronger than the signal you want to keep. THAT WAS NEVER SUPPOSED TO HAPPEN IN THIS CASE. A little safe spacing (a 'guardband') had been established long ago in the frequency allocations, and everyone designed equipment accordingly. When the FCC decided to let LS deviate from previously approved use of that bit of spectrum in the way that LS asked, the FCC could and should have known the results would not be pretty. They knew full well the kind of gear that was being used out here in the real world, and ought to have anticipated the results. Either they're technically incompetent and did not anticipate this, or they're a bunch of goofs who sold out an entire industry to promote an agenda. So the leadership of the FCC either winds up looking like a bunch of idiots, or a bunch of idealogues. Take your pick. Neither is acceptable.

This post has been edited by ecanderson: 16 August 2011 - 02:54 PM

[Woodstramp]

"A little safe spacing (a 'guardband') had been established long ago in the frequency allocations,..."

That is the way I understood things were done to prevent broadcasters from walking all over each other. You also couldn't have a 98.5 FM radio station and a 98.4 FM station in the same town.

"...and everyone designed equipment accordingly."

GPS manufacturers didn't have a crystal ball. They just assumed the allocated band wouldn't be encroached upon. Why build a tank for an environment that is supposed to be safe for bicycles?

[gcbiker]

Two recent related developments:

1) John Deere has estimated impact of LS proposal to the agriculture industry at $30B: http://www.bloomberg...html?cmpid=yhoo

2) Dish Network has now asked FCC to let it build a similar solution for terrestrial broadband: http://www.theregist.../dish_networks/

The Dish proposal is to use satellite frequencies for non-satellite communications. In a weird way, this might move the battle over to the correct topic -- intended use of frequencies, rather than "interference".

This post has been edited by gcbiker: 26 August 2011 - 04:39 AM

[7rxc]

Googles project to open up the White Space frequencies (locally unused TV channels) seems to be proceeding as well...
That is the so called 'WiFI on Steroids' project. Verizon seems to have outbid them on the frequencies, but Google was mostly promoting the solution, not wanting to be the provider. At least it doesn't seem to threaten much of anything except active TV stations and that has been addressed in the project docs... through Smart technology that senses existing TV signals etc.
Seems to be going ahead well from what is on the web.

I'm wondering just how much market there is for all this bandwidth, since there is only so much the mobile users will carry in terms of hardware... move a bit and need another completely different system at additional expense, sort of thing.

Since the US is gearing up for yet another election campaign, perhaps it's time to make it campaign issue, Not the internet, but the state of the FCC. Still not seeing much on the international aspects of these projects. Some of it will spill over into other countries that probably strongly disagree with threats to satellite frequencies of any sort. Has Lightsquared et al made it to the ITU table yet? Anyone seen anything about the 'mini cube cell site' boxes that hit the news not to long back? I lost track of that one...

Doug 7rxc

[Egnix]

A couple articles from GPS World from this month on the topic:
Expert Advice: Who Won?
Out in Front: A Pawn in Their Game

[Woodstramp]

egnix,

I think that second article you linked is probably what was really going on. Fake a crazy frontal attack with something expendable and during the distraction, make a flank move to secure the real goal. That tactic has be used a few times before.

[BAMBOOZLE]

Egnix, on 30 August 2011 - 09:43 AM, said:

A couple articles from GPS World from this month on the topic:
Expert Advice: Who Won?
Out in Front: A Pawn in Their Game

Good articles.....with so much MONEY involved we are indeed far from safe.

[seldom_sn]

BAMBOOZLE, on 30 August 2011 - 10:35 AM, said:

Egnix, on 30 August 2011 - 09:43 AM, said:

A couple articles from GPS World from this month on the topic:
Expert Advice: Who Won?
Out in Front: A Pawn in Their Game

Good articles.....with so much MONEY involved we are indeed far from safe.

Don't forget, soccer moms vote. How many driving gpsrs are on the road? When soccer moms can't find directions to the next match, they'll write their congressmen. Congressmen may love big money, but they are deathly scared of soccer moms.

This post has been edited by seldom_sn: 30 August 2011 - 10:49 AM

[michaelnel]

I bet the majority of people who use navigation systems in their cars don't even know they are using a GPS, and wouldn't understand any of this discussion if you told them.

[Alfresco2006]

BlueDeuce, on 12 January 2011 - 06:28 PM, said:

Who starts any formal letter with "Dear"?

Okay Einstein, how are you supposed to start a formal letter. Dear Sir/Madam if you do not know the name is widely recognized as the international protocol for starting any formal letter!!!

[seldom_sn]

michaelnel, on 30 August 2011 - 02:50 PM, said:

I bet the majority of people who use navigation systems in their cars don't even know they are using a GPS, and wouldn't understand any of this discussion if you told them.

They may not be able to follow this discussion, but when their GPSrs stop working they'll know how to complain.

[7rxc]

Egnix, on 30 August 2011 - 09:43 AM, said:

A couple articles from GPS World from this month on the topic:
Expert Advice: Who Won?
Out in Front: A Pawn in Their Game

Sounds like some of what I've been saying, especially the 2nd one.
There could be a way for them to achieve the project by 'partnering' and using their resources to provide the downlinks to the remote stations for connecting on some other band altogether... especially since they claim to be in wholesale rather than supplying end users.

I see that here in Canada, the end of analog TV is tomorrow in larger centres... and that the auction of the White Space frequencies to internet providers will begin soon... Some of those providers will need a data link soon I think.
As I said that is heading to completion in the States as well... and not much of it will be anywhere near the GPS band.

Doug 7rxc

[RamblinBear]

I read this quote on the Washington Post website, and I thought it was just a breathtaking example of how the FCC appears to be divorced from reality, and seems somehow to be trying to put a positive spin on what must be a complete debacle for them (unless, and more worryingly, if they really believe this).

“The process we set up has been tremendously successful, yielding a deeper understanding of the issues by both LightSquared and the GPS industry,” said Tammy Sun, an FCC spokeswoman.

Good to know that your tax dollars are being so wisely spent - to help LightSquared and the GPS industry understand the issues.

[ecanderson]

Let the investigations begin!

http://www.thedailyb...help-donor.html

http://www.iwatchnew...tions-were-made

[fizzymagic]

ecanderson, on 15 September 2011 - 11:44 AM, said:

Let the investigations begin!

http://www.thedailyb...help-donor.html

http://www.iwatchnew...tions-were-made

I was just coming to post these! Maybe the Solyndra debacle will have an upside in preventing the Lightsquared debacle.

[ecanderson]

fizzymagic, on 15 September 2011 - 01:11 PM, said:

I was just coming to post these! Maybe the Solyndra debacle will have an upside in preventing the Lightsquared debacle.

Perhaps. At least LightSquared / Falcone isn't (yet) operating on my tax dollars.

The outfit that really got burned on this deal was Sprint - not that their management was probably paying attention, as usual - when Sprint inked that 15 year deal with LightSquared in late July for build-out that depends upon LS spectrum availability.

[seldom_sn]

Anybody know about the international implications of this system? Will this disrupt the Canadians and Mexicans? Germans and Chinese?

This post has been edited by seldom_sn: 16 September 2011 - 07:03 AM

[DragonsWest]

Now the big dog speaks...

http://www.defense.g...e.aspx?ID=65355

[Wintertime]

DragonsWest, on 16 September 2011 - 07:22 AM, said:

Now the big dog speaks...

http://www.defense.g...e.aspx?ID=65355

Dragons, I was just about to post the same link. :-) Here's an excerpt:

Quote

“Based on test results and analysis to date, LightSquared’s network would effectively jam vital GPS receivers, and to our knowledge thus far, there are no mitigation options that would be effective in eliminating interference to essential GPS services in the United States,” the general told the subcommittee members.

[coggins]

Well, they claim they fond a fix: link

[Wintertime]

coggins, on 16 September 2011 - 11:24 AM, said:

Well, they claim they fond a fix: link

Here's the full article that DefenseSystems.com summarized:

http://www.reuters.c...E78D7CB20110914

A couple of excerpts:

Quote

A LightSquared executive told reporters on Wednesday that the company had partnered with a leader in GPS technology to develop a prototype device that can provide the same precision performance.

Carlisle said the new prototype receiver uses technology that can be adapted to other devices and could be put into commercial production within several months.

Translation: Everyone would have to buy new GPS receivers that would be free from interference by LightSquared's system.

In the case of the DoD, that means our tax dollars would have to be used to overcome the interference problem. No thank you!

[seldom_sn]

Wintertime, on 16 September 2011 - 01:05 PM, said:

Everyone would have to buy new GPS receivers that would be free from interference by LightSquared's system.
In the case of the DoD, that means our tax dollars would have to be used to overcome the interference problem. No thank you!

The way I read the Reuters article the only affected units would now be "high precision" ones (Trimbles etc.) So the only surveyors, farmers, and the military. Still, who owns the spectrum? Shouldn't Lightsquared (or the FCC) have to make everybody whole and provide new GPSrs to all injured parties? Otherwise, its a taking.

[ecanderson]

coggins, on 16 September 2011 - 11:24 AM, said:

Well, they claim they fond a fix: link

What they found was a design that could work - and doesn't address the bazillion dollars of equipment already in the field. Note that there is also no mention of cost vs. existing technology for this new equipment.

[Woodstramp]

Just happened to have the Sean Hannity show (Fox) on right now. They are discussing current administration scandals (Solyndra/stimulus money squandering, etc).

They are talking about Lightsquared and how someone in the WH coerced a general to go along with the LS deal. Just a heads-up. They generally replay Hannity later if you want to catch it.

[7rxc]

seldom_sn, on 16 September 2011 - 07:02 AM, said:

Anybody know about the international implications of this system? Will this disrupt the Canadians and Mexicans? Germans and Chinese?

All I've seen (haven't wasted the time to do much reading) is that Lightsquared has a satellite licence for one bird from the Canadian Gov't. Since Sat's are well used up here, they probably won't get too far with anything that consumes Sat bandwidths for any purpose.

Also since Canada has started to switch to digital TV channels, there will soon be an auction of 'white space' frequencies for the so called 'WiFi on Steroids' here as larger markets have now switched to digital on Sep 1 or so. That will probably fill our wireless requirements for quite a while. Since rural markets are usually single channel local transmitters (analog) of low power, some may have more than one channel, but there will still be many unused 'white space' frequencies for WiFi use, even if the locals stay on analog signals.

As for Europe, I saw one article (look up above somewhere recently) that mentioned that LS had gone to the ITU for sanction...
They might find some for some countries, but not many phones use that close to GPS band frequency set...

Since the US 'white space' market is going ahead full steam apparently, they may just get sunk by lost market share, by being late to arrive at functionality. Only the US seems to allow over development of services... most countries factor in need and network sharing agreements etc.

Doug 7rxc

[7rxc]

coggins, on 16 September 2011 - 11:24 AM, said:

Well, they claim they fond a fix: link

Glad they find their idea to be affordable (whatever it is), since they will be the ones paying to try it out...
Probably has something to do with EVERYONE joining the US Military!

Anyone know what your Homeland Security would have to say about any other organization that came this close to disabling a major military / civilian service? Regardless of the original intent... they drop on someone who buys just a little too much fertilizer!
Not to mention the odd miss-placed Geocache.

Doug 7rxc

[DragonsWest]

Wintertime, on 16 September 2011 - 01:05 PM, said:

coggins, on 16 September 2011 - 11:24 AM, said:

Well, they claim they fond a fix: link

Here's the full article that DefenseSystems.com summarized:

http://www.reuters.c...E78D7CB20110914

A couple of excerpts:

Quote

A LightSquared executive told reporters on Wednesday that the company had partnered with a leader in GPS technology to develop a prototype device that can provide the same precision performance.

Carlisle said the new prototype receiver uses technology that can be adapted to other devices and could be put into commercial production within several months.

Translation: Everyone would have to buy new GPS receivers that would be free from interference by LightSquared's system.

In the case of the DoD, that means our tax dollars would have to be used to overcome the interference problem. No thank you!

Don't overlook LS adding their pinch to the price of each unit for using their technology.

Yeah. What a load of BS.

[ecanderson]

seldom_sn, on 16 September 2011 - 07:02 AM, said:

Anybody know about the international implications of this system? Will this disrupt the Canadians and Mexicans? Germans and Chinese?

Germans and Chinese, no. But if LS were to deploy terrestrial systems at the originally planned frequencies near either border .. well, RF doesn't know about international boundaries.

[Team Krammer]

Have they ran any tests of the system lately? Because the other day I was out caching and the gps said 20m to cache, then 30, then 40, then 50, all the way up to 160 m away while standing in the SAME spot. Then it slowly came back down to 20ish meters away.

[ecanderson]

Team Krammer, on 18 September 2011 - 04:33 AM, said:

Have they ran any tests of the system lately?

AFAIK, the tests are as 'done' as they're going to get, and the working group has made its final report. However, there are other devices out there that can ruin your GPS signal .. in particular GPS jammers that some truckers are using to prevent the company-installed systems from tracking their routes. It's a known problem, and has been a real PITA for LaGuardia airport where truckers on I-95 have been fouling GPS signals at the airport.

Here's the FAA's take on the LaGuardia issue: http://www.faa.gov/a...l2010_final.pdf
You'll find the comments quickly if you search for the phrase "New Jersey Turnpike".

The Chinese are flooding the market with these bloody things. A few more articles:

http://www.newscient...-your-life.html
http://www.foxnews.c...dangerous-risk/

[7rxc]

Interesting bit in the last mentioned article... not news really, but interesting.

"Ronald Repasi, the FCC's Deputy Chief for the Office of Engineering and Technology, said selling, importing, owning, or using a GPS jammer in the U.S. is illegal, and he said the agency actively pursues those who use the devices."

Wonder if he is talking to his boss much?
Also depending on how broadband those devices (especially the cheap ones) are, they would be quite effective at blocking LS signals as well perhaps... they were designed at first to block cell phones... so I think they are very broad systems.

A signal like that would in itself be fairly easily tracked down with standard (?) RF tracking gear. Like an in band receiver with a signal attenuator... not even directional, but that would be easily done as well. Like a Geocache, just keep getting closer to the signal source... by increasing attenuation or via S meter or both. We used to build 'fox hunting' devices like that for sport.
I'd have to get one to play with as to how hard it would be... but I think a W9DUU box would do the trick on all levels except attenuation and it doesn't need to do that... but a broad band signal is not so easy to hunt that way. On a highway, especially limited access roads, you simply need signal strength and a bit of vehicle separation. If the driver turns it off, he just confirms you have the right vehicle. Charges? Just let his boss know he is jamming the company device... no job, no jamming etc.

Doug 7rxc

[RamblinBear]

seldom_sn, on 16 September 2011 - 07:02 AM, said:

Anybody know about the international implications of this system? Will this disrupt the Canadians and Mexicans? Germans and Chinese?

I think the European Space Agency and the European Aviation authorities have written to the FCC registering grave concerns. It would certainly adversely affect the safety of European air traffic entering US airspace.

I think there's also the concern that if the US opens the door on this one, then other nations may feel the pressure to follow.

On a more general front, I think this whole thing could seriously undermine international confidence in the GPS system - after all, if the US government isn't going to take robust action to protect its own system, then it reinforces the need for nations to have their own, independent systems, and the US loses its lead.

[ecanderson]

RamblinBear, on 19 September 2011 - 04:20 AM, said:

On a more general front, I think this whole thing could seriously undermine international confidence in the GPS system - after all, if the US government isn't going to take robust action to protect its own system, then it reinforces the need for nations to have their own, independent systems, and the US loses its lead.

Not wishing to appear dependent upon our system, the alternatives are already planned and the programs in place. It's just a matter of time until there are three full systems in operation anyway.

[7rxc]

ecanderson, on 19 September 2011 - 05:29 AM, said:

RamblinBear, on 19 September 2011 - 04:20 AM, said:

On a more general front, I think this whole thing could seriously undermine international confidence in the GPS system - after all, if the US government isn't going to take robust action to protect its own system, then it reinforces the need for nations to have their own, independent systems, and the US loses its lead.

Not wishing to appear dependent upon our system, the alternatives are already planned and the programs in place. It's just a matter of time until there are three full systems in operation anyway.

I'm afraid I haven't looked at the other sat nav systems specs... I'm wondering if you know whether they use the same band as the US system, or more likely other independent bands that may be affected by band misuse such as what LS is proposing? In fact does the alternate frequency usage by LS put their bands in more jeopardy by the move away from the US bands?

Doug 7rxc

[ecanderson]

7rxc, on 19 September 2011 - 07:34 AM, said:

I'm afraid I haven't looked at the other sat nav systems specs... I'm wondering if you know whether they use the same band as the US system, or more likely other independent bands that may be affected by band misuse such as what LS is proposing? In fact does the alternate frequency usage by LS put their bands in more jeopardy by the move away from the US bands?

The following are give-or-take center freqs, so it's all plus and minus.

GLONASS is on L1 (1602MHz) and L2 for military (1246MHz). Their L1 is therefore further from LS than we are.
We're on L1 (1575MHz) and L2 for military (1228MHz).
I believe the Galileo freq still TBD. Originally, the U.S. wanted it far enough away that they could block it without blocking our own. However, as I recall the original proposal, it centers their L1 at around 1575, same as ours. I don't know how they'll work that out in the end.

[ecanderson]

Anyone else enjoy watching Falcone squirm on FoxNews just a few minutes ago?

[jholly]

ecanderson, on 19 September 2011 - 10:24 AM, said:

Anyone else enjoy watching Falcone squirm on FoxNews just a few minutes ago?

Didn't see it, maybe you could give a summary.

[seldom_sn]

jholly, on 19 September 2011 - 11:00 AM, said:

ecanderson, on 19 September 2011 - 10:24 AM, said:

Anyone else enjoy watching Falcone squirm on FoxNews just a few minutes ago?

Didn't see it, maybe you could give a summary.

Or a website link? Youtube? Fox?