Expert GPS analysis requested

See short presentation at

and the report at

Specifics of the effects on military-grade systems beyond the above will almost certainly be classified.

--
Rich Webb     Norfolk, VA

here is a link I got from google that seems to explain some of this

ir-best-to-destroy-gps

This brings selective availability back, except on a regional level. Big cities will be without GPS coverage. I'll let you fill in your own conspiracy theories.

Probably little impact on military systems since the US military usually doesn't target areas in the continental US. The military can always impose a limit where the LS towers can be placed in proximity to bases. Plus, the government has the money to retrofit all their equipment and pay for development of the tighter front-ends their systems will need. That will only be a few billion $. Think of it as stimulus money.

The bigger impact is on commercial use which covers agriculture (John Deere is complaining), transportation, timing services, and survey (land and waterway).

May need to dust off those old Mini Ranger systems.

They have satellite connectivity in the field with both fixed and mobile stations.

They get GPS data AT the actual link location, not from some tower.

Most boots-on-the-ground do as well, or can get synch from the more accurate terminal in theater. Doesn't matter, everyone now knows exactly where they are pretty much all the time.

Sounds like it might be a worthwhile application for stripline filters or some forms of ceramic filters. The military can probably retrofit, maybe you can get in on designing some retrofit gear.

?-)

be

My guess is that the best military systems are already "retrofitted" as a step toward hardening the receivers against deliberate jamming by an enemy. That portion of Gen. Shelton's teestimony was classified.

It depends on the military-use GPS system.

If they use the civilian-style receiver (a "one-bit" ADC that depends on noise for linearity, a ton of conversion gain for SNR ratio, and, evidently, no filters for cheapness), then they'll be hosed. But that just means that if I'm North Korea or Iran or whatever the technically competent rogue nation is this month, that marketable GPS jamming systems are just a power oscillator away.

If the DOD systems engineers are even minimally competent then they've known for years that the first thing that a funded and informed enemy is going to do is to generate a lot of RF energy at the (published!) GPS frequencies, to try to overwhelm receiver front ends. If they're even minimally sensible, they'll include specifications in their procurement contracts for receivers that are resistant to that.

Any opinions about whether they actually _are_ competent is straying into politics, though -- now isn't it?

--
www.wescottdesign.com

Yes, but that is a different kind of politics.

My last experience with military GPS was a for training/evaluation system that used the cheapest possible GPS receivers to identify player positions. However, my earlier experience with military electronics systems gives me some confidence that the really critical systems are equipped with the best possible electronics, or that there exist hyper-secret modes of operation such as switching over to unpublished frequencies.

On a sunny day (Mon, 19 Sep 2011 23:21:23 -0700 (PDT)) it happened Richard Henry wrote in :

Nothing a spark gap does not fix :-)

Nothing a H.A.R.M won't take care of. :}

Kind of expensive if there's 500 of them.

Best regards, Spehro Pefhany

--
"it's the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

Well, you could put a 555 in there to delay the start-up. Destroying a

555 with a $500K missile is kind of amusing.

Best regards, Spehro Pefhany

--
"it's the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

It's called attrition. :) Sooner or later you run out of volunteers.

Or a $500K missile with a 555... ;-)

How much power does the typical jammer put out?

How much power does a spark gap put out? What fraction of that is in the GPS band?

I remember seeing WW II era carbon arc searchlights used for advertising setups. How much power do them emit? Did it wipe out the local radios and TVs?

Next time you see one, please try your GPS near it.

--
These are my opinions, not necessarily my employer's.  I hate spam.

On a sunny day (Tue, 20 Sep 2011 15:56:34 -0500) it happened snipped-for-privacy@ip-64-139-1-69.sjc.megapath.net (Hal Murray) wrote in :

Some years ago there was a website selling these things, little parabolic refector, car battery for power, portable units. Maybe they still exist. They listed power too, quite incredible numbers actually. There is a reason all car ignition leads had to be made RFI free. It sure f*cked up teevee in the early days. Low energy sparks (from a DC fan motor) cause bit errors in the 10 GHz or so satellite band.... You need the right shape and size cavity - antenna I think. Sparks are cool :-)

No, they're not. I have the burn scars to prove it :-)

-- "For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)

On a sunny day (Wed, 21 Sep 2011 11:39:12 -0700) it happened Fred Abse wrote in :

Yes, me too, the RF burns nice brown spots on your skin, and smells in a special way :-). I remember a doctor removing a wart in the long ago past with a RF probe, burning them.

My only injury of the VietNam war occurred when I stuck my little finger into the last stage of an ARC-51 transmitter module while I was blade-tweaking the stage beside it. It was 600 volts and around

350-400 MHz. It made a nice little black hole right through the fingernail and out the other side of the finger. It felt like it had been hit with a hammer.