[time-nuts] Story in the Economist about GPS jamming

Jim Lux jimlux at earthlink.net
Wed Jul 31 07:54:04 EDT 2013


Yes.. You put a gain antenna on the space craft, so for the same tx power, you get the same flux density on the ground.   The gps height was chosen for a variety of reasons.  It is out of the debris band, for one.  There's also a tradeoffs on launch costs, etc.  GPS world magazine had a great multipart article on the history and design last year

On Jul 31, 2013, at 5:25, Magnus Danielson <magnus at rubidium.dyndns.org> wrote:

> The MEO/GEO distance difference isn't all that great, and comparable signal strength is seen from the WAAS/EGNOS (SBAS in general) without too much difficulty in design.
> 
> Cheers,
> Magnus
> 
> On 30/07/13 16:51, bg wrote:
>> Satnav are not LEO but MEO. Which is good - less sv to cover the earth. Less good because distance is higher compared to LEO regarding signal power at earth.
>> 
>>  --
>> 
>> Björn
>> 
>> 
>> Skickat från min Mobil
>> 
>> -------- Originalmeddelande --------
>> Från: Scott McGrath<scmcgrath at gmail.com>
>> Datum: 2013-07-30  14:50  (GMT+01:00)
>> Till: jfor at quikus.com,Discussion of precise time and frequency measurement<time-nuts at febo.com>
>> Kopia: Discussion of precise time and frequency measurement<time-nuts at febo.com>
>> Rubrik: Re: [time-nuts] Story in the Economist about GPS jamming
>> 
>> Any competent engineer could have told the powers that be that a satellite system based in LEO has a relatively high risk profile from the Universe/hostile activity/spoofing and jamming
>> 
>> Yes GPS is/was oversold.
>> 
>> Trouble is Clarkes law applies here (any sufficiently advanced technology is indistinguishable from magic).  And this applies double to the technological illiterates in DC
>> 
>> See Sen 'Tubes' Stevens for the canonical example
>> 
>> Sent from my iPhone
>> 
>> On Jul 29, 2013, at 12:46 PM, "J. Forster"<jfor at quikus.com>  wrote:
>> 
>>> It seems to me that GPS has been oversold as the be all, end all system
>>> that made all other systems obsolete and GPS has become all but an
>>> indespensible utility.
>>> 
>>> Reports like this, could well be used to promote a backup, like LORAN or
>>> eLORAN, just as public buildings have backup generators.
>>> 
>>> YMMV,
>>> 
>>> -John
>>> 
>>> ==================
>>> 
>>> 
>>>> 
>>>> http://www.economist.com/news/international/21582288-satellite-positioning-data-are-vitalbut-signal-surprisingly-easy-disrupt-out?fsrc=scn/tw/te/pe/outofsight
>>>> 
>>>>                                 -Bill
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
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