Well which is it:?

Question:  LOS jamming of the civilian code is easy; However why do you think the use of LEO [MEO] aids this?
Your response: "It doesn't"

Then you state:  " It" [ from context, the use of MEO orbit] "simply increases the risk that GPS will be made unavailable due to events outside the operators control"

You cannot have it both ways. Either "it doesn't", or "it increases".

Please be specific; In terms "Any competent engineer" would use, how does the choice of a LEO or MEO or even GEO orbit "simply increases the risk..." ?

Lester B Veenstra  MØYCM K1YCM W8YCM
lester@veenstras.com

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-----Original Message-----
From: Scott McGrath [mailto:scmcgrath@gmail.com]
Sent: Tuesday, July 30, 2013 2:46 PM
To: lester@veenstras.com; Discussion of precise time and frequency measurement
Cc: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Story in the Economist about GPS jamming

It doesn't    It simply increases the risk that GPS will be made unavailable due to events outside the operators control    Hence system risk profile is high

Was not so high when LORAN was available as aviation, maritime and timing applications could gracefully degrade to LORAN in the event GPS was unavailable

Now if GPS availability is denied we are back to maps bowdoins sextants and chronometers for navigation except for the vanishingly small number of ships and planes equipped with INS

Scott

Sent from my iPhone

On Jul 30, 2013, at 1:28 PM, "Lester Veenstra" lester@veenstras.com wrote:

Don't junk your ADF just yet.

On 07/30/2013 11:46 AM, Scott McGrath wrote:

--
Chuck Forsberg WA7KGX  caf@omen.com  www.omen.com
Developer of Industrial ZMODEM(Tm) for Embedded Applications
Omen Technology Inc      "The High Reliability Software"
10255 NW Old Cornelius Pass Portland OR 97231  503-614-0430

Hi

A sector antenna autocorrelateor  should be a pretty useful gizmo for tracking GPS jammers. You have most of the gear already in a cell site. Software patch and away you go. Of course you would need pretty good timing, but that's not impossible ….

Bob

On Jul 30, 2013, at 7:27 PM, Chuck Forsberg WA7KGX caf@omen.com wrote:

I was involved in some work on industrial controls that used 1588 for
timing.  We only needed microsecond accuracy, and it did that easily - the
basic hardware is simple, we were using STM32 microcontrollers with the
DP83640 PHY.  Since the MCU required a PHY anyway, the additional cost for
the IEEE1588 support was about $3.50/unit ($5 rather than $1.50 in 1000 up
quantities).

The PHY chip also has a (programmable) clock output locked to the 1588
timing, but it appeared to have quite a lot of phase noise on it - I didn't
bother doing any detailed measurements because we weren't actually using it.

On Wed, Jul 31, 2013 at 12:19 PM, Bill Hawkins bill@iaxs.net wrote:

The only switch I know that supports IEEE 1588 is the Cisco CGS 2520 and it was about 10 k before discount.  It's intended for use in smart grid applications

NICs are about 500 each from a variety of vendors.  Altera makes most of the silicon

Sent from my iPhone

On Jul 31, 2013, at 12:19 AM, "Bill Hawkins" bill@iaxs.net wrote:

Pretty much any industrial Ethernet vendor makes switches that support 1588

• we were using ones from Siemens.

On Wed, Jul 31, 2013 at 1:29 PM, Scott McGrath scmcgrath@gmail.com wrote:

On Wed, Jul 31, 2013 at 6:19 AM, Bill Hawkins bill@iaxs.net wrote:

A colleague of mine had a non-exhaustive look at the market 1.5 years ago
[1]. The cheapest PTP switch she could find was the Hirschmann MACH1000,
selling for 5.7 kCHF with 16 ports.

Cheers,

Javier

[1] http://www.ohwr.org/attachments/948/WRintro.pdf or animated PowerPoint
at http://www.ohwr.org/attachments/949/WRintro.pptx

In message 2072AA3475FF47539716716917CDBA99@system071, "Bill Hawkins" writes:

Yes.

If you don't need microseconds, you don't need a magic switch,
1588 gets you well below 1msec on regular switches, provided
you don't overload that network segment.

Regular NTP can also get there, if you tweak the poll-rate down,
but 1588 is a more robust protocol.

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG        | TCP/IP since RFC 956
FreeBSD committer      | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

On 30/07/13 16:03, J. Forster wrote:

The military receivers have not only better resistance than the average
civilian, but also enjoy the access to the PPS service, i.e. the keyed
signals which has greater capability in surpressing jamming signals.
With modern receivers even having the capability to lock directly into
the P(Y) signal without use of the much more vulnerable C/A code which
is the traditional way of locking into P(Y).

Cheers,
Magnus