Isn't received power 1/R-squared?

I think those calculations should be radius-squared/watts

I find it interesting that the products designed as jammers have ranges of
"only" a few 10s of meters while a recent message here said 1/2 mile from a
digital-radio link that was transmitting on 315 MHz.  (aka designed for
something else rather than as a jammer)

Similarly, the Monterey Bay jammer wasn't trying to be a jammer, and it wiped
out a huge area.

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

I think the problem with the Monterey Bay jammer was that he was jamming the
DGPS correction signal, not the GPS signal itself. The DGPS correction
signal is sent over the UHF band. Most marine GPS are DGPS because they need
the better resolution it provides, particularly to find buoys and channel
markers in the fog. The DGPS correction signal does not benefit from the
spread-spectrum modulation and associated jamming resistance of the GPS
signal itself.

Didier

On Sun, Nov 15, 2009 at 08:22:50PM -0600, Didier Juges wrote:

That is the first I've heard of a UHF DGPS correction transmission

can you provide a frequency and modulation mode ?    Most I know of are
re purposed LF NDBs or similar transmitters in the 200 to 400 KHz or
so range that transmit a PSK'd carrier with the DGPS data at fairly low
speed on it.

I have heard of cases of wide area GPS outages noted by many

folks with NON DGPS receivers (DGPS receivers  mostly will just indicate
no DGPS available and still show a pretty good position) that were
caused by UHF signals on the L2 frequency... though I am sure there are
incidents of accidental interference to LF or other distribution of
DGPS.

--
Dave Emery N1PRE/AE, die@dieconsulting.com  DIE Consulting, Weston, Mass 02493
"An empty zombie mind with a forlorn barely readable weatherbeaten
'For Rent' sign still vainly flapping outside on the weed encrusted pole - in
celebration of what could have been, but wasn't and is not to be now either."

I was shooting from the hip, I thought the DGPS signals were sent at UHF,
but maybe not, but that's not the point. The point is that you can
significantly affect DGPS operation without having to jam the GPS signal
itself.

I found a reference saying the Monterey Bay jammer was jamming the DGPS
station, rather than the DGPS signal. I have not found the original article
I was looking for about it, but I think I remember that the boaters and
Coast Guards were the most affected, as you should expect because they rely
on and need the additional accuracy of the DGPS system.

Didier

For the marina story, see:
http://www.gpsworld.com/gps/system-challenge/the-hunt-rfi-776

The L1 signal was unintentionally jammed.

John  WA4WDL

From: "Didier Juges" didier@cox.net
Sent: Sunday, November 15, 2009 9:55 PM
To: "'Discussion of precise time and frequency measurement'"
time-nuts@febo.com
Subject: Re: [time-nuts] The Demise of LORAN (was Re:
Referenceoscillatoraccuracy)

With SA off, the difference between marine DGPS and stand alone GPS is not
that significant. If my memory serves me right the Monterey jammer did jam
at L1.

--

Björn