On Sun, 18 Jul 2010 09:56:35 -0400, "JR" wrote
(with clarity & insight):

"Wayne R." wrote in message
.. .
On Sat, 17 Jul 2010 20:25:22 -0400, "JR" wrote
(with clarity & insight):

Washington DC and Fort Hood in upstate NY are just
two places I have personal knowlege of where GPS is
munged for security purposes.
Regards,
JR

I've been using plain ol' GPS devices in & around DC for years with no
issues. What am I missing?

I have a Ram Mount in my GMC Yukon we use as a travel car, On this
mount I place a laptop and more recentlya Netbook computer on the Ram
and use MS Streets & Trips with a USB "puck" as the GPS
receiver/antenna. On the many trips south from Pa to Fla as I use the
DC Beltway and with the GPS in tracking mode it becomes "lost". The
1st time this happened I thought it was the unit itself and told it
to recalculate the route from my current location. It couldnt
determine my current location until we were merging back onto I-95.
It simply didn't know where it was. Weather was not a factor (clear
skies) nor was it a lack of GPS signal (it still showed as tracking 8 sats).
This "problem" is repeatable 100% of the time on various trips thru
the area.

Similarly, During a trip for my daughters wedding and subsequent trips to Ft
Hood, when approching base housing the same thing happens. Every time.
When I asked my son-in-law about it he would only say "Yeah, kinda neat
huh?"
In conversations with my youngest daughters soon-to-be-husband who was
home on leave from Jihadistan, he indicated that even there a few sites are
so protected.

Now, in northern NJ and northern Wi there are coverage gaps where the GPS
can't resolve it's location, but these are a different situation as the unit tells
me it can't find itself and why.
Not so with the DC & Ft. Hood issues.
Regards,
JR

I've found places where I've seen repeatable problems with one type of
receiver but not another. (Sometimes problems come & go, and in those
circumstances I've attributed it to constellation/reflection
variations.)

I've spent a lot of time near the White House, Pentagon, Ft. Meade,
Langley, etc., in DC without any loss of lock - some of the places
that seem most likely to have constant jamming?

When your receiver "tells me it can't find itself and why", what does
it say?