GPS Out of service??

On my last two flights at Marfa Texas May 24 and May 10 I have lost
GPS navagation fixes for a few minutes on both flights. I have two
GPS receivers (cambridge GPS/Nav and a lx-7000) both units lost their
fix at the same time and came back together. Both flights are up on
the OLC if you want details. Anyone else have the same experience?
Is it anything I can fix?

Bill Snead
6W

are they using different antenna?
did you notice a power problem in the glider?

Maybe you flew through and area of GPS Jamming.
Different Jamming techniques will do different things, from totally denying
reception of GPS signals.. to tweaking the reception to make you think you
are going one way.. when the GPS is actually taking you off track


wrote in message
...
On my last two flights at Marfa Texas May 24 and May 10 I have lost
GPS navagation fixes for a few minutes on both flights. I have two
GPS receivers (cambridge GPS/Nav and a lx-7000) both units lost their
fix at the same time and came back together. Both flights are up on
the OLC if you want details. Anyone else have the same experience?
Is it anything I can fix?

Bill Snead
6W

On May 25, 7:44*pm, "BT" wrote:
are they using different antenna?
did you notice a power problem in the glider?

Maybe you flew through and area of GPS Jamming.
Different Jamming techniques will do different things, from totally denying
reception of GPS signals.. to tweaking the reception to make you think you
are going one way.. when the GPS is actually taking you off track

wrote in message

...



On my last two flights at Marfa Texas May 24 and May 10 I have lost
GPS navagation fixes for a few minutes on both flights. *I have two
GPS receivers (cambridge GPS/Nav and a lx-7000) both units lost their
fix at the same time and came back together. *Both flights are up on
the OLC if you want details. *Anyone else have the same experience?
Is it anything I can fix?

Bill Snead
6W- Hide quoted text -

- Show quoted text -

The two units have seprate antennas. The atmospheric pressure trace
was not effected. The units kept working (displays were on just no
nav info). I think the power was OK.

Bill Snead

Did you check the GPS Nav Center from USCG? They put up advisories on
GPS testing. They look like this:
http://www.navcen.uscg.gov/gps/gpsno...terference.pdf

If any of the testing areas are close, you have an answer. If there
was a magnetic storm, it could explain it, too - see space weather (I
doubt it right now, the sun is very quiet).

They also have prediction of dop - dillution of precision, or
accuracy, at http://www.navcen.uscg.gov/gps/pdop.htm (lower is
better).

If you report your gps problem at http://www.navcen.uscg.gov/gps/default.htm,
they will generally get back to you and tell you why there was a
problem.

Dan


On my last two flights at Marfa Texas May 24 and May 10 I have lost
GPS navagation fixes for a few minutes on both flights. *I have two
GPS receivers (cambridge GPS/Nav and a lx-7000) both units lost their
fix at the same time and came back together. *Both flights are up on
the OLC if you want details. *Anyone else have the same experience?
Is it anything I can fix?

Bill Snead
6W- Hide quoted text -

wrote

On my last two flights at Marfa Texas May 24 and May 10 I have lost
GPS navagation fixes for a few minutes on both flights. I have two
GPS receivers (cambridge GPS/Nav and a lx-7000) both units lost their
fix at the same time and came back together. Both flights are up on
the OLC if you want details. Anyone else have the same experience?
Is it anything I can fix?

Bill, I have on several occasions simultaneously lost both GPS and XM
radio signals in parts of west Texas, central New Mexico, and eastern
Nevada. I'm tempted to blame local interference from military or
commercial sources. The dropouts didn't last longer than a few minutes.
Maybe you encountered something similar near Marfa (perhaps involving
the tethered radar blimp west of the field)? Did anyone else have a
similar problem at about the same time or place?

Bill Collum
"TX"


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On May 25, 6:11*pm, " wrote:
On my last two flights at Marfa Texas May 24 and May 10 I have lost
GPS navigation fixes for a few minutes on both flights. *I have two
GPS receivers (cambridge GPS/Nav and a lx-7000) both units lost their
fix at the same time and came back together. *Both flights are up on
the OLC if you want details. *Anyone else have the same experience?

I had this same experience last year when soaring in a MOA in W'ern
Wisconsin. PIlots in MN on the same afternoon did not have dropouts.
A couple of people have suggested military electronic activity as a
cause.

DJ

These are common Monday through Friday and are usually announced in
advance. Check NOTAMS when you get your weather briefing.

Paul









wrote:
On my last two flights at Marfa Texas May 24 and May 10 I have lost
GPS navagation fixes for a few minutes on both flights. I have two
GPS receivers (cambridge GPS/Nav and a lx-7000) both units lost their
fix at the same time and came back together. Both flights are up on
the OLC if you want details. Anyone else have the same experience?
Is it anything I can fix?

Bill Snead
6W

On May 25, 7:44*pm, "BT" wrote:
are they using different antenna?
did you notice a power problem in the glider?

Maybe you flew through and area of GPS Jamming.
Different Jamming techniques will do different things, from totally denying
reception of GPS signals.. to tweaking the reception to make you think you
are going one way.. when the GPS is actually taking you off track

wrote in message

...



On my last two flights at Marfa Texas May 24 and May 10 I have lost
GPS navagation fixes for a few minutes on both flights. *I have two
GPS receivers (cambridge GPS/Nav and a lx-7000) both units lost their
fix at the same time and came back together. *Both flights are up on
the OLC if you want details. *Anyone else have the same experience?
Is it anything I can fix?

Bill Snead
6W- Hide quoted text -

- Show quoted text -

No ne else flying in the area except Burt who was giving rides. The
reason for the post was to see others had the same outage. I plan on
flying contests soon, therefore I was wondering about my equipment -
power ect.

Bill

On May 27, 7:49*am, wrote:
On May 25, 7:44*pm, "BT" wrote:





are they using different antenna?
did you notice a power problem in the glider?

Maybe you flew through and area of GPS Jamming.
Different Jamming techniques will do different things, from totally denying
reception of GPS signals.. to tweaking the reception to make you think you
are going one way.. when the GPS is actually taking you off track

wrote in message

...

On my last two flights at Marfa Texas May 24 and May 10 I have lost
GPS navagation fixes for a few minutes on both flights. *I have two
GPS receivers (cambridge GPS/Nav and a lx-7000) both units lost their
fix at the same time and came back together. *Both flights are up on
the OLC if you want details. *Anyone else have the same experience?
Is it anything I can fix?

Bill Snead
6W- Hide quoted text -

- Show quoted text -

No ne else flying in the area except Burt who was giving rides. *The
reason for the post was to see others had the same outage. *I plan on
flying contests soon, therefore I was wondering about my equipment -
power ect.

Bill- Hide quoted text -

- Show quoted text -

Another thought - I have had interference from my old cell phone to my
Volkslogger. Shutting down the cell immediately increased the number
of satellites available... I also wonder if the two GPS systems are
interfering with one another. Do you normally fly with two GPS
systems, or just when you're getting ready for a contest? Running
them from different power systems, and separating the cabling and
antennae may cure the problem.

I have a background in nav system electro-magnetic compatibility/
interference (EMC/EMI) flight test...

1. GPS is a receive only service, two units should not ever interfere
with one another even if very close.
2. Yes, some Military jamming is done on GPS signals as a part of
Electronic Warfare, flying near MOAs could give problems, but NOTAMs
should alert you of it.
3. I believe as long as the pressure altitute is running and the
outage is a reasonable length, OLC and Contest rules allow you to
ignore the time of no GPS signal.

Since I'm just a normal IS & RF background type, is the above a
correct set of observations and responses? Dan_the_wri?

4. I've had several outages in the White Mts of Ca, but usually due to
poor antenna orientation on a G76s unit that wants to lay flat to best
receive signals.

5. Does anyone know for sure how long an outage OLC allows?

Thanks,

Wayne