Wed 7/15 fantastic day, but SPOT??

On Jul 17, 10:34 pm, Darryl Ramm wrote:
You want to end the guessing game and tell us where your SPOT
messenger is mounted? On your harness? On your shoulder? Obstructed
by your head? What is the effective field of view of the antenna?

You were tracking roughly the same heading for all that time. And
that heading (very) roughly lines up with one of the inclined planes
of the GlobalStar constellation.

Darryl,

My SPOT is mounted in an indent in my glare shield (which is radio
transparent) well forward, and is oriented horizontally. While it
loses a little bit of the horizon to the rear (carbon fiber turtle
deck), it's a pretty good location. More to the point, as to why I
asked if anyone else had problems on that day in that locality, I've
NEVER seen more than two (maybe three, my memory isn't as good as it
used to be) dropped messages and here it was eight. Assuming rough
independence between dropped messages, that kind of jump (from 2 or 3
to 8 occurrences) would be highly unlikely. That's why I wondered what
happened.

While your theory about my track being fairly constant and possibly
aligned badly with the satellites is a possibility, I've never had
that problem before and whenever I fly from Hayward to the Tahoe area
I fly a roughly similar track. There's almost never any lift on that
part of the flight, so I fly pretty much direct.

Since no one else mentioned a big gap that day, I'm assuming the
problem was unique to me. One thing that came out of this: I've told
my wife not to look at the SPOT track to watch my progress. A huge gap
like that looks too much like a ship gone down.

Martin

On Jul 20, 7:27*pm, Hellman wrote:
On Jul 17, 10:34 pm, Darryl Ramm wrote:

You want to end the guessing game and tell us where your SPOT
messenger is mounted? *On your harness? On your shoulder? Obstructed
by your head? What is the effective field of view of the antenna?

You were tracking roughly the same heading for all that time. *And
that heading (very) roughly lines up with one of the inclined planes
of the GlobalStar constellation.

Darryl,

My SPOT is mounted in an indent in my glare shield (which is radio
transparent) well forward, and is oriented horizontally. While it
loses a little bit of the horizon to the rear (carbon fiber turtle
deck), it's a pretty good location. More to the point, as to why I
asked if anyone else had problems on that day in that locality, I've
NEVER seen more than two (maybe three, my memory isn't as good as it
used to be) dropped messages and here it was eight. Assuming rough
independence between dropped messages, that kind of jump (from 2 or 3
to 8 occurrences) would be highly unlikely. That's why I wondered what
happened.

While your theory about my track being fairly constant and possibly
aligned badly with the satellites is a possibility, I've never had
that problem before and whenever I fly from Hayward to the Tahoe area
I fly a roughly similar track. There's almost never any lift on that
part of the flight, so I fly pretty much direct.

Since no one else mentioned a big gap that day, I'm assuming the
problem was unique to me. One thing that came out of this: I've told
my wife not to look at the SPOT track to watch my progress. A huge gap
like that looks too much like a ship gone down.

Martin

Martin

My comment has no meaning if your SPOT messenger has a good all round
view. I was assuming it maybe did not and was just noticing the rough
alignment with the satellite tracks. I am as stumped as you.

Throwing out a random comment. If there is any reason the GPS does not
have a fix the SPOT messenger just won't send a TRACK message. (It
will send a HELP or 911 message with no fix, at least to let people
know you are in trouble). Now of course there is no reason to expect
the device not to have a GPS fix (and if you happened to look at it
while it was you would see the LEDs alternately blinking). Oh here is
one - any chance you were running the engine all that time and have
some really bad electrical interference? (yes I now an awful long
shot, especially given the SPOT is not electrically connected).


Darryl

Hellman wrote:
While your theory about my track being fairly constant and possibly
aligned badly with the satellites is a possibility, I've never had
that problem before and whenever I fly from Hayward to the Tahoe area
I fly a roughly similar track. There's almost never any lift on that
part of the flight, so I fly pretty much direct.

Since no one else mentioned a big gap that day, I'm assuming the
problem was unique to me.

Have you contacted the SPOT people about this? If there was a system
problem, they should know about it and be able to tell you if it caused
your track point losses. Possibly, some SPOTs might have problems, and
maybe they can determine if yours is one of them from what you report.
In about 75 flights with my SPOT, neither I nor my wife have noticed
more than two consecutive missing points.

One thing that came out of this: I've told
my wife not to look at the SPOT track to watch my progress. A huge gap
like that looks too much like a ship gone down.

This is an interesting point. My wife likes the track reports so much, I
don't want to tell her that, but maybe she and I should decide
explicitly how many missed points are needed before starting to worry,
or initiating a search.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* Sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

Some comments on the performance of my SPOT during flights this year,
2009, before and after I relocated it from my parachute harness to a
flat position on the forward instrument panel cover. BOTTOM LINE...
place you SPOT in the glider in a horizontal position with an
unobstructed view from horizon to horizon.

I fly "WX" a Discus 2A. Last year and for the first six flights this
year my SPOT was located on my parachute shoulder harness and is
aligned about 45deg to horizontal. Starting with my 06/28/09 flight at
Parowan it was re-located to a horizontal position on the forward
instrument cover.

Here are some statistics on the number of drop-outs during tracking
mode (updates every 10minutes). The percent number is the number of
dropout per flight. The number of track is the total (i.e. includes
the tracks that were lost). Results showed a dramatic improvement:

Date No Tracks No Drop Outs Per Cent Drops

03/15/09 12 2 17%
05/05/09 36 16 44%
06/19/09 22 8 36%
06/22/09 15 3 20%
06/23/09 28 5 18%
06/24/09 19 7 36%

Total dropouts cumulative: 31%

After re-locating to flat orientation forward instrument panel cover

06/28/09 29 0 0%
06/30/09 30 0 0%
07/01/09 25 1 4%
07/03/09 31 1 4%
07/04/09 23 0 0%
07/14/09 37 3 8%

Total dropouts cumulative: 4%

Walt Rogers, WX