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

On Jul 20, 9:54*pm, Eric Greenwell wrote:
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" atwww.motorglider.org

In addition to the occasionly missing messages, there are occasionly
delays of an hour or more till the message shows up on the shared
page. Sometime 2 or 3 messages will show up at once. This is likely a
delay in the Spot backend system, not the communication system. As a
result, I would say that delays of up to 2 hours should not be an
immediate concern.

Ramy

On Jul 17, 11:50*pm, Ramy wrote:
On Jul 17, 10:34*pm, Darryl Ramm wrote:





On Jul 17, 9:08*pm, Hellman wrote:

On Jul 16, 7:48*am, Steve Koerner wrote:

I did a serious investigation on the problem involving some
experiments and analysis and I made a presentation to my local club..
My presentation is available for download from my Wing Rigger website:www.wingrigger.com. *(click Extra Soaring Content in lower right
corner).

Steve,

Thanks for that detailed analysis ofSPOTbehavior. While it helps in
understandingSPOTgenerally, my question -- and big concern -- is why
that flight was different from all other flights. I don't believe I've
never had more than a 30 minute gap (2 missed transmissions) before,
yet this time the gap was 90 minutes (8 missed transmissions). I was
asking if anyone else had a track from that specific day and time (JUL
15, 1900-2020 Z) and general location (roughly from Oakland, CA to
Lake Tahoe). If so, I wanted to know if they had coverage or also had
around a 90 minute hole in their data.

Martin

Martin

You want to end the guessing game and tell us where yourSPOT
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.

The GlobalStar satelites orbit in a interweaved pattern with two
inclined planes at +/- 80 degrees or so (you can see a simulation herehttp://www.youtube.com/watch?v=G8VPEueequMoryou can actually play
with the SaVi software shown in the video, seehttp://savi.sourceforge.net).
It is quite possible that things happen like the satelites flying from
the south west to north east are obscured over your left shoudler if
say yourSPOTmessenger was to the right side of your head and all
those passes could be obscured and maye the next parallel path to the
east is too far away. That leaves the satellites tracking north-west
to south-east and just maybe again if your head partially obscured
those then the satellite does not see thespotuntil it is further
overhead and out of the optimal bent-pipe geometry to reach the
Alberta, Canada ground station. So maybe in the whole time you just
get maybe one shot when theSPOTfires off its track message where it
manages to see a satellite to get it a bent path to the Texas ground
station. Maybe you just managed to get things timed so bad that you
never happened to have a satellite with bent-pipe view to any ground
station when yourSPOThappened to fire the TRACK message.

This is all very uninteresting if theSPOTmessenger is mounted say on
your parachute harness and inclined or significantly obscured. Tell me
it is out flat in the open and I'll actually care.

Darryl- Hide quoted text -

- Show quoted text -

I don't think I agree with the notion that mounting aspoton the
parachute harness near the shoulder is bad idea. Mine is on the
parachute harness and I get around 10% drops, as good as anyone else
who mounts theirSpotperfectly horizontally. I just checked myspot
messages from today: 5 missing messages in 7.5 hours fligh = 10%
Since installing on the parachute harness is the easiest, and provide
easy access during flight, and will stay with you in case of bailout,
I wouldn't recommend against it.

Ramy- Hide quoted text -

- Show quoted text -

Couple of new feedbacks:

1 - Yesterday (8/9) I had 1 hour gap in messages along the Sierras
between Mammoth and Whitney. This was the longest gap I noticed so
far, long enough to get my wife concerned. As in Martin's case, there
was nothing special about this part of the flight then the rest. I
actually had more cloud coverage in other part of the flights then at
this section, so this rules out the clouds. My Spot is attached to my
parachute at 45 degrees. This is just FYI, not to restart the debate
re spot instalation...
2 - The Spot should not be attached to the parachute in the shoulder
area in a way that it may interfer with deployment. See important
notice from Allen Silver at
http://www.silverparachutes.com/file...ce_2009-07.pdf

Ramy

On Aug 10, 1:56*pm, Ramy wrote:
On Jul 17, 11:50*pm, Ramy wrote:





On Jul 17, 10:34*pm, Darryl Ramm wrote:

On Jul 17, 9:08*pm, Hellman wrote:

On Jul 16, 7:48*am, Steve Koerner wrote:

I did a serious investigation on the problem involving some
experiments and analysis and I made a presentation to my local club.
My presentation is available for download from my Wing Rigger website:www.wingrigger.com. *(click Extra Soaring Content in lower right
corner).

Steve,

Thanks for that detailed analysis ofSPOTbehavior. While it helps in
understandingSPOTgenerally, my question -- and big concern -- is why
that flight was different from all other flights. I don't believe I've
never had more than a 30 minute gap (2 missed transmissions) before,
yet this time the gap was 90 minutes (8 missed transmissions). I was
asking if anyone else had a track from that specific day and time (JUL
15, 1900-2020 Z) and general location (roughly from Oakland, CA to
Lake Tahoe). If so, I wanted to know if they had coverage or also had
around a 90 minute hole in their data.

Martin

Martin

You want to end the guessing game and tell us where yourSPOT
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.

The GlobalStar satelites orbit in a interweaved pattern with two
inclined planes at +/- 80 degrees or so (you can see a simulation herehttp://www.youtube.com/watch?v=G8VPEueequMoryoucan actually play
with the SaVi software shown in the video, seehttp://savi.sourceforge..net).
It is quite possible that things happen like the satelites flying from
the south west to north east are obscured over your left shoudler if
say yourSPOTmessenger was to the right side of your head and all
those passes could be obscured and maye the next parallel path to the
east is too far away. That leaves the satellites tracking north-west
to south-east and just maybe again if your head partially obscured
those then the satellite does not see thespotuntil it is further
overhead and out of the optimal bent-pipe geometry to reach the
Alberta, Canada ground station. So maybe in the whole time you just
get maybe one shot when theSPOTfires off its track message where it
manages to see a satellite to get it a bent path to the Texas ground
station. Maybe you just managed to get things timed so bad that you
never happened to have a satellite with bent-pipe view to any ground
station when yourSPOThappened to fire the TRACK message.

This is all very uninteresting if theSPOTmessenger is mounted say on
your parachute harness and inclined or significantly obscured. Tell me
it is out flat in the open and I'll actually care.

Darryl- Hide quoted text -

- Show quoted text -

I don't think I agree with the notion that mounting aspoton the
parachute harness near the shoulder is bad idea. Mine is on the
parachute harness and I get around 10% drops, as good as anyone else
who mounts theirSpotperfectly horizontally. I just checked myspot
messages from today: 5 missing messages in 7.5 hours fligh = 10%
Since installing on the parachute harness is the easiest, and provide
easy access during flight, and will stay with you in case of bailout,
I wouldn't recommend against it.

Ramy- Hide quoted text -

- Show quoted text -

Couple of new feedbacks:

1 - Yesterday (8/9) I had 1 hour gap in messages along the Sierras
between Mammoth and Whitney. This was the longest gap I noticed so
far, long enough to get my wife concerned. As in Martin's case, there
was nothing special about this part of the flight then the rest. I
actually had more cloud coverage in other part of the flights then at
this section, so this rules out the clouds. My Spot is attached to my
parachute at 45 degrees. This is just FYI, not to restart the debate
re spot instalation...
2 - The Spot should not be attached to the parachute in the shoulder
area in a way that it may interfer with deployment. See important
notice from Allen Silver athttp://www.silverparachutes.com/files/Important_Notice_2009-07.pdf

Ramy- Hide quoted text -

- Show quoted text -

Just noticed another gap in the same flight, even longer (80 minutes).
Both gaps are in the same general area around Bishop, one on the
Sierra the other on the Whites.

Ramy