SPOT Versus ELT Analysis (Long)

On Jul 5, 5:49*pm, Brian wrote:
Has anyone heard of any prospect of an improved SPOT coming out.

My biggest hang up is I don't like replacing batteries and I would
want to use it in tracking mode.

I tested battery life earlier this year by leaving on in tracking mode
on the dash of my car, and restarting it every 18-24 hours to ensure
it was operating 24/7. Sometime around day 12, the power LED turned
RED, and the SPOT continued to operate just fine for several more
days. So this means at least 300 hours of CONTINUOUS live tracking.
That's pretty much a typical season for a fairly active pilot.

The local grocery store sells a 4 pack of the batteries for $12 or
so. I'm sure they can be found elsewhere for even less.

Why on earth would you want to complicate things and add an external
power cord??? ;-)

The only improvement that could come from SPOT is if the unit
transmitted a NEW position every minute instead of what it does
currently, which is the same position every 10 minutes.

Think about it, if a new position were transmitted every minute, and
if 90% were lost, that would still provide a position every 10
minutes.

The compelling reason to fly with SPOT is that it provides a
RELATIVELY failsafe crash location. If I'm incapacitated in a crash,
then the PLB is useless. If there's major damage to the airframe,
then the ELT is useless. The SPOT will give rescuers a 10 minute
search radius and a flight vector. Yes, I understand that sometimes
SPOT leaves holes of 2, 3 or even more intervals, and it's possible I
chose to reverse course immediately after the SPOT sends a position
report. But this still provides an excellent starting point for S&R.

-Tom

And I do have an ELT as well. And am installing a transponder
tomorrow. ATC radar history is yet another passive way to find a
downed aircraft, especially if used in conjunction with SPOT to
isolate the VFR target.

One problem with a transmit every minute, rather than 10 minutes, would be
that it would shorten battery life considerably. I am guessing it would
approximate 10% of the present battery life. The 300 hours of transmit
quoted would be reduced to 30 hours.

Also, with transmissions every minute, the processing through the satellite
might be overloaded with present equipment, which would require more money
to correct - hence higher user fees.

The external antenna would reduce reliability considerably, and may not gain
much. The exposure to a satellite from a sailplane would be very high, so
the most reliable and simplest antenna should work well.

Colin Lamb

On Jul 5, 9:21*pm, "COLIN LAMB" wrote:
One problem with a transmit every minute, rather than 10 minutes, would be
that it would shorten battery life considerably. *I am guessing it would
approximate 10% of the present battery life. *The 300 hours of transmit
quoted would be reduced to 30 hours.

Also, with transmissions every minute, the processing through the satellite
might be overloaded with present equipment, which would require more money
to correct - hence higher user fees.

The external antenna would reduce reliability considerably, and may not gain
much. *The exposure to a satellite from a sailplane would be very high, so
the most reliable and simplest antenna should work well.

Colin Lamb

If they respin the packaging in future it would be pretty easy to fit
4 x Lithium AA cells inside the current packaging volume that only
holds 2 x Lithium AA cells.

I suspect the largest reasons things are as they are are likely not
techncial - it seems like marketing decisions targeted at an intended
user base of hikers etc.

A large issue with external power is maintaining a well sealed
packaging and SPOT wanted to claim good specs/complaince for water
resistance/sealing and how many hikers carry around 12 volt power?

I also suspect no external power and also the need to reset tracking
every 24 hours was in part, or in large, to prevent cannibalization of
exiting parts of the asset tracking market that Globalstar (who own
SPOT) services.

... but folks don't put of buying a SPOT now if you want one, just
becasue something better might be coming some time in the future.

Darryl

On Jul 5, 10:21*pm, "COLIN LAMB" wrote:
One problem with a transmit every minute, rather than 10 minutes, would be
that it would shorten battery life considerably. *I am guessing it would
approximate 10% of the present battery life. *The 300 hours of transmit
quoted would be reduced to 30 hours.

See other SPOT threads, but as I understand it, the SPOT does transmit
once a minute already. It is a "blind" transmission, so there's no
acknowledgment from the satellite. So in live tracking, it transmits
the same message 10 times, then updates the coordinates, and repeats.

An OK is also transmitted repeatedly, that's why both LEDs will flash
for 15-20 minutes after pressing OK.

Again, this is all part of the design, which is targeted at the hiking
market. An aviation unit might also include an altitude.

-Tom

On Jul 6, 7:25*am, 5Z wrote:
On Jul 5, 10:21*pm, "COLIN LAMB" wrote:

One problem with a transmit every minute, rather than 10 minutes, would be
that it would shorten battery life considerably. *I am guessing it would
approximate 10% of the present battery life. *The 300 hours of transmit
quoted would be reduced to 30 hours.

See other SPOT threads, but as I understand it, the SPOT does transmit
once a minute already. *It is a "blind" transmission, so there's no
acknowledgment from the satellite. *So in live tracking, it transmits
the same message 10 times, then updates the coordinates, and repeats.

An OK is also transmitted repeatedly, that's why both LEDs will flash
for 15-20 minutes after pressing OK.

Again, this is all part of the design, which is targeted at the hiking
market. *An aviation unit might also include an altitude.

-Tom

I don't think SPOT retransmits SPOTcast (tracking) locations, , it
relies on just sending a new location every 10 minutes. Delays people
see in web site updates for SPOTcasting may be elsewhere in the
system.The SPOT unit retransmits OK and help messages, I believe 3
times over a 20 minute period. I beleive the most retransmission that
SPOT does is every five minutes continuously in 911 mode.

Darryl

snip

I tested battery life earlier this year by leaving on in tracking mode
on the dash of my car, and restarting it every 18-24 hours to ensure
it was operating 24/7. Sometime around day 12, the power LED turned
RED, and the SPOT continued to operate just fine for several more
days. So this means at least 300 hours of CONTINUOUS live tracking.
That's pretty much a typical season for a fairly active pilot.

The local grocery store sells a 4 pack of the batteries for $12 or
so. I'm sure they can be found elsewhere for even less.

Why on earth would you want to complicate things and add an external
power cord??? ;-)
snip

I didn't realize the battery life was this good. Replacing the battery
once per year would be ok.
Does it auto power off after a period of time? Especially if it can't
get a GPS fix like when the glider is in the trailer.. I can certainly
see me leaving it on and having dead batteries when I go to fly. Or
course I do always have spare batteries.

If it did have an external power supply it would be nice if it could
automatically power up to track mode when power is applied, One less
thing to remember to turn on.
It could possibly even be programmed to send a position when power is
turned off. LIke an external OK or Help button.

I like things that stay in the glider and I don't have to mess with
them until I need them.

More batteries I don't need. I already have a 9V in my B40 and 9V in
my EW FR 4 AA in my GPS, a watch battery and lithium battery in my
PDA. All are connected to my aircraft power supply.

Thanks for the info,

Brian