SPOT Versus ELT Analysis (Long)

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

BTW some info on SPOT vs ELT/PLB is well discussed by Doug Ritter of
Equipped to Survive

see

http://www.equipped.org/blog/?p=82
and
http://www.equipped.org/blog/?p=83

Doug Ritter did some great work previously with problems with PLBs,
design issues and holes in the standards, you can fish around his blog
and find out more about that.

Darryl