[aprssig] Fwd: [atgp] How much power required for a backpack tracker?

[Robert Bruninga]

Forwarded from the Appalachian Trail APRS event list:

Any of the 5W APRS HT would do nicely, but only last about 6 hours of
a single day hike.

I want to focus on identifying a lightweight tracker that runs on AA
cells that is ONLY used for manual reporting when the hiker knows
he is high and in the clear and can push the manual POSIT button.
It can also be 5W since it is only on for maybe 20 seconds to get
a GPS fix and then 1 second TX at 5 watts.

So, with 6 AA cells of 2500 mAH and one report every hour or so for 10
hours hiking/day.  Probably keying up 3 times at each attempt to
assure better probability = 30 per day

For GPS, (60 mA for 20 secs) = 0.33 mh x 30 = 10 mAh/day
For 5W TX (600 ma for 1s) = 0.2 mAh x 30 = 6 mAh/day

For a total of 16 mAh per day to last maybe half of the 2500 mAh of an
alkaline battery where the 2500 mAh is rated down to maybe only 1v per
cell where the GPS and or TX may not work.  So lets assume maybe 1
200 mAh at full power.

So, such a light weight tracker would last about 75 days or about the
time of a full hike of the 2000 mile Appalachian Trail.  But 6 AA cells
is not lightweight.  For a 550 mAh 9V battery, the life would be about
ten days.  Still not too bad.

So, who makes a tracker board about the size of a 9v battery?
Bob, WB4APR

On Wed, Sep 29, 2021 at 9:50 AM Kevin Sterne, KJ4OAP <ksterne at vt.edu> wrote:
>
> I’ll echo the comment that it’s difficult to put a requirement on it.  Back of the envelope I’d think 5W.  For some of the better high peak digi-peaters in my area, I can get into them pretty well with just an HT.
>
> The more detailed result would involve SPLAT! simulations at every digi-peater location and tracing out the Appalachian Trail in the results to find the highest propagation loss figure along the 2000+ miles of trail and then set the requirement based on that high propagation loss figure.  I think some SPLAT! simulations were done a while ago?  But this is starts to sound like a lot of simulations and a lot of data.
>
> I think the return question is what is the spatial resolution for a backpacker to get into the network?  Is the farthest that the backpacker needs to move is 10 feet in order to find an optimal propagation path…or can it be several miles when they are on top of a mountain/hill/ridgeline?
>
> -Kevin, KJ4OAP
> Kevin Sterne | Research Associate
> SuperDARN HF Radar Lab
> Virginia Tech | Space at VT>
>
> From: atgp at groups.io <atgp at groups.io> On Behalf Of JeffH - W4JEW
> Sent: Wednesday, September 29, 2021 8:44 AM
> To: atgp at groups.io
> Subject: Re: [atgp] How much power would be required for a backpacking tracker
>
> I think it’s very difficult to find a one size fits all value. We see some of our group up north that can get away with using an HT on 5W and others on D700/710s that are running 30 to 50W.
>
> On Wed, Sep 29, 2021 at 8:28 AM Don Rolph - AB1PH <don.rolph at gmail.com> wrote:
> The higher the power, the more batteries which would be required.
> Any sense of how powerful the system would need to be to be useful on say the Appalachian Trail?
> AB1PH
> Don Rolph
> ———