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

[Greg Clark]

Correct -- it won't send any packets unless the GPS has a lock if the "send
only valid" option bit is set.

It has an LED that blinks at 1 hz when the device has a lock.

There is no "TX NOW" button, but you could change the timing to send once
every 15 seconds, and just leave it on for a minute or so once it gets a
lock.

Greg K7RKT

On Wed, Sep 29, 2021 at 2:01 PM Robert Bruninga <bruninga at usna.edu> wrote:

> Looks perfect.  From powerup, will it wait for GPS lock before sending
> first beacon?
> Does it have an easy access for an LED to indicate GPS fix available,
> and does it have a TX now input?    TNX, Bob
>
> On Wed, Sep 29, 2021 at 4:00 PM Greg Clark <k7rkt at bigredbee.com> wrote:
> >
> > here's something I offer:
> >
> >
> https://shop.bigredbee.com/collections/vhf-uhf-transmitters/products/2-meter-5-watt-aprs-transmitter
> >
> > Greg Clark
> > K7RKT
> > BigRedBee, LLC
> >
> > On Wed, Sep 29, 2021 at 12:54 PM Robert Bruninga <bruninga at usna.edu>
> wrote:
> >>
> >> 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
> >> > ———
> >>
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