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[aprssig] Group tracking

Tom Hayward esarfl at gmail.com
Mon Apr 30 22:03:07 UTC 2012


On Mon, Apr 30, 2012 at 15:41, John Goerzen <jgoerzen at complete.org> wrote:
...
> may not have been taken.  A lot of SmartBeaconing scenarios have 30 minutes
> between beacons at 20MPH, which is unreasonable for tracking someone in city
> traffic.  (And, according to my reading, could actually be even longer at
> speeds between the low and high speed, oddly enough)

Recall that SmartBeaconing includes Corner Pegging, so any change of
direction during city driving will be transmitted.

> For the hiking scenario, we could conceivably use a 440 frequency since it
> is unlikely that a digipeater would be of any help at all.  This puts less
> of an importance on restricting transmit rates.  A lot of testing suggests
> that battery drain on APRS HTs is usually due to engaging the RX side, not
> the TX side, so I would not have battery concerns on a simple 1-minute
> interval.

When hiking, I usually use a 1-3 minute beacon rate, depending on
whether I think anybody actually cares where I am :-) I usually know
what the APRS infrastructure is like in the area, and set my number of
hops to the minium needed to reach an i-gate, usually 1 (so a path of
WIDE1-1). I use proportional pathing so that my hiking/SAR buddies
hear me every 1-3 minutes (whatever I picked for that day), and the
i-gate hears me half that often (but usually due to packet collisions,
it's more like 1/3 as often, or every 3-9 minutes).

I think the key to accurate tracking of nearby assets is proportional
pathing, because it allows you to beacon more frequently locally than
you otherwise might. Unfortunately, proportional pathing cannot be
used with SmartBeaconing.

Tom KD7LXL



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