[aprssig] Proper TT3 Setup

Wes Johnston, AI4PX wes at ai4px.com
Tue May 13 11:42:15 CDT 2008

One of my annoyances of the smart beaconing is that it does not beacon when
you stop moving.

Smart beaconing on the TX side of things and dead reconing on the RX side of
things are both GREAT.  As long as smart beaconing sends a position
periodically and when a change in direction or significant change in speed
happens.  The emphasis in smartbeaconing seems to be only on turning, not on
delta velocity.

Smart beaconing seems to always TX once I start moving, but what happens
when I'm scheduled to beacon in a mile, but stop moving (ie break down on
side of road)?  My tracker will wait 10 minutes to beacon at which time the
dead reconed position will have me 10 miles down the road (assuming last
beacon sent was at 60mph).

I've mentioned this here before... it would be nice if the smart beacon
included one squawk at the point that you cross below slow speed threshold.
That way the home audience wouldn't have to wait 10 minutes to figure out
that I've stopped on the side of the road.

In fairness, under normal driving conditions, you drive into a parking lot
and turn sharply into a parking space triggering a beacon.... or you
parallel park by backing up causing a beacon.

So far I've tackled this problem with the open trak by making it change to
profile 2 and beacon when velocity <1mph or GPS fix is lost.  It switches
back to profile 1 when velocity >5mph and GPS fix is valid.  This hysteresis
allows me to inch up at a stop light w/o QRM'ing.

Ohh and one more note... We once put trackers on city busses used in an
evacuation drill.  I used smart beaconing for them.  I had set the low speed
threshold to something around 5mph.  Well the busses pulled into the staging
area off the main street an beaconed.  This put them on the map way in the
back of the parking lot.  As we loaded them, the busses in the rear crept
forward very slowly, never exceeding 5mph, so on the map they looked like
they were still all out at the main road.  Waiting 10 minutes for them to
beacon seemed like an eternity when trying to explain to the officials why
the bus was being loaded but still looked like it was deep in the parking
lot.  Lesson learned here was to set the low speed setting to 1 or 2mph.  I
had been in the habit of using 5mph from having used GPS when SA was on and
the GPS would drift in a good sized area, often reading a few mph
erroneously.  Today, you can trust the velocity averaging to stay at zero.


On 5/13/08, Bob Burns W9RXR <w9rxr_ at rlburns.net> wrote:
> At 07:51 AM 5/13/2008, Matt Murphy wrote:
> > I have set it up with "Wide2-1" (too many? not enough?) and turned on
> > smart beaconing.
> >
> Bruce gave you some good advice regarding the CornerPegging feature of
> SmartBeaconing.
> According to the TT3 manual, you can configure both the Minimum Turn Angle
> and the Minimum Turn Time. The angle is the minimum change in direction
> required to trigger a beacon. As Bruce states, you don't want that to be too
> small, probably no less than 15 degrees.
> The time is the minimum time between beacons generated by the change in
> direction. Let's say you are driving around in circles (looking for a
> parking spot at Dayton, no doubt <g>). If your Minimum Turn Angle is set to
> 15 degrees, you will send out 24 beacons by the time you make a complete
> circle. But the CornerPegging routine also looks at the Minimum Turn Time to
> decide whether or not it's too soon to send out another beacon. If you set
> that parameter to, let's say 30 seconds and it takes you 2 minutes to
> complete the circle, you will only send something like 4 beacons rather than
> 24.
> Bob...
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Where there's silence, there is no Hope.
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