[aprssig] Just my 2 cents worth on smart beaconing

Wes Johnston, AI4PX wes at ai4px.com
Tue May 24 15:14:38 EDT 2011

Kenwood has released a new firmware that up's the max speed setting in the
smart beacons.  Great.  But I think there is some misunderstanding in the
"fast speed" setting.  And your mileage may vary....  This speed setting
should not be of any interest for people in cars and trucks.

Ask yourself at which speed will you be making turns that we need to know
about?  Let's say you are travelling down the interstate or a main highway.
 Those roads have gradual curves.  Do we need to know when you get to the
middle of that long sweeping interstate curve?  Nope, we need to know when
you exit the road.  It's the difference between "data" and "intelligence".
 Sure you can transmit on every sweeping curve, but it's not very important
information.  The "fast beacon" rate is the point at which your tracker goes
from "transmit on a turn" mode to "beacon every xx miles" mode.

I set my "fast beacon" rate to 45mph but I see many people recommend 65 or
70.   I usually slow to well below 40 miles per hour to make a turn off of a
main road.  When I'm actually on the main road (except for stop lights) my
average speed is >45mph and time/distance beacons are fine.  If my 'fast
beacon" was set to 70 mph, I'd never get into time/distance beacon mode!

If you set your fast beacon rate to say 70mph, you will never get into
time/distance beacon mode in town.  Think about the curves in most roads in
your town that would needlessly trigger a beacon... so many that I'd be
willing to bet it would be akin to QRM.    I guess a lot of people want to
see dots on a map for every curve in the road but what us folks watching you
want to see is to see when you turn onto a side street.  Many clients like
Xastir and APRSce do display dead reconing that let us see your guestimated
position w/o you having to beacon very often at all.  Smart beaconing should
allow us to /reduce/ our beacon rates because we tend to transmit only when
there is a notable change.  The internet jockeys forget or don't know about
dead reconing because aprs.fi doesn't display guestimated positions and i'm
going to guess that they will want to transmit more often since their car
would appear stuck in one positon until the next TX.

In realistic terms, I'd love to know a)that you are moving, b) that you are
still moving, c)when you change roads.  Heck, if you program the turn slope
right, smart beaconing will TX when you turn into a parking space at the
local burger joint.

But please, set your "fast beacon" just a hair above the fasted speed you'd
expect to make a turn we'd need to know about.  Remember, we want to know
about TURNS not CURVES in the highway.

A really slick feature of the original ham hud is that it would transmit a
2nd time if it didn't hear itself digipeated.  This gave us a degree of
certainty that everyone knew about our change in direction.  The kenwoods
don't do that.  I think Agent data's OT2 has a "nice" setting where it'll
increase the TX intervals if it knows it's been digipeated (ie heard by the
network).  I'm not familiar with Byon's TT4 or the yaesu radios.

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