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[aprssig] info for TM-D710E in car

Keith VE7GDH ve7gdh at rac.ca
Mon Jan 14 21:20:51 UTC 2008


Bob WB4APR wrote...

> You are comparing apples and oranges.Decay has nothing to
> do with proportional pathing nor smart beaconing. It has to do
> with ALL packets transmitted on the APRS channel. That is,
> NEW or Changing data is transmitted with a higher refresh
> rate initially and then decays to lower and lower rates when
> the packet is old or no longer changing.

OK, I'll sorta agree there, but can't we have BOTH apples and oranges? Keep in 
mind that it is the position from mobile stations that is actually changing.

> There are two specified beacon rates for APRS, 10 minutes at
> events or DIRECT or ONE-HOP local use, and 30 minutes for 2 hops
> or more wider area use. So a parked car, if not turned off
> altogether, should decay to 30 minutes.  These standard rates
> are there so that APRS has a consistent expectation of latency
> for operating stations.

Are you saying that all stations should ONLY transmit every 10 minutes
(direct - no path) or every 30 minutes (2 hop path) and nothing other than
that? What about the mobile stations (hikers, skiers, hams on the road, SAR
teams, dog teams or whatever) whose position is constantly changing should not
be beaconing except every 10 or 30 minutes? Most people would consider that
unacceptable.

Even you stated on this list some months back that SmartBeaconing wasn't added
because SmartBeaconing was trademarked to Tony KD7TA and Steve KA9MVA. I'm
sure Kenwood have only have had to have asked to be allowed to use the term.
However, if they refused, there would have been nothing to prevent Kenwood
from implemented the same feature but just calling it by a different name.
At the time you said it wasn't in the D700 you offered no technical
explanation why it was left out - only that it was a trademark issue.
I stand by my statement that I think Kenwood would have included it
if you would have asked them to. It even states on Steve's website at
www.hamhud.net that...

"We offer it to other authors in the ham community (commercial interests
please inquire separately), asking only that they credit HamHUD.net and
use the term, SmartBeaconing™. SmartBeaconing has become the de facto
standard APRS position beaconing algorithm."

> Smart beaconing has a different objective than Proportional
> pathing. Proportional pathing wants to make sure that locally,
> a vehicle is reported more often than at a big distance. Hence
> it reduces channel QRM by an order of magnitude. It beacons
> every minute for good latency locally, but only every other
> minute do those go via a digi,and only once every 4 minutes do
> they go two hops. Thus, they are always reporting once a
> minute locally, but with reduced load further out.  Therefore
> they do not need to be tweaked between a special event, or long
> distance travel. So Proportional pathing wants to keep updates
> more reliable in the TIME domain while minimizing QRM.

OK, I have a better idea of the concept now. However, it still sounds it's
going out with a two hop path every four minutes. However, is that "no matter
what" or does it reduce then to every 30 minutes if it's stationary? See below 
for the Tracker 2 and T2-135 NICE feature.

> SmartBeaconing has the objective of a more accurate track in the
> spatial domain (on the map).  But all of its packets go the full
> path length to all surrounding areas.

If I look around me, most stations are not moving. Home stations, weather
stations, digipeaters and so on. The operator at the home station can set
responsible paths and set it at a low beacon rate. To be useful, the weather
stations should probably beacon more often... every 5 or 10 minutes. The
digipeaters we have sorted out with most of their own beacons going out direct
with no path, but with a one hop path once an hour and a two hop path once an
hour. That leaves the mobile stations who at least in populated areas seem to
be in the minority. I would have absolutely no argument with a station using
SmartBeaconing to beacon more often while actually moving. In town, most
vehicles are usually moving for a relatively short drive and then are parked
all day. Some beacon (at a slow rate!) while parked and some don't beacon at
all when the engine is off. My recommendation for ones that do continue to
beacon should be down at 30 or every 60 minutes. As soon as they start moving,
they beacon more often again until they stop again. On the highway, the long
distance drivers will come in and out of range of various digis & IGates and
then they are gone. Their effects are short term. I can also see that
proportional pathing has some merits too. Perhaps Proportional Pathing or
something similar with a different name can be can be added in future updates
of the HamHUD, Tracker 2, OpenTracker + (maybe) and TinyTrak 4.

However, even the current Tracker 2 and T2-135 which installs in the Alinco 
DR-135T has a NICE setting where it will skip the next X beacons if it hears 
itself having been digipeated, the idea being that it can beacon at a faster 
rate in areas with poor coverage, but hold off on the next several beacons if 
it hears itself coming back. Of course, this can be used in conjunction with 
SmartBeaconing, so in some ways, it already has both the apples and oranges.

I still think the D710 would have been a better radio if it had SmartBeaconing
as well as Proportional Pathing. Kenwood missed the boat, but perhaps it can
be added.

73 es cul - Keith VE7GDH
--
"I may be lost, but I know exactly where I am!"





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