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[aprssig] The best resolution of position from APRS

Curt, WE7U archer at eskimo.com
Tue Jan 3 17:28:07 UTC 2006


On Tue, 3 Jan 2006, Robert Bruninga wrote:

> >>> w9jbl at comcast.net 01/03/06 10:33 AM >>>
> >This begs the question of how many APRS users
> >have an APRS-capable Kenwood radio?
> >I personally know of only one ham who has a KW D-700.
>
> Around here, just about everyone that is into APRS
> for other than as a cute WEB application, has a D7
> or D700.   Looking globally, at data from FINDU, a
> year or so ago, 85% of everyone who receives APRS
> while mobile  uses a D7 or D700.

The key words above are "receives" and "while mobile".  They assume
one particular method of operation.  Why do mapping applications
get called "cute WEB applications"?  "Cute" implies less useful, and
what's "WEB" got to do with it?  Most if not all of the apps are
capable of being used with local maps and often are.  Check the APRS
Client Capabilities Chart for details.

Other methods of operation are useful also:  Many people run
transmit-only trackers, great for SAR and public-service events.
Often in this case only a small number of stations are needed to
keep track of multiple rovers.  A desktop application is used at
base and voice to/from the rovers (if needed) is often carried out
on another frequency, often a commercial frequency like we use for
SAR.

Sure, receiving/mapping/2-way messaging can generally make each
station more useful, but it's often unnecessary and comes at a
price, whether it's $$, space, size, weight, ruggedness, power
usage, whatever.

I maintain the capability to add a full mapping/2-way messaging
station to my mobile when required (truck-mount Linux box running
Xastir plus a TNC-X TNC).  Most of the time the extra capability
would go unused so I run an OpenTracker transmit-only unit instead.
I don't need/use dual-band radios, plus I require more from a TNC
than what the Kenwoods are capable of (talking about non-APRS
operation here).  This makes the Kenwoods overpriced for my needs,
even when you consider that I run two separate 2-meter mobiles so
that I can have QSO's and do APRS at the same time.

If the built-in TNC's were more full-featured, including support for
multiple long frames in KISS mode, I might weigh things a bit
differently and buy some.  My ideal unit would be a fully capable
KISS/APRS tracker TNC in a single-band radio, with
SmartBeaconing(tm) included.  Oh yea, throw in Base-91 compression
too so I can get the higher resolution but in the short packets.

I'm looking forward to Scott's up-and-coming TNC to replace my
OpenTracker.  This will give mapping on my GPS map display plus the
option to throw the Linux box into the Jeep without having to
replace the TNC as I do now (as long a full-blown KISS mode is
supported).  Less fuss for me that way and I can leave the TNC-X on
the home APRS station.

Alinco built-in TNC's are much in the same category as the Kenwood
TNC's (limited use outside APRS), but the latest Alinco's digipeat
and have APRS flooding protocols like the D700A (which the Kenwood
D7A TNC lacks but the D700A includes).  The Alinco DR-135TP (older
2-meter only radio with built-in TNC) can't digipeat and is
therefore of course missing the APRS flooding protocols too.

People who don't need TCP/IP capability but need a dual-band APRS
radio seem to prefer the Kenwoods.

FWIW my mobile APRS radio is a Kenwood too, but it's a single-band
2-meter mobile with no built-in TNC.  It's cost effective for me:
$130 for the radio, $30 for the GPS, $30 for the OpenTracker kit,
and a bit of wiring/assembly for a 50W capable mobile.  I usually
run it at the mid-power setting.  Add another $130 for another
mobile 2-meter and of course I'm running 2 antennas (but I already
had them).  Add another $50 for a TNC-X kit for when I need
full-blown mapping and/or TCP/IP communications.  I can then throw
in a PDA, laptop, or truck-mount PC for the full deal.

--
Curt, WE7U.   APRS Client Comparisons: http://www.eskimo.com/~archer
"Lotto:    A tax on people who are bad at math." -- unknown
"Windows:  Microsoft's tax on computer illiterates." -- WE7U
"The world DOES revolve around me:  I picked the coordinate system!"




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