APRS FIXED STATION SETTINGS

07.02.2010 16:48

 

NWAPRS serves: Alberta, British Columbia, Northwest Territories,
Washington, Oregon, Idaho, and Montana

 

NWAPRS FIXED STATION SETTINGS

 

The WIDEn-N paradigm settings are an attempt to optimize the APRS network using the currently available hardware. There are certainly better ways to build an APRS network, but until we can get the hardware needed to do the job in place, the NWAPRS group is suggesting that these settings be used.

A suggested standard path for a home APRS station is:

WIDE2-2

This will provide you with two hops via the RF network.

If you are in an area where fill-in digipeaters are needed to cover areas that are shadowed from the main digipeater's receiver, a suggested path is:

WIDE1-1,WIDE2-1

This will provide you with two hops via the RF network. WIDE1-1 will activate the fill-in digipeaters, which will boost you to the main digipeaters. This path asks the fill-in digipeaters for help with the first hop to get the packet to a nearby mountaintop IWDEn-N digipeater, where it is digipeated one time.

When within range of the main digipeaters, they will respond to the WIDE1-1 alias, adding the packet to the anti-duping list. The second alias again is acted upon by the same routine, so the digipeater knows whether it has digipeated the packet via the first alias already.

This is where the real "magic" of the WIDEn-N paradigm happens.

One thing to watch out for is to make sure WIDE1-1 is only ever used in the first hop position. 

If you used a (BAD) path such as:

WIDE2-2,WIDE1-1 (VERY BAD PATH)

You would get two hops via the main digipeaters, and one more hop via the main digipeaters, as well as every fill-in digipeater that is within range of those second hop digipeaters. This not a good thing, as the fill-in digipeaters are only supposed to help fill-in holes in receive coverage.

The periodicity of these settings is further described in http://nwaprs.info/aprssettings.htm and is briefly mentioned here:

Home stations should transmit a position report to WIDE2-2 every 30 minutes. This is usually a default setting when configuring APRS for home use.

Home weather stations may transmit a position report to WIDE2-2 every 15 minutes. Your weather station data is being collected and interpreted by the NWS and in support of Homeland Security for current weather conditions and weather propagation forecasting. Thanks for your help!


 

Basic TNC Settings for Home Operations

When you purchase a new TNC and turn it on for the first time, it contains several default settings that you must first re-program before operating it with APRS.

If the new TNC is a Kantronics KPC-3 Plus or KAM, in addition to the MYCALL and MYPBBS and other settings, you also must adjust INTerface from NEWUSER to TERMINAL. This opens additional fields for re-programming. Adjust HEAderline to OFF, and MCOM and MCON to OFF. For home ops you can use any BAUD rate setting, but I like to use 4800 because it keeps me consistent with all my TNCs since the Tracker TNCs require ABAUD 4800 for interface with the GPS. Whatever ABAUD setting you choose, remember it, as when you start APRS for the first time it will ask you, among other questions, what your baud rate is set at.

After starting APRS, and you believe you are communicating OK with the TNC, you can now watch for stations to appear, and your packets to begin sending over the system.

Your APRS application "should" select an outgoing transmit rate of once every 30 minutes. This is just fine, and you should not have to change it. The outgoing path should be WIDE2-2.


Note that you DO NOT have to purchase one of the brand-spanking new APRS/GPS capable TNC's in order to participate in APRS activities. Many older TNC's can be used, including the AEA PK-88, TAPR-2, TAPR-2 clones made by various manufacturers, etc. These units can be put to use as home stations or as mobile APRS stations. For a home station the position is set by the APRS application which sends out a position report about every 30 minutes. There is no need to adjust this. Likewise, for mobile APRS these TNC's must have a computer attached and running APRS software in order to update the position. You adjust how often the position report is updated in the APRS application, and should select an outgoing path of WIDE1-1,WIDE2-1 at about once every 2-3 minutes. The older TNC's are not usable as WIDE digipeaters, and are ill-suited as mobile/portable trackers unless some form of computer is attached constantly, and running an APRS application.

TAPR-2 clones can be upgraded with new EPROM's to make them GPS-aware. There are certain caveats with this, because the processor inside the TAPR-2 TNC's is slow and may not handle continuous sentences from a GPS. If your GPS has enable/disable for individual sentences then you may want to turn off all strings, and then re-enable just the $GPRMC or the $GPGGA string so the TNC can keep up with the data. See the TAPR Site for information about updated EPROMS. These updated EPROM's are only necessary if you wished to run a mobile APRS setup with no computer attached.

When using an older TNC for your house and fill-in digipeat station, insert your position fix in the BTEXT, set the TNC to beacon at 30 minute intervals, and set up an alias of "WIDE1-1". Here is an example:


	mycall AB7CD

	myalias WIDE1-1

	unproto APRS VIA WIDE2-2

	btext !0000.00N/00000.00W- 

	beacon EVERY 30 (might need to be 600 depending on TNC)

	txdelay 30

	digipeat ON

	xmitok ON

TNC's are now available that have two serial ports and a radio port. One serial port can connect to a computer, while the other connects to a GPS. If you already own TNC's that only have one serial port, don't despair, there is a way to hook up a GPS and the TNC to the computer at the same time: It's called an HSP (hardware serial port) adapter. You can either build or buy an HSP adapter, and it generally consists of a Y-adapter cable with a small circuit inside. The circuit switches between the TNC and the GPS based on a handshake line coming out of the computer. This handshake line is in turn controlled by the APRS software running on the computer. You merely have to inform the APRS program that you're using an HSP adapter. See the main NWAPRS web page for a pointer to the circuit, or visit the TNC manufacturer's web pages to see what they offer.


WEATHER STATION SETTINGS

If you have a weather station (Davis, Peet Brothers, Radio Shack, etc) at your home or remoted station, we want to see the weather data every 15 minutes. Not more, not less. Additionally, those with weather stations may use WIDE2-2 for their outgoing path from home, or if remoted as a WIDE digipeater on a mountaintop. The extra "hop" helps ensure that the wx data gets to the nearest iGate, which insures delivery to regional NWS stations.

Hooking up a home weather station and integrating it with APRS means you must have two available serial ports on your computer; one for the TNC, and the other for the WX station. If running APRS on a laptop with one serial port, input the weather on the serial port and the TNC via a serial-to-USB connector.


 

 

USING PRE-APRS (older) TNC
FOR HOME OPERATIONS

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