[aprssig] Using a TNC as a CW Beacon Only

Wes Johnston aprs at kd4rdb.com
Sun Feb 19 14:33:28 EST 2006

That would be a neat idea.... an app running on a laptop in the car that
recorded the time/date stamp and position of a $GPRMC sentance from a
GPS receiver in the car each time it receives a packet from the TNC...

So, on the digipeater TNC have it send a beacon every 30 seconds on a
freq other than 144.39.  Heck, even every 4 seconds would be a 25% duty
cycle... prob not too hard on the radio.  Seems like a Kpc3 tnc would be
suitable for this... one could remotely log in and alter the beacon
timer for the test and turn it off when done.

in the car, have a small program that watches two serial ports... one
with a GPS, the other with a TNC.

The program would receive the GPS sentences all the time, keeping the
current (ie last received) time and lat/lon in a few variables.

Each time ANYTEXT comes in on the serial port with the TNC attached,
write the current gps time and lat lon to a log file on disk.  A clever
person would format the log entries so that they resembled APRS packets
and could later be played back into your favorite aprs app to
graphically visualize the coverage area.


Stephen H. Smith wrote:
> fred at wb4aej.com wrote:
>>      I am wanting to set up a beacon that would transmit (in Morse
>> Code) my ID every two to ten minutes on a two meter simplex
>> frequency.  I want to do this so as to be able to do some coverage
>> tests (Have the radio/ID running at a proposed APRS location and drive
>> around the area gathering signal strength reports in the different
>> locations.  It would not be on the APRS frequency, but on a less
>> popular simplex frequency (probably somewhere near 147.5 megahertz
>> where I wouldn't likely be bothering anyone). 
>>      Could a TNC-2 be programmed to send a Morse Code ID (my callsign)
>> every two to ten minutes regardless of whether or not it receives
>> packet data?  Or would it only identify when it is processing packets? 
>>      Regards,
> If all you want is to do a signal strength/coverage survey, why couldn't
> you just set the TNC for a normal packet beacon (i.e. APRS posit) once
> every minute or two?   If this is not on 144.39 this shouldn't cause a
> problem.  As a bonus, you could run a laptop with the AGW Packet Engine
> softmodem connected to the mobile's speaker, and an APRS application. 
> This would let you verify that a packet burst is actually decodable in
> various locations.   [ With mobile data applications, it's perfectly
> possibile to have very high signal levels and still not decode anything,
> if the particular location happens to have a lot of multipath
> reflections smearing the data stream. ]
> Stephen H. Smith    wa8lmf (at) aol.com
> EchoLink Node:      14400    [Think bottom of the 2M band]
> Home Page:          http://wa8lmf.com
> "APRS 101"  Explanation of APRS Path Selection & Digipeating
>  http://webs.lanset.com/wa8lmf/DigiPaths
> Updated APRS Symbol Chart
>  http://webs.lanset.com/wa8lmf/miscinfo/APRS_Symbol_Chart.pdf  
> New/Updated "Rev G" APRS     http://webs.lanset.com/wa8lmf/aprs
> Symbols Set for UI-View,
> UIpoint and APRSplus:
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