My APRS-related pages begin here!

I have a Kenwood TH-D7 transceiver, APRS equipped.

Problem: how can I get station positions heard by TH-D7? (for example, to be used for display mapping on a chart).

Solution: use the small Ruby program below.

Preparation:

• turn on the TH-D7 and select the APRS frequency (for example, 144.8 MHz in Italy)
• press the TNC key of the TH-D7 until the "Packet" indicator appears on its display
• connect the RS232 cable from TH-D7 "GPS" port to the Linux PC (yes, we will use the GPS port where TH-D7 expects GPS data and sends GPS POIs)
• select 4800 speed, using command stty -F /dev/ttyS0 4800 on Linux PC (note: on some distributions this command may require root privileges)
• run the Ruby script below. The program will stop after receiving a packet if the /tmp/stop file is present.

Note:

• this is only useful if you have only one RS232 serial port and already need it to feed to TH-D7 some "static" GPS data (good for enabling automatic TH-D7 beaconing). On the same GPS port, you can then read heard station positions. If you want to fully decode incoming APRS packets, you will need to use the TH-D7 in "TNC" mode (thus either "listen only" mode, or needing two RS232 ports - one for "static GPS data" of your home, and the other for TNC data). TH-D7 APRS ''TNC listening'' mode is described here.

Normal output example:

5  2009-02-07 00:53:34  41:05'51"N 014:46'69"E  IW8ZZZ-11
6  2009-02-07 00:55:18  40:41'24"N 014:28'16"E  IZ8ZZZ
7  2009-02-07 00:59:14  40:48'64"N 014:21'43"E  IK8ZZZ-7
...

Final statistics output example:

13 stations:

IZ8ZZZ
  total packets: 3
  first packet on: 2009-02-06 23:55:17
  last packet on: 2009-02-06 23:59:16
  last different known positions:
    2009-02-06 23:57:16: 40:41'24"N 014:28'16"E
    2009-02-06 23:59:16: 40:41'22"N 014:23'52"E
...

The script I used to parse the GPS POI (point of interest) strings coming from the TH-D7:

#!/usr/bin/env ruby

def estra p
  "#{p[0..1]}:#{p[2..3]}'#{p[5..6]}\""
end

n,chi,qua,ore,pri = 0,{},{},{},{}

while s=gets
  x,t = s.split(/,/), Time.now.strftime("%Y-%m-%d %H:%M:%S")
  poi = x.last.split("*").first
  sta = poi.split("-").first.strip
  pos = "#{estra(x[1])}#{x[2]} #{x[3][0].chr}#{estra(x[3][1..-1])}#{x[4]}"

  unless chi.has_key?(sta)  # se mai sentito prima:
    chi[sta] = t            # ricordiamoci il primo orario che e' stato sentito
    qua[sta] = 0
    pri[sta] = {}           # inizializziamo la lista delle posizioni
  end

  ore[sta] = t              # timestamp ultima volta che e' stato sentito
  qua[sta] += 1
  pri[sta][pos] = t         # a che ora e' stato visto l'ultima volta li'
  n += 1

  print "%5d  " % n
  puts "#{t}  #{pos}  #{poi}"

  break if File::exists?("/tmp/stop")
end

puts "#{chi.size} stations:"
puts

chi.each do |sta, t|
  puts "#{sta}"
  puts "  total packets:   #{qua[sta]}"
  puts "  first packet on: #{t}"
  puts "  last packet on:  #{ore[sta]}"
  puts "  last different known positions:"
  pri[sta].each do |p, t|
    puts "    #{t}: #{p}"
  end
  puts
end