Tag Archives: APRS

APRSHOG Alert and Notification

During my lunch today, I was doing some testing with setting-up a receive-only APRS iGate. While I was watching the logs and troubleshooting a problem, I saw my callsign whiz by the screen. Oops! I had received a phone-call as I was getting out of the car, and forgotten to turn-off my HT! I quick went over to the NorCal APRSHOG site to see how “bad” I had been. Sure enough, I was already listed at #25 in the ranks at the time. I quickly ran-out to the car and powered off the HT.

This was all unintentional, and I am very conscious of the APRS traffic congestion, which is why I was working on setting-up a receive-ONLY APRS iGate. I decided I needed to find a way to try to monitor and make sure that I am alerted if this happens again. Next time this happens, I may not be watching APRS logs.

I wrote a little script that I called “aprshog-alert” to run on my Linux server. The script takes in my CALLSIGN and the threshold I want to be alerted on.

It will email me if my APRS callsign is ranked between 1 and 25 (considered a hog!):

[root@host ~]# ./aprshog-alert KI6ETL-9 25



RANK=`wget -q $SITE -O – | grep $CALLSIGN –before-context 1 | head -1 | sed -e :a -e 's/<[^>]*>//g;/

if [[ -z “$RANK” ]]; then
elif [[ “$RANK” -le “$LIMIT” ]]; then
echo You are on the APRSHOG list at a rank of $RANK . Check on $SITE | mail -s '# APRS HOG ALERT #' $EMAIL

I am confident that there are more elegant methods to accomplish this, but I wanted something usable immediately.

The final step is to add this as a cronjob on my Linux system, to run on an hourly basis. I don't want to abuse the APRSHOG site, so more frequent would be inappropriate.

AVRS – Automated Voice Relay System

I just got an email from APRSDepot about their new project regarding AVRS

Automated Voice Relay System

“When you send the command to APRSDEPOT like ‘C [CALLSIGN-SSID]’ (Example: ‘C N6GOF-1’ where N6GOF-1 is the party you want to reach) the system will automatically determine the IRLP Nodes that are nearest to the two parties (You and N6GOF-1 in the example above). Once that is determined it will then send messages to both parties with details on how to get interconnected (Node details for each party respectivley). In the event that the party your searching for has NOT been heard in the last 60 minutes, you will get an advisory message.”

This seems like a great idea… but not necessarily the most efficient. It would be great if APRS were some how extended to provide people (optionally of course) with the frequency the other user was on. This would allow people to use repeaters or simplex to communicate, instead of tying up a IRLP node. Regardless, this is certainly a step in the right direction.

Build Your Own GPS/APRS Tracker – FreeTrack 2.02

FreeTrack 2.02 – GPS to APRS Tracking Encoder

“This encoder will turn serial NMEA data from a GPS receiver into APRS format AX.25 data packets.
By using this hardware with a 2 meter ham radio and the freely available APRS computer software, you can track the location of the GPS on a map in real time. Latest release now supports the mic-e compressed data format for much smaller packets.

The unique aspect of the design is in how it creates frequency shift keying (FSK) tones with the PICs built in 4 bit voltage reference instead of a modem chip.
FreeTrak's built in configuration routines allow you to enter all it's parameters with any serial terminal program.”

Getting APRS working with my Kenwood D7A

I struggled to get APRS working with my Kenwood TH-D7A/G. The following things were done. I haven’t confirmed all of them were necessary…

On the GPS… (Magellan Meridian GPS)

    • Set speed to 4800Bps from GPS to radio.

On the Radio…

    • Made sure that GPS was sending information to the radio by using the POS button
    • Made sure that the radio was set for waypoints to be “….MGN” to work with the Magellan Meridian GPS I am borrowing.
    • Set Band A freqency to 144.390
    • Set Band A as the data band
    • Set Band A offset to “0.00” (default was .600)
    • Set CTCSS tone to ON for Band A (This is to squelch all the “modem” noise.)
    • Set My Callsign
    • Set My Icon
    • Set Data TX as AUTO
    • Set TX Interval to 2min
    • Set POS LIMIT to 150mi (help eliminate information I don’t care about)
    • *IMPORTANT* Set Packet Path
      From: RELAY,WIDE
      To: WIDE1-1,WIDE2-1
    • Pressed TNC so that ONLY TNC appeared (No “packet”).
    • Last but not least… pressed the “BCON” button.