I’ve come to talk with you again.
APRS – ™ By: Bob Bruninga, WB4APR Http://www.aprs.org
Back in 2001 when I first got my license. I was interested in APRS because it was something I can do with my new license. I went as far as setting up a part time digipeater and after only a couple of months, the digipeater went down and lost interest in APRS because the cost of a GPS receiver at the time (even though GPS is NOT a requirement to listen or participate on the APRS network).
GPS receivers are a lot cheaper compared to 10 years ago and I have a old Garmin GPS-V lying around. So I figured this would be the perfect time to get back into APRS. For those who don’t know what APRS is, It’s Automatic Packet Reporting System which is an Amateur (Ham) based system for real-time communications of information using a digital protocal (AX.25). There are many possible things you can do with APRS. You can send (Short) text E-mail, SMS Messages, send weather data (Which the NWS uses) and when hooked up to a GPS , will send position data. I am not going to go into much detail because there are websites that are dedicated to APRS.
I am going to be doing a couple of things with APRS. One thing is that I am going to set up a part-time iGate (internet gateway) to make use of the frequency scanner and antenna that is not being used. Packets of Information received from the scanner (tuned to 144.39mhz) will be sent over the internet using the APRS-IS network so it can be databased and displayed on such websites as aprs.fi .
The other thing I want to do is location tracking. In order to do tracking you’ll need 2 or 3 things. You’ll need a GPS receiver that has an output for NMEA data, TNC (Terminal Node Connector) and a transceiver (VHF [144-148mhz] is Most used). As stated earlier, I have a Garmin GPS-V lying around and I also have a Kenwood TH-78A. All that is missing is a packet TNC. A Real TNC can cost $100+ and needs a computer. However there are units designed and built for APRS that will encode the data from the GPS to the AX.25 protocol and transmit the signal using the transceiver. I’ve purchased one of these units called ” TinyTrack3+” from a company called Byonics. It’s as basic as it gets. You can either buy it as a kit or assembled, with or without a GPS Receiver, with or without cables for your transciver or with or without cables for various GPS models. I ended up going with a solder and assemble your self kit without any extra cables because I wanted to invest the least amount of money in it as possible.
Here is the kit as you would get it in the mail. It comes with the componets, board, case and instructions.
Here is the board soldered up. I used a 35W Pencil type soldering Iron. I filed the tip a little bit to assure that solder flows to the tip. It took about 1/2 to 3/4 of an hour to solder. If your new to assembling boards, I would go to the Byonics website and download the manual because the online .pdf manual will cover the assembly and everything else in great detail. As long as you follow the step by step instructions, it will turn out great. For newbies make sure the diodes are going in the right direction, LEDs in the right direction and make sure the notch (little cutout) is aligned with the silk screen image.
Now that board is done, time to make some cables! (Since I didn’t order any)
Here is the cable all assembled! It’s a DB-9 Connector (Radio shack P/n: 276-1538 US$2.69) , Pos and Neg power cords with Anderson power poles attached so it could powered by many different sources (7-35vDC), Sacrificed speaker microphone from the Wouxun for its cable, Ferrite Core choke (Optional, Radio Shack P/N: 273-105) and the DB-9 Case (Radio Shack P/n: 276-1539 US$2.09). I Got the wiring diagram from the Byonics website and took about 1/2 hour to make which ended up costing me around $5 since I already had the cable, choke and power connector
Just an FYI, I sacrificed a speaker microphone from my Wouxun. Power-Werx which distributes Wouxun products (as well as the power poles), has the exact same cable for this application for sale on their website. They also have a similar one but with a cigarette lighter plug (Both for US$20). Byonics also sells cables for this and many different radios. Also note that that wouxun speaker mic layout is the same for kenwood HT’s!
After you assemble the tracker and the cable. Apply power to unit and hopefully it comes to life by flashing the yellow and green LEDS three times. Only thing left to do is to program the tracker using your computer. This point it can get tricky. The TinyTrak3 needs a NULL modem cable (Or adapter) to program it and possibly a gender changer. I found that I didn’t have a null modem cable, all I have are straight through cables. Since I didn’t want to wait for an adapter I made one from old computer parts lying around my house
Here is the cable that I made from parts out of an old 486 that I had in the attic. It’s not pretty or rugged enough for daily use but once you program the Tracker and are satisfied with the operation then you will most likely not have to program it again.
Here is the complete setup. Right now I have the unit running off a 9V battery. I also used a cigarette lighter plug with power poles connected to it. Depending on how you programmed the tracker, It will only send when there is data from GPS. There are limitless things you can do with this setup. For SOTA members (Summits On The Air), They can bring this along with them so others can see their progress in their hike. If you helping out in a public service or public events which ham radio operators are helping, you can show your location to HQ without even telling them. It makes things a lot easier.
Here is my first track. I learned a lot when doing this. I found that my handheld in the truck has a hard time communicating with the digipeaters in the area. I might purchase a small 1/4″ wave mag-mount or a duplexer and switch to my dual band antenna for when I am running APRS in the truck.
Modifications
I added things to the Tinytrak3+ which I think will make it better for me to run. If I had to be really critical about the tracker is that the DB-9 connectors did not come with mounting screws. The first test out with my truck the power/radio connector became loose and eventually lost power to the tracker. To fix this I went scavenging parts off a old computer.
Now I can secure both the power and GPS connections. The screws came off the LPT and monitor ports of an old mother board. There is a small amount of space between the back plate of the connector and the board. So I had to grind down the bolts and nuts so It would not touch the board.
Another issue that might come is when I am portable (walking). More likely the power source for the tracker for this purpose will be a 9V battery. The tracker with all the LEDS running will consume around 18.6ma which means a 9V battery (.370Ah avg) could possibly last for about 9-12 hours (60% discharged). If you turn off the LEDs, the power consumption is 6.6ma. On a 9V battery, the tracker could last around 30 hours. The TinyTrak3+ can run without the LEDS by cutting a lead (tells you how in the directions). If you using a high-capacity 9V (.580Ah)with no LEDs it could last for more than 50 hours so it might be beneficial to cut the lead and add a jumper. The down side is that you will not know the status of the Tinytrak.
So what I did is cut the lead on the board and installed a bridge (shown in the picture above with the blue jumper). When jumped the LEDs are operational.
Also pictured are 2 bridges installed (on the left side) for jumpers J5 (outside pair) and J6 (inside pair). If J5 is jumped it will switch to what was programed in the secondary tab in the program (Program 2) . This would work great for an event which required either a different call and/or different settings. After the event, you can switch back to the primary settings. If J6 is jumped it will send a signal to power on the transceiver. This would involve another board with a relay to put power into the transceiver or modifying the transceiver. I don’t plan on messing around with it any time soon but since I am soldering on jumper bridges, why not.
Overall it was a really great build and I am having a blast with APRS. My plans are to find a way to make it all fit into a nice tiny package that I could carry when hiking or driving.
73 and thanks for reading!