APRS Tracking

After some minor hurdles I now seem to have my OpenTracker USB working correctly. So I am a lot closer to having a tracker ready for extreme testing.

Current setup contains a Garmin GPS-18x-PC connected directly into the Open Tracker via the serial connector. The Open Tracker then connects into a Yaesu VX-7R handheld.   The GPS and Tracker are connected to a bank of AA Batteries supplying 12volts, whilst the handheld uses its own battery.

Initial tests have been using the same AA's for several months with tests over that time being for several hours. I have been monitoring the voltage over this time dropping from 12volts , down to 9 volts and this morning on a drive to work , the voltage was at 7 volts. All the while the tracker and GPS were still operating. I am still only using standard AA's so nothing like what will be in the final version, but so far happy that the battery should last the trip.  I do hope to connect a few more devices up to the same power source such as a data logger, so this may test this power supply some more.

I have also discovered that the GPS seems to take time to obtain a GPS fix, this seems to add delay to the initial transmission. I need to nut this out further to ensure that it is just a GPS visibility problem as when the GPS was in clear view of the sky I couldn't reproduce the problem.  But want to ensure all is good for launch day otherwise its a waste of battery power waiting for a GPS fix before launch.

Opentracker USB take 2

After damaging the original radio mic cable that came with my tracker, I was starting to think that I may have damaged something in the tracker itself. Nothing I tried seemed to make the tracker key up my handheld. However, a couple of days ago my replacement mic cable arrived and I finally found some time to play with it.

Initially I wired up the cables as per the original , however nothing worked. I discovered that the mic cable was wired differently and needed to swap a few cables around. This seemed to do the trick and I am now TXing again. Phew...

Now that I am TXing again, I haven't yet seem my callsign appear on aprs.fi So again I was wondering if something wasn't right. So to test this out I downloaded some APRS tracking software that runs using  my PC's soundcard. After a few tweaks, like changing the baud rate to 1200, i had success. The application decoded my handhelds signal and I was able to read the coordinates. It accurate to about 5 meters, which probably isn't to bad seeing the GPS unit is on the window and probably not seeing a full sky.

So with a big smile on my face, I can finally after many weeks of downtime move on to get the tracker into a more portable form. Would be nice to see my callsign on APRS.fi to double confirm that everything is ok.

Garmin GPS18 PC - First test

It took a couple of weeks to arrive but my Garmin GPS18 was finally delivered. I couldn't wait to test it out, but don't have a GPS tracker yet, so had to use my laptop.

The GPS pictured below comes with a cig lighter plug and a sticker stating it will work with 8v - 30v.. I plan on removing the cig lighter plug and connecting directly to a portable power source. So I will need to run a few tests to determine what sort of battery I need. Obviously I need something that will last the duration of the flight and the recovery phase.

The serial connection will allow direct attachment to the GPS Tracker when I receive it, but for my first test it needs to connect to my laptop. As modern technology would have it my laptop doesn't have any serial ports. But this isn't a problem as I have a serial to USB adaptor which does the conversion.

Successfully downloaded the Garmin Web updater software and was able to update the firmware. So far so good. I then searched for some GPS software to test things out and found OziExplorer which I have used many years ago with a previous Garmin.

Had to set the GPS type and comm port details, as well as untick the USB GPS box, then I was in action. Had the GPS sitting inside on the window, so GPS signal was at first low, but after a few minutes the GPS updated and I had a signal fix.   Phew , it works...

Will hunt for a GPS Data Logging app so that I can just log the raw data, Maybe go for a drive around with it connected to the laptop and see what it picks up.

Trial GPS Receiver

Did some hunting around on Ebay for a GPRS receiver and came across a Garmin GPS 18 PC receiver. Decided to make the purchase after reading about it's success with another HAB project. I will use this to experiment with APRS on the ground first and if all goes well may send it into the sky.

Its supposedly a 010-00321-34 GPS 18x PC Receiver , which seems to be on the list of high altitude GPS's.

Will probably test it on a laptop first, as I don't have a APRS tracker yet. So stay tuned.

Choosing a Tracker

Currently researching the various options for getting the GPS data back to earth. There appears to be several. I'm not really in a position where I can build a board from scratch though if I had the time and patients I would love to give it ago. So more or less one of requirements is a pre-made board.

Checking out several sites, I came across Saskatoon Amateur Radio Club who provided some great information as to some of the gear they had used. They mentioned the OpenTracker which at first glances looks to do what I want and more. Looking further on the same Argent Data Systems site shows several other versions. Hmmmm

The same site also boasts a SRB MX145 Transmitter, which appears to be perfect as an APRS transmitter. Seems a possible solution. I would much prefer loosing an $80-$100 low power transmitter then using a handheld and lose that.

The SARC had also used a Byonics Pocket Tracker which also looked very impressive. What impressed me the most was the built in 2m Transmitter. So with this tracker I would just need to feed in the GPS data. Sadly they don't make them anymore, but have a similar Micro Trak 300 device.

The Micro Trak 300 outputs about 300 mW but I am a little unsure about the frequency I want to operate the APRS on. Should I just use the Australian 145.175Mhz , or pick another digital mode frequency and just collect the data myself.  Hmmm  Decisions.

Another option I discovered was the Spot Tracker which sends its GPS position via satellite approx every 10 mins. Not exactly what I am after, but as for a recovery tool it could be perfect. Though it may not function about 60000 Ft , it may well survive the final impact and be able to relay its location is the main transmitter fails. A bit of built in redundancy maybe.   I also wonder if anyone has modded these to be more suitable for Balloon operation.

Found another tracker - R Trak - which also has a 2m transmitter with changeable frequency. Nice..  It also has Five ADC channels for analog sensor readings which means I may be able to attach some extra stuff.

The search continues