Near Space Project



Shrink that Arduino

I purchased an Atmega328p chip in the hope that it will form part of my tracker. I followed the instructions from Freetronics which listed all the additional components I needed.

A resistor and a few capacitors with the 16 Mhz crystal will get you started, But you really need to consider how you are going to power it and how you are going to get your code onto the chip.

The instructions allowed for the connection of a voltage regulator so I can connect a battery power source at a later stage. But to really get the chip configured for the time being I have connected a USB FTDI board, which allows direct programming of the chip just like it was a really Arduino UNO board.

20151107_183526Ensure you get all the cap values right as I was getting an out of sync error, which was caused by the wrong cap between the USB FTDI and the chip.

One I have completed all the code for my tracker I will remove the FTDI and connect a battery power source hopefully the final piece of the tracker puzzle. This will allow me to use my nano for other projects and leave the cheaper chip on the board.

My Nano

Decoding a little further

I’ve been waiting a few weeks for a number of items to arrive in the mail, one of which is a MT8870 DTMF Decoder. dtmf

The idea is to allow the payload to be controlled with a DTMF tone. Mainly so I can initiate an emergency cut down if required.

I am using a Radiometrix RX2A for the receiver and have connected its output to one of the audio input channels of the DTMF Decoder.


I modified some code found here which takes the DTMF tone and allows it to be decoded via the arduino.

Initially the tones that are being received are displayed numerically on the screen just for a test. But I still need to allow a command to run when the right combination is received.

A few tests on the work bench, and it looks to be working. I don’t have much confidence in the receiver over a longer distance, so some testing will need to occur.

Tracker 2 Progress with Transmitter

Well, things are starting to heat up here in good old Sydney Town, both weather wise and in the shack. I’ve been playing with the 2nd tracker and attempting to get it transmitting some RTTY, and finally tonight after several nights of learning I finally have it working.20151006_223648

First of all I’m still using the FlexTrack code with a Radiometrix TX2EH but have modified the code slightly to work for my purpose. The code appears to use FSK for a 3v model whilst my transmitter is 5volts. For what ever reason I didn’t have any real success with it. I had to tune my radio to USB to hear any tones, and for some reason I was only getting a single tone.
I wanted to have the ability to decode using a handheld and my handheld doesn’t have SSB, so I looked into the AFSK option. Instead of varying the frequency of the transmitter I generate an audio tone and transmit tha20151006_230925_LLSt instead. Tested the receive with my Yaesu FT-857 and the frequency looks a little off from what I would expect, but this may just need some further tweaking of the code.

Consulting a AFSK tone table for RTTY on the KLOTH.NET website, I chose a 425 Hz shift and selected a 2295 Hz high tone and a 1870 Hz low tone. I then exchanged some lines of code that would normally cause the transmitter to frequency shift with the Arduino tone command. After some mucking around, I finally had some success and was able to successfully decode the RTTY

After setting the correct RTTY decode options in dl-fldigi a big smilefldigi came across my face as I was decoding the output from the tracker. The example screenshot is with the GPS disconnected, but with the GPS connected, the zero’s quickly filled with the GPS coordinates.

I’ve still got some tweaking to do, as I’m not happy with the transmitter, it seems unstable with frequency drift and you can tell from the waterfall image it is a little noisy. Hopefully I just need to tweak the code to get this right.

But at least I’ve managed to get it working, as I can now look at experimenting with other digital modes. I know RTTY is fairly old these days and other protocols do exist, but RTTY just seems simple and if it works from near space, then I’m happy.  Happy to hear from anyone who can suggest any improvements.

Next I want to de-key the transmitter between transmissions so that a receiver can be used to receive commands from the ground. May have to look at a DTMF decoder or something.

Looking at something like thisan Solu DTMF MT8870 Decoder Module for Arduino.

Further progress with GPS on Tracker 2

Connected my GPS up this evening to the Ublox U-center to confirm that everything was in working order. Changed the baud rate to 57600. (maybe someone can confirm if this is wise or not?) and yipee everything seems to be functioning.

I’ve read a a number of forums regarding the Ublox GPS and they advise to set the GPS into flight mode, of which I have done. I found this site useful to connect the GPS with U-center. Ublox GPS – U-center20150930_221843

Found some Arduino code on Git Hub for an RTTY based tracker based on Habduino, called Flextrack . It sounds as though it may work for my purpose if I want to use RTTY for the 2nd tracker. However I’m still awaiting the delivery of my UHF transmitter so only have the GPS working via the code so far.

Connected it all up to my Arduino Nano and I;m already getting the Flextrack GPS debug messages. So far so good..

The Ublox 7M seems to be working much better than the GPS in my primary tracker which is only a 6. Much faster in acquiring a fix.

Really need the transmitter to arrive so I can really start to get into the fun stuff.

GPS Arrived for backup tracker

Just received in the mail a GPS Arduino Module with a Ublox NEO-7M chip which will be built into a 2nd stand alone tracker for the payload.

Ublox 7M
Ublox 7M

The backup tracker is also waiting for its own transmitter and receiver module to enable communications with the payload mid flight.

This GPS will also run the cut down system where I want to enable the termination of the flight if a certain latitude is passed.

Got the iron heated up to add some pins so the experimenting can begin whilst I wait the other bits to arrive.

APRS Tracker

My tracker has come along nicely and initial tests look good.

I started out with something similar to the LANMU UNO R3 Atmega328p Atmega16u2 2014
and just added all the bit I needed.

I have mounted the components onto a PCB to keep things secure, but still need to to some final tidying up.

HAB Tracker

I’ve still got the Arduino sitting loose but with a proto shield on top. I’m still thinking about how I will finish this so I don’t disconnect anything on a rough landing.

The tracker includes a NEO-6M GPS Module with Antenna 

There is a temp sensor on the PCB and also on the external wire.
An accelerometer and a buzzer.

I’ve also fitted a radio transmitter, to send the APRS data. A HX1 made by Radiometrix.

Also in the picture is the Byonics – Microtrak VHF Antenna V6

Byonice V6
Byonice V6

Create a free website or blog at

Up ↑