FIZZLE Launch 2nd March

Jump to: navigation, search

The FIZZLE 868MHz 100mW RTTY Tracker was launched on the 2nd March 2013, taking advantage of the kind offer of a piggyback on the University's Project SHARP Flight.

Full Photo Album

Launch Video - Warning: V.V. syndrome!

Launch Site

The first major obstacle at the Launch Site was the lack of mobile internet. Using the 3G modem on a 2m high PVC pipe on top of the car roof only achieved an intermittent 2G connection, barely capable of holding my SSH-screen-irc connection.

dl-fldigi frequently timed out on the connection to habitat, resulting in very few strings being uploaded from the launch site.

The 100mW output from the transmitter appeared to overload the Funcube Pro Plus dongle when any antenna was plugged in. A variable attenuator will be used on the next launch.


Following problems with the Project SHARP CPU (Gadgeteer..), and an unfavourable prediction with the weight of SHARP on the flight, it was decided to launch the balloon with only ALPHA and FIZZLE on board.

After waiting for a helicopter to fly straight over the Launch Site, the balloon was launched without incident, rapidly ascending due to the spare lift.

As the balloon ascended past 400m, the Funcube Pro Plus dongle was still overloaded using the 3/4 wave magmount antenna. As the balloon ascended decodes started coming in, but the lack of internet meant that nothing was uploaded to habitat/spacenear.


Trying to find 3G

As there were no local receivers, my first thought was to drive to somewhere with some 3G, so that I could upload the strings from dl-fldigi to habitat. Unfortunately I was on my own in the car, meaning that when the payload drifted out of the passband, I had to pull over and retune, this often took a while to find a suitable stopping place, and I got the car stuck in a very muddy lay-by once! dl-fldigi froze at one point, forcing a restart and losing all the strings that were queued for upload.

Intermittent Transmitter

I finally found a small town with adequate 3G coverage, however by this time the RFM22 transmitter had become intermittent, losing the '$$$$' off the start of the transmission, and disabling the upload. As I was parked up the transmitter switched off completely.

With ALPHA having many listeners, and no payload for me to track, I set off towards the predicted landing site near Oxford.


With the news of ALPHA dropping back to a carrier due to COCOM limits, I pulled off onto some side road in search of a hill to be able to DF ALPHA with the yagi.

I got the direction reasonably accurate by the time that ALPHA recovered on it's descent, and so continued my drive towards Oxford.

Navigation to Landing Site

Despite having 3G in the car, with a heads-up map display and IRC comms, navigating the Oxford ring-road solo proved to be challenging, resulting in many missed-turnings, drastically delaying arrival at the landing site.

Finally I arrived at the landing site, where Andy M0SOT and the Project SHARP chase team had just arrived and walked into the field to recover the payload. On recovery I found FIZZLE transmitting again without the AVR CPU having rebooted, this was quite confusing at the time!


Rob M0DTS had no problem receiving the data at 600 baud, proving that this could be done. However I have chosen to use 300 baud for the next flight, in order to give us a little more headroom for dealing with overload conditions and the like.

  • 100mW transmitter causes RX overload at launch site, corrupting data.
    • Take variable RX attenuator next time.
    • Baud rate reduced to 300 baud.

  • Some sort of internet connection at the launch site is really desirable for an 868MHz Launch with not many local trackers.
    • Not sure what to do about this one.

  • Solo chasing/driving/navigating really doesn't work, could have done with at least someone on the phone to guide.
    • My brother has offered to join me next time.

  • Intermittent Transmitter caused by wiring error that left the RFM22 SDN pin floating. No ill effects seen in testing but voltage threshold changed with thermal conditions at altitude.
    • Wiring error corrected, FIZZLE has undergone 7 days of continuous freezer/in-sun testing with no ill effects.