The “Naked” Qualatex

Sven was trying an experiment with a foil balloon where he used concentrated sodium hydroxide to wipe off the aluminum layer from a Qualatex 90cm balloon. The removal of the aluminum worked fine, but we couldn’t measure any weight loss. At least it was below 0.05g. Still we wanted to launch this balloon to see if there is any difference. At our typical night launch we have lost visibility of the transparent balloon already after 200 meters. Usually you can see the reflections of the metallic foil balloon even after a mile at a regular launch, but this time it disappeared after a minute already.

The flight path during the night was unexpectedly low. There must have been a cloud layer that pushed the balloon back down at ~2700 m altitude. Possibly there was some little rain involved. In the morning hours when the sun came and dried the balloon, it finally continued the ascent up to 6521 m. Then the signal was lost just before the Russian border.

We’ve used a tiny Pecan Femto tracker powered by an AA Lithium Ultimate Energizer battery. When the balloon was lost, it certainly had still enough power. Many APRS packets were lost which indicates that the transmission was certainly not optimal. We’re investigating about the reason, but this was the first Femto flight with APRS software (Femto was originally RTTY only). Despite the small tracker, the payload weight was still ~20g due to the heavy AA battery.


One thought on “The “Naked” Qualatex

  1. Thomas, nice work on the Femto. What I’ve found with respect to this radio (si4x6x) is that its extremely sensitive to 2 things – a) any form of static/ESD – which is why I ultimately put a lightning and esd circuit on mine. Especially hanging under *plastic* envelopes you may find that one moment everything will be fine, and the next the payload will have stopped reporting; b) if the final match/lpf isn’t *in tune*, then the radio may die – I don’t believe there is any fold back smarts in the radio, I think it gets damaged. It sounds like the later is what happened, as they appear to degrade with time due to a bad match/filter. Any chance the frequency drifted? That could be another issue with temperature, etc?. My most recent approach is to use the switched match from the reference design, and then a minicircuits integrated LPF – the 490mhz one is good from 490 to about 100mhz after that I added an ESD circuit and a lightning high pass at the antenna. We’ll see how all this works out. At least it appears that I didn’t effect the current or transmitter output as a result of the above… Time will tell…. Say Hi to Sven …

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