[Space] Debriefing Notes

nils at shkoo.com nils at shkoo.com
Wed Feb 10 16:57:27 PST 2010


Here are my thoughts on the APRS problems:

It sounds like the transmit antenna was mounted horozontally.  This would 
make it very difficult for the digipeaters to pick up the signal, since 
most everything uses vertical polarization.  The difference in signal is 
on the order of tens of dB (reference 
http://en.wikipedia.org/wiki/Antenna_%28radio%29#Polarization).

Also with a horozontal antenna, you would only be broadcasting to a strip 
on the ground, and half the transmission is sent off into space.  With a 
vertical antenna you send the signal in all (horozontal) direcitons.

Also, the APRS packet takes about a second to transmit.  If the payload is 
rotating rapidly during that time, the coverage area of the transmitter 
will change so it'll be less likely any one digipeater will see the whole 
packet.

-nils

On Tue, 9 Feb 2010, Andrew Gerrand wrote:

> What was done well:
> - SMS messages
> - Data logger
> - Balloon fill (the fitting was the key)
> - Retrieval
> - Good launch site
>
> What went wrong:
> - Overfilled balloon
> - Didn't measure the pull
> - If we'd had three points of connection, 2-3 metres long, to the
> payload we would have had less or no swing
> - Android GPS bugs
> - Stressing the balloon through the angle of the fill (not having a hose)
> - APRS LI batteries got too cold
> - APRS system too immature - didn't play with it enough
> - Water condensation caused problems
>
> What we need to do:
> - Figure out how to calculate how much helium to put in a balloon to
> take it to height X
> - Maybe get a better balloon? We need more lift
>
> There was more but it got a bit rambly and I tuned out for parts =)
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