[Space] Debriefing Notes

Mikolaj Habryn dichro at rcpt.to
Thu Feb 11 01:51:01 UTC 2010

It's so obvious when you explain it :) This probably does explain all
of our APRS problems. So if we want to talk to both distant
digipeaters and to chase crews (who are aiming to be directly
underneath), what's the best thing to do? Dual antennas?


On Wed, Feb 10, 2010 at 4:57 PM,  <nils at shkoo.com> wrote:
> 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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