[Space] Debriefing Notes

Christie Dudley longobord at gmail.com
Thu Feb 11 04:30:16 UTC 2010

How big of a ground plane do you need?  We had a bit of a metal plate, but
it was pretty small, relatively speaking.

"The road of excess leads to the palace of wisdom." -- W. Blake.

The outer bounds is only the beginning.

On Wed, Feb 10, 2010 at 6:19 PM, <nils at shkoo.com> wrote:

> The digipeaters on the mountains will repeat via RF when they hear a
> packet, assuming your path is set right.  As long as you have a decent
> antenna on your receiver, you should pick those up fine, even if you're
> directly underneath the balloon.  At least in theory. :)
> On aprs.fi there are some info on some of the nearby repeaters and their
> power output:
> http://aprs.fi/?call=K6IXA-3
> http://aprs.fi/?call=K6TUO-3
> Also, I really recommend getting an external antenna to receive as well.
> Anecdotially, it makes a big difference for me when I'm using my HT. Just
> hanging out I generally manage to receive a beacon every couple minutes with
> the builtin duck antenna, but several a minute with the external antenna.
>  It's even more of a difference when I'm in a big metal box like my car.
> If we want to get really fancy we could set up a mobile digipeater with a
> directional antenna (like a Yagi or something) to receive, keep it located
> somewhat away from the balloon, and point the Yagi at the last beaconed
> location. :)
> -nils
> On Wed, 10 Feb 2010, Mikolaj Habryn wrote:
>  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?
>> m.
>> 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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