[Space] Debriefing Notes
nils at shkoo.com
nils at shkoo.com
Thu Feb 11 02:19:32 UTC 2010
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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>>> Space at lists.noisebridge.net
>>> https://www.noisebridge.net/mailman/listinfo/space
>>>
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