How big of a ground plane do you need? We had a bit of a metal plate, but it was pretty small, relatively speaking.<div><br></div><div>Christie<br clear="all">_______<br>"The road of excess leads to the palace of wisdom." -- W. Blake.<br>
<br>The outer bounds is only the beginning. <a href="http://www.flickr.com/photos/genriel/sets/72157623376093724/">http://www.flickr.com/photos/genriel/sets/72157623376093724/</a><br>
<br><br><div class="gmail_quote">On Wed, Feb 10, 2010 at 6:19 PM, <span dir="ltr"><<a href="mailto:nils@shkoo.com">nils@shkoo.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
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. :)<br>
<br>
On <a href="http://aprs.fi" target="_blank">aprs.fi</a> there are some info on some of the nearby repeaters and their power output:<br>
<br>
<a href="http://aprs.fi/?call=K6IXA-3" target="_blank">http://aprs.fi/?call=K6IXA-3</a><br>
<a href="http://aprs.fi/?call=K6TUO-3" target="_blank">http://aprs.fi/?call=K6TUO-3</a><br>
<br>
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.<br>
<br>
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. :)<br>
<br>
-nils<div><div></div><div class="h5"><br>
<br>
On Wed, 10 Feb 2010, Mikolaj Habryn wrote:<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
It's so obvious when you explain it :) This probably does explain all<br>
of our APRS problems. So if we want to talk to both distant<br>
digipeaters and to chase crews (who are aiming to be directly<br>
underneath), what's the best thing to do? Dual antennas?<br>
<br>
m.<br>
<br>
On Wed, Feb 10, 2010 at 4:57 PM, <<a href="mailto:nils@shkoo.com" target="_blank">nils@shkoo.com</a>> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Here are my thoughts on the APRS problems:<br>
<br>
It sounds like the transmit antenna was mounted horozontally. This would<br>
make it very difficult for the digipeaters to pick up the signal, since<br>
most everything uses vertical polarization. The difference in signal is<br>
on the order of tens of dB (reference<br>
<a href="http://en.wikipedia.org/wiki/Antenna_%28radio%29#Polarization" target="_blank">http://en.wikipedia.org/wiki/Antenna_%28radio%29#Polarization</a>).<br>
<br>
Also with a horozontal antenna, you would only be broadcasting to a strip<br>
on the ground, and half the transmission is sent off into space. With a<br>
vertical antenna you send the signal in all (horozontal) direcitons.<br>
<br>
Also, the APRS packet takes about a second to transmit. If the payload is<br>
rotating rapidly during that time, the coverage area of the transmitter<br>
will change so it'll be less likely any one digipeater will see the whole<br>
packet.<br>
<br>
-nils<br>
<br>
On Tue, 9 Feb 2010, Andrew Gerrand wrote:<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
What was done well:<br>
- SMS messages<br>
- Data logger<br>
- Balloon fill (the fitting was the key)<br>
- Retrieval<br>
- Good launch site<br>
<br>
What went wrong:<br>
- Overfilled balloon<br>
- Didn't measure the pull<br>
- If we'd had three points of connection, 2-3 metres long, to the<br>
payload we would have had less or no swing<br>
- Android GPS bugs<br>
- Stressing the balloon through the angle of the fill (not having a hose)<br>
- APRS LI batteries got too cold<br>
- APRS system too immature - didn't play with it enough<br>
- Water condensation caused problems<br>
<br>
What we need to do:<br>
- Figure out how to calculate how much helium to put in a balloon to<br>
take it to height X<br>
- Maybe get a better balloon? We need more lift<br>
<br>
There was more but it got a bit rambly and I tuned out for parts =)<br>
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