Hi Chris<br><br>Sounds like a cool project :) The reason we went with 10mW was that the transmitter costs about $5 and weighs about 1 gram. Our entire payload including 2 cameras, spot tracker, electronics, batteries for 5hours + and insulation etc only came to 900 grams and I reckon we can reduce the weight some more. 10mW also saves on battery weight. We also don't really need a faster data rate unless we want to transmit video, which we have considered doing. Obviously our 4 baud data rate wouldn't be up to that :P<br>
<br>Cheers :)<br>Andre<br><br><div class="gmail_quote">On Tue, Jan 8, 2013 at 8:08 AM, Chris Hellyar <span dir="ltr"><<a href="mailto:chris@trash.co.nz" target="_blank">chris@trash.co.nz</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div text="#000000" bgcolor="#FFFFFF">
<div>Hi Andre,<br>
<br>
Can I ask a possibly not relevant question: why only 10mW?<br>
<br>
There is unlicensed spectrum in the PRS band for telemetry, or you
could get a ham involved and run licensed in the 70cm band
(Although not that frequency, that's in the repeater uplink
section of the band) . Both options would let you run a higher
bandwidth downlink.<br>
<br>
Just curious about the design decision as a rapid ascent balloon
is one of my (many) unfinished projects.<br>
<br>
I made the payload container a couple of years ago and got as far
as making the camera controller and researching GPS's. My cunning
plan was to launch to time the burst with an ISS overhead pass and
relay telemetry off the APRS digipeater on board. It was my main
motivation to getting my amateur license at the time, although now
I've got the DX bug and that's a whole other bowl of cornies.<br>
<br>
Cheers, Chris H.<div><div class="h5"><br>
<br>
<br>
<br>
On 07/01/13 23:58, André Geldenhuis wrote:<br>
</div></div></div><div><div class="h5">
<blockquote type="cite">Partial success I'm afraid :P<br>
<br>
The spot tracker stopped above 60k feet which we expected but I
had hoped it would start working once below that again. It
appears not for whatever reason. We also had a 10mW radio on
board the balloon transmitting location, altitude and temperature
which the recovery team managed to track all the way out to 80km
with good decoding except when the balloon was low on the
horizon. The last GPS fix was at 3436m at a composite position of
-44.04174, -173.04946. The position is composite as the last two
messages only contained one of latitude and longitude due to
signal breakup. It puts the payload out to sea south of akaroa
harbour.<br>
<br>
<br>
The balloon ascended much slower than anticipated and we are not
sure why yet, we are still going though the data to try and figure
out what happened. The slow assent was the reason the balloon
went out to sea, it took much longer to reach its burst altitude.
Next time we will have cut downs :P<br>
<br>
We are hoping it washes up and someone finds it and returns it to
us. The electronics will be wreaked but the two camera SD cards
and data logger SD cards might still be ok and it would be nice to
see the pictures :)<br>
<br>
We got about 80% of the objectives for the flight though and we
planned to iterate all the electronics and replace the spot with a
spot 2 which has a ublox GPS unit so will work above 60k feet.
We will fly the next iteration soonish.<br>
<br>
<br>
I'll let the list know if we get any picures back<br>
<br>
Cheers<br>
Andre<br>
<br>
<br>
<div class="gmail_quote">On Mon, Jan 7, 2013 at 8:51 PM, Mark
Atherton <span dir="ltr"><<a href="mailto:markaren1@xtra.co.nz" target="_blank">markaren1@xtra.co.nz</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi Andre,<br>
<br>
Looks like it was a sucess, well done.<br>
<br>
From <a href="http://goo.gl/1o6o6" target="_blank">http://goo.gl/1o6o6</a> password microprize
...<br>
<br>
Launch time close to 10:42, with signal loss 12:51, so just
over 2 hrs flight time (?)<br>
<br>
Not obvious what altitude you managed, or I haven't found the
correct button yet.<br>
<br>
Any chance of a quick report here and maybe a fuller report
with photos at the next Tait-meeting ?<br>
<br>
Regards,<br>
<br>
Mark<br>
<br>
<br>
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