highaltitude.log.20091218

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[15:37] <jcoxon> 3 radiometrix ntx2 modules on their way...
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[16:35] <jcoxon> afternoon RocketBoy
[16:36] <Randomskk> woo one airwire left to route
[16:36] <Randomskk> I love how I leave the hardest and longest trace until last
[16:39] <jcoxon> hehe
[16:39] <jcoxon> surely you should do that one first
[16:40] <SpeedEvil> Ah - fun.
[16:40] Action: SpeedEvil has been doing insulation.
[16:40] <SpeedEvil> more floor.
[16:40] <jcoxon> hmmm any thoughs anyone where i can get some funding for high altitude stuff
[16:40] <SpeedEvil> ESA?
[16:40] <jcoxon> really?
[16:41] <SpeedEvil> dunno
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[16:41] <SpeedEvil> I was just randomly throwing out ideas.
[16:41] <jcoxon> oh right
[16:42] <jcoxon> its finally destroying my bank account
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[16:56] <RocketBoy> I ordered up a Soft66RF SDR kit today - I'm gonna put on the IF output of my IC-R7000
[16:57] <Randomskk> ooh, sweet.
[16:57] <RocketBoy> and plug that into some form of webSDR and make the R7000 tuner available on the internet
[16:57] <jcoxon> RocketBoy, wow that sounds great
[16:57] <RocketBoy> so - it can be tuned 30MHz to 2GHz
[16:57] <Randomskk> RocketBoy: then you need to get a quad yagi rotator setup to match
[16:59] <RocketBoy> yeah - yagi-tron (to differentiate it from the CUSF track-a-tron) ;-)
[16:59] <Randomskk> hehe yea
[16:59] <Randomskk> I was looking into what'd be needed to make one
[16:59] <Randomskk> but I guess the mechanics are somewhat involved. also expensive motors are expensive?
[16:59] <RocketBoy> I have a heavy-duty TV camera pan and tilt unit for the yagis
[17:00] <Randomskk> going with a premade mechanical unit seems to be the easiest way, cusf have a telescope pointer
[17:00] <RocketBoy> I need to get some stepper motors for it
[17:01] <RocketBoy> One of the simplest ways is to use a pair of standard yagi rotators - cheap ones are about £40 on ebay
[17:02] <Randomskk> that could work
[17:02] <Randomskk> how does the websdr decode 20m, 40m and 80m at the same time? does the radio tune to all those frequencies?
[17:02] <RocketBoy> they run on 24V AC - so you can count cycles
[17:02] <Randomskk> I mean, I get that it's software doing the filtering to let ou just listen to one bit
[17:02] <RocketBoy> just need a mains transformer and some triacs
[17:03] <RocketBoy> (and a cycle counting circuit)
[17:03] <Randomskk> but then what, does the radio and antenna etc just pass that entire band?
[17:03] <RocketBoy> I made one years ago that interfaced to a PC parallel port
[17:04] <RocketBoy> well you could use a log periodic - wide band yagi
[17:04] <Randomskk> guess so
[17:05] <jcoxon> RocketBoy, oh you know you were trying to find a cheap unixy microcontroller for your complicated code :-)
[17:05] <jcoxon> http://www.skpang.co.uk/catalog/product_info.php?products_id=598
[17:05] <jcoxon> it can run FreeRTOS
[17:06] <jcoxon> so not exactly what you wanted but slightly closer
[17:07] <RocketBoy> tis cool all right
[17:08] <RocketBoy> might just bite the bullet and get asus eee box http://event.asus.com/eeepc/microsites/eeebox/en/
[17:10] <Randomskk> looked at e.g. beagleboard, gumstix?
[17:10] <RocketBoy> anyway - I'm gonna use this old 1GHz PC to start with
[17:10] <RocketBoy> beagleboard no - gumstix yes
[17:11] <jcoxon> how much grunt do you need?
[17:12] <jcoxon> yeah start with a big pc and work down wants you've worked out the difficulties
[17:13] <jcoxon> bbl
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[18:23] <SpeedEvil> Alternate HAB superpressure construction?
[18:24] <SpeedEvil> http://www.youtube.com/watch?v=rE7wBkTF40E&feature=player_embedded
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[18:36] <rjharrison_> Hey jcoxon
[18:36] <rjharrison_> Any flights due?
[18:36] <jcoxon> rjharrison_, ummm nothing at the moment
[18:37] <jcoxon> i did some flight graphs from the data
[18:37] <jcoxon> http://www.pegasushabproject.org.uk/wiki/doku.php/missions:ballasthalo:ballasthalo3
[18:42] <rjharrison_> nice write up
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[19:59] <DanielRichman> RocketBoy, can you confirm that the balloon and chute you posted to Reading School has not been signed for?
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[20:06] <Randomskk> hmm, pcb routed
[20:06] <Randomskk> now the question is who I get to make it
[20:06] <Randomskk> batchpcb and gold phoenix are closed for the holidays
[20:09] <jcoxon> yeah holidays are annoying concerning ordering stuff
[20:09] <Randomskk> I could do a batchpcb order and get them sent to cambridge
[20:09] <Randomskk> suspect the batchpcb price for four of them will be close to the gp price for a whole panel though
[20:10] <Randomskk> and then I get black soldermask
[20:11] <Randomskk> https://randomskk.net/u/pics/mc.png
[20:13] <jcoxon> ooo nice
[20:13] <jcoxon> hehe - I've now got some very keen French Hams to help out tracking :-p
[20:14] <Randomskk> haha excellent
[20:14] <Randomskk> a few days late for bh3 but just in time for bh4 eh? :P
[20:15] <jcoxon> indeed
[20:15] <jcoxon> though BH4 is still in planning stages!
[20:15] <DanielRichman> Randomskk, I like the pac-man
[20:15] <jcoxon> need some christmas cash
[20:16] <Randomskk> jcoxon: exactly, this motor controller is gonna be costly to populate four of
[20:16] <Randomskk> at least I've got the sensors
[20:16] <Randomskk> DanielRichman: hehe thanks
[20:16] <Randomskk> all that spare pcb space, may as well put something on it
[20:16] <Randomskk> the ghost is on the bottom layer :X
[20:16] <jcoxon> Randomskk, i've ordered a new ntx2 so i guess thats a start
[20:22] <RocketBoy> DanielRichman: I gave sbasuita the tracking no - anyway it has been delivered today as it says "Your item with reference BRxxxxxxxxGB was delivered from our READING Delivery Office on 18/12/09"
[20:22] <DanielRichman> ping sbasuita,
[20:22] <DanielRichman> sbasuita, I visited both the office and the parcel drop off place with steve; we opened a few laptop parcels but found no balloons. Can you check what the tracking page says?
[20:23] <Randomskk> DanielRichman: last day of school?
[20:23] <DanielRichman> Randomskk, yep
[20:23] <Randomskk> eep
[20:25] <DanielRichman> Signature Time: 10:03:00GMT 18/12/09
[20:25] <DanielRichman> ugh; that's like, 30mins after I visited there
[20:26] <Randomskk> ah
[20:26] <Randomskk> lol better go to school tomorrow morning :P
[20:26] <DanielRichman> No. Way.
[20:26] <Randomskk> haha
[20:26] <DanielRichman> there's like, 1mm of snow out there!
[20:26] <DanielRichman> I could get hurt!
[20:26] <Randomskk> pfft I used to go to school every saturday morning for hours for seven years
[20:26] <DanielRichman> We used to have saturday school; that's gone now
[20:27] <Randomskk> always the last thing I wanted to be doing when I woke up on saturday morning
[20:27] <Randomskk> okay saturday school is worse
[20:27] <Randomskk> this was to go fencing and then later to teach kids fencing
[20:27] <DanielRichman> http://photos-b.ak.fbcdn.net/hphotos-ak-snc3/hs039.snc3/12652_206961563259_162002743259_2977139_7107208_n.jpg
[20:28] <Randomskk> lul
[20:29] <RocketBoy> DanielRichman: do you know who the signature is
[20:29] <DanielRichman> RocketBoy, I have absolutely no clue :)
[20:30] <RocketBoy> looks like E Connyle
[20:32] <DanielRichman> Since the printed name is EVE that would make sense
[20:33] <DanielRichman> I'm amased you managed to read that signature; it's a total mess here
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[20:36] <RocketBoy> (tis upside down)
[20:39] <RocketBoy> rebooting
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[20:50] <jcoxon> i'm not sure i can bring myself to start from scratch with dl-fldigi
[20:50] <jcoxon> the plan was to do a version 2 and make everything much more clean
[20:50] <jcoxon> but going through the code - i forgot how much work we did on it!
[20:51] <DanielRichman> if edmoore's making his own rtty decoder then your "version two" could be that
[20:52] <RocketBoy> doesn't it just read the recived characters and pload them to the server (plus the callsign template stuff?)
[20:52] <jcoxon> true, but i think that he is struggling to make it real-time deocding
[20:52] <DanielRichman> Hmm.
[20:52] <DanielRichman> Perhaps if you do make a version 2
[20:52] <DanielRichman> You could go and overhaul the whole tracker
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[20:53] <DanielRichman> since HTTP doesn't lend itself to streaming listening data
[20:53] <jcoxon> RocketBoy, well yes but it also grabs xmls about hte payload, decodes them, has all the graphical changes, checks the strings then uploads them
[20:53] <DanielRichman> Doesn't fldigi only upload when the CRC is ok?
[20:53] <jcoxon> it doesn't check the CRC
[20:53] <DanielRichman> hmm ok
[20:54] <jcoxon> it passes them whatever, thats the servers job -the theory is that its best to get all teh data onto the server
[20:54] <RocketBoy> that makes sense - otherwise potentially useful data would get lost
[20:54] <DanielRichman> Indeed
[20:54] <jcoxon> yeah
[20:54] <DanielRichman> I thought that it was discarding based on the Checksum though
[20:54] <jcoxon> you don't actually need a checksum
[20:54] <jcoxon> the server is, not dl-fldigi
[20:55] <DanielRichman> Ok. Perhaps you could, for version 2, modify the decoder and send the raw output up, bit by bit, so that if a start bit gets skipped the server can detect and correct that
[20:55] <DanielRichman> Synch the clocks on all the listeners
[20:55] <jcoxon> - perhaps this is a far bigger job - something for the summer
[20:55] <DanielRichman> Produce a % value for each bit rather than a 0 or a 1
[20:55] <DanielRichman> then average, factoring in distance from payload
[20:56] <DanielRichman> The latter ideas would be easier to implement with edmoore's decoder, I imagine
[20:56] <jcoxon> hehe thats far too complicated
[20:56] <DanielRichman> pssh :P
[20:56] <jcoxon> the whole listening network relies upon we have a number of receivers, brute numbers increase our accuracy
[20:56] <jcoxon> as in someone will get a clean string
[20:56] <Randomskk> but not optimally - we still need at least one person to get the entire string okay
[20:57] <Randomskk> theoretically we could have it to having many people means each person only needs to get a digit or two
[20:57] <DanielRichman> Yes, we should only need a majority to get a correct byte, for each byte in turn
[20:57] <jcoxon> but the amount of work to implment that for the additional benefit just isn't worth it
[20:57] <RocketBoy> with a checkum there are many possible correct solutions - so like monkeys and keyboards someone may get a sring that passes the checksum but is wrong
[20:58] <Randomskk> yea, we'd need a better checksum
[20:58] <Randomskk> equally someone could get the checksum digit wrong
[20:58] <jcoxon> i think people are falling into a trap here
[20:58] <DanielRichman> Indeed. A more robust checksum would be great
[20:58] <jcoxon> the whole listening concept really relies on a number of listeners and a lot of strings being passed
[20:59] <RocketBoy> sure - but the chances of the crc being hit rather than the data is much lower - and worst case you have lost a good string
[20:59] <jcoxon> as in one dodgey string out of 20 isn't an issue
[20:59] <Randomskk> we usually end up with like 3 or 4 listeners though :P
[20:59] <DanielRichman> I don't think that is the way you should be taking the listening concept
[20:59] <jcoxon> but that was why we implmented it
[20:59] <RocketBoy> with a crc the chances of a corrupt string getting through are very low
[21:00] <jcoxon> the whole setup grew out of this concept
[21:00] <DanielRichman> But that doesn't mean that you have to stick to the original concept
[21:00] <Randomskk> I still think the concept is good, better than one really powerful listening station
[21:00] <jcoxon> i personally think its a lot easier to kick 2 or 3 people to listen in then a lot of these additions
[21:00] <jcoxon> the last flight is a poor example
[21:00] <Randomskk> true
[21:00] <jcoxon> but the last icarus flight was a great example
[21:00] <Randomskk> also the last flight went over the horizon for most of the UK :P
[21:00] <jcoxon> a completely clean flight
[21:02] <RocketBoy> implementing a CRC would be only a little more difficult than the checksum - there are quite a few examples out there
[21:02] <Randomskk> once I get a bit further with my quadcopter I think I'll whip up a flight computer, should be fun
[21:03] <Randomskk> I think cusf are planning to launch a few balloons to train new people, with a load of arduino trackers on, and lots of people attending the launch and tracking, to see how it's all done
[21:03] <Randomskk> or at least, that was the plan.
[21:03] <Randomskk> the "build an arduino tracker" session was fun but no one actually built a basic tracker
[21:05] <RocketBoy> yeah - i guess the CUSF folk need to pass the baton on to some extent
[21:05] <Randomskk> I think they have a few years left in them :P
[21:06] <jcoxon> http://www.nongnu.org/avr-libc/user-manual/group__util__crc.html
[21:10] <RocketBoy> yeah - thats a bitwise CRC - CRC16 could just be put as 4 hex digits at the end rather than 2 for the checksum
[21:11] <RocketBoy> there is bytewise crc16 code about as well - it uses a table to speed things up - but the bitwise code is simpler
[21:12] <RocketBoy> ccitt crc16 is probably the best one to use
[21:13] <jcoxon> so with a CRC, you take the string, calculate the crc, add it to the string and transmit
[21:13] <jcoxon> as the other end you compare the crc to string+crc and that should equal 0
[21:14] <RocketBoy> Randomskk: sorry I didn't mean to suggest that they were getting old - but I guess they may leave Cambridge over time
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[21:17] <RocketBoy> jcoxon: is there any C in the server - or is it all PHP?
[21:18] <jcoxon> RocketBoy, that i don't know
[21:19] <jcoxon> i think its just php
[21:19] <RocketBoy> jcoxon: yes - it would just replace the checksum calculation (i.e. run it over the stuff between the $$ and the *) and then add the 4 crc digits rather than the 2 checksum digits
[21:19] <jcoxon> i've never seen any C in their
[21:20] <jcoxon> and so would be more accurate at detecting errors due to the uniquness
[21:20] <jcoxon> rather then the number of combinations with a XOR checksum
[21:20] <RocketBoy> yes - much more accurate
[21:20] <Randomskk> hmm
[21:21] <Randomskk> $54 for 5 copies of my PCB from batchpcb, in a few months, with usps cheap shipping...
[21:22] <Randomskk> or $150 for approx 25 copies from goldphoenix, in about a month, with fedex
[21:22] <Randomskk> I need 4 copies, with one or two spare.
[21:22] <Randomskk> D:
[21:22] <Randomskk> price breaks suck
[21:23] <Randomskk> GP also means I get custom soldermask, but I'd have to pay another $20 to get the bottom silkscreen.
[21:23] <jcoxon> RocketBoy, i'm happy to try out CRC16 on BH4
[21:23] <RocketBoy> a step beyong crc would be to calculate a FEC block (e.g reed solomon or turbo code) and put it on the end
[21:24] <RocketBoy> that way you could correct any errors
[21:24] <RocketBoy> personally I suggest CRC as the next step
[21:25] <jcoxon> yeah one step at a time
[21:29] <jcoxon> will chat with rob about implmenting crc16 decoding on the server
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[21:31] <russss> you can probably correct a small amount of errors with the CRC by brute-forcing it
[21:31] <russss> but your demodulator needs to allocate confidence levels for each bit
[21:32] <russss> the code I'm hacking to demodulate air traffic control messages does that (not very well though, that's why I'm hacking it)
[21:32] <DanielRichman> russss, you could factor in the fact that the messages always follow a pattern, eg, you know where there should be $s and numbers, and therefore guess bit flips better
[21:32] <russss> yeah
[21:33] <russss> you know it's all got to be standard ascii too, which helps
[21:33] <DanielRichman> But really to start doing that you have to consider start/stop bits and whether they've flipped
[21:33] <russss> true
[21:33] <DanielRichman> .. one "enthusiast" has managed to cram over $25,000 worth of gear into a $500 car. The car is rigged for just about every conceivable communications band including FM, UHF, VHF, HF, and WTF.
[21:33] <russss> heh yeah I saw that
[21:33] <DanielRichman> http://tech.slashdot.org/story/09/12/18/2016201/25000-of-Communications-Gear-In-a-500-Car
[21:33] <russss> it's a little excessive.
[21:34] <Randomskk> but like, an ft817 can do all those modes
[21:34] <DanielRichman> A little excessive?
[21:34] <russss> yeah.
[21:35] <Randomskk> jeeez look at the antennas on the thing
[21:35] <Randomskk> it's bristling with them
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[21:41] <icez> that makes the car in back to the future look like crap
[21:44] <SpeedEvil> Downside:
[21:44] <SpeedEvil> It can't do 88MPH due to drag from antennas.
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[21:51] <JohnTeddy> Anyone have advice/guide on making an amateur gyro for a weather balloon? the payload is a styrofoam beer cooler. I want there to be parallel shifts only with the payload, so the camera footage is stable/quality.
[21:52] <JohnTeddy> Also, advice for length of rope, from (balloon)<>(parachute)<>payload ... it seems like it is has potential to be more stable on the way up, and far less stable on the way down.
[21:53] <JohnTeddy> Is it advisable for stability on the way down, to use all 4 pounds of weight allowed by the FAA.
[21:53] <jcoxon> JohnTeddy, well you're ascent is slower then your descent
[21:53] <JohnTeddy> So we have more tension on the line between the payload and the parachute, so the payload will be more stable.
[21:53] <jcoxon> so i'd focus on that
[21:53] <JohnTeddy> jcoxon: I want to make both stable if possible.
[21:53] <jcoxon> descent is much more unstable imaging wise
[21:53] <JohnTeddy> at least relatively more
[21:54] <JohnTeddy> jcoxon: Is there a way to help mitigate that?
[21:54] <jcoxon> okay so there are a number of things:
[21:54] <JohnTeddy> If I have 1 pound payload (and a camera is in the payload), it will be less stable than a 4 pound payload right?
[21:55] <JohnTeddy> Since the 4 pound payload will put more tension on the line to the parachute. Where if there is little tension, it allows the payload to flop around more easily.
[21:55] <JohnTeddy> That is my thought anyway, I'm not sure if practically that would work.
[21:55] <jcoxon> :-)
[21:56] <jcoxon> i wouldn't add weight just to improve stability
[21:56] <JohnTeddy> But do you agree it would improve stability?
[21:56] <JohnTeddy> relatively
[21:56] <jcoxon> usually the general consensus is to go light as possible
[21:56] <Randomskk> http://www.sparkfun.com/commerce/product_info.php?products_id=9530 could go nicely on a balloon
[21:56] <jcoxon> i think it would add slightly more stability
[21:56] <Randomskk> pcb the size of a microsd socket with a micro on the other side, send it shit over serial and it saves it to the card
[21:56] <jcoxon> i'd also use a long line on hte payload
[21:57] <jcoxon> to improve stablility
[21:57] <JohnTeddy> jcoxon: Our primary goal is to go as high as possible (I believe we'll get over 150k feet perhaps), and to have great image data.
[21:57] <JohnTeddy> yea, I was going to ask about the length
[21:57] <JohnTeddy> 5 feet from parachute<>balloon ?
[21:57] <jcoxon> JohnTeddy, well if you want to go as high as possible you want to be as light as possible
[21:57] <JohnTeddy> and 3 feet from parachute<>payload?
[21:58] <JohnTeddy> jcoxon: I see.
[21:58] <jcoxon> as you use less helium
[21:58] <JohnTeddy> jcoxon: What about making the line stiff between the parachute<>payload
[21:58] <JohnTeddy> So the line always has tension.
[21:59] <jcoxon> hmmm JohnTeddy i think your two aims aren't really going to match
[21:59] <JohnTeddy> yea, I'm seeing that
[21:59] <jcoxon> but i think you'll be suprised how good your images are with no attempts to stabilise
[21:59] <jcoxon> remember there is good light up at altitude
[21:59] <JohnTeddy> There might be a way to keep the payload light and get high altitude, but at the same time get stabilisation on the way down.
[22:01] <JohnTeddy> jcoxon: Have people used home made gyros before?
[22:01] <jcoxon> not to my knowledge
[22:01] <jcoxon> a couple of people are looking at active stabilisation
[22:01] <jcoxon> such as reaction wheels
[22:02] <jcoxon> as they plan to mount a telescope
[22:02] <jcoxon> also as you get higher the payload doesn't swing as much
[22:05] <jcoxon> also as you descend your parachute doesn't really work till much later
[22:05] <jcoxon> so the initial descent is very chaotic
[22:06] <jcoxon> i'm not an expert on this
[22:06] <jcoxon> there are a couple of regulars on here that might be able to expand on some of the details
[22:06] <JohnTeddy> I see, that makes sense.
[22:07] <JohnTeddy> Because the air isn't dense up there.
[22:07] <JohnTeddy> So that brings aerodynamics into the picture.
[22:09] <JohnTeddy> jcoxon: Is there data on how high people typically get, with a certain balloon size, a certain payload weight, and a certain cubic footage of helium?
[22:09] <jcoxon> yes
[22:09] <JohnTeddy> We have less than 2 pound payload, 800gram weather balloon, and we're not sure about how much helium.
[22:09] <jcoxon> have you seen: http://ukhas.org.uk/
[22:10] <jcoxon> regarding balloons and helium:
[22:10] <jcoxon> http://ukhas.org.uk/guides:balloon_data
[22:10] <JohnTeddy> no, thanks great
[22:10] <jcoxon> with an 800g and a 900g (2lb) payload you could get 25 - 30km altitude perhaps
[22:11] <Randomskk> jcoxon: was it you who ordered PCBs from seeed studio?
[22:11] <jcoxon> Randomskk, yes
[22:11] <Randomskk> any issues?
[22:11] <jcoxon> Randomskk, no
[22:11] <Randomskk> seems like they might work out best for doing a run of 5
[22:11] <jcoxon> very pleased especially with cost
[22:12] <jcoxon> considering i got 5 for $18
[22:12] <Randomskk> but last time I used seeed studio half my silkscreen got cut :/
[22:12] <Randomskk> yea
[22:12] <JohnTeddy> So weight is very important
[22:12] <jcoxon> JohnTeddy, oh yes, basically to get high you want to use as little helium as possible
[22:13] <JohnTeddy> jcoxon: So how much free lift do you recommend?
[22:13] <jcoxon> as the balloon will burst at a set volume
[22:13] <jcoxon> so if you use less helium you'll get higher
[22:13] <JohnTeddy> jcoxon: If we "stretch" the balloon, meaning fill it up with air, and let it deflate, will that help? or just harm it?
[22:13] <jcoxon> JohnTeddy, that'll probably harm it
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[22:13] <JohnTeddy> figured
[22:13] <jcoxon> those balloons are very stretchy
[22:14] <jcoxon> JohnTeddy, it depends really on your weather
[22:14] <jcoxon> oh that spreadsheet is here: http://www.srcf.ucam.org/~cuspaceflight/calc/
[22:15] <jcoxon> JohnTeddy, basically you want to go up as slow as possible but you don't want to be blown too far
[22:15] <tonyb486> How do you know what diameter you want to use?
[22:15] <tonyb486> I mean, for an estimation
[22:15] <jcoxon> its more the other way round
[22:15] <jcoxon> so play with the figures and see the results
[22:15] <jcoxon> and decides what you want
[22:16] <JohnTeddy> jcoxon: How far do people typically have to travel to get their balloons?
[22:16] <jcoxon> e.g. a diameter of 2m, 800g balloon, 900g payload
[22:16] <jcoxon> JohnTeddy, depends where you are based
[22:16] <tonyb486> We're on a island. long island.
[22:16] <jcoxon> in the UK we had a flight on monday that went 420km :-p
[22:16] <JohnTeddy> If we want maximum alititude, and we do 20 feet a minute ascension, will we have to drive 300 miles?
[22:16] <jcoxon> but other flights can go 10-20km
[22:17] <JohnTeddy> damn, 420km
[22:17] <JohnTeddy> jcoxon: How high did it get?
[22:17] <jcoxon> but that was a long duration flight
[22:17] <jcoxon> just as an example
[22:17] <jcoxon> its all to do with weather
[22:17] <JohnTeddy> So fly in no wind
[22:17] <tonyb486> we're going for cheap-as-hell flight
[22:17] <jcoxon> so if you get a period of low wind it'll go no where
[22:17] <jcoxon> have a play with this as well : http://www.srcf.ucam.org/~cuspaceflight/predict/index.php
[22:17] <JohnTeddy> yea, tonyb486 is in the same group
[22:17] <jcoxon> this is a flight predictor
[22:18] <tonyb486> I played with a different flight predictor, it made a cool kml file
[22:18] <jcoxon> it uses weather data to calculate a flight
[22:18] <JohnTeddy> We spent $65 so far, and we have an 800 gram balloon, styrofoam beer cooler, disposable phone, batteries, and camera.
[22:18] <JohnTeddy> We only need a parachute, and helium at this point.
[22:18] <jcoxon> my advice is only launch when the weather is good
[22:18] <JohnTeddy> This is our first flight
[22:18] <jcoxon> don't risk it especially if the predictors say it'll land in the sea or a very long way away
[22:19] <tonyb486> being on an island we are surrounded by water. which I'd assume is bad.
[22:19] <jcoxon> tonyb486, it makes it harder
[22:19] <tonyb486> we have to go to new jersey or something, I guess
[22:19] <jcoxon> most of the people here are based on an island as well
[22:19] <jcoxon> so we've had a couple land in the sea
[22:19] <JohnTeddy> tonyb486: yea, we're going to Jersey
[22:20] <JohnTeddy> Is what we talked about Wednesday, so we'll have 100 mile buffer
[22:20] <tonyb486> JohnTeddy: Are we doing it over the winter break?
[22:20] <JohnTeddy> instead of 15
[22:20] <tonyb486> (i.e. soon)
[22:20] <JohnTeddy> tonyb486: Well as jcoxon says, it all depends on the weather.
[22:20] <tonyb486> Yeah
[22:20] <JohnTeddy> We're going to get nailed with a snow storm this weekend supposedly
[22:20] <tonyb486> Yeah
[22:20] <JohnTeddy> Once we have everything ready, we'll just wait for a Sat/SUn with less than 5mph wind, and go that day I suppose.
[22:20] <tonyb486> Does the temperature make much of a difference
[22:21] <JohnTeddy> jcoxon: temp?
[22:21] <jcoxon> not really
[22:22] <JohnTeddy> jcoxon: If we put a handwarmer packet on our camera/phone, will we have problems with temperature at high altitudes of electronics failure?
[22:22] <jcoxon> considering after about 10mins of flight the external temp will be -5 or -10
[22:22] <tonyb486> celsius?
[22:22] <jcoxon> it will get cold, very cold but we haven't ever had any issues with the cold
[22:22] <jcoxon> yeah
[22:22] <tonyb486> its -2 now though
[22:22] <jcoxon> oh right well it'll go down to -50 or so
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[22:23] <jcoxon> but if you seal up your box well, and its styrofoam it'll be fine
[22:23] <JohnTeddy> jcoxon: Have you guys experienced electronics failures because of cold?
[22:23] <SpeedEvil> maybe
[22:23] <jcoxon> only once in memory on a long duration flight
[22:23] <SpeedEvil> there were some GPS oddities
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[22:23] <jcoxon> but thats not a normal flight
[22:23] <JohnTeddy> Any of you used aprs?
[22:23] <JohnTeddy> Or do you stick with a cheap disposable cell phone?
[22:24] <JohnTeddy> or what
[22:24] <SpeedEvil> aprs illegal in uk
[22:24] <jcoxon> your electronics will generate quite a bit of heat
[22:24] <JohnTeddy> I see.
[22:24] <Randomskk> well, on a balloon anyway
[22:24] <JohnTeddy> tonyb486: Is aprs illegal in the states?
[22:24] <tonyb486> I don't think so
[22:24] <SpeedEvil> GPS = microcontroller + 433MHz i0mW transmitter
[22:24] <jcoxon> SpeedEvil, well ithe freqs are illigal in the UK
[22:24] <tonyb486> I think you need a HAM license
[22:24] <SpeedEvil> 10mW
[22:24] <jcoxon> nah its fine in the US
[22:24] <tonyb486> Like a 900mhz radio or something
[22:24] <jcoxon> balloons helped develope the APRS system
[22:24] <SpeedEvil> and 50bps
[22:24] <jcoxon> but you'll need a ham radio
[22:24] <Randomskk> can't do amateur transmissions on any kind of aircraft in the UK
[22:24] <JohnTeddy> We have access to that.
[22:25] <Randomskk> jcoxon: shame really, aprs would solve the distributed listener problem nicely
[22:25] <jcoxon> Randomskk, oh completely
[22:26] <jcoxon> would have taken that route a long time ago :p
[22:26] <jcoxon> ballooning in the UK would be completely different :-p
[22:26] <JohnTeddy> jcoxon: the rope length between the payload and the parachute/balloon will have an effect on stabilization right? Is there any data/formulas for what the optimal length is?
[22:26] <Randomskk> yay, have emailed seeedstudio the pcb then, hopefully that'l even arrive before next term
[22:26] <Randomskk> not holding out much hope for that though, will probably have it sent to cambs
[22:27] <Randomskk> I guess I'd better get around to ordering the parts from farnell now
[22:27] <Randomskk> oh wow, farnell have massively dropped prices on some things, including 44% down on STM32s
[22:27] <jcoxon> JohnTeddy, oh i'm not sure - i really wouldn't dwell on it too much
[22:28] <jcoxon> just long
[22:29] <JohnTeddy> 5 feet? 10?
[22:29] <JohnTeddy> 1.5 or 3 meters?
[22:30] <jcoxon> 3m would be good
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[22:33] <JohnTeddy> jcoxon: 3 meters total? or 3m between balloon<>parachute, and 3m between parachute<>payload?
[22:33] <jcoxon> 6m in total is good
[22:33] <JohnTeddy> ok
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[22:34] <jcoxon> but as i said - its better to makesure your payload works rather then focusing on stability
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[22:34] <JohnTeddy> yea, our payload works
[22:35] <jcoxon> good good
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[22:35] <JohnTeddy> We have a disposable camera ($20) that reports GPS to use over cellular network
[22:35] <JohnTeddy> and a canon powershot 1100is, that takes a picture every second and rolls it into a motion jpeg video codec/container. (chdk)
[22:35] <JohnTeddy> an antenna for the cell phone as well
[22:35] <jcoxon> chdk is great
[22:35] <JohnTeddy> and battery backups
[22:35] <JohnTeddy> (double AA)
[22:36] <jcoxon> what batteries?
[22:36] <JohnTeddy> Although I am going to test the camera and see if we need that or not.
[22:36] <JohnTeddy> lithium ion
[22:36] <jcoxon> good
[22:36] <jcoxon> sounds all good
[22:36] <JohnTeddy> That is pretty much our payload
[22:36] <JohnTeddy> and styrofoam beer cooler
[22:36] <jcoxon> once you are above 1000m you won't get any gps data
[22:36] <jcoxon> till you land
[22:36] <JohnTeddy> paint it black (not with standard spray paint)
[22:36] <JohnTeddy> put some tin foil in it maybe
[22:36] <JohnTeddy> right
[22:37] <JohnTeddy> We're trying to find a way to dump gps data to ascii text file on the phone
[22:37] <JohnTeddy> So we get telemetry data.
[22:37] <jcoxon> oh wait - with the cellphone antenna will extend your altitude of reception
[22:37] <JohnTeddy> But our primary goal is the image data, telemetry data would be cool but not necessary.
[22:38] <jcoxon> fair enough
[22:38] <JohnTeddy> any recommended parachutes to buy?
[22:39] <jcoxon> hobby rocket suppliers sell parachutes
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[22:46] <JohnTeddy> jcoxon: What about parachute size?
[22:46] <JohnTeddy> for a 2 pound payload
[22:49] <jcoxon> http://ukhas.org.uk/guides:parachute_sizing_chart
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[22:52] <JohnTeddy> thanks
[22:56] <JohnTeddy> So ~1.5 meter parachute for a ~1kilogram payload
[22:56] <JohnTeddy> thanks a lot jcoxon, I appreciate all the help.
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[23:04] <RocketBoy> for 1Kg i'd go for about 1m or just over
[23:04] <RocketBoy> i.e. between the 2 tick lines on the chart
[23:04] <JohnTeddy> I see.
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[23:07] <Laurenceb> RocketBoy: how much power do you need to use the ISS repeater?
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[23:07] Action: Laurenceb is trying to work out how much interference you see on the 434MHz band at altitude
[23:07] <Laurenceb> I thought that might give some good clues
[23:07] <SpeedEvil> hmm
[23:08] <SpeedEvil> http://www.electronicsweekly.com/Articles/2008/06/26/44019/crfs-maps-uk-radio-environment-for-ofcom.htm
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[23:08] <SpeedEvil> If open data - it's not AIUI
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[23:14] <Laurenceb> I need to get my CC1020 eval board up and running
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[23:17] <Laurenceb> looking at the datasheet I think you can derive a 1 bit sampled baseband from the "GUASS_FILTER" register on the chipcon transceivers
[23:17] <Laurenceb> the architecture is really nice - direct downconversion then digital filtering - just a pity its too packedged up with rather lame modem hardware
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[23:20] <Laurenceb> the baseband output is sent through a comparitor then that goes into a counter thats reset and dumped into GUASS_FILTER on MODEM_CLK edges
[23:21] <Laurenceb> is you sample fast enough I think you can derive a 1 bit sampled baseband replica
[23:23] <Laurenceb> but it needs to be tried with the actual hardware...
[23:24] <RocketBoy> Laurenceb - it all depends on your antenna (steerable yagi or not) - but I think they say about 20w into x dipoles gives a reasonable range
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[23:24] <Laurenceb> oh ok, thats lower than I expected
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[23:56] <Laurenceb> interesting - assuming the ISS is interference limited, I get 50Km range with 10mw for an uplink
[23:57] <Laurenceb> but thats assuming interference sources evenly distributed over the surface
[23:57] <SpeedEvil> at 433?
[23:57] <SpeedEvil> didn't edmoore or someone do a reciever at 433 at altitude/
[23:57] <SpeedEvil> though on reflection it ended up over the sea at distance, so that's not a completely representative noise environ
[00:00] --- Sat Dec 19 2009