highaltitude.log.20080513

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[00:53] <rcaron> furan: we were getting fantastic aprs packets at 82kft. did your batteries fail?
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[01:36] <akawaka> its quiet a way from 85k to 150k :)
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[02:07] <furan> rcaron: the theory is that the antenna orientation caused a loss of 30db
[02:07] <furan> I just got into this project at the last minute
[02:07] <furan> so I can't take credit for anything but commentary and balloon handling
[02:07] <furan> but it was fun
[02:52] <rcaron> furan: interesting. antenna loss that bad is like a polarization issue. do you know any more about it (freq, ant type/orientation?)
[03:34] <furan> it was oriented pointing horizontal
[03:35] <furan> not sure about freq or type, seemed like a yagi
[03:36] <akawaka> yagi would be a strange choice for the balloon itself i think
[03:37] <akawaka> don't know enough about antennas to suggest another antenna type though
[03:37] <akawaka> we just went with a 1/4 wave antenna for our aprs
[03:37] <akawaka> whip antenna
[03:38] <rcaron> yeah, same here, except w/ a ground plane too
[03:38] <rcaron> i'd do a 1/4 wave, a dipole
[03:38] <rcaron> something generally with a wide transmission angle
[03:39] <akawaka> do you point the dipole up or down?
[03:43] <rcaron> well, the dipole points both up and down
[03:43] <rcaron> but it was vertically oriented
[03:44] <akawaka> i mean, do you place the ground plane above or below the rest of the antenna
[03:44] <akawaka> probably a stupid question
[03:44] <rcaron> irrelevent
[03:44] <akawaka> but don't fully understand how the groundplane works
[03:46] <akawaka> what do you do you use for the groundplane
[03:46] <akawaka> i'm planning on putting a 30m beacon on my next balloon, not sure what the best antenna would be
[03:46] <rcaron> for a dipole? its a copy of the radiating element
[03:47] <akawaka> oh okay, i see
[03:47] <rcaron> for a quarter wave it can be a lot of things
[03:48] <rcaron> ground radials, usually four, tilted at an angle from the perpendicular plane of the radiating element
[03:49] <akawaka> okay, thats what i was thinking of
[03:49] <rcaron> that's the standard
[03:49] <rcaron> but it can be a lot of different things
[03:50] <akawaka> how long should those radials be?
[03:50] <rcaron> approximately 1/4 wave
[03:50] <rcaron> shorter if you move more elements
[03:50] <akawaka> yeah, 1/4 would be a little big at 30meters
[03:51] <rcaron> oh, you're HF. thinking you were VHF/UHF
[03:51] <akawaka> we'll have vhf on there too, but want to try something a little more adventurous
[03:53] <rcaron> ah, i'd still run a dipole. one down from the payload, one above it to the balloon
[03:53] <rcaron> probably 24 gauge
[03:54] <rcaron> or 28 gauge
[03:54] <rcaron> its likely low power, so if properly tuned you'll be ok
[03:55] <rcaron> the higher gauge / lower diameter makes tuning more sensitive
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[08:02] <jcoxon> morning all
[08:03] <jcoxon> i have a question, what is the best connector to use to connect wires together?
[08:04] <jcoxon> DB9s are a little heavy but I'm not sure whats better
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[15:40] <edmoore> appletizer: welcome ;)
[15:40] <appletizer> hello ;)
[15:41] <edmoore> curiosity got you!
[15:41] <appletizer> so are these passive fliers or do you deal with active ones too?
[15:41] <appletizer> yeah you could say that :)
[15:41] <edmoore> the payloads?
[15:43] <appletizer> oh sorry am reading the wiki
[15:43] <appletizer> my mistake, scrape the question
[15:43] <edmoore> lol ok
[15:44] <edmoore> well this channel gets much more active in the UK evenings
[15:44] <edmoore> so maybe 4/5 hours time
[15:45] <appletizer> fair enough :)
[15:46] <edmoore> do you have an interest in electropnics?
[15:47] <appletizer> a little bit :) i did take e.e. eng
[15:47] <appletizer> yourself?
[15:47] <edmoore> ha, ok :)
[15:47] <edmoore> currently taking e-eng
[15:48] <edmoore> well, control-eng, but boils down to pretty much the same stuff
[15:48] <appletizer> oh cool :)
[15:48] <appletizer> i'd say the mech eng people might be able to better answer your question earlier =]
[15:49] <edmoore> yeah, not really our field :)
[15:50] <edmoore> I'll email my fluids supervisor, although I guess the email in return will be 'this is not examinable.... do some revision!' or something equally helpful
[15:50] <appletizer> do your pictures have GPS data encoded in them?
[15:50] <appletizer> lol
[15:50] <edmoore> nope, but all time-stamped in a sperate file
[15:50] <edmoore> we don't go near the cameras - just stick a mosfet across the shutter button and fake pressing the button every 20 seconds
[15:54] <appletizer> that's actually pretty neat :) i suppose you could extrapolate that info from the flight log anyway
[15:55] <edmoore> yeah, if we wanted to find the info out it'd be do-able
[15:55] <edmoore> there'll be a python library for it somewhere
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[16:00] <edmoore> fnoble: are you about?
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[17:11] <Cooleo> Hey All.
[17:12] <natrium42> hi
[17:13] <Cooleo> Should get my full out Weather Balloon proper launched before august, Massive delays before >.<. Stupid Exams.
[17:14] <natrium42> the crops will be high :P
[17:14] <Cooleo> What is the point in my RE GCSE tommorow?! No one cares about Religon, and when they prove god isn't real in years to come, We will look stupid, Taking a subject in things which arn't real!
[17:14] <Cooleo> Yep :)
[17:14] <natrium42> lol, so why are you taking it
[17:15] <Cooleo> No choice, Compolsry Subject in england >.<
[17:16] <natrium42> ouch
[17:16] <Cooleo> I dont mind it so much, but its 1 hour 45 mins long. And then next week, 4 Hours of Science exams then 2 hours of english :@
[17:16] <natrium42> is this high school?
[17:16] <Cooleo> Yep
[17:16] <natrium42> ah
[17:16] <Cooleo> :)
[17:16] <Cooleo> Oh well, Science is easy. If you cant do Physics, You should be shot. Its dead easy.
[17:17] <natrium42> high school physics is :P
[17:17] <Cooleo> True :P
[17:18] <Cooleo> Speed = Distance/Time. If you dont know how to do that...
[17:20] <Cooleo> Hmm.
[17:20] <Cooleo> Wish I had the cash for Helium, Got my payload sitting next to me.
[17:21] <natrium42> you could try hydrogen, if you're careful...
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[17:21] <natrium42> or maybe one of the UK guys lets you piggy-back
[17:22] <Cooleo> Hmm Yeah. But its probably more expensive to grab some tickets down to meet the UK guys then it is to buy the helium
[17:22] <natrium42> i want to try making hydrogen...
[17:22] <Cooleo> Haha :P
[17:22] <Cooleo> Fill balloons up with it, and then pop them
[17:24] <rcaron> hydrogen is complicated. you have to do nitrogen purges first and stuff
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[17:59] <Cooleo> http://www.instructables.com/id/SBVUJKYF6B7W6U5/
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[18:00] <Cooleo> Has anyone seen that? Hes made a rocket out a Soda Bottle
[18:12] <jcoxon> evening all
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[18:18] <Hiena> Good evening!
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[18:24] <Cooleo> Evening
[18:25] <Cooleo> Haha, I just tried to launch my rocket. I made a flamethrower instead of propelling it >.<
[18:26] <jcoxon> careful Cooleo, don't blow yourself up!
[18:27] <Cooleo> Nearly did :P
[18:27] <Cooleo> I tried Nail Varnish Remover, Didn't vapourise
[18:27] <Cooleo> So ill use Deodrant instead
[18:28] <Hiena> Yeah, there are more skilled peoples for this purpose here. ;)
[18:28] <Cooleo> Might make a video later :)
[18:28] <edmoore> Cooleo, RS is a free GCSE
[18:28] <edmoore> don't complain
[18:28] <Cooleo> Im doing RE, Re is the half GCSE which is compulsory
[18:28] <Cooleo> RS is the Chosen one
[18:29] <Cooleo> But yes, its boring
[18:29] <edmoore> that's what I did
[18:29] <Hiena> What are you trying to build? A liquid propellant engine?
[18:29] <Cooleo> anyhow, Im gonna go launch this rocket :)
[18:29] <Cooleo> Hiena, A small rocket :)
[18:29] <edmoore> half a GCSE, but on the CV it's still another A/A*
[18:29] <Cooleo> Haha :P
[18:29] <Cooleo> Deodrant should fuel it fine, Being it vapourises quickly and its very flammable
[18:30] <edmoore> it's got no momentum though, annoyingly
[18:30] <Hiena> Cooleo, and what are you using for oxidiser?
[18:30] <edmoore> you really need some oxidiser to call it a rocket
[18:30] <Cooleo> Oxygen :P
[18:30] <Cooleo> Im looking on Instructables at the rockets people have made
[18:30] <Hiena> Cooleo, where are you lives?
[18:31] <Cooleo> Lowestoft,Suffolk, UK
[18:31] <Hiena> Ok. I guess better if you try to make some rocket candy instead the liquid rocket engine.
[18:31] <Cooleo> Anyhow, I want to go see if Lynx is up to the test :)
[18:32] <edmoore> oh to be 16 again :p
[18:32] <jcoxon> edmoore, cause you are so old ;-)
[18:32] <edmoore> I bloody am!
[18:32] <edmoore> jcoxon: what kinds of cables to what kinds of cables?
[18:32] <jcoxon> hehe
[18:33] <Hiena> Yeah, the first time, when I set myself on fire, and made my trademark 30m fireball....
[18:33] <jcoxon> ummmmm well between say my gumstix and the telit breakout board
[18:33] <jcoxon> i'm not sure what gauge wire i've got
[18:33] <edmoore> well standard header connectors are pretty good
[18:34] <edmoore> 0.1" pitch, single or double row
[18:34] <jcoxon> as in the ones you use on a pcb say?
[18:34] <Hiena> Cooleo, read this: http://www.jamesyawn.com/rcandy/index.htm
[18:34] <edmoore> jcoxon: yes
[18:34] <jcoxon> but just left floating
[18:34] <edmoore> but actually if you want to make it inline rather than to a pcb, db9 is indeed a good call
[18:34] <jcoxon> right, yeah inline is what i want
[18:35] <Hiena> Cooleo, I use the "tamed" version this mixture as smoke mixture on the glider.
[18:37] <jcoxon> db9 are bulky :-( oh well
[18:39] <edmoore> bbl
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[18:39] <Laurenceb> hi all
[18:40] <Cooleo> Hmm, It really just made a giant flame thrower again and melted the bottle :S
[18:41] <Cooleo> Do you think isopropyl would do it?
[18:47] <Laurenceb> oh dear what are you doing?
[18:47] <Laurenceb> this sounds silly
[18:48] <Laurenceb> http://news.bbc.co.uk/1/hi/wales/north_west/7367631.stm
[18:48] <Laurenceb> ^ maybe not as silly as that
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[19:03] <Hiena> Well, well, well, looks like i have an early xmass.
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[19:35] <edmoore> Cooleo
[19:35] <edmoore> I was 16 about 5 years ago
[19:35] <edmoore> exactly 5 years ago, in fact
[19:35] <edmoore> I know how it is - when you're 16, you are invincible, and the laws of thermodynamics do not apply to you
[19:36] <edmoore> but you need a fuel and oxidiser mate, seriously
[19:37] <edmoore> and the oxidiser needs to be much more than atmospheric air, because you need a stoichiometric (exact molecule for molecule matching up of fuel oxidiser to get the most nag for the buck) mixture at much higher concentrations that you would get from just atmospheric oxygen
[19:37] <edmoore> think about it - an atmospheric air rocket engine is a jet engine, and that has enormous compressors on the front to suck air in and compress it
[19:38] <edmoore> and they have a tiny fraction of the power density of a rocket
[19:38] <edmoore> hybrid rockets are what I think you want to look at
[19:38] <edmoore> all car tuning shops sell nitrous
[19:39] <edmoore> and you can make the fuel with sugar
[19:39] <edmoore> and you will have a rocket that'll make you shit your pants
[19:40] <edmoore> shit your pants is a recognised term in thermodynamics
[19:41] <akawaka> its a recognised term in many fields
[19:42] <edmoore> not digital electronics
[19:42] <edmoore> that just makes you weep
[19:42] <edmoore> right, pizza time
[19:42] <edmoore> bbl
[19:43] <Cooleo> Just got back. LOL! Shit your pants, Must use that in my GCSE exam :P
[19:44] <Cooleo> Suposedly though I dont need an Oxydizer according to: http://www.instructables.com/id/SMQYQ44F6B7W6UP/
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[21:04] <phatmonkey> hey guys
[21:04] <phatmonkey> brb
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[21:06] <phatmonkey> hi jcoxon & Laurenceb
[21:06] <phatmonkey> you around?
[21:08] <Laurenceb> hello
[21:08] <Laurenceb> ?
[21:08] <jcoxon> hey phatmonkey
[21:10] Action: Laurenceb retreats back to the library
[21:15] <phatmonkey> hey, sorry
[21:15] <jcoxon> hey
[21:15] <phatmonkey> I'm about to colocate a server for a site I run
[21:16] <phatmonkey> and i'll probably put xen on it
[21:16] <jcoxon> oh okay
[21:16] <phatmonkey> I could set up a virtual server for ukhas
[21:16] <jcoxon> that would be great
[21:17] <jcoxon> started exams yet?
[21:17] <phatmonkey> almost... next monday!
[21:17] <jcoxon> :-)
[21:17] <phatmonkey> i'm not prepared at all really :/
[21:17] <edmoore> eeeeeeeeek!
[21:17] <jcoxon> well after they are all done its time for you to launch!
[21:20] <phatmonkey> yeah, we'll see
[21:20] <phatmonkey> i've got a busy summer ahead...
[21:20] <edmoore> no
[21:20] <edmoore> you will launch
[21:20] <edmoore> says ed
[21:20] <edmoore> who has not launched anything
[21:21] <phatmonkey> i'd like to put together a real simple payload
[21:21] <phatmonkey> just so i've done it
[21:21] <phatmonkey> all this planning and involvement and, well, I never did anything...
[21:21] <jcoxon> well the launch team, when kitted out in their new caps are always ready to launch
[21:21] <edmoore> but only when they have caps
[21:21] <jcoxon> phatmonkey, hehe you were here with me in the beginning
[21:21] <edmoore> because caps make all the difference
[21:21] <jcoxon> yeah i'm working on that
[21:21] <edmoore> and the launch leader gets aviators
[21:21] <edmoore> and has to talk in texan
[21:21] <jcoxon> we need to revise the logo
[21:22] <jcoxon> oh and he gets safety goggles
[21:22] <edmoore> which he wears at the same time
[21:22] <jcoxon> they can be put up on top of his head
[21:22] <jcoxon> oh i've applied to NASA for my elective next year
[21:22] <jcoxon> hopefully they should some space
[21:22] <jcoxon> have*
[21:23] <edmoore> good pun
[21:23] <jcoxon> :-)
[21:23] <jcoxon> it was slightly ruined by the need for a corection
[21:23] <jcoxon> correction*
[21:23] <jcoxon> oh dear
[21:23] <jcoxon> i'll shut upo
[21:23] <jcoxon> up*
[21:23] <jcoxon> :-p
[21:24] <Laurenceb> hello again folks
[21:24] <Laurenceb> jcoxon: good luck
[21:24] <phatmonkey> hello again!
[21:24] <Laurenceb> yo
[21:24] <jcoxon> Laurenceb, i've only emailed to see if there are still places
[21:24] <jcoxon> the application is quite long, but its the first step
[21:25] <Laurenceb> I see
[21:25] <Laurenceb> I'm bored :-(
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[21:55] <akawaka> Laurenceb: how would you go about doing afsk in software
[21:55] <akawaka> two bandpass filters?
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[22:25] <Laurenceb> akawaka: local oscillator
[22:27] <Laurenceb> akawaka: http://rfengineer.net/direct_conversion/fig4.gif
[22:28] <Laurenceb> gtg, sorry
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[23:23] <Laurenceb> akawaka: back for a bit
[23:24] <akawaka> say i have the audio signal
[23:24] <Laurenceb> ok... so youd have two of those decoders, one for each frequency
[23:24] <Laurenceb> then take sqrt(I^2+Q^2)
[23:24] <Laurenceb> for each, and compare to give signal out
[23:26] <Laurenceb> also, low pass filter the diference and use it to adjust the local oscillator, tracking the signal
[23:26] <akawaka> so i'm mixing the audio signal with the key frequency (and it out of phase by 90 degrees) ?
[23:26] <Laurenceb> yes
[23:27] <Laurenceb> all digitally of course
[23:27] <Laurenceb> the thing is you have to define where one bit starts and another ends
[23:27] <akawaka> what am i getting out of the comparison though?
[23:28] <Laurenceb> I was looking at a way to do this with a phase locked loop... but its a bit tricky and not sure if it will work
[23:28] <Laurenceb> thats the problem
[23:28] <Laurenceb> you have to integrate to find I and Q over fixed time steps
[23:28] <Laurenceb> ideally one time step is a bit
[23:28] <Laurenceb> in which case you need to be syncronised
[23:29] <Laurenceb> a PLL arrangement would work nicely, but youd need to be transmitting continuously
[23:30] <akawaka> okay, why not just use two bandpass filters?
[23:30] <Laurenceb> alternatively you could just oversample and look for a zero crossing
[23:30] <Laurenceb> then "simulate" the operation of a hardware UART
[23:31] <Laurenceb> this *is* two bandpass filters
[23:32] <akawaka> heh, okay
[23:33] <Laurenceb> but yes, how to actually use the output confuses me
[23:33] <Laurenceb> you could have a early, a prompt, and a late decoder
[23:35] <Laurenceb> then take |sqrt(I_t^2+Q_t^2)-sqrt((I_(t+1)^2)+(Q_(t+1))^2)|
[23:35] <Laurenceb> for the early and late decoders, and conpare
[23:36] <Laurenceb> use this to adjust the sound card sampling rate
[23:37] <Laurenceb> this is your taking the magnitude.... so I think the early and late decoders have to be 1/4 of a bit either side of the prompt decoder in that case
[23:39] <Laurenceb> so basically your decoders will "lock onto" the state where the prompt decoder is getting the data perfectly
[23:40] flowolf (n=flowolf@unaffiliated/flowolf) left irc: "Leaving"
[23:42] <Laurenceb> any you have a bit in -> bit out device...
[23:43] <Laurenceb> then you need a way to send packets through it, probably by having a packet header, then imagine sticking your bit stream into a correlator, to find packets
[23:45] <rcaron> akawaka: there are plenty of afsk software packages around. are you reinventing the wheel?
[23:47] <akawaka> rcaron: in some ways yeah
[23:47] <akawaka> but have an interest in knowing how it works
[23:47] <akawaka> and eventually doing it on a microcontroller
[23:47] <akawaka> Laurenceb: looks like there is usually a preamble before and after the data
[23:47] <akawaka> uh pre-/post-amble
[23:48] <Laurenceb> http://www.sparkfun.com/commerce/images/TrackingResults.jpg
[23:48] <rcaron> understandable. note that there are PIC and AVR afsk/packet decoders around already
[23:48] <Laurenceb> ^ thats actually a good illustration
[23:48] <akawaka> rcaron: got any links?
[23:48] <Laurenceb> L=late, E=early,P=prompt
[23:49] <Laurenceb> you can see that the prompt signal is twice the size of the early and late
[23:49] <rcaron> akawaka: on a different computer i do. i really need to syncronize my bookmarks. but a quick google of aprs and avr got me plenty
[23:50] <Laurenceb> thats a bit different as its spread spectrum, wheras my idea was to look at changes from one time step to the next
[23:51] <Laurenceb> so a correctly syncronised decoder will see 0,1,1,0,0,1,0,1 ect
[23:51] <Laurenceb> ie large changes from one bit to the next
[23:52] <Laurenceb> wheras if its out of sync not as much
[23:52] <Laurenceb> - not as much change from one time step to the next
[00:00] --- Wed May 14 2008