highaltitude.log.20140106

[00:00] <mfa298> In theory you should be able to work out the shift. With the typical deviation it should be 2KHz/V. If you work out the difference between high and low voltages you can work out the shift.
[00:01] <MLow> is there any advantage to using a wide shift?
[00:01] <mfa298> you need wider shifts for higher baudrates
[00:02] <MLow> hm
[00:02] <MLow> but as far as 50 baud is concerned
[00:03] <mfa298> shouldn't make any difference for 50baud
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[00:03] <mfa298> shift needs to be >= baud
[00:05] <MLow> 5v arduino doesnt seem to have enough granularity in pwm(not sure if thats the word) to get exact
[00:08] <SpeedEvil> http://en.wikipedia.org/wiki/Hedon must be an awesome place.
[00:08] <mfa298> you can stick in a series resistor between the arduino and ntx2b to get a better granularity
[00:09] <mfa298> (there's a 100K resistor internally between txd and gnd in the ntx2b so work it out from there)
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[00:11] <MLow> AFK in DL-FLDIGI seems to be broken or something, it just drifts to the left until it cant decode
[00:11] <MLow> AFC*
[00:12] <mfa298> ntx2b datasheet recommends a 68K series resistor for 5V logic (which would probably give 0-3v at the ntx2 input)
[00:13] <mfa298> I've not had an issue with AFC (although with no signal to follow it will do odd things)
[00:13] <MLow> trying out 300 baud
[00:13] <MLow> 600hz shift
[00:14] <MLow> or as close as i can get it
[00:14] <MLow> decodes perfectly fine but AFC drifts slowly to the left until it doesnt decode
[00:14] <daveake> Is your shift correct?
[00:14] <daveake> check it at 50 baud
[00:15] <MLow> k
[00:16] <daveake> Personally I wouldn't do the 68k thing ... that's leaving the input impedance quite high hence liable to pick up noise
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[00:17] <MLow> AFC seems to work fine at 50 baud
[00:17] <mfa298> you need to adjust the receive filter bandwidth in dl-fldigi for higher baud rates
[00:18] <daveake> yeah it /should/ auto-adjust but you may need to do it manually
[00:19] <MLow> hm?
[00:19] <mfa298> go into the rtty settings
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[00:19] <mfa298> at the bottom there's a slider probably set to 68
[00:20] <mfa298> change it to at least match the baud rate
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[00:21] <MLow> yes and auto checked
[00:21] <MLow> or more?
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[00:21] <mfa298> if auto is checked you should be ok (it will match the baud rate set)
[00:23] <MLow> cant do small shifts accurately
[00:24] <mfa298> if you're trying different baud rates it might be worth start at 50baud and work your way up (100/300/600) and see how well they work. Timing can be a bit more critical for higher baudrates
[00:24] <daveake> I've found dl-fldigi AFC very good with the higher baud rates. It can cope with a much more rapid change in rx frequencies
[00:24] <MLow> i can get 800 super accurate
[00:24] <MLow> 600 even
[00:24] <MLow> 425 is off a bit
[00:24] <mfa298> and unless you're doing ssdv there's probably not much need for 600baud
[00:25] <MLow> well im just testing the radio
[00:26] <MLow> and my decode setup which will be mobile and stationary
[00:27] <MLow> s/n is something i want high?
[00:27] <MLow> thats signal to noise ratio?
[00:29] <daveake> yes and yes. If it isn't high for a local tx then something's wrong
[00:29] <mfa298> for the stable dl-fldigi then 20s for s/n if good
[00:30] <MLow> well, i tried several pwm values, for 425hz, and one gave higher s/n radio
[00:30] <MLow> ratio*
[00:30] <daveake> Oh, you're PWM-ing. Why?
[00:30] <MLow> just following upu's tutorial....
[00:30] <MLow> *blush*
[00:30] <daveake> Yes, but why?
[00:31] <daveake> Just that it's not needed for RTTY
[00:32] <MLow> whats the counter argument i guess then?
[00:32] <MLow> use more parts, resistors and such and 2 digital pins?
[00:32] <daveake> No you don't need 2 digital pins
[00:32] <daveake> IO was hoping that misconception was dead by now :-)
[00:33] <daveake> Yes you need to set the shift with resistors rather than s/w
[00:33] <SpeedEvil> 25 And the Lord spake unto the Angel that guarded the eastern gate, saying 'Where is the flaming sword that was given unto thee?'
[00:33] <SpeedEvil> 26 And the Angel said, 'I had it here only a moment ago, I must have put it down some where, forget my own head next.'
[00:33] <SpeedEvil> 27 And the Lord did not ask him again.
[00:33] <daveake> But it's simpler. Much simpler. And you don't have to worry about filtering the output
[00:33] <mfa298> with my pwm-ing experience for domino I found working in the middle of the pwm range seemed to work better than the ends - although that was Pi PWM so might be slightly different to arduino
[00:34] <MLow> im using the very center
[00:36] <mfa298> if you're only doing RTTY then I'd probably go the resistor method. It's a lot simpler to understand.
[00:36] <mfa298> and if you want to do DominoEX with the arduino I think you need the series resistor and the value needs to be carefully chosen to get the right inter tone shift.
[00:40] <MLow> do you still have the images from CLOUDY because the website is showing none
[00:41] <daveake> No but there's a way
[00:41] <daveake> ping fsphil
[00:41] <mfa298> they disappear from the front page after a while
[00:41] <daveake> You can specify dates
[00:42] Action: fsphil googles his own code
[00:42] <daveake> lol
[00:43] <fsphil> http://ssdv.habhub.org/CLOUDY/2013-12-28
[00:43] <fsphil> there is also a partial image on the 29th
[00:44] <mfa298> damn, I was remembering the right format just got the wrong date.
[00:44] <mfa298> should have realised 4th Jan was only yesterday not last week :p
[00:44] <fsphil> I've been meaning to replace the front page on ssdv.habhub.org with instructions
[00:45] <fsphil> or a recent activity list
[00:45] <mfa298> dropdowns of callsigns and dates could be an easy way of doing it.
[00:48] <MLow> thats is really some awesome stuff man
[00:48] <MLow> ok so im playing around and still cant get 425 all that accurate
[00:48] <MLow> 600/850 is dead on though
[00:49] <MLow> would it be bad somehow to use 600hz shift and 50 baud
[00:49] <MLow> no antenna on sdr or ntx2b, 36dB s/n
[00:50] <fsphil> what I usually do is get a variable resistor and use that to find what resistance I need for whatever shift I'm using
[00:50] <mfa298> shouldnt be anything wrong with 600Hz shift for 50 baud.
[00:50] <fsphil> I nearly wrote a bad word there :)
[00:51] <MLow> hm
[00:51] <fsphil> 600Hz is a custom shift we added, but it'll work fine
[00:51] <MLow> something odd happens to my sdr when i plug an antenna into it
[00:51] <fsphil> I bet it's getting overloaded
[00:51] <MLow> it shifts up hardcore lol
[00:51] <MLow> go figure :P
[00:51] <fsphil> ah, rtl-sdr?
[00:51] <MLow> ya
[00:51] <fsphil> yea mine does that too
[00:51] <fsphil> the frequency drifts when I move it
[00:51] <MLow> i expected it, it's just funny
[00:52] <MLow> sounds funny lol
[00:52] <fsphil> it's very sensitive
[00:52] <MLow> fldigi didnt miss a bit though
[00:52] <fsphil> to temperature I suspect
[00:52] <MLow> yes but it happened when i plugged in an antenna to it
[00:52] <MLow> which for an rx is kinda odd to me, but im no radio expert
[00:53] <fsphil> it's the receiver itself drifting
[00:53] <fsphil> not the transmitter
[00:54] <MLow> right right
[00:54] <MLow> i know im just perplexed by silly things sometimes
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[00:56] <MLow> hm
[00:57] <MLow> 425hz s/n is 28, 600hz is 35
[00:57] <fsphil> is your shift exactly right?
[00:58] <fsphil> ie, is the fldigi lines matching exactly with the two lines in the signal
[00:58] <MLow> its hard to tell
[01:01] <MLow> 800hz is 33dB
[01:01] <WillTablet> My parents think hams are dodgy now because I mentioned whips :-)
[01:02] <MLow> haha
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[01:06] <MLow> 425hz http://screencloud.net/v/nK7e
[01:07] <MLow> 600hz http://screencloud.net/v/qKlD
[01:07] <MLow> 850hz http://screencloud.net/v/etVj
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[01:08] <MLow> 600hz seems to be the sweet spot
[01:08] <MLow> at least testing indoors, etc, so far
[01:09] <MLow> would love some feedback though, im just hacking through this im definitely in the weeds above my head
[01:11] <fsphil> not sure why the difference
[01:11] <fsphil> looks fine though
[01:12] <MLow> ill be sure to test more going forward, im also looking into dominoex
[01:19] <MLow> DominoEX test not going well lol
[01:20] <MLow> trying to make 175k ohm is hard
[01:24] <MLow> not nearly the same decode quality
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[01:26] <MLow> but i think this mode gets x1000 cool points, totally personal bias for bad ass sound
[01:27] <MLow> http://screencloud.net/v/vBbl
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[01:34] <Lunar_LanderB> yeah DominoEX sounds cool
[01:34] <Lunar_LanderB> RTTY as well
[01:35] <Lunar_LanderB> when I am testing the system at uni, I'm always asked about "ah are you making those spaceship sounds again?"
[01:35] <Lunar_LanderB> :P
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[01:38] <Lunar_LanderB> evening DL1SGP
[01:38] <MLow> major badass points there lol
[01:40] <gurgalof> building spaceships tha send rtty :)
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[01:45] <Lunar_LanderB> xD
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[06:48] <heathkid> faster than CW many decades ago
[06:48] <heathkid> :)
[06:50] <heathkid> October 4, 1957...
[06:53] <heathkid> great year for Chevy's... not so much for the US Space Program
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[09:01] <LeoBodnar> morning
[09:01] <qyx_> morning
[09:01] <x-f> morning
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[09:27] <MLow> morning
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[09:29] <Lunar_LanderU> morning
[09:34] <maxell> hai all
[09:34] <maxell> I mean morning
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[09:42] <MLow> so maybe i sound like a broken record, and i've googled as much as I can but i cant seem to find an explanation
[09:42] <MLow> of what baudrate rtty to choose
[09:43] <x-f> go with 50 for your first launch - more reliable
[09:43] <x-f> how many listeners do you expect?
[09:43] <MLow> me
[09:44] <x-f> :)
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[09:46] <MLow> why is 50 more reliable?
[09:48] <x-f> because it's slower, you will get successfull decodes on a longer distance and with a weaker signal
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[09:49] <MLow> ok
[09:49] <x-f> if you have many sensors and quite long telemetry string then it might be ok to use 100 or 300 baud RTTY
[09:50] <MLow> i guess it just confuses me
[09:50] <x-f> you just have to be closer
[09:50] <MLow> seems like the faster the baud it would get more chances for a decode
[09:50] <MLow> but im just learning
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[09:58] <gonzo_> as the baud rate goes up, the bandwidth to transmit it increases, so you need more transmit power to get the same signal to noise ratio
[09:59] <gonzo_> if you can't increase the power, then it has the effect of the singal strength getting weaker
[09:59] <MLow> got it
[09:59] <MLow> so lower bandwidth IE lower shift is good?
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[10:00] <gonzo_> also faster baud makes your timings in softwaer harder to do accuratly
[10:01] <gonzo_> the shift is not really important. Apart from, a wider shift means that as the signal drifts within your receiovers audio bandwidth (drift due to temp changes etc). Then the receiver sites have to retune more often to keep is auidible
[10:02] <gonzo_> the bandwidth is only affected by the baud rate. The shift has no effect
[10:03] <gonzo_> think of the two signal traces (mark and space signals) as being two separate transmissions, being keyed on and off.
[10:03] <gonzo_> As you key them faster, the width of each trace starts to get wider.
[10:04] <gonzo_> So the receiving stations must open out their decode filter widths to get that energy into the decoder (that's a simplification, but is good enough for now)
[10:05] <gurgalof> timing is easy, just use a hardware time in your MCU
[10:05] <gurgalof> but yeah faster baud takes more bandwith
[10:06] <gonzo_> as the rate goes up, and the trace spreads out. It spreads the power that you are transmitting over a wider band. So the signal seems weaker at the receive site (again, a simplification there)
[10:06] <gonzo_> gurgalof, a lot of people are using simple timing loops for the rtty timings. But I agree interrupt driven is the way to go
[10:08] <eroomde> back at work
[10:08] <eroomde> whoopeeeee
[10:09] <gonzo_> I was back last week for a couple of days. So breaking myself back into it slowly
[10:09] <gonzo_> (and boy did I need a lot of tea on those two days!)
[10:11] <gurgalof> isn't it a holiday today?
[10:13] <eroomde> not in the uk
[10:13] <eroomde> i've been on holiday for the last 2 weeks
[10:14] <gurgalof> okay, in Sweden it's a holiday today
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[10:14] <eroomde> i'm starting gently with a big farnell order for a pcb i made just before xmas
[10:15] <Steve_G0TDJ> 'Morning Guys
[10:15] <eroomde> has anyone tried the RS website today?
[10:15] <eroomde> apparently they've made fixes for 2014
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[10:25] <number10> did they fix john
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[10:51] <Joel_re> hey do you guys have any DIY recommendations for a HAB amp
[10:51] <Joel_re> or a 70cms amp I could build
[10:51] <Darkside> it would involve designing a pcb
[10:52] <Darkside> so by the time you're done, you may as well just buy a habamp
[10:53] <gurgalof> it's more fun designing your own
[10:53] <Darkside> tbh its pretty simple, with MMICs anyway
[10:53] <gurgalof> mm
[10:54] <gurgalof> almost too easy
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[10:59] <Upu> morning gurgalof
[10:59] <Upu> sent you a mail
[11:00] <gurgalof> morning
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[11:01] <gurgalof> I just saw it, I'll take 5, sending monies soon
[11:02] <Upu> ok cool thx
[11:08] <Joel_re> the PSA4-5043 seems hard to source
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[11:09] <Upu> cheers gurgalof will post today
[11:10] <gurgalof> thanks, seems like I'n not the only one ^^
[11:11] <Joel_re> Im visiting the UK for a few days next week, hoping to pickup the HAB amp or else I might be out of luck to source a preamp
[11:11] <Joel_re> shipping to here would be pretty expensive
[11:12] <Joel_re> hence I considered building one
[11:13] <Upu> where is here Joel_re ?
[11:13] <Joel_re> Upu: India
[11:13] <Upu> its not that expensive
[11:13] <Upu> £9.50 I think
[11:13] <Joel_re> Upu: and I'd have to pay some customs
[11:14] <Upu> ok
[11:14] <Upu> Sadly no SAW filters atm
[11:14] <Joel_re> its ok, I should have requested earlier
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[12:58] <cuddykid> http://www.speedtest.net/result/3211622696.png :)
[12:59] <jedas> nice
[13:01] <Joel_re> cuddykid: would you mind hosting some servers for me :P
[13:01] <Joel_re> <kidding>
[13:01] <cm13g09> cuddykid: lucky sod.....
[13:01] <cuddykid> if only that connection was here... :(
[13:02] <cm13g09> lol
[13:02] <cuddykid> on a new VPS in new york
[13:03] Action: cm13g09 feels slightly better with his 3Mbps down/1Mbps up line in the office!
[13:04] Action: mfa298 checks FTTC date: Still not been updated to 31/3/2014 (from 31/12/2013)
[13:04] <cm13g09> lol
[13:05] <cm13g09> fttc, what's that?
[13:05] <Joel_re> Fiber to the Chair
[13:05] <mfa298> all hail living in the city with an exchange only capable of 8mbps down
[13:05] <cm13g09> lol
[13:06] <cm13g09> Joel_re: i was being slightly sarcastic
[13:06] <Joel_re> me too :p
[13:06] <cm13g09> lol
[13:07] <cm13g09> http://www.samknows.com/broadband/exchange/EAARD is our local exchange
[13:08] <Lunar_LanderU> cuddykid: awesome stats :)
[13:08] <cm13g09> cuddykid: presumably a Windows VPS?
[13:08] <mfa298> that looks very similar to the exchange I'm on.
[13:08] <cuddykid> cm13g09: centOS
[13:09] <cm13g09> with a GUI!?
[13:09] <cuddykid> python script
[13:09] <cuddykid> https://github.com/sivel/speedtest-cli/raw/master/speedtest_cli.py
[13:09] <cm13g09> ah!
[13:09] <cm13g09> useful!
[13:09] <cuddykid> and use --share to output link to pic
[13:10] <Lunar_LanderU> University Internet here http://www.speedtest.net/result/3211646240.png
[13:10] Nick change: KipK -> KipK_away
[13:10] <cm13g09> Lunar_LanderU: nice!
[13:10] <Lunar_LanderU> thanks :)
[13:11] Action: Joel_re bets hes on the slowest link
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[13:12] <cm13g09> Joel_re: you'll have to be doing very badly to get worse than our office....
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[13:13] <cm13g09> http://www.speedtest.net/result/3211652870.png
[13:13] <cm13g09> That's the office
[13:15] <jedas> don't wanna brag, but we've got quite good/cheap optic service here in lithuania http://www.speedtest.net/my-result/3211654924
[13:15] <cm13g09> nice
[13:16] <jedas> last year we were second in the world by this measure, now other countries has moved up
[13:16] <cm13g09> lol
[13:16] <cm13g09> should point out that home >>> office
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[13:17] <cm13g09> http://www.speedtest.net/result/3211659664.png is my home connection
[13:17] <mattbrejza> http://www.speedtest.net/my-result/3211658356
[13:17] <jedas> matt - winner :)
[13:18] <mattbrejza> annoyingly it peaks at 300 down before reducing :(
[13:18] <cuddykid> nice mattbrejza
[13:18] <mattbrejza> btw in uni
[13:18] <cm13g09> mattbrejza: but that's UoS-ternet
[13:18] <cm13g09> which had the awesome mfa298 behind it - so of course it'll be good :)
[13:18] <cuddykid> get ~80 down and ~50 up at uni most of the time
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[13:19] <fsphil> we have a 100mbit fibre connection here at the office
[13:19] <fsphil> we use it for email :)
[13:19] <cm13g09> lol
[13:20] <mattbrejza> despite the speed sometimes it just doesnt load parts of webpages :( http://i.imgur.com/Bci78hM.png
[13:20] <fsphil> bad QoS?
[13:20] <mattbrejza> also the speed graph isnt exactly constant :( http://i.imgur.com/Lrrirr3.png
[13:21] <fsphil> or no qos from the sounds of it
[13:21] <qyx_> gigabitz \o/
[13:21] <qyx_> like
[13:21] <mattbrejza> firefox doesnt do it
[13:21] <mattbrejza> http://www.speedtest.net/my-result/3211668821
[13:21] <mattbrejza> thats with firefox ^
[13:22] <qyx_> we have also in the office but that fhashy thing cannot measure it
[13:22] <qyx_> flashy
[13:22] <cuddykid> er what, 700+ upload! wow
[13:22] <mattbrejza> hmm that was a different server too, maybe the first was slower than me :P
[13:22] <cuddykid> back up the computer in no time
[13:22] <fsphil> lol
[13:23] <mattbrejza> yea changing server makes quite a difference
[13:24] <qyx_> thats the worst thing, most of the servers are slower than your connection
[13:24] <qyx_> generally i have no feeling of "fast internet"
[13:24] <mattbrejza> i uploaded a whole load of habbing pictures to flicker, didnt even see a progress bar
[13:25] <qyx_> and the cloud based services are even slower
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[13:28] <mattbrejza> im fairly sure my upload is probably faster than the hdd in my laptop...
[13:42] <cm13g09> lol
[13:48] <Joel_re> mattbrejza: incorrect MTU values could cause partial page loads
[13:48] <mattbrejza> hmm
[13:48] <mattbrejza> thats a setting of my network adapeter?
[13:48] <Lunar_LanderU> do you drive the NTX2B the same way like NTX2?
[13:48] <mattbrejza> Lunar_LanderU: yep
[13:48] <Joel_re> mattbrejza: yeah
[13:48] <Lunar_LanderU> thanks
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[13:51] <VK4HIA> UPU, are you around?
[13:51] <Upu> depends if I need to use my brain
[13:51] <VK4HIA> haha, not really.
[13:51] <VK4HIA> Wondering why the aprs data shows as HB-VK4HIA on aprs.fi
[13:52] <VK4HIA> out of intrest
[13:52] <eroomde> it thinks you're a pencil
[13:52] <eroomde> you're welcome.
[13:52] <VK4HIA> :)
[13:53] <Upu> don't mind Ed
[13:53] <Upu> Someone is importing Habitat Data to APRS
[13:53] <Upu> we know not why
[13:53] <VK4HIA> OK makes sense
[13:53] <Upu> KJ4ERJ
[13:54] <Upu> "HabHub Monitor"
[13:54] <DL1SGP> heh
[13:54] <eroomde> we could spike it to write a rude word across the USA
[13:54] <Upu> lol
[13:54] <Upu> http://aprsisce.wikidot.com/kj4erj-story
[13:54] <VK4HIA> Thx fer the info
[13:55] <VK4HIA> OK, so I use APRSISCE for my mobile IGATE, that be why. Via local digi peater its VK4HIA
[13:55] <VK4HIA> -11
[13:56] <mfa298> eroomde: you've got almost 4 months to plan how and what :p
[13:57] <eroomde> what happens in 4 months?
[13:57] <craag> April
[13:57] <mfa298> sorry almost three months
[13:58] <mfa298> end of april might be a bit late
[13:58] <eroomde> i think they nailed that last year
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[14:16] <mattbrejza> http://uk.farnell.com/cymbet/cbc012-d5c/battery-3-8v-12uah-5x5-dfn/dp/2061689
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[14:16] <mattbrejza> lipo in dfn package
[14:16] <mattbrejza> lolwut
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[14:18] <Upu> wow
[14:18] <Upu> 0.012mAh
[14:18] <Upu> btw : http://imgur.com/a/5frwe
[14:19] <Upu> testing the cell capacity atm
[14:20] <qyx_> mattbrejza: lol
[14:20] Action: Joel_re ended up soldering the ublox module wrong 3 times
[14:20] <Joel_re> but it still works :p
[14:20] Action: Upu notes that down for the returns process
[14:20] <LeoBodnar> not what I have expected
[14:20] <Upu> sadly no LeoBodnar
[14:20] <Upu> however just testing capacity atm
[14:21] <LeoBodnar> so it's 3V chemistry?
[14:21] <Upu> yep
[14:21] <Upu> drops to 2.6v under 100mA load
[14:22] <LeoBodnar> I think 3V is more natural to Li based chemistries. This is why it took awhile for 1.5v ones to appear as it needed some jumping through hoops.
[14:22] <LeoBodnar> So it makes sense for 9v = 3 x 3v
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[14:22] <Upu> yep
[14:23] <LeoBodnar> Li has very low (lowest among common metals?) electrochemical potential
[14:24] <LeoBodnar> Sad
[14:24] <LeoBodnar> AAA + hacksaw?
[14:24] <LeoBodnar> lol
[14:24] <LeoBodnar> don't
[14:24] <LeoBodnar> it stinks
[14:24] <LeoBodnar> I have tried
[14:25] <Upu> haha
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[14:34] <LeoBodnar> Laurenceb: here?
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[14:36] <Laurenceb> brb
[14:38] <Laurenceb> i have to http://i.imgur.com/gWwistu.png
[14:38] <LeoBodnar> lol
[14:39] <steveb_groove> quick question: putting together my first project soon and I'm wondering if there was an optimal angle for camea placement?
[14:39] <LeoBodnar> be diligent when doing nonsense measurements
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[14:39] <steveb_groove> ie pointing straight ahead or angled slightly towards the Earth....
[14:40] Nick change: aadamson_ -> aadamson
[14:41] <daveake> Aim it horzontally. There's normally enough swinging of the line to cover most angles
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[14:42] <steveb_groove> thanks daveake, useful info
[14:42] <eroomde> for my part i've often pointed it with about 15 degrees of downward angle
[14:42] <eroomde> but we often designed payloads to not swing about
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[14:48] Nick change: KipK_away -> KipK
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[15:16] <Laurenceb> back
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[15:16] <Laurenceb> some comedy gems
[15:16] <Laurenceb> so, we need to make a new version of <X> that is water resistant to 10m depth
[15:16] <Laurenceb> boss: can't we just used existing device in a plastic carrier bag
[15:16] <gonzo_> not sure I want to know what angle eroomde points his part
[15:17] <cm13g09> Laurenceb: brilliant ;)
[15:18] <gonzo_> at a previous company, we had to test a datalogger to 10mtrs depth. They spent ages phoning and driving around to find a 30ft swimming poole etc, that we could have for a few weeks
[15:18] <cm13g09> gonzo_: I know somebody who works for Qinetiq down at Portsmouth....
[15:19] <cm13g09> needless to say they have no problem testing stuff
[15:19] <cm13g09> to depths
[15:19] <gonzo_> I betthis was a long time ago
[15:19] <eroomde> kwintikew will happily lend your their tank for a very reasonable £100k/day
[15:19] <eroomde> someone's gotta pay for all those 100 people doing the work of 5 people
[15:20] <cm13g09> eroomde: lol
[15:20] <gonzo_> I pointed out that only the pressure mattered, so an enclosure with a pressure apl;lied would work. And that the pressure only needed a head of water. (We made pressure kit, but maintaining 1bar taked effort
[15:21] <gonzo_> si I lashed up a drum wuth a 10mtr pipe on, tie wrapped it to the fire escape and filled it from the top with a jug
[15:21] <eroomde> though gas is likely a more stressful test than water in this case, in general the working fluid is also as much a function as its pressure
[15:21] <eroomde> we've had a hell of a time sealing liquid helium, for example
[15:21] <gonzo_> total time, half a day (to make). Time spent by mgmt arsing about, months
[15:23] <gonzo_> ours was just waterproof to x mtrs. Which it would never be used at. In the same way that watches that are proofed are probably not. But it's cheaper to just refund the odd one that does get dived with
[15:24] <LeoBodnar> Laurenceb: is there a vapour-pressure equilibrium model for single-component system?
[15:25] <LeoBodnar> like VLE for Dummies book?
[15:25] <LeoBodnar> *vapour-liquid
[15:25] <eroomde> here's a fun result
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[15:26] <eroomde> within certain ranges, when designing a water-cooling system for a rocket engine, the cooling performance is better if you warm up the water before it goes into the cooling channels
[15:26] <eroomde> just because of viscosity
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[15:28] <LeoBodnar> basically, there is x kg of i-butane in plastic bag at temperature T and pressure P. Q: what is the volume of the bag?
[15:28] <Laurenceb> if its pure isobutane
[15:28] <Laurenceb> then theoretically it is either liquid or gas
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[15:28] <Laurenceb> its only when there is something else in there that it gets complex
[15:30] <KT5TK> If it can be considered as ideal gas you could use pV=nRT
[15:30] <LeoBodnar> so as T crosses over the boiling point it just collapses at once?
[15:30] <Laurenceb> yes
[15:30] <LeoBodnar> Sounds counter-intuitive
[15:31] <Laurenceb> obviously in real world it cant
[15:31] <Laurenceb> as it needs to dump or absorb the energy from somewhere
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[15:31] <LeoBodnar> Time-wise there is hysteresis due to latent heat of course
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[15:32] <LeoBodnar> but if we were to do it slowly and plot V against T at constant P (or ~P at constant T) then the transition is step-like?!
[15:33] <Laurenceb> yes
[15:34] <LeoBodnar> ok, if it blows up we are in this together
[15:34] <KT5TK> You always have the liquid and the gas component and sum them up, but usually the volume of the liquid phase is neglectible, so put it at 0
[15:35] <LeoBodnar> "always" ?
[15:35] <KT5TK> exept if you want to consider the solid phase as well
[15:37] <LeoBodnar> so any balloon always has a little bit of liquid Helium in it, right?
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[15:39] <KT5TK> Why not? You can't tell if two helium molecules are by accident so close together that they form a 2 atomic liquid.
[15:39] <KT5TK> But it's neglectible
[15:39] <Laurenceb> only if there is other gas in there
[15:39] <Laurenceb> which there will be
[15:39] <Laurenceb> i think
[15:39] <Laurenceb> im confused now
[15:40] <Laurenceb> yeah, so there will be some liquid helium
[15:40] <LeoBodnar> consider it's single-component mix
[15:40] <Laurenceb> then no
[15:41] <LeoBodnar> Right, liquid Helium at standard pressure and room temperature?
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[15:41] <Laurenceb> if tis pure He gas, then it will all be in the gas phase
[15:42] <LeoBodnar> that's better than "always"
[15:42] <Laurenceb> oh, same with impurities
[15:42] <Laurenceb> its just a case of partial pressures
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[15:42] <Laurenceb> vapour pressure of helium at room temperature is huge
[15:42] <Laurenceb> so its all going to be gas
[15:42] <LeoBodnar> yep
[15:43] <Laurenceb> it gets complex with something like water
[15:43] <LeoBodnar> It shouldn't be if there ia no air
[15:44] <Laurenceb> if there is no air, then water goes from liquid straight to gas at 100C, at 100kPa
[15:44] <LeoBodnar> It's like saying there is "always" a little bit of ice in any water
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[15:47] <LeoBodnar> Latent heat is reasonably massive
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[15:48] <LeoBodnar> So there could be a limit of how quickly gas can condense given natural convection/conduction
[15:48] <LeoBodnar> *time limit
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[15:48] <LeoBodnar> At constant pressure
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[15:49] <Laurenceb> yes
[15:49] <Laurenceb> its set by how fast the envelope reaches thermal equilib
[15:51] <LeoBodnar> needs flying
[15:51] <LeoBodnar> i-butane for winter needs I think
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[15:56] Action: SpeedEvil sighs.
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[16:06] Action: Laurenceb is playing with stm32f429i-discovery
[16:07] <Laurenceb> i need a usb otg cable to run the demo :-/
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[16:09] <Laurenceb> it needs a µGFX port
[16:09] <Laurenceb> http://www.youtube.com/watch?v=qtNLctyoxU8
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[16:12] <Carry_> Hello, I'm a Grade 12 student from Canada and I'm just wondering what it takes (time, resources, etc.) to make a functioning high altitude balloon.
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[16:13] <daveake> lots of both
[16:13] <daveake> What's grade 12 in age?
[16:13] <Carry_> 17, nearly 18
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[16:14] <Carry_> I'm looking into a project for school, thinking this would be amazing.
[16:16] <mfa298> Time depends (at least in part) on what you want to send up, how you want to track it, and what you can legally do in your country (or what legal loopholes you have to go through)
[16:16] <mattbrejza> you wouldnt be the first canadian so there a couple of people you can speak to regulation wise
[16:17] <Carry_> Alright, that's good to know.
[16:17] <Carry_> In terms of cost, is it very expensive to do something like this?
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[16:18] <mfa298> Balloon and Gas are potentially the more expensive parts - and not re-useable. Everything else should be re-useable so the cost per launch will drop if you do more than 1 launch
[16:18] <gonzo_> (if you can recover the payload)
[16:19] <Carry_> Ideally I like would recover the payload
[16:20] <mfa298> http://habhub.org/calc/ will give some idea of gas needed to lift a particular weight to a particular height (you probably want an ascent rate >5m/s)
[16:21] <Carry_> Awesome thank you, does any one have a link to a site that sells good balloons...Hell, I don't even know what makes a good balloon..
[16:21] <gonzo_> most of us have recovered and reflown payloads. But we have all lost a few to the sea/trees/etc
[16:22] <Upu> www.randomengineering.co.uk
[16:23] <mfa298> For the UK/Europe most people use http://randomaerospace.com/Random_Aerospace/Welcome.html It's possible there are some better places for Canada/USA (although the guy behind that shop appears here from time to time)
[16:24] <Upu> tbh I'd get it from the UK
[16:24] <Carry_> Okay, I'll shop around and get an idea
[16:24] <Laurenceb> http://3.bp.blogspot.com/-6iGm5rNxK9E/UspkR0q6-HI/AAAAAAAAPKw/HB2k6jtijDI/s1600/laser11.jpg
[16:24] <Upu> I understand the Americans are having issues with Scientific Sales
[16:24] <Laurenceb> interesting - laser rangefinder
[16:25] <Carry_> Well being in school I might have better access through my teachers
[16:27] <KT5TK> Laurenceb: They put a measurement pad at every single trace on the PCB
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[16:27] <Laurenceb> http://avnetexpress.avnet.com/store/em/EMController/Freescale-Semiconductor/SC540219FCR2/_/R-11083040/A-11083040/An-0?action=part&catalogId=500201&langId=-1&storeId=500201&listIndex=-1&page=1&rank=3
[16:27] <Laurenceb> uses that
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[16:29] Action: cm13g09 -> home
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[16:31] <gonzo_> you may be able to source your gas through the science dept too, if it's for a school project
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[16:34] Nick change: evilerik -> wankers
[16:34] <eroomde> oh dear
[16:35] Nick change: wankers -> bitches
[16:35] Nick change: bitches -> evilerik
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[16:35] #highaltitude: mode change '+o 6JTAAYCJH' by ChanServ!ChanServ@services.
[16:35] <eroomde> evilerik: can we avoid that in this channel
[16:35] <gonzo_> probably know as a number of otherthings, by those who know him
[16:35] Nick change: Upu -> UpuWork
[16:35] Nick change: 6JTAAYCJH -> Upu
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[16:36] <Upu> watch those nick changes please evilerik
[16:36] <mfa298> at a guess he's doing it for the benefit of another channel
[16:36] <Upu> I suspect as much
[16:36] <eroomde> yes i assume so
[16:36] <mfa298> not sure what benefit
[16:37] <gonzo_> 'ChanServ gives channel operator status...' probably sounds like the kerchunk of a pump shotgun. Intended as a warking
[16:38] <gonzo_> warning
[16:38] <UpuWork> I think its the IRC equivalent of the beers going down and the record player getting knocked off
[16:39] <gonzo_> that special knock at the door, that only comes from coppers, or neigbours suffering TVI
[16:40] <craag> lol gonzo_
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[16:44] <Laurenceb> http://diydrones.com/profiles/blogs/peta-drones-vs-hunters-hunters-win-first-round
[16:44] <Laurenceb> what the hell
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[16:48] <LeoBodnar> looks like quadcopters will soon get the same status and public opinion division as guns
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[16:50] <eroomde> it's a /names
[16:50] <eroomde> yippe
[16:51] <Laurenceb> OMG
[16:51] <Laurenceb> http://diydrones.com/profiles/blogs/merry-christmas-diy-drones
[16:51] <Laurenceb> its _that_ guy
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[16:52] <Laurenceb> mr Monroe Lee King Jr.
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[16:53] Nick change: cuddykid_ -> cuddykid
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[16:55] <eroomde> Laurenceb: you know him?
[16:55] <eroomde> I know him
[16:56] <Laurenceb> hes the maddest person on the interwebs
[16:57] <Laurenceb> resonsible for flamewarz across every topic on spacefellowship and n-prize forum
[16:57] <eroomde> i gave up with nprize because of him
[16:57] <Laurenceb> heh
[16:57] <Laurenceb> wise move
[17:03] <eroomde> he's harmless on he's on aRocket which is the annoying bit
[17:03] <eroomde> as that's meant to be slightly more serious
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[17:12] <eroomde> there are several sdr packages in debian that are maintained/QA'd by the splendidly named 'Maitland Bottoms'
[17:13] <mont> Hi All. I'm a newby to the site.
[17:13] <eroomde> greetings mont
[17:14] <mont> Thanks eroomde. I've spent most of the Christmas reading up on various near space projects and thought it was about time to join this site
[17:14] <mont> I'm planning on doing a launch in the summer for my University
[17:14] <eroomde> excellent
[17:15] <mont> But have an aweful lot of learning to do first
[17:15] <eroomde> where are you/the university, in the world?
[17:15] <mont> I'm doing a masters at London Business School
[17:15] <eroomde> wow, one of the more unusual degrees among hab flyers :)
[17:16] <mont> Yes. Not many engineers their. I'm a mechanical engineer by training, but its been over 10 years since i did any coding. Starting back to basics - real basics - Arduino Uno flashing LED stuff
[17:17] <eroomde> best place to start
[17:18] <eroomde> and this is the right place to hang out
[17:18] <LeoBodnar> what the minimum requirement for GPS frontend acquisition in SPS and length of continuous data?
[17:18] <LeoBodnar> *is
[17:18] <mont> Thanks eroomde
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[17:18] <eroomde> LeoBodnar: hmm
[17:19] <LeoBodnar> say for a single position fix
[17:19] <eroomde> so if you had a really good bandpass/lowpass filter such that you could get all the power into about 2MHz, then I gues 4MHz sample rate
[17:19] <eroomde> 1 bit ADC is enough
[17:20] <LeoBodnar> So SPI + DMA would do
[17:20] <eroomde> but you obviously have to get the rf front end exactly right in terms of gain, so that the noise is amplified to be equiprobably 1 or 0
[17:20] <eroomde> yes
[17:20] <eroomde> as for length for a position fix, if you already know the time and have the ephemeris, probably just 3-4ms
[17:21] <eroomde> if you have none of those, minutes
[17:21] <eroomde> i say 3-4ms so you can get a couple of whole frames from each bird in there
[17:21] <LeoBodnar> And minutes have to be continuous stream?
[17:21] <eroomde> yes
[17:21] <eroomde> to pick up the ephemeris
[17:21] <eroomde> which the sats send down at 50-baud
[17:22] <eroomde> you could possibly only sample for a short length of time within each 20ms bit period
[17:23] <eroomde> but the clock sync would have to be very good
[17:23] <eroomde> and the SNR would have to be good
[17:23] <eroomde> as you're basically just giving up integration time/power
[17:24] <LeoBodnar> Say if startup time is not critical can you scan for PRNs/doppler through varying datasets or it has to be the same?
[17:24] <eroomde> you could do like a soft uart and sample 4 times every bit period
[17:24] <eroomde> i'm not sure i understand the q
[17:25] <LeoBodnar> I understand that the raw data has to be exhaustively searched with varying PRNs and LO freqs
[17:25] <eroomde> yep
[17:26] <LeoBodnar> Say if you are memory limited but not MIPS limited can you do these sweeps while input data is changing for each sweep?
[17:27] <LeoBodnar> Statistically peak still be a peak
[17:27] <LeoBodnar> *will
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[17:27] <LeoBodnar> I.e. you compute FFT on live stream without storing it
[17:28] <eroomde> oh i see
[17:28] <eroomde> so keep the PRN static
[17:28] <LeoBodnar> yep
[17:28] <eroomde> and let the data convolve underneath it
[17:28] <eroomde> correlate*
[17:28] <eroomde> yes, you can do that, that's how it's often done in hardware
[17:29] <eroomde> but you still have to track, which can be complicated
[17:29] <LeoBodnar> So if signal properties do not vary significantly it should work
[17:29] <eroomde> indeed
[17:29] <Laurenceb> you can easily fix with 1ms of data
[17:29] <Laurenceb> and people have gone down to 2msps
[17:29] <Laurenceb> but i dont like it
[17:29] <Laurenceb> SSTL sell a range of receivers that are 2Msps
[17:29] <eroomde> yeah, in theory 2msps gets you 1.023MHz spreading with nyquist
[17:29] <eroomde> just
[17:30] <Laurenceb> 4 is probably a bit better
[17:30] <LeoBodnar> I am thinking of a ghetto GPS
[17:30] <Laurenceb> just a little
[17:30] <eroomde> but with dopper and everything else, it's a bit yuck
[17:30] <Laurenceb> yes
[17:30] <Laurenceb> but 1ms will work for aquisition
[17:30] <Laurenceb> i now have sim working it octave
[17:30] <Laurenceb> and it does indeed fix
[17:30] <LeoBodnar> what for cold start? or with known ephemeris?
[17:30] <eroomde> not if you want to keep a static prn
[17:31] <Laurenceb> you need to take out the satellite time and have it as another state variable
[17:31] <Laurenceb> with known ephemeris
[17:31] <Laurenceb> and rtc time
[17:31] <Laurenceb> so a few seconds time error
[17:31] <Laurenceb> and tens of Km position error
[17:31] <LeoBodnar> Right so what would be the lowest possible hardware requirement for this?
[17:31] <Laurenceb> but id probably try to use 2ms of data, dunno
[17:32] <Laurenceb> stm32f4 and se4110
[17:32] <Laurenceb> tho stm32f4 is probably overkill
[17:32] <Laurenceb> as it could do full aquisition like this is 3ms
[17:32] <Laurenceb> *in
[17:32] <LeoBodnar> say 4MSPS 1 bit 2msec?
[17:32] <eroomde> wait until you've done it before declaring it overkill :)
[17:32] <Laurenceb> yeah
[17:33] <Laurenceb> 4msps 1bit 2ms would take ~5ms to process
[17:33] <LeoBodnar> Let's say you can do any heavy data crunching on the PC minutes before launch
[17:33] <Laurenceb> doing a full search for 4 sats and the position solve
[17:33] <Laurenceb> no need
[17:33] <Laurenceb> stm32 will handle it
[17:33] <eroomde> LeoBodnar: probably just another ublox on the ground via an umbilical would be fine
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[17:33] <LeoBodnar> How about dsPIC33?
[17:33] <Laurenceb> pic32 is faster than stm32f4
[17:34] <Laurenceb> try pic32
[17:34] <eroomde> don't know enough about them
[17:34] <Willdude123> mfw I really don't understand this conversation
[17:34] <eroomde> is it really faster than an f4?
[17:34] <LeoBodnar> I never worked with MIPS
[17:34] <mont> I have a quick question. I bought a Yaesu FT-790R on eBay yesterday (hasn't arrived yet) to receive GPS data from my payload. Are there any tests I can run on the unit to test it works? Any advice much appreciated. Never ever owned a radio before.
[17:34] <eroomde> i'd be surprised
[17:34] <Laurenceb> eroomde: lol
[17:34] <Laurenceb> yeah they may have cooked the books
[17:34] <Laurenceb> on paper its 30% faster
[17:34] <eroomde> mont: see if there's a local 70cm repeater near you
[17:34] <eroomde> which is a thing that hams use to talk locally to each other
[17:35] <eroomde> you can see if you can listen to that
[17:35] <eroomde> Laurenceb: at what?
[17:35] <LeoBodnar> HW people target known performance testing scenarios and ignore real life apps
[17:35] <Laurenceb> DMIPS and coremark
[17:35] <mont> Ok. It doesnt come with an ariel though, so would it still work?
[17:35] <eroomde> get an ariel
[17:35] <mont> OK
[17:35] <eroomde> great radio though
[17:36] <eroomde> i wonder if coremark includes floating point...
[17:36] <mont> Will research them tonight. Read really great reviews about the radio. Thats why I bought it.
[17:36] <Geoff-G8DHE> Mont good starting point to find repeater info is http://www.ukrepeater.net/
[17:37] <mont> Thanks Geoff-G8DHE
[17:37] <Geoff-G8DHE> the resources section has maps and frequencies etc.
[17:37] <eroomde> mont: you could also try and listen to a HAB if one flies soon
[17:37] <mont> I'd definitely be up for that.
[17:38] <LeoBodnar> 4msps 1 bit 2 msec is 1KByte of RAM is this for real?
[17:38] <eroomde> it's fo real
[17:38] <eroomde> and you can do your correlation with xor
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[17:39] <Laurenceb> lol
[17:39] <LeoBodnar> fo shizzle
[17:39] <Laurenceb> yeah
[17:39] <Laurenceb> only you dont need correlation for this
[17:39] <Laurenceb> you need FFT
[17:39] <LeoBodnar> and bit counting with lookup tables
[17:39] <Laurenceb> thats for correlator channels
[17:39] <eroomde> yeah, FFT would be massively quicker, probably
[17:39] <Laurenceb> that can come later, but i wrote the asm for that already
[17:39] <Laurenceb> you can fit 24channels on stm32f4 :P
[17:39] <Laurenceb> at 4msps
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[17:40] <LeoBodnar> My head is going to explode, is there a calm walkthrough this?
[17:40] <Laurenceb> lol
[17:40] <eroomde> i deliberately didn't cover FFT+circular correlation in my talk
[17:40] <Laurenceb> to run a correlator, you first need to "tune it in"
[17:40] <eroomde> as i didn't want to lose everyone in the audience
[17:40] <Laurenceb> thats what the fft is for
[17:40] <eroomde> but it's much more elegant
[17:41] <Laurenceb> but if you want basic gps on a pico
[17:41] <Laurenceb> you can skip the correlators
[17:41] <eroomde> you can search all possible code phases simultaneously
[17:41] <Laurenceb> and just use 1ms of data with fft
[17:41] <Laurenceb> and speedy (<10ms) acquisition of position with ~100m error
[17:41] <eroomde> if you recall I did it with the naive exhastive search and it took minutes and i possibly even interrupted it
[17:42] <eroomde> then did it with another bit of code that took <1s
[17:42] <LeoBodnar> yep
[17:42] <eroomde> that was doing FFT+circular correlation
[17:43] <Geoff-G8DHE> Another Pano from BABSHAB at 6Kms http://360.g8dhe.net/default.php?1027
[17:44] <eroomde> xsorry i'm being sloppy
[17:44] <eroomde> circular convolution
[17:44] <LeoBodnar> So what are the other theoretical requirements? Can RTC be derived from decoding input stream with fixed doppler?
[17:44] <LeoBodnar> and PRN
[17:44] <Laurenceb> RTC uses real time clock
[17:44] <Laurenceb> at least this is how i was thinking of doing it
[17:45] <Geoff-G8DHE> !babs
[17:45] <LeoBodnar> So you are not getting it from the sat?
[17:45] <Laurenceb> you can
[17:45] <Laurenceb> but then you need the correlator to be locked
[17:45] <Laurenceb> and to do that you need to find the sat
[17:45] <LeoBodnar> freq-wise?
[17:45] <Laurenceb> yes
[17:46] <Laurenceb> so big search space
[17:46] <LeoBodnar> Ah, chicken and egg
[17:46] <Laurenceb> yeah
[17:46] <Laurenceb> so it takes a second or so to fix
[17:46] <Laurenceb> rather than milliseconds
[17:47] <LeoBodnar> second will do for a balloon
[17:47] <Laurenceb> its also more work that way :P
[17:48] <Geoff-G8DHE> ! babs
[17:48] <Laurenceb> http://i.imgur.com/XP6UK.png
[17:49] <LeoBodnar> The gap between potential solution and what is available for the moment seems massive. I.e. UBLOX needs 10-20 sec to come out of sleep and get "hot-started"
[17:49] <eroomde> i hot start shouldn't take nearly so long
[17:49] <eroomde> must be a bug
[17:49] <LeoBodnar> It tends to wake up and sit there without answering polls
[17:50] <Geoff-G8DHE> ! Babs
[17:50] <Laurenceb> with hardware acceleration and hot start it should only be limited by SNR
[17:50] <Laurenceb> so ~1ms
[17:50] <eroomde> what are you trying to do Geoff-G8DHE ?
[17:50] <LeoBodnar> Or refusing to go to sleep immediately, taking 15-20 seconds to go to sleep
[17:50] <eroomde> that's not a valid zeusbot command
[17:50] <Geoff-G8DHE> What's the command for checking when las seen ?
[17:51] <LeoBodnar> Laurenceb: have you ordered them?
[17:51] <daveake> seen
[17:51] <Geoff-G8DHE> Is there a command list somewhere ?
[17:51] <Laurenceb> LeoBodnar: i have some on my desk
[17:51] <Laurenceb> the RF probably needs improving
[17:52] <LeoBodnar> Ah
[17:52] #highaltitude: mode change '-o Upu' by ChanServ!ChanServ@services.
[17:52] <Laurenceb> i havent bothered assembling the rf side
[17:52] <Geoff-G8DHE> Yar that's it!
[17:52] <Laurenceb> just been using as stm32f4 dev board
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[17:52] <SpeedEvil> Laurenceb: The basic idea of a FFT correlation is simply that each PRN time sequence has effectively a PRN frequency spectra too. When you do a FFT, you are going from a problem in which it's unknown in position and rate to one where it's unknown in phase and frequency span.
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[17:53] <Geoff-G8DHE> iNDEED ;-)
[17:53] <SpeedEvil> Laurenceb: But phase instead of needing lots of searching is looking at the IQ values of one bin
[17:54] <SpeedEvil> Or is there something beyond 'correlate the frequency spectrum generated against PRNs'
[17:54] <LeoBodnar> Laurenceb: are you feeding it pre-recorded data stream?
[17:54] <SpeedEvil> he's got some test recorded data from last year
[17:55] <SpeedEvil> LeoBodnar: And 'memory poor' was basically how old GPSs used to do it.
[17:55] <SpeedEvil> LeoBodnar: They had one correlator (or a few).
[17:55] <LeoBodnar> Is there any sampled data online to play with
[17:55] <eroomde> it's the circular convolution bit that is the clever hack
[17:55] <eroomde> and the fact that FFTs are cheap
[17:56] <SpeedEvil> eroomde: Is it relying on the fact that in most cases, you will get 10 identical bits?
[17:56] <SpeedEvil> chips
[17:56] <SpeedEvil> err
[17:56] <SpeedEvil> what's the term
[17:56] <eroomde> i don't think so
[17:56] <eroomde> it would work with any random sequence
[17:56] <SpeedEvil> LeoBodnar: And they used to simply slew the clock around slowly enough to get a lock.
[17:57] <Laurenceb> i suspect thats how lassen iq works
[17:57] <LeoBodnar> On one channel?
[17:58] <LeoBodnar> pull actual system clock?
[17:58] <Laurenceb> i dont think so
[17:58] <Laurenceb> just channel clock
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[18:00] <LeoBodnar> Right, so SPI as frontend sampler, XOR as multiplier and lookup table as bit counter. Is that it?
[18:01] <Laurenceb> no
[18:01] <Laurenceb> you cant use lookup table
[18:01] <SpeedEvil> http://www.colorado.edu/geography/gcraft/notes/gps/gps_f.html is of use
[18:01] <Laurenceb> you dont have 4GB
[18:01] <LeoBodnar> on a byte baseis
[18:01] <LeoBodnar> *basis
[18:01] <eroomde> look up table to count bits in the xor'd result
[18:01] <Laurenceb> nooo
[18:01] <eroomde> per byte
[18:01] <Laurenceb> wheres my pastebinned code...
[18:01] <LeoBodnar> some people still use 16 bit system you know
[18:02] <SpeedEvil> LeoBodnar: you've got to recover this from very, very low SNR.
[18:02] <SpeedEvil> LeoBodnar: you need to take the incoming signal, and multiply it with the PRN code you know the satellite was transmitting to recover any data. (barring FFT)
[18:02] <eroomde> i think he knows this SpeedEvil
[18:02] <SpeedEvil> LeoBodnar: This means you need to know the offset - code phase, and doppler.
[18:02] <eroomde> the discussion is specifically about how to quickly get the optimisation score
[18:02] <SpeedEvil> k - sorry - I'm not properly awake
[18:02] <eroomde> er, correlation score
[18:03] <SpeedEvil> I should also read more scroll.
[18:03] <LeoBodnar> yeah, I am dreaming up a ghetto GPS SpeedEvil
[18:03] <SpeedEvil> LeoBodnar: Well...
[18:03] <SpeedEvil> LeoBodnar: At this point the value of that is extremely questionable.
[18:03] <SpeedEvil> LeoBodnar: yes, you can make a GPS by taking 1-5ms of samples, and slowly crunching it on a PIC - for example.
[18:04] <LeoBodnar> biggest concern is energy per fix
[18:04] <LeoBodnar> I can't make UBLOX to spend less then 10-20 seconds on a fix
[18:04] <SpeedEvil> LeoBodnar: But - if it's plausible to do so on a stm32 class processor, and get actual decent performance out of it - while still keeping stupidly low in energy - it seems like a total win
[18:05] <SpeedEvil> Especially when such massive computing power costs under a fiver.
[18:05] <LeoBodnar> indeed
[18:05] <SpeedEvil> That's basically what Laurenceb's been going on about for the last month or so - it seems possible with really cheap hardware - perhaps under a tenner total BOM - to get a 'competitive' GPS that may in some ways beat existing ones.
[18:06] <LeoBodnar> Well cost is not really such a massive factor - power consumption is
[18:06] <eroomde> for some metrics
[18:06] <mont> Cheerio folks. I'm off to make an antenna. http://widerimage.co.uk/docs/Mountain_Yagi_434_4Element.pdf
[18:06] <SpeedEvil> ^including power saving.
[18:06] <eroomde> i guess for hab it doesn't matter if the position fix is +/- 300m
[18:06] <LeoBodnar> I mean if the solution costs £15 for GPS side I am happy
[18:06] <mont> Will check back in soon
[18:07] <SpeedEvil> It - probably - can't meet power numbers of normal GPSs continuous tracking.
[18:07] <SpeedEvil> But it seems not implausible that it can at 30s or longer intervals.
[18:07] <mfa298> mont: you can probably start off with something a bit simpler if you want to
[18:07] <eroomde> afk for a bit
[18:07] <Laurenceb> http://pastie.org/8572000
[18:08] <SpeedEvil> Especially as it enables hacks like 'get 1ms of data every half hour overnight, process and transmit when sunlight is around'
[18:08] <mont> mfa298: Really?
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[18:08] <Laurenceb> http://pastie.org/8572348
[18:08] <Laurenceb> iirc thats still a bit broken
[18:08] <Laurenceb> latest code is on another machine
[18:08] <LeoBodnar> cool
[18:08] <mfa298> a simple dipole or ground plane antenna will probably do for most things, yagi's are good for hunting for a payload as they're more directional.
[18:09] <Laurenceb> line11 is 32bit count ones
[18:09] Action: SpeedEvil wonders idly about sampling the GPS signal at 1.023MHz (plus and minus a bit, I and Q)
[18:09] <LeoBodnar> SpeedEvil: exactly, GPS people seems to be obsessed with 10Hz update rate and other unnecessary bling
[18:09] <LeoBodnar> -s
[18:09] <SpeedEvil> Jitter would be an issue :)
[18:09] <mfa298> I use a variation of http://ukhas.org.uk/guides:payloadantenna on a piece of wooden dowel for listening to balloons.
[18:10] <mont> Thats really helpful
[18:10] <mont> Thanks mfa298
[18:11] <mont> Got to go for dinner. Thanks again. Will give it a shot.
[18:11] <LeoBodnar> We need a collective proof of concept
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[18:12] <SpeedEvil> All that's needed now is a lightweight laser gimbal, and we're almost there.
[18:13] <LeoBodnar> Might as well use motorised sextant
[18:13] <SpeedEvil> LeoBodnar: I mean for comms.
[18:13] <LeoBodnar> ah
[18:14] <SpeedEvil> I find the concept of a global not shitty bandwidth DIY communications network costing in principle ~100K or so hugely amusing.
[18:15] <Laurenceb> http://www.theregister.co.uk/2014/01/06/chocolate_factory_plans_oz_loon_trials_reports/
[18:15] <LeoBodnar> home run
[18:16] <SpeedEvil> yeah - that sort of thing, but
[18:16] <SpeedEvil> cheaper
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[18:49] <LeoBodnar> What determines the position accuracy in a single fix assuming SNR is sufficient? length of data?
[18:50] <eroomde> sort of
[18:50] <eroomde> yeah
[18:50] <eroomde> how well aligned your local PRN is, the more data you have, the more observations, the lower the varience, the better the estimate
[18:51] <LeoBodnar> I assume short snapshot reduces accuracy of determining precise chips edges?
[18:51] <eroomde> hence all the work on kalman filters to get the tracking as good as possible
[18:51] <eroomde> yes
[18:51] <eroomde> higher sample rate helps though
[18:51] <eroomde> to localise an edge
[18:53] <eroomde> there might be a clever sparse-sampling technique with non-constant intervals that maximises the time estimate accuracy for a given number of samples
[18:53] <eroomde> but i don't know much about sparse sampling
[19:01] <LeoBodnar> i see
[19:02] <LeoBodnar> 1ms seems like a tiny amount of data for any reasonable accuracy
[19:06] <SpeedEvil> eroomde: I was wondering about that. Problem is jitter, I guess.
[19:15] <eroomde> yes
[19:15] <eroomde> jitter on the LO is a problem
[19:16] <eroomde> for example, the RTL-SDR dongles are really crap because their xtal is some random old PoS
[19:16] <eroomde> you need a very good L.O.
[19:16] <eroomde> LeoBodnar: I suspect it might be a very small amount of data on its own
[19:17] <LeoBodnar> if signal is sampled with 4msps rate then each sample is about "75metres apart" does this define most of the accuracy limits?
[19:17] <eroomde> the spreads you see which are sort of 500m x 300m when people make a GPS are usually ms samples, and that's with a PLL that has had a bit of time to lock on
[19:17] <eroomde> no, because you can do several samples to improve accuracy
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[19:18] <eroomde> so if fifty of your samples say it's at position a and 50 say it's at a+75m, then you can say it's at a+37.5m with some confidence
[19:19] <eroomde> i don't hacve data to illustrate on this pc annoyingly, but you can definitely see if in the graphs
[19:19] <eroomde> you see a very dithered step
[19:19] <LeoBodnar> I don't agree. You need some natural gaussian noise source mixed in to make this work
[19:20] <LeoBodnar> In a noiseless system you san sample as long as you want but 10 bit will stay 10 bit forever on a constant signal
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[19:20] <eroomde> yes, it needs noise
[19:20] <eroomde> i was assuming that
[19:20] <eroomde> and there's plenty with this 1-bit ADC method of doing GPS :)
[19:20] <LeoBodnar> so LOs and ionosphere
[19:21] <LeoBodnar> haha indeed
[19:21] <eroomde> yeah, though the ionosphere is noisy in a different sense
[19:21] <eroomde> it introduces error, but it's more an offset over the sort of time periods we're considering
[19:21] <LeoBodnar> well, "wobbly" more like
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[19:23] <eroomde> the gps sets send down correction factors for that
[19:23] <eroomde> you plug them into a big polynomial
[19:23] <LeoBodnar> I admire people who can sit down and draw a spec for GPS-like system. It's not something that can go through 12.3c versions before it sort of works
[19:24] <eroomde> yeah
[19:24] <eroomde> they had to know their bananas
[19:24] <eroomde> although it has evolved a bit over the years
[19:24] <LeoBodnar> They should have a go at UKHAS binary protocol
[19:25] <eroomde> every time I study information theory I become more amazed by CLaude Shannon
[19:25] <eroomde> to have such complete insight into a field that he sort of invented as a mental exercise is incredible
[19:27] <eroomde> to keep that much state in your head, to go from funamentals to quite complicated proofs of the noisy channel coding theorem, must be like building a tower of cards on quicksand
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[19:29] <eroomde> as for the ukhas protocol, there's an information-theoretic way to do it, and then there's lots of heuristic faffery
[19:29] <eroomde> of which the latter seems quite in favour
[19:29] <eroomde> all this stuff about encodings and human readability and putting the redundant bits afterwards
[19:29] <eroomde> it's all a bit strange
[19:30] <SpeedEvil> quite
[19:31] <eroomde> you can just represent the data in ascci or whatever your heart desires, and the 'proper' way to do it is then: data --> compress --> encode --> modulate --> transmit over noisy channel --> demodulate --> decode --> decompress --> data
[19:31] <eroomde> as far as people using fldigi are concerned, that model is just
[19:31] <eroomde> data --> [black box] --> data
[19:31] <eroomde> so all this talk of human readability is all wierd
[19:32] <eroomde> it'll just spit out whatever you put in
[19:32] <SpeedEvil> There is some merit in people without the software being able to decode strings.
[19:32] <LeoBodnar> dragging such a horrible system as APRS into this is even worse if you want to know my opinion
[19:32] <eroomde> SpeedEvil: but they can't
[19:32] <eroomde> no one can decode rtty or dominex by ear
[19:32] <eroomde> you need software
[19:33] <SpeedEvil> Without the software = without an up-to-date fldigi
[19:33] <eroomde> LeoBodnar: yes i agree. better to just design something from first principles
[19:34] <eroomde> SpeedEvil: sure, but modes/standards have to start somewhere
[19:34] <SpeedEvil> I'm not disagreeing.
[19:34] <eroomde> you could have just stopped at Morse if you wanted to avoid inventing something new
[19:34] <eroomde> and there's definitely room here
[19:35] <eroomde> if you can do those stages in that flow diagram properly, shannon says you can get 13kb/s from a hab with a whip 100km to you with a whip (and decent ham radio)
[19:35] <LeoBodnar> packetised binary communication is not a shock to any modern man so why trying to avoid it like plague?
[19:35] <eroomde> so you can really blow away any of the amateur modes
[19:35] <SpeedEvil> eroomde: at 10mW?
[19:35] <eroomde> yes
[19:35] <eroomde> and 2.4kHz bandwidth
[19:35] <SpeedEvil> Sounds in the range that does not totally surprise me.
[19:36] <SpeedEvil> Given the SNR, and dialup
[19:36] <eroomde> so i think designing a mode that doesn't try to do something 20% better than dominoex or whatever, but instead says 'let's just make 2.4kbps standard' is achievable and worth a stab
[19:36] <SpeedEvil> v32
[19:36] <SpeedEvil> :)
[19:36] <eroomde> yeah basically :)
[19:38] <eroomde> it's especially good for this floaters trying to save power if you can send your message in 1s instead of 5s
[19:38] <eroomde> though to get near the limit you'd need a linear PA which is not so efficient
[19:38] <mikestir> a lot of internet of things protocols seem to have this human readable obsession as well. I'm glad it's not just me that finds that a terrible waste of channel capacity
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[19:39] <LeoBodnar> indeed
[19:39] <eroomde> crystal pulling FSK is probably the best information-rate-per-joule from a system point of view, considering the batteries and everything
[19:40] <eroomde> mikestir: well, it all gets compressed anyway usually, by the time it gets to the physical layer
[19:40] <LeoBodnar> direct PLL modulation is better, you can sleep the MCU
[19:40] <eroomde> websites tend to send their js gziped
[19:40] <SpeedEvil> http://science.slashdot.org/story/14/01/06/1340259/polar-vortex-sends-life-threatening-freeze-to-us
[19:40] <mikestir> eroomde: not in the case of a lot of the open source stuff with the cheap sub gig radios
[19:40] Action: SpeedEvil is really glad it's going there, not here.
[19:40] <eroomde> ah sure
[19:41] <eroomde> mikestir: i worked with some people in a framework 7 project
[19:41] <mikestir> here they are just sending "temperature=12" in ASCII using the radio's packet engine
[19:41] <eroomde> (EU unis and industry spending taxpayers money)
[19:41] <fsphil> I really wish IMAP had compression
[19:41] <eroomde> they had weather stations on the almps
[19:41] <eroomde> they wanted to mesh them all up to get the data back
[19:41] <eroomde> each station had wind speed, surface temp, temp 1m above surface, humidity, that kinda thing
[19:41] <eroomde> a few bytes basically
[19:41] <SpeedEvil> Are the almps in framce?
[19:42] <eroomde> they invented a Super Clever diy mesh system with low power UHF radios
[19:42] <eroomde> the best part was that instead of just sending the bytes, they
[19:42] <fsphil> hey if you've got the bandwidth, no reason not to be verbose
[19:42] <SpeedEvil> xml?
[19:42] <eroomde> [drumroll]
[19:42] <eroomde> sent XML
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[19:42] <SpeedEvil> Sigh.
[19:42] <fsphil> ok not that verbose
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[19:42] <fsphil> someone thought XML was cool right?
[19:42] <nats`> I saw xml....
[19:42] <nats`> gimme the gun !
[19:42] <fsphil> "I dunno what it's for but I'm going to use it because stuff"
[19:43] <nats`> the more unreadable human readable file format
[19:43] <eroomde> literally: <measurement><tempererature><surfaceT>2</surfaceT></temperature></measurmeent>
[19:43] <eroomde> all sent as ascii
[19:43] <eroomde> to send 1 byte
[19:43] <nats`> oO
[19:43] <eroomde> so that caused them loads of problerms
[19:43] <eroomde> so they sort of invented their own compressed xml
[19:43] <nats`> at least they took ascii :D
[19:43] <eroomde> which just had shorted names in the tags
[19:43] <nats`> they could have take UNICODE :p
[19:43] <fsphil> I bet the person who came up with it was well paid
[19:43] <eroomde> it made me ill
[19:43] <mikestir> lol
[19:43] <LeoBodnar> I suggested xml before as terminal destination in "make it human readable" direction
[19:43] <fsphil> rather than well fired
[19:44] <mikestir> I like the idea of trying to standardise an open, binary name/value pair protocol
[19:44] <mikestir> something a bit like bson
[19:44] <eroomde> but their needed to encode their compression spec to all the nodes so they made a big xml wrapper for the compression table
[19:44] <mikestir> but with the application layer standardised
[19:44] <eroomde> to which my boss said
[19:44] <nats`> LeoBodnar if you find xml too human readable just use CDATA ;)
[19:44] <fsphil> the format I'm working on is just a series of values
[19:44] <fsphil> not even names
[19:44] <eroomde> 'XML is like violence. If it doesn't seem to be working, you need to use more of it'
[19:45] <nats`> eroomde trhey redid XSL
[19:45] <nats`> :D
[19:45] <nats`> yep because XML is just the bright side of the monster :D
[19:45] <eroomde> it was really bad
[19:45] <mikestir> eroomde: reminds me of the project files for the keil ide
[19:45] <number10> I wonder if this human readable issue is just a worry about where the data will be decoded (local PC or habitat)
[19:45] <eroomde> that was a rough old project
[19:45] <eroomde> we lost the blimp too
[19:45] <fsphil> <ukhas><callsign>swift</callsign><timestamp> *shoots self*
[19:45] <eroomde> i loved and cared for that blimp
[19:45] <number10> as long as the local chase PC (fldigi) can decode the position data to readable there is no issue
[19:45] <eroomde> and it got smashed into a mountain
[19:45] <fsphil> totally number10
[19:46] <eroomde> but, all of this stuff is *fine* if you are cognizent of how the layers are meant to work
[19:46] <eroomde> XML is massively compressible
[19:46] <nats`> anyway I can tell you you should be prepared to see more horror in the coming years
[19:46] <nats`> IPV6 over sug gig RF \o/
[19:46] <eroomde> it's just people don't seem to thinking of it in terms of entropy
[19:46] <nats`> they call that IOT
[19:46] <nats`> I try to avoid it at work but seems impossible to remove
[19:46] <eroomde> they just start looking at funny binary encodings which don't see the wood for the trees
[19:46] <Reb-SM3ULC> SpeedEvil: funny that it is "life threatening cold"... alaska/canada/etc has those temps every year....
[19:46] <LeoBodnar> Apple .plist nightmare
[19:46] <SpeedEvil> Reb-SM3ULC: Well - yes.
[19:47] <SpeedEvil> Reb-SM3ULC: but if you're not used to it - it's a fair point.
[19:47] <nats`> LeoBodnar taht those manifest for executable with list in them ?
[19:47] <mikestir> compression's all very well, but you are still having to do extra work on the node
[19:47] <mikestir> needs extra memory, pushes up device complexity and node cost
[19:47] <nats`> I did 1 software for MAc os X in C with a CLI :p
[19:47] <nats`> I gave up 2 hours after launching XCode
[19:48] <mikestir> when you could just keep the nodes super simple and move the complexity to the rf hub end, where you can translate to something like IP
[19:48] <eroomde> nats`: OSX comes with vim
[19:49] <eroomde> and gcc (used to anyway)
[19:49] <eroomde> it's fine
[19:49] <fsphil> vim and gcc is all you'll ever need
[19:49] <eroomde> mikestir: a huffman code is trivial to do and much better than nothing
[19:50] <mikestir> yeah - but note that I'm still talking about small scale sensor networks here with an easy radio path
[19:50] <fsphil> huffman codes are nice and easy to scan for in a bitstream
[19:50] <eroomde> ah yes, you could just send a list of sensor readings
[19:50] <eroomde> your address, some bytes, a checksum
[19:50] <eroomde> pop the whole thing through a really simple block code or something
[19:50] <mikestir> I suppose ultimately it's a trade off on power - you either spend the power on RF or on computation
[19:51] <LeoBodnar> XCode is fine as soon as you don't stray into Objective-C by mistake
[19:51] <eroomde> right, i am still at work
[19:51] <eroomde> and now I'm going to recitfy
[19:52] <eroomde> ttfn
[19:53] <nats`> eroomde I love vim but clearly I started to understand the use of an IDE sometimes ago :)
[19:53] <nats`> especially when you need to take the code from someone else
[19:54] <nats`> and for advanced refactoring
[19:54] <nats`> LeoBodnar Objectiv C is a lovely language that's sad they took such a weird syntax
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[20:06] <LeoBodnar> Early 1990's was a period of FUD http://www.drdobbs.com/embedded-systems/object-oriented-programming-in-assembly/184408319
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[20:11] Nick change: Geoff-G8DHE_ -> Geoff-G8DHE-M
[20:12] Nick change: KipK -> KipK_away
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[20:35] <Laurenceb_> hi
[20:36] <SpeedEvil> hi
[20:37] <LeoBodnar> hi
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[20:40] <eroomde> no
[20:41] <eroomde> nats`: ctags
[20:41] <Laurenceb_> http://pastie.org/8607722
[20:41] <eroomde> i am totally at peace with other people's code when i have ctags
[20:41] <Laurenceb_> but i think it could be done faster using a few more tricks
[20:42] <Laurenceb_> PhD corrections + life happened...
[20:42] <Laurenceb_> raw data -> preprocessor -> intermediate easy to process format -> correlator channels
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[20:44] <SP9UOB-Tom> evening All
[20:44] <Laurenceb_> bbl cooking
[20:44] <SpeedEvil> Laurenceb: when is that over?
[20:45] <eroomde> depends on how efficient he is in the kitchen
[20:46] <LeoBodnar> He should use macros and unrolled loops like in his code
[20:47] <LeoBodnar> *while cooking
[20:51] <SP9UOB-Tom> LeoBodnar: how fast You can retune CDCE913 over i2c?
[20:51] <LeoBodnar> I can't remember Tom
[20:51] <LeoBodnar> Fast enough for APRS AFSK
[20:52] <SP9UOB-Tom> aah ok
[20:52] <SP9UOB-Tom> samples just arrived ;-)
[20:53] <LeoBodnar> cool
[20:53] <eroomde> exciting if you're an EE, less so if you're a gastroenterologist
[20:53] <SP9UOB-Tom> eroomde: EE ?
[20:54] <eroomde> electronics engineer
[20:54] <SP9UOB-Tom> ah ok :-)
[20:55] <eroomde> been in oxford 2 days since leaving parents house, trying to re-learn moderation
[20:56] <eroomde> i could go and eat a lot of cheese and have half a bottle of wine and pick at ham and stuff
[20:57] <SP9UOB-Tom> my wife is preparing now herring in onions :-) Yummy
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[21:33] <tweetBot> @NORB_HAB: NORB H2 proposed launch date: Saturday 15th February. Now to design and build the box... #ukhas #hamr #NORB!
[21:34] <eroomde> bold words
[21:34] <eroomde> the weather is listening
[21:34] <fsphil> indeed
[21:34] <mattbrejza> we've been waiting since the end of nov...
[21:35] <eroomde> if someone can find a clip of the dealer in Withnail and I saying 'bold words my friend' then they get a biscuit
[21:35] <eroomde> it's the ideal clip to send people who tempt the weather so
[21:40] <MLow> hello everyone
[21:40] <MLow> something odd arrived at my door today
[21:41] <fsphil> I don't remember calling
[21:41] <nats`> [21:55:59] <eroomde> been in oxford 2 days since leaving parents house, trying to re-learn moderation
[21:41] <nats`> [21:56:30] <eroomde> i could go and eat a lot of cheese and have half a bottle of wine and pick at ham and stuff
[21:41] <nats`> learn moderation and keep the bottle for me :)
[21:42] <MLow> late xmas presents, big tv and tool chest
[21:42] <nats`> MLow chest is where the breast are no ?
[21:42] <nats`> oO
[21:43] <MLow> https://www.dropbox.com/s/ttwe735p64kgfen/2014-01-05%2016.31.50.jpg
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[21:43] <eroomde> nats has learnt some new english today
[21:43] <nats`> ?
[21:43] <nats`> isn't it ?
[21:43] <eroomde> i do like the idea of keeping my spanner in a nice decolletage
[21:44] <nats`> :D
[21:44] <eroomde> chest can also be a box
[21:44] <eroomde> like a treasure chest
[21:44] <nats`> draw me like one of your french girl :)
[21:44] <fsphil> well this channel's got weird quickly
[21:44] <MLow> that picture is how the day looked, monotone and harsh shadows
[21:44] <eroomde> nice chest though MLow
[21:44] <nats`> fsphil I didn't know chest is also a "box"
[21:44] <eroomde> and also the toolbox looks good
[21:45] <MLow> really it was an excuse to buy MORE TOOLS hahaha
[21:45] <nats`> so a tool chest seems weird :p
[21:45] <fsphil> english is a weird language
[21:45] <MLow> american makes more sense
[21:45] <eroomde> brazil nuts are not actually nuts, did you know
[21:45] <eroomde> they're seeds
[21:46] <fsphil> it's very easy to make a boob
[21:46] <bertrik> a lot of berries are not true berries
[21:46] <fsphil> peanuts are not nuts
[21:46] <nats`> eroomde not sure we talk about fruit right here :p
[21:46] <MLow> i am learning too much is this IRC?
[21:46] <eroomde> :)
[21:47] <MLow> hey so lets talk pens
[21:47] <nats`> eroomde for new year we opened a chateu haut brion with my best friend
[21:47] <MLow> while we are sharing life wisdome
[21:47] <nats`> you would have loved it soooo much
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[21:47] <eroomde> nats`: wow! was it good?
[21:47] <nats`> totally
[21:47] <nats`> 10 years
[21:48] <nats`> in my friend cave
[21:48] <DL1SGP1> nats`: sounds delicious!
[21:48] <eroomde> MLow: rotring mechanical pencil and pelikan m800
[21:48] <eroomde> those are my two friends in writing/drawing life
[21:48] <nats`> Rotring such a beauty
[21:48] <eroomde> nats`: very good! i have a nice bottle of fizz waiting for when the sale of the house completes
[21:48] <nats`> I still have a full set of them
[21:48] <MLow> what size lead on the pencil?
[21:48] <eroomde> 0.5
[21:49] <eroomde> and 2B leads
[21:49] <MLow> so 800?
[21:49] <eroomde> M800 is a fountain pen
[21:50] <MLow> http://www.jetpens.com/Rotring-800-Drafting-Pencil-0.5-mm-Black-Body/pd/6767
[21:50] <eroomde> http://www.cultpens.com/acatalog/rotring-Rapid-Pro-Pencil-Black.html
[21:50] <eroomde> that looks even more fancy than mine
[21:51] <nats`> eroomde you don't use tubular one ?
[21:51] <nats`> with chinese ink
[21:51] <arko> heh
[21:51] <arko> i bought one of those in oxford
[21:51] <arko> now i have two
[21:51] <arko> :P
[21:51] <eroomde> i have a pot of ink for the pen
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[21:51] <eroomde> it has a suction filling thing through the nib
[21:51] <arko> wat
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[21:52] <eroomde> cultpens is a bit dangerous
[21:53] <arko> or jetpens
[21:53] <arko> i can easly spend money
[21:53] <eroomde> yes
[21:53] <eroomde> i won't today
[21:53] <eroomde> i will resist
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[21:54] <arko> "God grant me the serenity to accept the pens I cannot buy; courage to buy the pens I can; and wisdom to know the difference."
[21:55] <arko> terrible
[21:55] <arko> no wonder i never became an english major
[21:55] <MLow> i am lost on that page
[21:55] <cm13g09> remind me why variable length data is bad :P
[21:56] <arko> neat, spacex launch http://www.spacex.com/webcast/
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[21:57] <eroomde> MLow: think of the tools you could buy
[21:57] <eroomde> or the house
[21:57] <eroomde> if you resist your desires on that page
[21:57] <MLow> i have credit
[21:58] <eroomde> brazil nuts are among the most radioactive foods in the world
[21:58] <MLow> well i cant find my f301
[21:58] <MLow> so i am completely lacking any BALLPOINTS
[21:58] <MLow> :'(
[21:58] <LeoBodnar> Drinking tea in England could be too
[21:59] <LeoBodnar> *London
[21:59] <arko> radioactive?
[21:59] <LeoBodnar> yeah Pt
[21:59] <arko> yay!
[21:59] <arko> i'll remember to drink more this year
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[21:59] <arko> cant wait to come back :)
[21:59] <LeoBodnar> *Pu bah
[22:00] <eroomde> radium is the culprit in brazil nuts
[22:00] <LeoBodnar> Especially if you are Russian
[22:00] <arko> Chernoybl expresso
[22:03] <SP9UOB-Tom> or plutonium - Litwinienko style...
[22:03] <arko> i really should visit Armenia
[22:03] <arko> some day
[22:03] <eroomde> yes
[22:04] <SP9UOB-Tom> arko: im planning to visit Chenrnobyl, Pripiat and DUGA complex in this spring
[22:04] <arko> :D
[22:04] <arko> take lots of high res photos plz
[22:04] <SP9UOB-Tom> arko: sure!
[22:04] <arko> http://www.spacex.com/webcast/
[22:04] <arko> less than 2 mins
[22:05] <MLow> eroomde: https://www.dropbox.com/s/1epg6a7tegnzxcb/2014-01-06%2016.03.09.jpg
[22:05] <arko> its just fire and stuff, but still neat
[22:05] <eroomde> nice
[22:05] <eroomde> there's a most diverting website i used to read
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[22:05] <arko> MLow: i have the uni Kuru Toga
[22:05] <arko> amazing pencil
[22:06] <eroomde> it's called: Dave's Mechanical Pencil Blog
[22:06] <arko> rolls as you write
[22:06] <MLow> very nice mech pencil
[22:06] <arko> brilliant japanese engineering
[22:06] <MLow> yeah
[22:06] <MLow> well, each press
[22:06] <MLow> 8
[22:06] <MLow> 7
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[22:06] <eroomde> the url is immaginatively: davesmechanicalpencils.blogspot.com
[22:06] <MLow> that looks CG
[22:06] <MLow> i call bs
[22:07] <MLow> that sounds so cool
[22:07] <MLow> almost sounds like a pulse jet
[22:07] <LeoBodnar> 100FPS cameras?
[22:08] <MLow> LeoBodnar: some of the old cannons can be hacked
[22:08] <MLow> for high speed video, with a low resolution
[22:09] <eroomde> the new gopro probably does 100fps at some resolution
[22:09] <MLow> nope
[22:09] <eroomde> http://davesmechanicalpencils.blogspot.co.uk/p/top-10-drafting-mechanical-pencils.html
[22:09] <MLow> i dont really do drafting though
[22:10] <eroomde> http://davesmechanicalpencils.blogspot.co.uk/p/top-10-general-mechanical-pencils.html
[22:10] <MLow> a lot of what i do has to be in pen as well, and i am starting to really dislike gels
[22:10] <eroomde> fountain pen
[22:10] <arko> http://davesmechanicalpencils.blogspot.com/2008/04/uni-kuru-toga.html
[22:10] <arko> the best
[22:10] <eroomde> every note is like a fatcat writing a fat cheque
[22:10] <arko> its comfortable too
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[22:14] <arko> ahh i love introducing people this video https://www.youtube.com/watch?v=W2VygftZSCs
[22:14] <arko> my friend was just saying how much he likes the spacex webcast
[22:14] <arko> and launches
[22:14] <arko> 45minutes of pure shuttle porn right there
[22:14] <eroomde> yes it's great, that'n
[22:14] <eroomde> i saw the guy talking in it give a talk
[22:15] <eroomde> who was one of the authors of the columbia accident investigation report
[22:15] <eroomde> best talk on engineering i've ever seen
[22:15] <arko> oh?
[22:15] <arko> irl talk?
[22:15] <arko> or video?
[22:15] <eroomde> irl talk
[22:15] <eroomde> at astrium
[22:15] <arko> nice!
[22:21] <SP9UOB-Tom> nigth all
[22:21] <SP9UOB-Tom> night
[22:21] <SP9UOB-Tom> ;-)
[22:21] <arko> nighhtt
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[22:21] <SP9UOB-Tom> ;-)
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[22:28] <LeoBodnar> oh it's a real film, beauty! arko
[22:28] <arko> :)
[22:29] <LeoBodnar> light leak on a spool at ca. 16 min
[22:29] <arko> hehe
[22:29] <arko> this whole thing
[22:30] <LeoBodnar> not your average digitally compressed rubbish :D
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[22:31] <arko> yeah
[22:31] <arko> i like watching this some nights with scotch
[22:31] <arko> great way to spend the evening
[22:33] <gonzo_> I'm there already, but watching james may toy stories
[22:33] <LeoBodnar> did you download the DVD iso from the link?
[22:33] <LeoBodnar> or have private 35mm projection room?
[22:34] <LeoBodnar> though it looks 16mm rather
[22:35] <arko> chromecast+hd tv
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[22:43] <LeoBodnar> so 1-2msec sample will only contain one full PRN from each sat?
[22:43] <eroomde> yes
[22:44] <LeoBodnar> I.e. there is a discrete uncertainty of ca. 300km
[22:44] <LeoBodnar> in each pseudorange
[22:44] <LeoBodnar> is this right?
[22:45] <LeoBodnar> so local RTC has to keep local time with accuracy better than 0.5mec between the fixes?
[22:46] <LeoBodnar> to maintain time continuity?
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[22:47] <SpeedEvil> not quite
[22:48] <SpeedEvil> EAch PRN sequence is repeated 20 times to make a bit time
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[22:49] <SpeedEvil> Which not very coincidentally is about the radius of earth
[22:49] <LeoBodnar> if the receiver has been aligned to the GPS time previously
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[22:50] <SpeedEvil> If the bit changes halfway through your sample, you have a 50, not a 1ms uncertainty in the time - if you have no other knowledge
[22:50] <LeoBodnar> it can derive whole number of msec from RTC and then maintain alignment from sampled data?
[22:50] <SpeedEvil> That is - you know that the time is an integer second divided by 50, not divided by 1000
[22:50] <SpeedEvil> something like that works, yes
[22:51] <LeoBodnar> I mean RTC in a generic sense
[22:51] <LeoBodnar> local clock rather
[22:51] <SpeedEvil> If you can use known broadcast data edges in future - in principle you can do drift free up to a few milliseconds. Depending on your sample length
[22:52] <SpeedEvil> For example - I assume that all satelites broadcast at least on integer TOWs.
[22:52] <SpeedEvil> If they don't all broadcast on integer 6 second boundaries.
[22:52] <LeoBodnar> I am just getting into concept [slowly]
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[22:53] <SpeedEvil> so if for example, you tuneed on the reciever during the TOW packet preamble
[22:55] <LeoBodnar> so in practice I assume local timer is sampled at the start of the packet acquisition and then exact timing calculated from the beginning of the acquisition in the packet to a whole second edge and local time is corrected?
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[22:57] <ibanezmatt13> Does anybody know how the Taoglas antenna (think it's calleda patch antenna) should be orientated in the box for flight? :/
[22:58] <LeoBodnar> Local timer based on 0.5 PPM TCXO would require a periodic quick (1-2msec) fix at least each 2000 seconds, right ?
[22:59] <LeoBodnar> to maintain GPS time without reading it from the packet data?
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[23:04] <Laurenceb_> i guess
[23:04] <Laurenceb_> i was thinking of using so called carrier based acquisition
[23:04] <Laurenceb_> same technique as "A-GPS"
[23:05] <Laurenceb_> so you grab at least 1ms of data to get timing offsets for at least 4 sats with 1ms ambiguity
[23:05] <Laurenceb_> then with almanac + rough time + rough position you can solve to ~100m CEP
[23:05] <Laurenceb_> this is what can be run in a few ms on an stm32
[23:07] <craag> ibanezmatt13: Top upwards
[23:07] <craag> ie PCB right way up
[23:07] <craag> logo facing sky
[23:07] <craag> v important, will not work upside down!
[23:07] <ibanezmatt13> awesome, thought so. Just checking :)
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[23:08] <ibanezmatt13> This Taoglas is ok for the flight right craag?
[23:08] <craag> ibanezmatt13: Oh yes, it may have difficulties getting a lock on the ground if it lands upside down, but you'll just have to be nearby to catch it :)
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[23:09] <ibanezmatt13> that's fine, we will hopefully havea backup :) cheers
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[23:09] <craag> np. When's your launch?
[23:09] <ibanezmatt13> Feb 15th, weather depending
[23:10] <ibanezmatt13> one final thing to check, I have a Canon powershot cam. I was wondering what the risks where of interference with GPS
[23:10] <craag> fingers crossed!
[23:10] <SpeedEvil> LeoBodnar: sigh
[23:10] <craag> Erm should be ok, but worth extensive testing on the ground to make sure
[23:11] <ibanezmatt13> Well, my idea of testing is to fire it up so it's txing as normal, then start the camera videoing right next to it and see what happens. Is that a good approach?
[23:11] <daveake> The Canons are pretty good. You have to get a chip antenna pretty close to one for it not to get a lock
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[23:11] <craag> Yeah I reckon so
[23:11] <Laurenceb_> LeoBodnar: aiui as long as they dont mess with the GPS constellation, if you wanted rough position you could use very old almanac data
[23:11] <ibanezmatt13> see, for the box design, I was thinking of putting it so close that it was almost touching :/
[23:11] <ibanezmatt13> and then had doubts :P
[23:11] <craag> Try leaving the camera videoing and powering up the board while it's sitting against it, see what happens
[23:11] <ibanezmatt13> yeah I'll try that too in the morning
[23:12] <craag> (I did a lot of this with my 808 camera for the pico flight. Had no problems getting a lock with the gps chip antenna sitting underneath the running cam!)
[23:12] <ibanezmatt13> oh wow. Should be fine then, but will test in the morning for a bit
[23:13] <craag> yep, test test test. You'll feel so much better come launch day!
[23:13] <daveake> I don't have a suitable pic, but I had camera + tracker inside a 150mm foam ball
[23:13] <daveake> I did put some bacofoil between camera and GPS
[23:13] <daveake> This one http://www.daveakerman.com/?p=715
[23:14] <SpeedEvil> LeoBodnar: Laurenceb: On reading closely the GPS standard - it seems that GPS navigation messages are always broadcast every six seconds - starting on midnight sunday - or whenever the epoch is. So - this guarantees eight bits which are fixed - the preamble bits - 160ms. Then you have the TOW message in each frame - this is a 17 bit counter which counts every 6 seconds. So each satellite broacasts the same bitstream - the time - 340ms -
[23:14] <SpeedEvil> every 6 seconds.
[23:14] <Laurenceb_> interesting
[23:14] <ibanezmatt13> yes daveake, our antenna will be pretty much touching it like that
[23:14] <MLow> dave your name is david?
[23:14] <daveake> yes dave is short for david
[23:15] <ibanezmatt13> :P
[23:16] <Laurenceb_> MLow is this you: http://diydrones.com/profile/MonroeLeeKingJr ?
[23:16] <MLow> what?
[23:16] <Laurenceb_> ill take that as a no?
[23:16] <MLow> no ma'am
[23:16] <SpeedEvil> I think locking on the preamble - which is 10001011 - will let you determine time, if you sample the 3 bit times in the middle of the word - that is 6ms - with an error allowable of +-6ms or so
[23:17] <Laurenceb_> that is very good news
[23:17] <Laurenceb_> i saw you were in Austin
[23:17] <MLow> Austin?
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[23:19] <SpeedEvil> Err - above is wrong - 3 bit times are of course 60ms, and the allowable error is about 80ms
[23:19] <nats`> I see there are some quadcopter hobbyist here I need some advice
[23:20] <nats`> my little brother wants to build one I think about taking a kit he doesn't have any knowledge
[23:20] <nats`> do you have some advice on "cheap" and robust kit
[23:20] <nats`> I don't know anything on that topic myself
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[23:20] <MLow> its kinda a $500 thing
[23:22] <SpeedEvil> Laurenceb: So with a very bad clock - 100ppm - you can keep perfectly locked with one 60ms sample every 600 seconds. A few PPM clock makes one, or even two hour samples plausible.
[23:23] <MLow> Laurenceb_: why are you saying im in austin
[23:24] <SpeedEvil> If you know your time only to +-1s, then you still only need to grab about 2.5 seconds of GPS - at the right time to guarantee that you've got an unambiguous time.
[23:25] <SpeedEvil> But at that point - you'll have run out of almanac.
[23:25] <SpeedEvil> Unless you've got a bad clock
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[23:30] Nick change: davo_ -> davo
[23:31] <SpeedEvil> ^oops. I forgot that the satellites will be in different locations. This probably knocks the above 60ms minimum sample if you know your time to within 60ms, to about 20ms.
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[00:00] --- Tue Jan 7 2014