highaltitude.log.20090105

[00:00] <Xenion> Gute Nacht / good night :-)
[00:00] <edmoore> cya Xenion
[00:00] <Xenion> unbelievable .. i've spen't the entire day doing stuff in eagle ...
[00:00] <Xenion> :-)
[00:01] <Xenion> night folks
[00:02] <rjharrison> hi Laurenceb
[00:02] <rjharrison> Laurenceb on the RHS is me
[00:03] <Laurenceb> hello :P
[00:03] Action: Laurenceb waves from the internets
[00:03] <rjharrison> sorry playing avr
[00:03] <rjharrison> Fixed bad bug in code from launch on sat
[00:04] <Laurenceb> the decimal points?
[00:05] <Laurenceb> Xenion: ever used PCB?
[00:06] <Laurenceb> I've been playing with it, looks good, just not as big a part library
[00:07] <Xenion> Laurenceb, my first time
[00:07] <Xenion> Laurenceb, i've created all my parts myself
[00:07] <Xenion> that is one reason why i like eagle
[00:07] <Xenion> you can speciy your parts by the exakt mil or mm
[00:07] <Xenion> that really helped me
[00:07] <Xenion> :-)
[00:07] <Laurenceb> I find the part editor is horrible
[00:07] <Laurenceb> in eagle
[00:08] <Laurenceb> also the parts seem to be grouped together into lbr files
[00:09] <Laurenceb> acessing the individual parts if you e.g. want to use a standard package and relable the pins isnt easy
[00:09] <Laurenceb> apparently PCB is a lot more obvious, but I havent tried playing with parts yet
[00:09] <Xenion> Laurenceb, maybe, ok im off .. good night
[00:09] <Laurenceb> cya
[00:09] <Xenion> i'm nearly sleeping on the kbd
[00:10] <rjharrison> Laurenceb yep the dp problem
[00:14] <natrium42_> nice landrover :)
[00:14] <natrium42_> but the steering wheel is on the wrong side
[00:14] <natrium42_> :P
[00:30] <rjharrison> thanks natrium42_
[00:31] <rjharrison> having fun with temp sensor and frezer spary
[00:31] <rjharrison> spray
[00:31] <rjharrison> got it down to -55
[00:31] <natrium42_> haha
[00:31] <natrium42_> whoa
[00:38] <rjharrison> nitgh time
[00:38] <rjharrison> work tomorrow
[00:38] <edmoore> cya
[00:39] <rjharrison> Will need to test tracker real soon
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[10:40] <Xenion> Good Morning / Guten Morgen :-)
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[11:05] <rjharrison_> morning all
[11:06] <rjharrison_> Fixed code last night so we won't be getting a repeat experience on the next launch
[11:07] <Laurenceb> cool
[11:07] <Laurenceb> I like the idea of using freezer spray
[11:08] <Laurenceb> are you using a DS1820S ?
[11:17] <Laurenceb> I'd be interestedf to hear how you interfaced it
[11:18] <Laurenceb> theres an interesting atmel application note on 1 wire
[11:20] <Xenion> freezer for what ?
[11:21] <Laurenceb> www.atmel.com/dyn/resources/prod_documents/doc2579.pdf
[11:21] <Laurenceb> Xenion: I guess its liquid propane or something
[11:21] <Laurenceb> in an aerosol
[11:21] <Laurenceb> for freezing pipes
[11:21] <Xenion> i see
[11:22] <Laurenceb> I made a peltier cooling unit, but it can only reach -25C
[11:22] <Xenion> hm
[11:22] <Laurenceb> if you run the peltiers at 16V you can get better performance
[11:22] <Laurenceb> but I only have a 12V PC power supply
[11:23] <Xenion> i need to test my equip down to -85° .
[11:24] <Laurenceb> maybe peltiers in series
[11:25] <Laurenceb> but you could only cool a small volume
[11:54] <Laurenceb> I'm off, cya all
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[13:37] <edmoore> hi hallam
[13:37] <edmoore> rjharrison_: recovered?
[13:38] <hallam> Hi ed
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[14:05] <edmoore> hallam: sorry I wandered off. trying to clean car windows without leaving a smear. It's a tricky one
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[14:42] <hallam> Hi Ed
[14:43] <hallam> Do you have a squeegee?
[14:50] <edmoore> yo
[14:50] <edmoore> hallam: yes
[14:50] <edmoore> but
[14:50] <edmoore> newspaper is the trick!
[14:51] <edmoore> lint free and the ink polishes the glass
[14:51] <hallam> magic
[14:51] <edmoore> it works likema charm
[14:52] <edmoore> trying to figure out the best way to mount the3 icom too
[14:52] <edmoore> i think going full the full seperate head and body elsewhere sacrifices a lot in terms of speed and conveninece of jumping in the car and chasing
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[14:55] <edmoore> found a 3 element yagi design with a really really good front to back dB ratio - should be ideal for close-up finding once landed
[14:56] <hallam> how deep is the icom?
[15:07] <edmoore> hallam: sorry, you might have to include my username in messages so it makes a ping and attracts my attention - irc is burried under a whole bunch of other windows atm
[15:08] <edmoore> hallam: will grab the dimensions, in the mean time - http://www.hamradio.co.uk/acatalog/Accs_SWR-PWR.html - av-601 look ok?
[15:08] <edmoore> if so I'll fire of a quick email to the other guys
[15:22] <rjharrison_> hi edmoore
[15:22] <edmoore> hi rjharrison_
[15:22] <edmoore> all well?
[15:22] <rjharrison_> How is the icom going
[15:22] <rjharrison_> Yep
[15:22] <rjharrison_> Fixed buggs in coe
[15:22] <edmoore> I love it, but I'm not sure how to put it in my car
[15:22] <edmoore> I have a silly curvy dash
[15:22] <rjharrison_> not in typing though
[15:22] <edmoore> :)
[15:23] <edmoore> I am thinking about building a plate to allow the head unit to be put under my sat-nav
[15:23] <edmoore> that would actually work pretty well as a solution, I think
[15:23] <edmoore> so both tomtom and head unit are on the same suction cup thingamie
[15:24] <rjharrison_> I have the same problem
[15:24] <rjharrison_> Just put blue tack under the radio but not good for permanent solution
[15:24] <edmoore> i don't really want to be drilling things into the dash, tbh
[15:24] <rjharrison_> You need to power the main unit too
[15:24] <edmoore> indeed
[15:25] <edmoore> I think I may go for a seperate main unit and head
[15:25] <edmoore> it does increase the options
[15:25] <rjharrison_> Could you not mount it in the footwell of passenger side and bring up the head unit
[15:25] <hallam> hang it from the roof somehow?
[15:25] <hallam> IMO it would be better not to separate the head unit, but your call
[15:25] <edmoore> that's probably what I'll do - but balloon chases often involve muddy feet so I'm slight cautious!
[15:25] <edmoore> my car was pretty trashed after teddy bears
[15:26] <edmoore> hallam: agreed, for reasons already discussed
[15:26] <rjharrison_> should be able to keep it high on the side wall
[15:26] <rjharrison_> of the foot well
[15:26] <edmoore> I think i'll just make a mounting plate for the whole thing and have it on the dash. it'll be ok
[15:26] <rjharrison_> Cool
[15:26] <edmoore> the only issue to seperating them is that it takes time to install it then
[15:26] <edmoore> when you kind of want to just jump int he car and get going
[15:27] <rjharrison_> That's why I like my 817
[15:27] <rjharrison_> It's small and cig lighter powered
[15:27] <edmoore> yeah
[15:27] <rjharrison_> but not an all rounder
[15:27] <edmoore> I can certainly power mine from cig for receive
[15:28] <rjharrison_> 1am
[15:28] <rjharrison_> amp
[15:28] <edmoore> it's just not recommended if you're going to be transmitting 100W - but then I won't be for the most part
[15:28] <rjharrison_> Just when you find it
[15:28] <edmoore> we'll still have the ft-790
[15:28] <rjharrison_> I nearly pulled in the HAMs this w/e to located the tracker
[15:28] <rjharrison_> Was going to put a call out on the local repeater if I couldn't find it
[15:29] <edmoore> what *would* be good is a little unit to auto swtich from car to battery when car is unplugged
[15:29] <edmoore> and maybe charge the battery when car is plugged in
[15:29] <edmoore> if something exists for the right side of £30, I'll get it
[15:29] <edmoore> hallam - thoughts on power splitting?
[15:30] <rjharrison_> I need to launch again to test the the s/w fixes
[15:30] <edmoore> I'm kind of siding with you generally - none of this stuff is too difficult to DIY but it's just a PITA and maybe we should just spend some money
[15:30] <rjharrison_> Any one busy this w/e
[15:30] <edmoore> i'm back in cam this sat
[15:30] <edmoore> i'll be around sunday for launching
[15:31] <hallam> what kind of battery is it?
[15:31] <edmoore> hallam: i don't have a battery for it atm
[15:31] <edmoore> was thinking of a cycle-able SLA
[15:31] <edmoore> about 10Ah
[15:31] <edmoore> can always go more expensive though
[15:32] <hallam> yeah weight isn't really an issue
[15:32] <hallam> but I was going to say
[15:32] <rjharrison_> Humm, I'll see if I can get a pass from the misses
[15:32] <edmoore> zeusbot !msg fuzzylugnuts Hey Fuzzy can you email me (eam52[at]cam[dot]ac[dot]uk) with details of those nice lithium batts you used for your mobile rig? thanks
[15:32] <edmoore> whoops
[15:33] <rjharrison_> hehe
[15:33] <edmoore> msg fuzzylugnuts Hey Fuzzy can you email me (eam52[at]cam[dot]ac[dot]uk) with details of those nice lithium batts you used for your mobile rig? thanks
[15:33] <hallam> you could do it with two diodes and the battery
[15:33] <edmoore> third time lucky
[15:33] <edmoore> that worked on the third time
[15:33] <edmoore> :)
[15:33] <edmoore> he'll get the message
[15:33] <hallam> i.e. a diode OR gate from the battery and the car to the radio
[15:33] <edmoore> hallam: yeah, was thinking that
[15:33] <hallam> doesn't give you charging, but it does the auto switch and it's very simple
[15:34] <edmoore> but) a) 0.6V drop with perhaps some fairly hefty amps
[15:34] <edmoore> b) charging
[15:34] <edmoore> i agree in a pinch it's the solution
[15:34] <edmoore> i'll ask #hamradio if there's something about for the right price
[15:34] <hallam> a) use Schottky if you really care, but it'd be fine with a reasonably chunky rectifier diode, it's what they're made for
[15:34] <hallam> charging would be nice I agree
[15:36] <edmoore> will see what they say - if there's something for the right price, it's gotta be worth it
[15:36] <edmoore> hallam: what do you think to the av-601? http://www.hamradio.co.uk/acatalog/Accs_SWR-PWR.html
[15:37] <edmoore> has got some nice reviews, looks like a quality unit that will give us good service
[15:37] <hallam> crikey, 70 GBP
[15:37] <hallam> but sure
[15:37] <hallam> i have no idea what to look for in an SWR meter
[15:38] <hallam> I expect it will do the job
[15:40] <edmoore> that's about the going rate, it seems
[15:40] <rjharrison_> What do you want the swr meter for?
[15:40] <hallam> seeing how badly our antennas suck
[15:41] <hallam> although it would be nice to test the TX side, but I don't know how to do that in-system
[15:41] <rjharrison_> are you having any issues?
[15:41] <edmoore> it's also to tune antennas we build
[15:42] <edmoore> we can definitely get more gain with the balloon array, I'm quite sure of that
[15:42] <rjharrison_> humm I'm quite happy with my 1/4waveGP
[15:42] <edmoore> this is still with a 1/4 wave gp
[15:43] <rjharrison_> array?
[15:43] <rjharrison_> =2
[15:43] <edmoore> but you can probably match it a bit better to the radio metrix if you actually have a look with the meter
[15:43] <rjharrison_> truebut I thought it need 5w
[15:43] <hallam> a few mm here and there can really mess up the SWR
[15:43] <edmoore> this is all or a couple of dB here and there, nothing step-changing
[15:43] <rjharrison_> needed
[15:45] <edmoore> also, we saw the difference when we switched from a yagi that looked ok to actually one that was tuned correctly
[15:45] <edmoore> so there may be a hidden nugget of dBs on the balloon side aswell
[15:45] <edmoore> going from a 1/4 GP that looks ok to one that's actually been tuned for sure
[15:46] <edmoore> i'm thinking mainly about ZPs here - we'll be pushing the range limits
[15:46] <rjharrison_> Do you thinks so
[15:46] <rjharrison_> I'm no expert but I was getting sig strength 8 in Leeds from dover
[15:47] <rjharrison_> well from 8k above
[15:47] <edmoore> it's when we get near the horizon that it'll get interesting i think
[15:47] Action: hallam refrains from snarky comments about repeaters
[15:47] <rjharrison_> that was using a triband pole in the back garden
[15:48] <rjharrison_> vertical (watson 2000)
[15:48] <edmoore> it also means we could try a switch up to 300baud if we're sure we've got everything set up as well as we can - I'm basically of the opinion that knowing is better than hoping :)
[15:50] <rjharrison_> http://www.radioworld.co.uk/~radio/catalog/w2000-watson-6m2m70cm-base-station-vertical-antenna-p-1949.html?osCsid=a47384e4f9977ac3f7dde2ce3573d013
[15:50] <rjharrison_> Do you need 300 baud
[15:50] <edmoore> hallam: of note is that rjharrison_'s antenna on the balloon has a slightly swept back ground plane - about 20-30 degrees isn't it rjharrison_ ?
[15:50] <rjharrison_> Yep
[15:50] <edmoore> that points things out a bit more to the horizon
[15:50] <edmoore> which seems to be A Good Thing when it coems to longer range flights
[15:51] <rjharrison_> Like ir says in the arrl manual
[15:51] <edmoore> rjharrison_: don't need 300 baud, but it a) makes us better ham citizens, and b) allows some scope to add a whole bunch of error correction stuff in the packet whilst still getting slight higher results
[15:51] <rjharrison_> I'm sure you could send a signal from orbit with the set up
[15:52] <edmoore> og for sure
[15:52] <edmoore> it's only a few hundred km
[15:52] <edmoore> most of which are vacuum, so very low losses
[15:52] <rjharrison_> of mainly nothing ness
[15:52] <edmoore> n-prize sat is basically a smd version of your tracker
[15:53] <rjharrison_> Talking of smd I'm going to go for that for the eagle file
[15:53] <edmoore> yep, always good. they're actually much easier to solder
[15:53] <rjharrison_> but how do you do thrugh hole and smd on the same board
[15:53] <edmoore> put a dam on each diagonal pin
[15:53] <rjharrison_> do you need two levels of cables
[15:54] <rjharrison_> print?
[15:54] <edmoore> then sweep the tip down one side of pins, and they all just solder up nicely
[15:54] <edmoore> rjharrison_: are you getting them sent off to be made?
[15:54] <rjharrison_> yep
[15:54] <edmoore> ok
[15:54] <edmoore> double sided?
[15:54] <rjharrison_> Don't know really
[15:55] <edmoore> I would say yes
[15:55] <rjharrison_> Should I do tht if i want the components all on the same side
[15:55] <edmoore> it's the standard before you start spending lots of money
[15:55] <edmoore> yes it still helps to have a 2-sided pcb
[15:55] <edmoore> as you have a lot more options fro routing
[15:55] <edmoore> and you can do good-practice things, like making the bottom layer one big solid ground layer, as much as possible
[15:55] <edmoore> with the signals on the top
[15:56] <rjharrison_> I basically want smb the compentents other than the headers and the radiometrix
[15:56] <edmoore> that gives you good EMI tolerance
[15:56] <hallam> it's fine to mix smd and through-hole components
[15:56] <rjharrison_> We'll have a chat when i make the board
[15:56] <edmoore> yep, not a problem - they fill the hole for the through-hole with conductive plating
[15:56] <edmoore> it's called PTH - plated through hole
[15:56] <rjharrison_> Cool
[15:57] <rjharrison_> I can do all that on eagle>
[15:57] <rjharrison_> ?
[15:57] <edmoore> yes no problem
[15:57] <hallam> yes, it pretty much does it for you
[15:57] <hallam> strictly speaking the hole isn't filled, i.e. plugged
[15:57] <hallam> the inside surface of the hole is plated, which makes it conductive
[15:57] <hallam> but you can still poke things through it
[15:57] <edmoore> pedant :p
[15:57] <hallam> if nothing is poked through it, it's called a via
[15:57] <rjharrison_> Great
[15:58] <hallam> vias can be made pretty small depending on the PCB manufacturer
[15:58] <rjharrison_> I was quite pleased with my last board for my second atempt at soldering
[15:58] <edmoore> yeah it looked good
[15:58] <hallam> yup
[15:58] <edmoore> rjharrison_: sparkfun have a good tutorial on eagle
[15:58] <rjharrison_> Only toasted one AVR and nearly a temp sensor
[15:58] <edmoore> ironic
[15:58] <hallam> toasted from soldering?
[15:58] <hallam> that's kind of hard to do IME
[15:58] <rjharrison_> no put the temp sensor in the the wrong way
[15:59] <edmoore> you have to try pretty hard to break stuff with soldering irons
[15:59] <edmoore> ah ok, that does break things :)
[15:59] <rjharrison_> wondered wy it wasnt working untill I burnt my fingers on it
[15:59] <edmoore> :D
[15:59] <rjharrison_> put it in the oter way around after 60 secs of this and it still worked fine
[15:59] <rjharrison_> amazing
[16:00] <rjharrison_> I now use it as a test sensor with long cables on
[16:00] <rjharrison_> Got it down to -55 last night with som freexe spray from maplins
[16:00] <edmoore> a diode on the power-in is always a sensible thing
[16:00] <rjharrison_> and loose 0.6v
[16:00] <edmoore> it's too easy to wire up the entire board backwards to the batt in the heat of pre-launch faff
[16:01] <edmoore> if you've got a linear regulator, you'll loose that power anyway
[16:01] <edmoore> makes no diff to loose it in the diode of the linear reg - it all goes to heat in the end
[16:01] <rjharrison_> Ahh put it b4 the regulator?
[16:01] <edmoore> yeah
[16:01] <rjharrison_> silly me
[16:01] <hallam> do you know the cunning trick with protection diodes?
[16:01] <rjharrison_> that's my lack of elec. coming though
[16:01] <edmoore> do tell
[16:02] <hallam> instead of putting it in series with the supply, forward biased
[16:02] <edmoore> rjharrison_: now you know. one step at a time!
[16:02] <hallam> you put it in parallel, reverse biased
[16:02] <hallam> if the battery is put in backwards, diode gets a bit hot but board is untouched
[16:02] <hallam> if battery is the right way round, no 0.6V drop
[16:02] <edmoore> cunning!
[16:02] <hallam> most batteries have enough IR that the diode won't actually fry if it's backwards
[16:02] <edmoore> i'm not sure that a Lipo would like that so much though :)
[16:03] <hallam> prolly not
[16:03] <rjharrison_> humm
[16:03] <rjharrison_> interesting
[16:03] <hallam> the diode would get smoky and let you know though
[16:03] <edmoore> if you've got a linear reg anyway, it makes no diff
[16:03] <hallam> well
[16:03] <rjharrison_> I think I'll pop that component on
[16:03] <hallam> depends what your margin is
[16:03] <edmoore> assuming the batts at high enough above linear reg output
[16:03] <hallam> right
[16:04] <hallam> what are you using, 9V batt and 7805?
[16:04] <rjharrison_> no 4*aa
[16:04] <rjharrison_> and that was to make a bit of heat
[16:04] <rjharrison_> could easily gt away with 3*aa
[16:04] <edmoore> rjharrison_: I assume you've got a 3.3V system?
[16:04] <rjharrison_> the 4 block has a 9v connector
[16:05] <rjharrison_> making it harder to connect around the wrong way and a warning not to power on before connecting the battery
[16:05] <edmoore> rjharrison_: challenge: build the pcb so it's the same size as a 4xAA holder
[16:05] <edmoore> one that holts all its batts side by side in a row
[16:05] <rjharrison_> and shove it all in the box
[16:06] <edmoore> it'd make a very neat unit
[16:06] <edmoore> you can get 'PCB mount' 4xaa holders - they have a pair of metal legs
[16:06] <rjharrison_> I quite like it open at the moment it looks more tecky
[16:06] <edmoore> hang on, lemme find
[16:06] <rjharrison_> techy
[16:06] <edmoore> oh you'd see the pcb on this one
[16:06] <rjharrison_> ooh my new lassen iq has shipped
[16:06] <rjharrison_> just got the email
[16:07] <rjharrison_> and i ordered a new one as I thought this one was lost
[16:07] <rjharrison_> I think it's a good idea to shove it all in a small box
[16:07] <edmoore> :)
[16:07] <edmoore> http://www.rapidonline.com/netalogue/specs/18-2970.pdf
[16:08] <edmoore> so you cold make a board that piggy-backs onto the back of the batt holder
[16:08] <rjharrison_> I have one of those from maplins
[16:08] <edmoore> a few turns of elec tape round the whole lot to stop the batts popping out on landing, and you're laughing
[16:08] <edmoore> could throw it on any payload too as a backup
[16:09] <rjharrison_> Will look at the dimentions of the avr lassen and radiometix
[16:09] <rjharrison_> dimensions
[16:09] <rjharrison_> dimentions even
[16:10] <hallam> I think it's dimensions
[16:10] <edmoore> sions
[16:10] <hallam> EAGLE is nice for that, you can just plop them on the PCB layout tool and see how big they are
[16:10] <edmoore> agreed
[16:10] <rjharrison_> ahh
[16:10] <hallam> I can send you EAGLE libs for the lassen and radiometrix
[16:10] <edmoore> same
[16:10] <edmoore> damn you henry, if i knew you already had radiometrix
[16:11] <edmoore> would have saved a whole 15 mins
[16:11] <rjharrison_> so I don't even have to think about it
[16:11] <rjharrison_> please for the radiometic
[16:11] <rjharrison_> x
[16:11] <rjharrison_> sf has lassen ig
[16:11] <rjharrison_> iq
[16:11] <rjharrison_> well the smd header and boundry
[16:12] <hallam> I'll dig it out unless Ed has it handier?
[16:12] <rjharrison_> do you mount vertically or horizontally
[16:12] <hallam> yeah I was going to say, you can do either
[16:12] <rjharrison_> I lay it on it's back as it's tidier
[16:12] <hallam> I'm partial to horizontal, though I think my lib is for vertical
[16:12] <edmoore> pcb design is a bit of an art, but really it just takes some good common sense
[16:13] <rjharrison_> and use the pcb antenna connector so as not to bend the pins much
[16:13] <edmoore> you can rotate them no problem, it's one click on a button
[16:13] <hallam> nah Ed
[16:13] <hallam> not that axis
[16:13] <edmoore> but yeah, some common sense things like not putting the sensitive ADCs right next to the radio output, or whatever
[16:13] <edmoore> oh i see, sorry hallam
[16:14] <edmoore> my one is vertical too
[16:14] <hallam> in theory the RF out should be connected to an SMC or whatever socket directly without being conducted through a PCB trace
[16:14] <edmoore> tricksey in practice
[16:16] <hallam> if it's vertically mounted you can quite nicely solder a PCB mount socket at right-angles into the blobs of solder on the radiometrix
[16:16] <hallam> not a very good explanation, but did it with some of the earler NOVA trackers
[16:18] <rjharrison_> Did you see how i did it on the strip board?
[16:18] <edmoore> yes - that is a good solution too
[16:19] <edmoore> keep chatting, going to dash to shops to get a couple of computer cables. bbiab
[16:19] <edmoore> good tech talk
[16:19] <hallam> agree, the way you did it on the stripboard is good
[16:20] <hallam> it probably doesn't make much difference as long as the distance is as short as that anyway
[16:22] <rjharrison_> http://www.robertharrison.org/images/icarus2/IMG_0375.JPG
[16:22] <rjharrison_> should the rf gound go out on the strips?
[16:23] <hallam> don't think it matters
[16:23] <hallam> I've always hooked it up similar to yours
[16:23] <rjharrison_> I didn't knwo if it was good to spread the rf ground around or not
[16:24] <rjharrison_> The connector is soldered to the strips on the bottom and it's connected to rf ground so for of the strips are rf ground
[16:24] <rjharrison_> I could trim them
[16:24] <rjharrison_> for = four
[16:24] <hallam> they're connected inside the radiometrix anyway
[16:25] <rjharrison_> and are they connected to the RM case too
[16:25] <hallam> I think it's important to bring them out to the antenna connector, but how/whether you connect them to the common ground of the rest of the circuit shouldn't be a big deal
[16:25] <hallam> yes
[16:25] <rjharrison_> No I dont link the two grounds
[16:26] <hallam> well they are linked in the radiometrix anyway
[16:26] <hallam> IIRC, the datasheet for the radiometrix lists the pins as "gnd" rather than specificaly "rf gnd"
[16:26] <rjharrison_> I just thought rf gound would be ok if it was under the tx
[16:26] <hallam> though obviously with them placed as they are, they're intended to make it easier to keep a sort-of-coaxial shield around the RF OUT
[16:26] <rjharrison_> IIRC?
[16:26] <hallam> if I remember correctly
[16:28] <rjharrison_> You don't IIRC they are labeled rf gnd
[16:28] <rjharrison_> Just had a look
[16:28] <rjharrison_> http://www.radiometrix.co.uk/dsheets/ntx2nrx2.pdf
[16:29] <rjharrison_> That was why I was treating them differently
[16:29] <rjharrison_> They are bloody temp unstable
[16:29] <rjharrison_> I let mine cool befor launch
[16:30] <rjharrison_> to 0deg c
[16:32] <hallam> heh, you think they're temp unstable, try some of the competitors
[16:32] <hallam> the sock method works really well though
[16:32] <hallam> you could do that to your whole flight computer
[16:33] <rjharrison_> hallam if you can see that pic, could just replace the red link wire above the jumper with a forward facing diode and then sorted?
[16:33] <rjharrison_> sock?
[16:34] <hallam> yes, should be fine
[16:34] <rjharrison_> What's the soc menthod
[16:34] <rjharrison_> method
[16:35] <hallam> though as mentioned you might run into trouble if you use 4.5V batteries, they drop from temp to say 4.2, your diode drops it to 3.6V and then you have a regulator with a highish dropout voltage -- I'd recommend sticking with 6V batts, as you say the heat helps anyway
[16:35] <hallam> sock method = wrap up the radiometrix in a ton of insulation
[16:36] <hallam> fergus used multiple alternating layers of space blanket and thin foam
[16:36] <hallam> so that it looked like it was in a fluffy sock
[16:36] <hallam> keeps the temperature very consistent
[16:36] <rjharrison_> I would have to wrap the board to be fair I didn't have to change the frequency for the whole duration of the flight
[16:37] <rjharrison_> It changes the most from 22 - 0 deg c
[16:37] <rjharrison_> 0 to -22 seems not so bad
[16:38] <hallam> interesting
[16:38] <rjharrison_> not sure why but a can of freezer spay is a fun toy
[16:38] <hallam> definitely
[16:38] <hallam> watch out that the NTX2 operating temp rating only goes down to -10C
[16:39] <rjharrison_> if you cool to 0 then launch I'm pretty sure you won't need to change freq as you will remain in the tollerence of the rtty s/w
[16:39] <hallam> crystals and capacitors that aren't appropriately rated can suddenly start going funny around -20
[16:39] <hallam> so I would try to keep the radio and GPS in its rated operating range if poss
[16:40] <rjharrison_> -13.1 was the coldest I got to on sat
[16:41] <rjharrison_> -10 is the lowest op range
[16:41] <rjharrison_> not sure about the lassen i thought it was -40 IIRC
[16:41] <rjharrison_> :)
[16:42] <hallam> I guess your payload box is pretty well insulated then :)
[16:42] <hallam> Nova 9 got down to about -20 internal after some prolonged cold soak at altitude
[16:43] <hallam> I take that back, it was -10, never mind
[16:45] <hallam> ok, I'm going to get on with some work now
[16:45] Nick change: hallam -> hallam|CFD
[16:45] <rjharrison_> I wanted more heat loss but jc convinced me not to put the pp3 heater i made in
[16:46] <rjharrison_> ok
[16:46] <rjharrison_> mee too
[16:46] <rjharrison_> pp3 + 240R
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[16:52] <edmoore> hallam|CFD: i like your username
[17:06] <hallam|CFD> I just want it to be oooooover
[17:07] <edmoore> :)
[17:07] <edmoore> how's it going?
[17:08] <hallam|CFD> I think I'm vaguely nearly there
[17:08] <hallam|CFD> lost all motivation a couple months ago, lost all interest about 6 weeks ago
[17:09] <hallam|CFD> either don't take this class, or get it over with in the first month
[17:09] <edmoore> fair enough
[17:14] <edmoore> so I was on vnc watching jame's listening post for most of rob's flight
[17:14] <edmoore> there were about three instances i recall when the signal just dropped away
[17:14] <edmoore> I'd like to see jame's full logs though
[17:14] <edmoore> but basically I wonder if they were moxon nulls
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[17:54] <edmoore> hi RocketBoy
[17:57] <RocketBoy> hey edmoore
[17:58] <RocketBoy> how are you getting on with the antenna tracker?
[17:58] <edmoore> hitting the scrappie tomorrow with a shopping list and a socket set
[17:59] <edmoore> i will try and do it so it can be easily copied
[18:00] <RocketBoy> I bought a heavy duty CCTV pan and tilt unit a couple on months back - it was going cheap on on ebay
[18:00] <edmoore> that said I am also going to try and get rid of the last of the teddy-nauts chase mud from the inside of my car
[18:00] <edmoore> the feild it landed in was like the Somme
[18:01] <edmoore> suspect it could be a bit of a mission
[18:02] <RocketBoy> yeah HABing and Muddy fileds go together
[18:02] <RocketBoy> (as does rocketry)
[18:02] <RocketBoy> I have to replace the pan and tilt AC mains motors with some steppers methinks
[18:02] <RocketBoy> but then it will be ideal
[18:03] <edmoore> you got a CCTV thing?
[18:03] <RocketBoy> yeah a pan and tilt unit (like you see cameras in the street on)
[18:04] <RocketBoy> it seems ideal as a 2D antenna rotator
[18:04] <edmoore> that would alctually be perfect
[18:04] <edmoore> if there was an outlet of surplus ones somewhere
[18:05] <RocketBoy> the guy that sold me one seemed to have several
[18:05] <RocketBoy> I'll see if I can get the details
[18:06] <edmoore> that would be weatherproof too which is the big downside of my cheapo one
[18:07] <RocketBoy> yeah this one is dicast aluminium with a nice rubber seal
[18:08] <edmoore> would be good it it came with the original lampost :)
[18:08] <RocketBoy> damn I'm going to have to re-boot the router - it gets confused every time I use the iPhone
[18:09] <edmoore> odd
[18:09] <RocketBoy> BB in a mo
[18:09] <edmoore> ok
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[18:18] <natrium42> hi
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[18:25] <natrium42> hola
[18:25] <akawaka> yo
[18:25] <akawaka> hope everyone has a good christmas
[18:28] <edmoore> akawaka: thanks, you too
[18:30] <edmoore> all well?
[18:32] <akawaka> yeah
[18:32] <akawaka> i got engaged
[18:32] <edmoore> oh awesome :)
[18:33] <edmoore> congratulations
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[18:33] <akawaka> thanks
[18:33] <akawaka> and i got a telescope
[18:35] <edmoore> win-win!
[18:35] <edmoore> what kind of telescope?
[18:37] <akawaka> orion xt8
[18:38] <akawaka> 8" dobsonian reflector
[18:38] <akawaka> seemed like a good started scope
[18:38] <edmoore> I'd love to get one. The stars have been great here recently
[18:39] <akawaka> saw some of the orion nebula last night, the first night out, and it blew me away
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[18:39] <akawaka> i was expecting to be disappointed, since there are so many good images online
[18:40] <edmoore> wow!
[18:41] <edmoore> I always understood that they were a different ball-game to what you could actually see with eyes because they're very long exposures with ccds sensitive to hydrogen wavelengths
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[18:43] <natrium_> fixed my intertubes
[18:43] Nick change: natrium_ -> natrium42
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[20:27] <rjharrison> quick question should flowing zeros be removed from lat and long eg 53.45000 = 54.45
[20:28] <rjharrison> following
[20:30] <natrium42> it doesn't really matter
[20:31] <natrium42> only if you want to shorten the message?
[20:31] <rjharrison> Ok, its actually easier to read the data if it's more or less consistant lenght
[20:31] <rjharrison> length
[20:32] <natrium42> now, CRC would be nice :)
[20:33] <rjharrison> Yep after my rather embarasing claim to another 400 meters from my log
[20:33] <rjharrison> and a 2 had become a 6
[20:34] <natrium42> hehe
[20:34] <natrium42> you can just do a simple checksum as in nmea
[20:34] <rjharrison> go on
[20:34] <natrium42> http://en.wikipedia.org/wiki/NMEA
[20:35] <natrium42> "The asterisk is immediately followed by a two-digit checksum representing a hex number. The checksum is the exclusive OR of all characters between the '$' and '*'. According to the official specification, the checksum is optional for most data sentences, but is compulsory for RMA, RMB, and RMC (among others)."
[20:35] <natrium42> so just XORing each byte would work
[20:35] <rjharrison> That dosent sound so hard
[20:37] <natrium42> yeah, pretty easy
[20:38] <natrium42> that way the tracker will know which positions are most likely correct
[20:38] <natrium42> the others can be added as semi transparent markers or something
[20:38] <natrium42> i.e. where the checksum is wrong
[20:40] <RocketBoy> A checkum would have certainly detected the single bit error - but it wouldn't have indicated where the error is
[20:40] <natrium42> yeah, we could use something more advanced
[20:41] <natrium42> to correct single bit errors
[20:42] <RocketBoy> somthing like turbo codes or reed solomon
[20:43] <RocketBoy> I think TCs transmit the data block in clear (i.e. un-encoded) followed by the correction codes
[20:43] <RocketBoy> that way you can human read it - and then correct it if required
[20:45] <RocketBoy> alternativly packet radio includes a CRC which is uesed to discrasdd the packet if corrupted (not much good if the comms link is marginal)
[20:55] <akawaka> that bit us
[20:55] <akawaka> lots of aprs packets lost because of a few messed up bits
[21:02] <rjharrison> Humm I think that will be the listener version 2
[21:04] <rjharrison> I liked natriums xor on the bytes
[21:07] <rjharrison> I think we may not need much more than xor if we have multiple listeners
[21:08] <rjharrison> What do we think
[21:08] <rjharrison> I'm hoping that most flights are going to have at least 2 listeners and we can reject packets that arn't matched twice
[21:09] <rjharrison> natrium42 you might think differently if you're on your own launching
[21:09] <rjharrison> BTW are you going up again soon
[21:12] <RocketBoy> yeah I would think a simple checkup (NMEA like) would be the way to go then - we could simply chuck way corrupt packets and take the OK ones from another station
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[23:28] <natrium42> hi zeusbot
[23:29] <Laurenceb> bbl
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[23:34] <hallam|CFD> so my coursework project is on simulation of supersonic flow in a duct
[23:34] <hallam|CFD> I'm hoping by clever geometry to turn it into supersonic flow in a duck, which would be much more interesting
[23:35] <gordonjcp> hallam|CFD: it would be quite easy to make a supersonic duck
[23:35] <gordonjcp> all you'd really need is a conventional subsonic duck, something to produce additional thrust, and some gaffa tape to keep the PETA whiners quiet
[23:35] <rjharrison> nights
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[23:37] <hallam|CFD> yeah I guess it's almost a solved problem
[23:38] <hallam|CFD> but the quacks would only propagate backwards
[23:47] <Laurenceb> lol
[23:47] Action: Laurenceb searches for dual element PIN diodes
[00:00] --- Tue Jan 6 2009