highaltitude.log.20151112

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[10:38] <RealBorg> eroomde, a nozzle for low ambient pressure would be almost a half sphere while one for high pressure would tend to resemble a pipe, correct?
[10:39] <eroomde> no
[10:41] <eroomde> their shape is the same regardless, to a first approximation. It's the area ratio (mouth/throat) that you care about
[10:41] <eroomde> higher for higher pressure ratios
[10:42] <eroomde> but pipes vs spheres is not a helpful way to think about it
[10:44] <RealBorg> so in vacuum the mouth would only be slightly larger than the throat
[10:44] <eroomde> no
[10:44] <eroomde> the opposite
[10:57] <Laurenceb> http://www.cs.cmu.edu/afs/cs/usr/mnr/st/std155
[10:58] <Laurenceb> https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CCMQFjABahUKEwiz65383IrJAhXEWBQKHWQwBto&url=https%3A%2F%2Fengineering.purdue.edu%2FAAE%2FAcademics%2FCourses%2Faae539%2F2007%2Fspring%2Fhandouts%2FAFISPCodeTutorial.ppt&usg=AFQjCNGrnls6z-Y-4zHFDmvOqKTOFsirtQ&cad=rja
[10:59] <Laurenceb> you could play around with that
[10:59] <Laurenceb> if you can find a copy of the executable
[11:00] <Laurenceb> used to be on dtic.mil but I cant find it
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[11:10] <Laurenceb> https://web.archive.org/web/*/www.dunnspace.com/isp2001.zip
[11:12] <day> RealBorg: in a vacuum your exhaust needs to be equalized to zero pressure, that means you need to expand the gas much further, that means you need a bigger nozzle. eroomde correct me if im wrong
[11:15] <eroomde> you are correct
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[11:17] <day> eroomde: does the nozzle diameter expand linear towards the end or exponential?
[11:18] <RealBorg> if you had no nozzle you would waste a lot of energy to ehaust epanding sideways, correct?
[11:18] <RealBorg> +xx
[11:20] <eroomde> RealBorg: yes
[11:20] <eroomde> day: open research
[11:20] <eroomde> have a google for truncated ideal nozzle
[11:20] <eroomde> that's about as good as we can do in theory
[11:21] <eroomde> in theory it asymptotically approaches parallel, in practice we can't have infinitely long nozzles so we truncate, with a small adjustment for end effects
[11:21] <RealBorg> " in theory it asymptotically approaches parallel" <- thats what I was trying to say in the first place
[11:24] <eroomde> it's parabolic (for decent ones) in both cases
[11:24] <eroomde> no half sphere stuff
[11:24] <eroomde> the shape is normalised, to an extent
[11:25] <eroomde> there is some consideration to be made for the transition from throat to nozzle
[11:25] <RealBorg> I just wanted to ask the other extreme - so parabolic is between cone and sphere
[11:25] <eroomde> yes
[11:26] <eroomde> for cheap stuff you might get away with a cone
[11:26] <eroomde> you really worry about truncated ideal parabolas when you're chasing after the last %s
[11:26] <eroomde> which is of course A Really Big Deal for orbital launchers because of the exponential nature of the reocket equation
[11:26] <eroomde> but not such a big deal for a cheaper missile or whatever
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[11:32] <Laurenceb> I'm using a cone on my rockoon
[11:32] <Laurenceb> gives ~1% ISP penalty compared to bell, so *shrug*
[11:33] <FuzzyLemon> can you use a PITS and an AstroPi together on the same RaspberryPi?
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[11:38] <day> eroomde: oh. they look a lot more complicated than i thought
[11:39] <eroomde> yes
[11:39] <eroomde> now try and make one that works at all altitudes
[11:41] <RealBorg> https://en.wikipedia.org/wiki/Aerospike_engine
[11:42] <day> eroomde: shouldnt throttling the power at higher altitudes help to keep the exhaust pressure in check? :p
[11:43] <eroomde> yes but you lose thrust
[11:43] <eroomde> so your gravity losses go up
[11:43] <eroomde> no-show
[11:43] <eroomde> also many engines can't be throttled that much
[11:43] <day> i just wanted to be a smartass :p
[11:43] <eroomde> they go unstable
[11:43] <day> seems like an unsolvable problem to me, unless you modify the exhaust form during the flight :/
[11:45] <day> maybe with detachable ring segments something could be done cheaply
[11:45] <eroomde> detacheable != cheap
[11:45] <eroomde> the opposite
[11:45] <eroomde> we've done it without detaching anything
[11:46] <day> you did it cheaper?
[11:48] <eroomde> yes, assuming this is towards making a very cheap way of launching stuff orbitally
[11:48] <eroomde> be definition you don't want disposable things
[11:48] <eroomde> you mightaswell just make the rocket disposable and charge $200M/flight like they do now
[11:49] <day> well if you factor in reusability i can see how it would be cheaper. but for one way things, i cant imagine how a highly complex exhaust with dozens of microcontroller controlled elements would be cheaper than simply detaching a few things :/
[11:50] <eroomde> who said anything about that? dozens of microcontrollers?
[11:50] <adamgreig> not that dozens of controlled elements is the way to do an altitude compensating nozzle perhaps
[11:50] <adamgreig> but like
[11:50] <adamgreig> "simply detaching"
[11:50] <eroomde> i think you're very confused day
[11:50] <eroomde> read up on how shock waves interact, and start to think about how you might use that to your advantage
[11:51] Action: day /wc s adamgreig
[11:52] <eroomde> there exist solutions that require absolutely no actively controlled parts, just some insight into the fluid and thermodynamics
[11:55] <adamgreig> day: you need a _bigger_ nozzle at higher altitudes
[11:55] <adamgreig> detachable parts do not help much with that really
[11:56] <eroomde> i wasn't even going to go there given the whole notion of detachable or microcontrollers which such a completely false dichotomy
[11:56] <eroomde> but yes, even if it were true, i'm not sure how detachable helops
[11:56] <eroomde> helps*
[11:56] <adamgreig> what you want is like, a series of bigger and bigger nozzles, sprung loaded
[11:56] <adamgreig> you throw away the small ones
[11:56] <adamgreig> as you gain altitude
[11:56] <adamgreig> slotting the bigger ones into place
[11:56] <eroomde> in a magazine
[11:56] <adamgreig> right?
[11:56] <adamgreig> right
[11:56] <eroomde> you could store them in the payload bay
[11:56] <adamgreig> bonus: you can dump heat into the nozzles you throw away
[11:56] <SpacenearUS> New vehicle on the map: 03VE2WMG-11 - 12http://tracker.habhub.org/#!qm=All&q=VE2WMG-11
[11:57] <day> adamgreig: you need more imagination man //\\. Drop the inner part, voila bigger nozzle :p *ignore the 2tons more you carry*
[11:58] <adamgreig> uhm
[11:58] <adamgreig> I mean I guess that would alter your area ratio
[11:59] <eroomde> anyway yes, the aerospike article that RealBorg linked to is a potential solution
[12:00] <adamgreig> but like https://en.wikipedia.org/wiki/Altitude_compensating_nozzle
[12:01] <adamgreig> whole wikipedia article about this
[12:01] <adamgreig> https://en.wikipedia.org/wiki/Nozzle_extension is like the opposite of your throwing-bits-away idea day
[12:01] <adamgreig> I don't think you could drop bits out of the middle in any sane system
[12:01] <adamgreig> like, how would your combustion chamber mate to that
[12:05] <eroomde> i swear hackerspace mailing lists are contributed to by markof chains
[12:06] <russss> a lot of the time markov chains would be more useful
[12:06] <eroomde> there is a massive subculture of people who have managed to get PhD funding for something that involves 'exploring the intersection of' two things that it had never occured to me might intersect, usually to do with a specific technology and some social issue
[12:06] <eroomde> so the latest was something about virtual realtity experiences of domestic violence (PhD, funded)
[12:07] <eroomde> and the corresponding hackerspace mail about how they need someone to just quickly code up the occulus rift bit
[12:07] <eroomde> or something
[12:08] <eroomde> i don't understand
[12:08] <adamgreig> I assume it's like the phds that would get funded in social sciences and would have been quite reasonable there, and the people doing them would have been doing these normal social science PhDs
[12:08] <adamgreig> but it's cool and trendy to add some modern technology to the mix
[12:09] <eroomde> the last thing that made me angry was something described as a 'digital tumour' which was a plastic bag with a fan that would inflate if the number of unhappy words on twitter in the last hour went above some threshold
[12:09] <eroomde> (funded research)
[12:09] <adamgreig> wonder what they do for 3 years
[12:09] <eroomde> i sat through a whole 30 min talk in this vein at a conference last year
[12:10] <eroomde> and nearly opened my own vein at the end
[12:10] <gonzo_> would it not be easier to offer real experiences of domestiv violence. Take socits into a room and em a kacking
[12:11] <gonzo_> we need a B ark
[12:11] <eroomde> adamgreig: well exactly. the only social good seems to be keeping them employed in some sense for 3 years
[12:11] <eroomde> not that academia exists for pure utility
[12:12] <eroomde> but i don't think publically funding a fan in a bin bag is ok
[12:12] <chris_99> wonder which funding body funded it?
[12:12] <adamgreig> it seems like maybe some EPSRC types shoudl sit on the ARC funding committees
[12:13] <adamgreig> AHRC even
[12:13] <eroomde> there was one thing i saw (not funded research, just at a gallery) which was a projector showing white noise, with an audio track in the backround that osscasionally had someone screaming
[12:13] <eroomde> the curatorial note by the artist was along the lines of 'my work explores the delicate interface between information and data'
[12:13] <fsphil> lol
[12:14] <eroomde> at which point you want to get out a can of red spray paint and grafitti something like 'NO BITCH, THAT WAS SHANNON'
[12:15] <eroomde> and then perhaps a reasoned essay about how this bollocks doesn't even approach the insight and beauty of shannons exploration of that (quite robust, actually) interface and if only you'd payed more attention during maths class you might actually be able to have some conception of...
[12:15] <eroomde> etc
[12:15] <eroomde> but instead you just move on to the next painting
[12:15] <eroomde> and then get a nice sandwich at the gallery restaurant
[12:15] <eroomde> it was quite a nice visit overall, actually
[12:21] <adamgreig> it's a shame as you feel that in principle someone might be able to do some nice art with this sort of thing
[12:21] <adamgreig> and sometimes people do pull it off
[12:21] <adamgreig> i still really like Listening Post at the science museum
[12:22] <Darkside> yes that was cool
[12:22] <Darkside> still would like to know what IRC channels it looks t
[12:22] <Darkside> (if it does actually look at any)
[12:23] <fsphil> could be playing back logs
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[13:28] Action: Laurenceb is having "fun"
[13:29] <Laurenceb> trying to fit an 868mhz antenna onto a 18mm diameter rockoon
[13:29] <adamgreig> lol
[13:29] <chris_99> cool, using a tracker on the rocket now?
[13:30] <Laurenceb> chris_99: I realised I could get an 868mhz tracker down to 800mg
[13:30] <Laurenceb> so it might as well go on
[13:30] <Laurenceb> but I "just" have to fit the antenna
[13:30] <chris_99> sweet, what type of modulation/power will it use
[13:30] <Laurenceb> CW, 20mW x piss poor antenna efficiency
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[13:37] <ntx2> Hi - have a question about generating payload document
[13:37] <ntx2> in the parser configuration, it is asking me for a description for no gps lock
[13:38] <ntx2> my payload sends 0 when there is no lock
[13:38] <ntx2> and that is what is present in the sample I gave to the configurator
[13:39] <ntx2> so if I say that it sends a 1,2 or 3, then the GPS location should be marked as good
[13:39] <ntx2> will that be ok?
[13:39] <ntx2> or is there a better way to do this?
[13:40] <chris_99> oh interesting Laurenceb, so CW means essentially just turning on/off a carrier wave?
[13:40] <Laurenceb> no
[13:40] <Laurenceb> just turning it on
[13:40] <chris_99> surely you have to turn it off too?
[13:40] <Laurenceb> my design is a PLL and a GMR sensor IC to turn it on
[13:41] <Laurenceb> nope it just runs until the lipo is flat
[13:41] <chris_99> how does it convey data then?
[13:41] <Laurenceb> it doesnt need to
[13:41] <chris_99> oh!
[13:41] <Laurenceb> it just provides the ground stations with something to track
[13:41] <chris_99> but you could convey data, if you modulate it on/off right
[13:42] <Laurenceb> yes
[13:45] <chris_99> so would it be triangulation you'd use to pinpoint it's location
[13:45] <ntx2> Hey - I just created my flight document for a planned launch this Sunday 15/11 from south of Paris, France. Document id - ID:fb6492b1e3c094f025fdbae0fbc1ca6e. How to ask for permission to be included in the calendar etc?
[13:45] <adamgreig> more like a weird trilateration
[13:45] <chris_99> ah i always get those mixed up
[13:48] <eroomde> trilateration is for when you can't do it right now
[13:48] <jonsowman> heh
[13:49] <UpuWork> [13:49] <SpacenearUS> Payload parse status: 1 untested (b503)
[13:49] <ntx2> hello: sorry to interrupt. Is this the right forum for flight document approvals? Or should I ask on the habhub IRC?
[13:49] <UpuWork> please test your payload ntx2
[13:49] <ntx2> is there something wrong?
[13:49] <UpuWork> Join #habhub
[13:49] <UpuWork> lets discuss in there
[13:50] <chris_99> eroomde, whatcha mean, by right now?
[13:50] <eroomde> it was a bad joke
[13:50] <adamgreig> I giggled :P
[13:52] <chris_99> out of interest, say you had enough fuel etc. how easy would it be to beacon the altitude of a rocket, once out of the atmosphere
[13:52] <chris_99> would you need GPS, or.. could you do it a simpler way
[13:52] <adamgreig> measuring the altitude is more of a problem than transmitting it
[13:52] <chris_99> yeah
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[13:53] <adamgreig> barometric sensors don't work so well above 30km or so
[13:53] <chris_99> GPS sats would be high enough though right?
[13:53] <eroomde> yes
[13:53] <adamgreig> oh yea, GPS sats are used for satellites
[13:53] <chris_99> oh heh interesting
[13:53] <adamgreig> LEO satellites
[13:53] <eroomde> assuming you're not going above low earth orbit
[13:53] <adamgreig> but most commercially available GPS receivers won't output a position above some tens of km
[13:53] <chris_99> so GPS would be the only way?
[13:53] <adamgreig> eh
[13:54] <adamgreig> you might anticipate they had ways of doing this before the GPS constellation was operational
[13:54] <adamgreig> GPS is probably easiest though I guess
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[13:54] <chris_99> what did they use prior?
[13:54] <adamgreig> I guess a lot of it was probably ground radar systems
[13:54] <eroomde> exactly so
[13:54] <chris_99> ah makes sense
[13:55] <adamgreig> onboard the rocket you can do an alright job of estimating altitude from adding up accelerations or from having good models of your motor
[13:55] <chris_99> ah, kind of dead-reckoning
[13:55] <adamgreig> probably some other clever options.. wonder if many things flew a radar on the rocket that ranged the ground
[13:57] <adamgreig> probably a bit of a pain to do that well while flying
[13:58] <eroomde> some sats use gps signals as radar
[13:58] <adamgreig> Above leo?
[13:58] <eroomde> they directly measure their own pos with gps then catch reflections of gps signals off the oceans
[13:59] <eroomde> to measure ocean levels
[13:59] <eroomde> no this is LEO
[13:59] <adamgreig> Oh neat
[13:59] <adamgreig> Aren't the oceans all 0m ASL :P
[13:59] <SpacenearUS> New vehicle on the map: 03car_chase - 12http://tracker.habhub.org/#!qm=All&q=car_chase
[14:01] <eroomde> ho.
[14:05] <Laurenceb> in the "old days" almost everyone used trilateration and related methods
[14:05] <Laurenceb> to get very accurate orbital parameters
[14:06] <Laurenceb> its still very useful, although lots of people use laser retro-reflectors now
[14:09] <chris_99> could you use a ublox chip on a rocket then out of interest? assuming the velocity is < 512m/s
[14:11] <eroomde> and acceleration limits
[14:14] <chris_99> ah yeah 39.2 m/s^2 apparently
[14:21] <eroomde> 4G between friends
[14:23] <chris_99> i can't really see the point of adding such limits, as the people who are capable of building a guided missile would surely just use an SDR
[14:24] <eroomde> they were worrying about this in the 1970s
[14:24] <eroomde> the situation is somewhat different now but only recently
[14:25] <SpacenearUS> New vehicle on the map: 03FRINUS - 12http://tracker.habhub.org/#!qm=All&q=FRINUS
[14:25] <eroomde> but yes DIY gps would be the way to go for anything more than a super gaza-strip special drainpipe rocket
[14:25] <chris_99> hehe
[14:28] <eroomde> are you thinking of building a rocket then chris_99 ?
[14:29] <chris_99> first a simple HAB, i've got my 868+433 silab modules now, but a rocket does sound fun!
[14:30] <eroomde> they are fun, certainly
[14:31] <chris_99> i await with interest on Laurenceb's ones :)
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[14:43] <mfa298> Br0ads1d3
[14:44] Action: mfa298 chages passwords quickly
[14:44] <Laurenceb> bro.. aids?
[14:44] <chris_99> heh
[14:44] <mfa298> luckily nothing to important, just screen password at work
[14:44] <Laurenceb> yeah right
[14:50] <mfa298> most things use a couple of different passwords
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[15:05] <mfa298> and Laurenceb you obviously don't know your beers. At least not some of the good Suffolk ones.
[15:05] <Laurenceb> oh i see
[15:05] <eroomde> he was oxford
[15:05] <eroomde> cusf people know adnams stuff properly
[15:06] <Laurenceb> think I worked out the antenna
[15:06] <chris_99> oh broadside heh
[15:06] <Laurenceb> foil helix around the rocket
[15:06] <mfa298> now I'll need to find some other good beer for a password :p
[15:08] <adamgreig> Laurenceb: would be interested in seeing a foil helix
[15:09] <Laurenceb> not sure how much I trust EZNEC
[15:09] <adamgreig> would have thought a magnet wire helix would be a fair bit easier if you don't need th ebandwidth
[15:09] <Laurenceb> aiui skin effect leads to poor efficiency
[15:10] <Laurenceb> foil helix should be quite easy, just glue the foil on starting at an angle and wind it
[15:10] <Laurenceb> fact that Klima motors are cardboard/phenolic resin helps a lot
[15:11] <mattbrejza> Laurenceb: the datasheet/appnotes for the si4012 have stuff about loop antennas
[15:11] <mattbrejza> that IC can also autotune for them too
[15:12] <Laurenceb> really?!
[15:12] <mattbrejza> (its a 868 part)
[15:12] <mattbrejza> yea
[15:12] <Laurenceb> wow, reading
[15:12] <Laurenceb> thanks
[15:12] <mattbrejza> np
[15:12] <Laurenceb> xtal less wow
[15:12] <fsphil> autotuning at 869mhz, that's odd
[15:12] <Laurenceb> fsphil: for matching to loop antenna
[15:13] <FuzzyLemon> is there a gas cylinder on earth that can withstand 5000bar pressure?
[15:13] <Laurenceb> which is an almightly pain
[15:13] <fsphil> ah
[15:13] <Laurenceb> FuzzLemon: plenty of nice CF stuff that can
[15:13] <Laurenceb> or steel if you want cheap and heavy
[15:13] <chris_99> if you're in suffolk mfa298, you're near old chimneys brewery :)
[15:13] <Laurenceb> looks for some of the scuba kit
[15:14] <Laurenceb> 3.9v max voltage
[15:14] <Laurenceb> why silabs, whyyyyy
[15:15] Action: Oddstr13 looks at the RFM69's max voltage of 3.6V
[15:15] <Oddstr13> meh :P
[15:16] <mattbrejza> Laurenceb: i have one running from a coin cell. I guess 10mW might be a bit less than you wanted?
[15:17] <adamgreig> what's 3dB between friends
[15:17] <Laurenceb> 10mW is fine
[15:17] <Laurenceb> its got many tens of dB of link margin
[15:17] <Laurenceb> but I've got one of the 300mg full river lipo cells to power it
[15:17] <Laurenceb> which is 4.2v
[15:17] <adamgreig> it's probably fine lol
[15:17] <adamgreig> abs max is usually +-10% or so ;)
[15:18] <Laurenceb> yeah Leo runs silabs off 4.2v
[15:18] <mattbrejza> https://drive.google.com/open?id=1sP_3sj-TVsLFedsxd0yKPfKGzacXqfb-rA
[15:18] <mattbrejza> attaching battery was an afterthought
[15:18] <Laurenceb> nice
[15:18] <Laurenceb> but heavy xtal lol
[15:18] <Laurenceb> thats going to be half your mass
[15:18] <adamgreig> well don't use hc49 tin cans anywya
[15:19] <mattbrejza> yea these were for attaching to lampposts with magnets
[15:19] <adamgreig> modern xtal is like 2x1mm or something stupid
[15:19] <Laurenceb> oh
[15:19] <mattbrejza> hc49 because its cheap
[15:19] <mattbrejza> https://drive.google.com/open?id=1iBOhrrOeRl8BHntDDlc8UKVO08DrMcF-kA
[15:19] <mattbrejza> also the ukhasnet stuff needs better accuracy than the crystaless mode
[15:21] <Laurenceb> hmm
[15:21] <Laurenceb> in theory that si4012 could run with a pcb 16mm diamter loop
[15:21] <Laurenceb> I think
[15:22] <mattbrejza> i seem to remember a long appnote about antennas if you havnt already found it
[15:23] <adamgreig> SI's app notes are more like app books
[15:23] <Laurenceb> yeah
[15:23] <Laurenceb> only disadvantage is that it needs a micro
[15:23] <adamgreig> si4010
[15:23] <Laurenceb> also helix antenna has quite high efficiency
[15:24] <adamgreig> micro builtin
[15:24] <adamgreig> same RF
[15:24] <Laurenceb> oh
[15:24] <Laurenceb> cool
[15:25] <Laurenceb> what c compiler do you use?
[15:25] <mattbrejza> does the 4010 have the same rf part as the 4012?
[15:25] <adamgreig> sdcc
[15:25] <adamgreig> yes mattbrejza
[15:25] <Laurenceb> ok
[15:25] <mattbrejza> ok
[15:26] <Laurenceb> what programmer do you use?
[15:32] <adamgreig> eugh
[15:32] <mattbrejza> where is the pic of it..?
[15:32] <Laurenceb> this baby?
[15:32] <Laurenceb> http://www.silabs.com/Support%20Documents/TechnicalDocs/EZRadioDevKit-UG.pdf
[15:32] <adamgreig> heck no
[15:32] <Laurenceb> lol
[15:32] <adamgreig> the silabs debug toolstick with programming daughterboard
[15:32] <adamgreig> which to be fair is <£20 and available on farnell
[15:32] <Laurenceb> OK
[15:32] <Laurenceb> sounds nicer
[15:33] <adamgreig> but I've shed so many tears that my plan is to make my own programmer for their c2 interface
[15:33] <Laurenceb> ok
[15:33] <Laurenceb> what interface software is there?
[15:33] <adamgreig> something something studio
[15:33] <adamgreig> eclipse based
[15:33] <adamgreig> runs linux/windows/mac
[15:33] <Laurenceb> ok
[15:34] <adamgreig> free
[15:34] <adamgreig> it's alright enough
[15:34] <adamgreig> you can use sdcc to build a .hex and they have a java thing that talks to their programmer,reads a .hex, flashes a chip
[15:34] <adamgreig> it's a bit gross and works only 40% of the time which is annoying
[15:35] <Laurenceb> ok
[15:35] <Laurenceb> sounds like old school avr
[15:35] Action: Laurenceb is getting confused by loops
[15:35] <Laurenceb> http://www.antenna-theory.com/antennas/smallLoop.php
[15:37] <Laurenceb> I get max power -12dBm using a 16mm diameter loop at 686 and the si4010 PA
[15:37] <Laurenceb> not very hot
[15:37] <Laurenceb> wait I'm stupid
[15:38] <Laurenceb> it needs matching balun and crazy stuff
[15:38] <Laurenceb> direct drive wont work
[15:38] <Laurenceb> helix starts to look simpler :P
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[15:48] <Laurenceb> the problem is that small loops are massively inductive
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[15:55] <Laurenceb> I suspect a 3 turn helix + scalple to trim the end would work
[15:57] <gonzo_> why do you need a loop?
[15:58] <gonzo_> horisontal polarisation?
[15:59] <Laurenceb> I dont need a loop, its just nice from a mechanical point of view
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[16:00] <mattbrejza> you could almost manage a dipole along the outside casing?
[16:00] <Laurenceb> not really
[16:00] <Laurenceb> only 110mm tall
[16:01] <mattbrejza> folded dipole?
[16:01] <Laurenceb> maybe lol
[16:01] <Laurenceb> I suck at this stuff
[16:01] <SpacenearUS> New vehicle on the map: 03N7ERU-12 - 12http://tracker.habhub.org/#!qm=All&q=N7ERU-12
[16:01] <SpacenearUS> New vehicle on the map: 03KA7NSR-9 - 12http://tracker.habhub.org/#!qm=All&q=KA7NSR-9
[16:02] <SpacenearUS> New vehicle on the map: 03KA7NSR-15 - 12http://tracker.habhub.org/#!qm=All&q=KA7NSR-15
[16:02] <mattbrejza> does it even matter if an antenna wire trails or sticks out the top?
[16:02] <craag> helical dipole..
[16:02] <Laurenceb> thats kind of what I'm designing atm
[16:02] <craag> sounds as if it would be perfect rf polarisation wise too
[16:03] <craag> (we use severl on the websdr for V+H dual pol)
[16:03] <Laurenceb> interesting
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[16:04] <Laurenceb> got 1.1SWR with 2.5 turns
[16:07] <craag> yeah they're basically a mildly loaded dipole
[16:07] <craag> but you also get a bit closer to isotropic too
[16:07] <Laurenceb> http://i.imgur.com/subsiIE.png
[16:07] <Laurenceb> silly EZNEC elements limit :P
[16:07] <Laurenceb> but it proves the principle
[16:07] <craag> http://www.g8jnj.net/mixedmodehelical.htm
[16:07] <Laurenceb> top is the "PCB"
[16:10] <Laurenceb> and the graphics is glitchy in wine
[16:10] <adamgreig> your wires are 1mm thick and 1e-24 m long?
[16:10] <Laurenceb> yes
[16:10] <adamgreig> seems quite short
[16:10] <Laurenceb> it seems to be something to do with fonts
[16:10] <Laurenceb> I see a ton of errors
[16:11] <Laurenceb> and for some reason that gives incorrect exponents on the GUI
[16:11] <adamgreig> lol
[16:11] <Laurenceb> BW is quite nice
[16:12] <Laurenceb> considering a loop is equivalent to well over 10 SWR even at resonance
[16:12] <Laurenceb> its just not possible to get enough power into it without loads of balun crazyness
[16:14] <Laurenceb> which I strongly suspect might break the autotune
[16:14] <Laurenceb> but I guess I'll read the App note when I get time lol
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[16:34] <Laurenceb> unless... http://i.imgur.com/JiRHr3L.png
[16:40] <eroomde> good lord Laurenceb
[16:40] <Laurenceb> my first circuit
[16:41] <Laurenceb> c==1.5pF
[16:43] <Laurenceb> http://uk.rs-online.com/web/p/products/7710561/?grossPrice=Y&cm_mmc=UK-PLA-_-google-_-RS+UK+Shopping-_-Google+Shopping&mkwid=sTMUKcNdn_dc|pcrid|64872701163|pkw||pmt||prd|7710561&gclid=CNSbtouqi8kCFdQaGwoddK4JbA
[16:43] <Laurenceb> that actually looks like okish value
[16:46] <Laurenceb> oh god
[16:46] <Laurenceb> https://github.com/dimhoff/ser4010/blob/master/firmware/common/PLACE%20SI4010%20COMMON%20FILES%20HERE.txt
[16:47] Action: Laurenceb isnt a fan of that sort of stuff
[16:48] <adamgreig> lol awful
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[16:48] <adamgreig> you can avoid all that stuff
[16:48] <adamgreig> though it's a bit more work
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[17:16] <SpeedEvil> http://imgur.com/gallery/wUrWRIW - retrieving stuff from trees at height can be dangerous
[17:17] <chris_99> lol
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[17:39] <chrisstubbs> Howdy, I'm selling my Yaesu FT-817 if anyone is interested
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[17:57] <SpacenearUS> New vehicle on the map: 03CALLSIGN123_chase - 12http://tracker.habhub.org/#!qm=All&q=CALLSIGN123_chase
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[18:46] <Lunar_Lander> evening
[18:52] <Laurenceb> https://www.youtube.com/watch?v=Za54_iYGXeo&t=0m40s
[18:52] <Laurenceb> lulz
[18:54] <SpeedEvil> heh
[18:59] <Laurenceb> this is interesting - adding a ring to the bottom allows only 1.5 turns to work
[18:59] <Laurenceb> and its winder too
[19:00] <Laurenceb> 3dB bandwidth of 70Mhz
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[19:05] <michal_f> hi
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[19:23] <chrisstubbs> Hi michal_f
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[20:00] Nick change: Geoff-G8DHE -> Geoff-G8DHE_
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[20:18] <SpacenearUS> New vehicle on the map: 03Subaru_chase - 12http://tracker.habhub.org/#!qm=All&q=Subaru_chase
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[20:23] <Laurenceb> does anyone here have full version of EZNEC?
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[22:15] <OZ1SKY_Brian> hi
[22:26] <Lunar_Lander> HI
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[23:00] <Laurenceb_> decisions decisions
[23:00] <Laurenceb_> to si010 or not to si4010
[23:02] <Laurenceb_> I missed an important detail
[23:02] <Laurenceb_> http://www.edom.com.tw/userfiles/Image/RF_6.jpg
[23:02] <Laurenceb_> that design has built in balun
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[23:46] <superkuh> re: multi-mode helix with center feed: you can feed an axial helix at both ends and get two 50 ohm feeds of opposite polarity too.
[23:46] <superkuh> Or if it's a tapered helix opposite polarity with frequency offset for up and downlink freqs.
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[23:49] <Laurenceb_> v interesting
[23:49] <Laurenceb_> I seem to have a design that works very well in eznec now
[23:49] <Laurenceb_> single turn helix with copper foil rings on either end
[23:50] <Laurenceb_> gets 100mhz 3dB bandwidth arund 868Mhz
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[23:51] <Laurenceb_> just noticed si4010 needs 480ohm load :-S
[23:51] <Laurenceb_> thats far from easy
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[00:00] --- Fri Nov 13 2015