#qi-hardware IRC log for Sunday, 2015-03-15

Mike25226hmmmm... Do you think researching/making an amplifier would be a better option since, like you said, PCB antennas are fairly standard00:06
whitequarkthese are commodity hardware00:07
Mike25226Not sure I'm following.  If the design is fairly standard... how else can you improve such an antenna, if not with some sort of amplifier00:09
whitequarkwhat exactly do you want to achieve00:14
Mike25226better range00:14
Mike25226as well as good signal level00:15
whitequarkand you want an omnidirectional antenna with an amplifier?00:18
whitequarkand illegal, too00:19
whitequarkpointless because signal drops off as 1/r^2 (for a more powerful transmitter), in addition to receiver picking up garbage on the same channel from afar (for a more sensitive receiver)00:20
whitequarkyou could a) use a directional antenna b) set up a network out of several routers00:21
Mike25226Inverse square law?00:24
DocScrutinizer05generally an antenna with good gain would help. Hardly feasible as PCB antenna though00:26
DocScrutinizer05decen ground plane antenna has quite a bit of gain from 2D (omni)directional00:27
DocScrutinizer05however will fail when you want to go vertical between AP and client00:28
DocScrutinizer05I.E. a ground plane antenna in attic is rather contraproductive for clients inhouse "under" the antenna00:29
DocScrutinizer05use MIMO00:30
DocScrutinizer05it basically acts like an adaptive virtual directional antenna00:31
Mike25226MIMO is a multiple antenna design right?00:31
DocScrutinizer05also see http://en.wikipedia.org/wiki/Smart_Antennas00:33
Mike25226Wouldn't a wireless card have to support it? I'm guessing it's not as simple as  MAIN--= ,   AUX--=  , = is 2 antennas 00:37
DocScrutinizer05yes, and many wireless cards _do_ support MIMO00:37
whitequarkactually, you would frequently encounter cards with literally these ports00:38
DocScrutinizer05and it is like they have 2 antenna connectors00:38
whitequarkmy latop has one00:38
DocScrutinizer05recently I've seen APs with even 3 or 4 antennas00:39
DocScrutinizer05unclear if that's one antenna for 2.4 and one for 5, or MIMO-2 with 2 multiband antenna connectors00:41
DocScrutinizer05often it's even configurable in vard's registers00:41
whitequarkI think 2.4 and 5 usually use the same antenna00:42
Mike25226there is only one PCB antenna and both MAIN and AUX go to it00:42
DocScrutinizer05usually, but not generally00:42
whitequarkread some appnotes, they say it's good enough00:42
DocScrutinizer05suggests MIMO00:47
DocScrutinizer05http://www.ebay.co.uk/itm/Genuine-Intel-Dual-Band-7260NGW-AN-WiFi-module-802-11abgn-2x2-MIMO-NGFF-M-2-/251849854651  >>Genuine Intel Dual Band 7260NGW AN WiFi module 802.11abgn 2x2 MIMO NGFF M.2<<00:48
Mike25226my laptop only uses 100:49
Mike25226watching a disassembly video to verify 00:54
whitequarkcrack it oopen00:55
DocScrutinizer05wMIMO only makes sense with multiple physically distinct antennas. When your laptop only has one, it can't do MIMO00:58
DocScrutinizer05conecting both antenna jacks of a mimo card to same antenna is contraproductive00:59
Mike25226I've opened it before, and was 90% certain it only had one (twice actually).  But I always feel the need to assure myself when i have the smallest bit of doubt.  Guess you could say I lack confidence01:00
Mike25226only has one01:01
DocScrutinizer05which btw is the reason to call one "main" and one "aux". The "aux" is the one to leave unconnected when only one antenna is used01:01
Mike25226Can a PCB antenna act as 2?01:02
DocScrutinizer05the card will (either automatically or by config) shut down the "aux" antenna and use only one01:02
Mike25226I imagine that would cause issues being that close01:02
DocScrutinizer05no, no antenna can act "as 2"01:03
Mike25226well, with a PCB... couldn't it be done?01:03
Mike25226just tracing on back and front of PCB01:03
DocScrutinizer05that's two antennas, not one01:04
DocScrutinizer05however you must keep the antenna area clear of all conducting objects and traces, also of a second antenna01:04
DocScrutinizer05IOW one antenna per dedicated area01:05
Mike25226This image as an example: http://www.sequoia.co.uk/images/product/png/3364.png   so the front could be lets say antenna 1, and back be antenna 2?01:05
DocScrutinizer05this is one antenna in that picture01:06
DocScrutinizer05the bottom side of the PCB MUST kept clear of *all* traces and conducting objects01:06
Mike25226ahhh, gotcha01:06
DocScrutinizer05of course you can have two of those on one PCB, with a small distance between them01:07
Mike25226so that confirms that my laptop is only using one antenna, even though both main and aux connect to it01:07
Mike25226you mean side by side?01:07
DocScrutinizer05I guess that's pretty wrong a thing to do. Unless the data sheet of the card *explicitly* states to do so01:08
DocScrutinizer05yes, side by side01:08
DocScrutinizer05ideally in more than 1/2 the length of antenna as distance between them01:09
Mike25226hmmm, guess I need to take a closer look.  Since it would be pointless to have aux connected if it isn't the case (side by side).01:09
DocScrutinizer05you MUST NOT split antenna cables01:10
DocScrutinizer05like Y-cable01:10
DocScrutinizer05this is generally absolutely forbidden01:10
DocScrutinizer05so when your laptop has two antenna connectors, it quite likely has two antennas01:11
DocScrutinizer05unless some jackass retrofitted the WLAN DIY without having faintest clue01:14
kristianpaulwpwrak: had you had tiem for trying docker?01:19
Mike25226Made this picture with 3 figures.  Figure 1 is how my laptop is setup http://oi61.tinypic.com/402uw.jpg01:25
Mike25226Figure 2 is what I am thinking I can do.  Figure 3..... I doubt01:26
DocScrutinizer05figure1 is BS, done by somebody with no clue about RF basics. Figure2 is the standard setup. Fig3 is obscure, no idea what it means01:30
DocScrutinizer05adamnt rule of RF: one connector, one cable, one antenna01:32
DocScrutinizer05you cannot do Y-cables 01:32
Mike25226hmmm... then lenovo really messed up.... which might explain why my signal isn't better01:33
DocScrutinizer05you could add a band splitter to attach two antennas (one 2.4, one 5GHz) to one antenna input. Which would indeed look like fig3 then01:33
DocScrutinizer05ech of the "small PCB" in fig3 would need to be a band splitter then, basically a special filter that routes 2.4GHz signals to and from one antenna and 5GHz signal to and from the other01:35
DocScrutinizer05and of course this only makes sense when the antennas are actually made for only one band and can't handle the other01:36
Mike25226would that be better? (I could be wrong, but it would then use a different antenna when probing/scanning for networks while connected to a network)01:36
DocScrutinizer05no, that's not exactly how it works01:37
Mike25226do cards only probe when requested to do so?01:37
DocScrutinizer05the "advantage" is that the antennas get the signal they can handle. 01:38
DocScrutinizer05for the antenna it's irrelevant if the card is "probing" or talking or listening 01:38
Mike25226Is proximity of the 2.4GHz and 5GHz antennas important? Should they be some what distanced?01:43
DocScrutinizer05do you even have 2.4 and 5GHz antennas?01:55
DocScrutinizer05look, I'm not looking forward to discussing all possible permutations of configuring a multiband MIMO system, with all the gotchas this introduces01:57
DocScrutinizer05when your PC has ony one antenna, connect it to "main" and leave "aux" open. When it actually has 2 antennas, you connect one to "main" and one to "aux"01:58
DocScrutinizer05antenna *design* is an art rather than a science. Some even say it's voodoo01:59
Mike25226I plan to purchase 2 new antennas01:59
Mike25226or make them myself for fun02:00
DocScrutinizer05and where do you plan to place those?02:00
DocScrutinizer05mind you, they need to stay away a few cm from *all* conductive materials02:00
DocScrutinizer05even isolated ones02:01
whitequarkmy laptop somehow fares fine despite a solid aluminium lid02:01
whitequarkwith the antennas at the very bottom of the screen02:01
DocScrutinizer05well, when you *know* what you're doing, you can even integrate the antenna into the aluminium case02:02
DocScrutinizer05but then user MUST NOT "hold it wrong" X-P02:03
DocScrutinizer05the joy of doing RF tests in freefield, without anything resembling sth annoying like a user's hand ;-)02:04
DocScrutinizer05"the device works perfectly, unless a planet is near"02:05
DocScrutinizer05on a more honest less funny comment: you _can_ design antennas so they work near conducting surfaces. Actually a groundplane is exactly such a design. But you need to know your RF voodoo for that02:07
Mike25226I plan to place the antennas flat down on both sides of the keyboard02:08
DocScrutinizer05I guess that's about the worst place for antennas you could possibly find in a laptop02:09
Mike25226that's where lenovo placed the one antenna lol02:09
DocScrutinizer05assuming the kbd has an alu or steel base, and below the antennas would be main PCB, right?02:09
Mike25226screen casing is metal02:09
DocScrutinizer05see above02:10
DocScrutinizer05on a more honest less funny comment: you _can_ design antennas so they work near conducting surfaces. Actually a groundplane is exactly such a design. But you need to know your RF voodoo for that02:10
DocScrutinizer05sorry there's no simple answer to your problem02:11
DocScrutinizer05odds are whatever you implement DIY in good failth will be inferior than what lenovo implemented02:12
DocScrutinizer05so all I can recommend is: get the original service manual for your laptop and check what the manufacturer says how antenna is placed and built and how it shall get connected02:14
DocScrutinizer05compare to what you got, and fix any weird "improvements" somebody might have applied (is this a laptop you bought used? was the WLAN card retrofitted by a cheap cheesy repair shop?)02:16
Mike25226well, like I said, they use one antenna (or single small PCB).  It is oriented horizontally (flat) to the right of the keyboard02:16
Mike25226Whole body is aluminum except the surface with touchpad and keyboard02:17
DocScrutinizer05that's all pretty fine but not sufficient info for me to recommend anything better than I already did02:17
DocScrutinizer05"there's a small PCB and two cables come from that" is no info an EE can use to give any recommendations02:19
DocScrutinizer05for all I know the "small PCB" might even have TWO antennas on it02:20
DocScrutinizer05impossible to tell from the available info02:21
DocScrutinizer05and "to the right of the keyboard" is not identical to what I understood when you said "flat down on both sides of the keyboard"02:22
DocScrutinizer05I understood that as "under the kbd" not as "to the right/left of the kbd"02:23
Mike25226Guess I'll just experiment and test.  First like my figure 2 diagram, and then figure 3 after I do some research, using splitters like you said (for fig 3), 02:23
Mike25226it's to the right of the kbd02:24
Mike25226not under the kbd02:24
DocScrutinizer05figure3 would only make sense when you had dedicated singleband antennas. Why would you want to do that? it's an inferior solution to a multiband antenna02:25
Mike25226Btw, thanks for your help.  Really appreciate it, and I am learning some things I did not know before02:25
DocScrutinizer05and excuse when I'm wrong here, but to me it seems you didn't understand what's a band splitter02:26
DocScrutinizer05so your "small PCB" in fig3 is pretty unspecific02:27
Mike25226Oh, I was under the impression it was advantageous to have them separated  02:27
DocScrutinizer05no it isn't02:27
DocScrutinizer05sorry afk, busy02:28
Mike25226k, thanks again for the help02:28
DocScrutinizer05he's gone, nevertheless prolly the term "band splitter" isn't exactly to the point, rather "frequency-separating filter" or "crossover"03:11
DocScrutinizer05or diplexer03:32
wpwrakkristianpaul: hmm no, didn't need to make any mini-VMs yet :)06:32
ahmed89_can you tell me whice psu is better ? this http://i.imgur.com/ntIyCsC.jpg or http://i.imgur.com/RSnEbXM.jpg07:22
ahmed89_can you tell me whice psu is better ? this http://i.imgur.com/ntIyCsC.jpg or http://i.imgur.com/RSnEbXM.jpg07:41
eintopfnormally I would say that with the higher watt value07:52
eintopfbut the terminator sounds cool enough07:52
eintopf(terminator) has no watt value printed, but it's high enough to burn cables ;)07:53
eintopfthe other one has a FAN SENSCACONTROL :D07:54
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