It's been a couple years since I did any long distance links. Apparently I've turned stupid. You are right, my math is totally wrong.
Also: this. http://www.ubnt.com/airlink/ On Tue, Sep 17, 2013 at 10:22 AM, Colin Stanners <[email protected]>wrote: > Actually that barn side is not illegal, it's a PtMP client and so 45dbm > transmit is legal. > > Also that math is wrong, he would not get -14dbm on that link as on the > client side you put the transmit power, not antenna gain. > > > On Tue, Sep 17, 2013 at 10:12 AM, chris kluka <[email protected]> wrote: > >> This antenna will give you 24 dbi gain (for the barn end). >> >> >> http://compare.ebay.ca/like/200771492500?var=lv<yp=AllFixedPriceItemTypes&var=sbar&_lwgsi=y&cbt=y&lpid=33&item_id=200771492500 >> >> This antenna will give you 12 dBi gain (for the house end). >> >> >> http://www.ebay.ca/itm/TP-Link-Network-TL-ANT2412D-2-4GHz-12dBi-Outdoor-Omni-directional-Antenna-/360694522161?_trksid=p3284.m263&_trkparms=algo%3DSI%26its%3DI%26itu%3DUCI%252BRTU%26otn%3D21%26pmod%3D200771492500%26ps%3D54 >> >> Using one highly directional antenna and one omni will also solve your >> hidden node problem. >> >> This simple slide deck has 2 important numbers for you: >> >> http://www.mouser.com/pdfdocs/Site_Surveys_for_Wireless_Networks.pdf >> >> 1) The dBi loss formula for free space transmission is 36.56 + >> 20Log10(2400000000) + 20Log10(0.062). You are going to loose approx 83 dBi >> of signal strength at 150m. >> >> 2) The freznel zone clearance radius for transmission is (i can't type it >> with out a math font... but look at slide 6). for 150m, it's approx 9 feet. >> >> >> >> If your base radio transmission power is 21 dBm (assuming you have >> DIR-615 c2's) and you stick a 12 dBi omni at your house and a 24 dBi >> directional dish at your barn, you will have (21+12 = 33 dBi transmit = >> approx 2Watts (1995mw)) at your house and 21+24=45 dBi transmit = 34 Watts. >> Yes... 34 watts. This is a staggeringly illegal transmit power. >> >> You'd have to turn down the power on your radio in the barn to about 12 >> dBm (approx 15.8 watts), or get a directional dish with lower than 24 dBi >> gain. >> >> >> >> The result is that you can *EASILY* hit your legal transmission limits >> without any amplifiers. >> >> if you have (33 + 36) = 69 dBm gain on your link... and 83 loss from the >> distance of 150m. This means your effective rssi should be approx (69 - 83) >> = -14. >> >> Now, assuming you need to put some cable between your DIR-615's and your >> antennas (so they can be housed indoors or at least not in the snow), i'll >> add to this 5 meters of LMR400 cable with connectors to each end: >> >> >> http://www.timesmicrowave.com/calculator/?productId=52&frequency=2400&runLength=15&mode=calculate#form >> >> so you will lose 1 dBm for antenna cable distance (per end) and 1.2 dBm >> for the assemblies (per end) >> >> so, -14 and -4.4 = -18.4. >> >> >> For a frame of reference... -18.4 is still an AMAZING signal level... >> >> >> [image: Inline image 1] >> >> >> >> >> On Tue, Sep 17, 2013 at 9:41 AM, chris kluka <[email protected]> wrote: >> >>> Also, for 150m, you don't need 2 directional antennas. >>> >>> You could get a single omni antenna at your house and a single parabolic >>> grid antenna at the barn. You probably don't even need amplifiers. >>> >>> Source: I built the wireless deployment at the blue bomber stadium. >>> >>> >>> On Tue, Sep 17, 2013 at 9:39 AM, Rob Guderian <[email protected]>wrote: >>> >>>> Neat. I have a wrt54g in my garage right now (as a prototype project). >>>> I was going to leave it there, but might have to repurpose it. >>>> >>>> On Tue, Sep 17, 2013 at 9:32 AM, Adrian Stoness <[email protected]> >>>> wrote: >>>> > the wrt54g's seem to handle the cold prity good had one going in -40 >>>> temps >>>> > for a while with no heating >>>> > >>>> > >>>> > >>>> > On Tue, Sep 17, 2013 at 9:22 AM, Rob Guderian <[email protected] >>>> > >>>> > wrote: >>>> >> >>>> >> Yeah, I'm talking outdoors, but not extreme distance. I could throw >>>> >> money at this project, but origin of the project was to build a >>>> >> cantenna - I just needed an application for it to motivate myself. >>>> I'm >>>> >> also choosing to to this on the cheap as part of the challenge. >>>> >> Reliability/throughput is ... not a huge deal - I don't exactly have >>>> >> clients waiting on me. >>>> >> >>>> >> Somewhat better breakdown of the problem domain: >>>> >> Farmyard. Main house, 2 outlying buildings that are about 100-150m >>>> out >>>> >> from the house. Both have south-facing windows I can use to warm an >>>> >> area to consumer-grade hardware levels using both a greenhouse >>>> effect, >>>> >> or with some kind of heater if required. >>>> >> >>>> >> So, stage 1 is get wireless to the outlying buildings. Stage 2 is to >>>> >> install sensors indoors, and outdoors. I'll probably go with >>>> Raspberry >>>> >> pis - and have them report back with images, humidity, temperature, >>>> >> etcetcetc. But that's longer term, and will grow organically. >>>> >> >>>> >> >Note the 2 antennas are on the same "radio" / in the same collision >>>> >> > domain so you can't point them to different places or use them as >>>> separate >>>> >> > "networks". >>>> >> >>>> >> That's true. I'm planning on keeping them on the same network, and it >>>> >> will cause a hidden node problem at the hub router in the house, but, >>>> >> I'm not going to be pushing massive throughput, and I think it'll be >>>> >> minor. >>>> >> >>>> >> Adam: Which kind of Cantenna dis you build? I guess it was >>>> successful, >>>> >> what kind of range are you getting? >>>> >> _______________________________________________ >>>> >> SkullSpace Discuss Mailing List >>>> >> Help: http://www.skullspace.ca/wiki/index.php/Mailing_List#Discuss >>>> >> Archive: https://groups.google.com/group/skullspace-discuss-archive/ >>>> > >>>> > >>>> > >>>> > _______________________________________________ >>>> > SkullSpace Discuss Mailing List >>>> > Help: http://www.skullspace.ca/wiki/index.php/Mailing_List#Discuss >>>> > Archive: https://groups.google.com/group/skullspace-discuss-archive/ >>>> _______________________________________________ >>>> SkullSpace Discuss Mailing List >>>> Help: http://www.skullspace.ca/wiki/index.php/Mailing_List#Discuss >>>> Archive: https://groups.google.com/group/skullspace-discuss-archive/ >>>> >>> >>> >> >> _______________________________________________ >> SkullSpace Discuss Mailing List >> Help: http://www.skullspace.ca/wiki/index.php/Mailing_List#Discuss >> Archive: https://groups.google.com/group/skullspace-discuss-archive/ >> > > > _______________________________________________ > SkullSpace Discuss Mailing List > Help: http://www.skullspace.ca/wiki/index.php/Mailing_List#Discuss > Archive: https://groups.google.com/group/skullspace-discuss-archive/ >
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