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/ >
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