I would try to get between .6 and 1. If you expose the second zone then the phase canceling starts and reduces your signal level.
Thank You, Brian Webster -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Mike Hammett Sent: Tuesday, January 08, 2008 9:24 AM To: WISPA General List Subject: Re: [WISPA] Radio Mobile So then should I be engineering my customer links to .6 Fresnel instead of the > 1 that I've been trying to achieve? ----- Mike Hammett Intelligent Computing Solutions http://www.ics-il.com ----- Original Message ----- From: "Brian Webster" <[EMAIL PROTECTED]> To: "WISPA General List" <[email protected]> Sent: Wednesday, January 02, 2008 8:26 AM Subject: RE: [WISPA] Radio Mobile > Mike, > As mentioned by another, try adjusting the height of one end or the other > to increase signal level. As Mac will tell you, higher on a site is not > always better. If you can engineer a path to obstruct as much of even > number > Fresnel zones as possible it will help your signal level. Even and odd > number Fresnel zones cancel each other out. Using an obstruction to cover > up > as many even number zones as possible gives some gain. This is why you > hear > people say that you want to design a microwave backhaul with a .6 Fresnel > zone clearance. The danger in doing that with Radio Mobile, is the level > of > detail in your terrain files. Radio Mobile is capable of using 10 meter > resolution terrain data from the USGS Seamless data distribution site (the > default that the program downloads from the internet is 30 meter), or if > you > want, Roger (the Radio Mobile author) can create the data in SRTM format > to > use in Radio Mobile http://www.lurodata.com/. While this gives excellent > terrain data details, it still does not show your clutter (trees, > buildings). Take a look at this site to see the differences in terrain > data > http://www.sector14.net/~curt/ned/ > > You can do some visualization of clutter data in Radio Mobile at 1 > kilometer resolution for free. If you download this file > http://www.geog.umd.edu/landcover/1km-map/UMD1km_L.zip you will have the > world clutter data at 1 KM resolution. This file can then be overlaid in > Radio Mobile as a map layer. It will not let you use it as part of a > prediction, but you can get an idea of the type of land cover to expect > for > any given area. You can also use this file in conjunction with the "RM > Path" > program in Radio Mobile to insert the clutter in your path profile > inspections. To do this you must first edit the "landheight.dat" file > (using > notepad) in your Radio Mobile main directory. The numbers in this file > correspond to the color coded legend on a land cover map layer merge. Each > value is in meters and would be changed to represent the average clutter > heights for each clutter class in your area. Once this is complete you > would > then do a path profile in Radio Mobile. In that window do a file "export > to > RMPath", chose the custom option and I like to use 1000 points in my > export. > This will save a file (name it whatever you want or just overwrite the > default) and open the RM Path program window. In this path profile you > will > see the terrain cross section with the clutter data layered on top. The > colors match what you would see as a merged layer on the map. At this > point > you will NOT have a new signal level calculated based on clutter > absorption, > but you will know what to expect for path blockages. You can also manually > edit the test file that was exported to insert any know obstructions in > your > path. Keep in mind, this data is very general in that it paints a whole > square kilometer with the same class of clutter. Its not the best in the > world, but for free it gives you a lot more to look at before you do a > truck > roll. This used in conjunction with Google Earth is just one more tool a > WISP can use. > > I have been in the wireless industry for 18 years (including Senior RF > Engineering Manager at EarthLink). I currently have Planet, ICS Telecom by > ATDI and Radio Mobile as RF prediction tools. While Radio Mobile does not > do > many of the advanced features I need to design PCS and Cellular networks, > I > will attest that given the same data to start with, I can do predictions > that match or beat the expensive commercial tools when it comes to simple > field strength plots (which is what you want for coverage maps and path > studies). Where the commercial tools excel, is when I can get high > resolution clutter and building data. Radio Mobile simply does not have > these capabilities (although I work with the author on a regular basis to > improve Radio Mobile). I would highly recommend each WISP get one person > on > their staff to become somewhat proficient in this software. It can save > you > a lot of aggravation. > > > > Thank You, > Brian Webster > www.wirelessmapping.com <http://www.wirelessmapping.com> > > > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] > Behalf Of Mike Hammett > Sent: Tuesday, January 01, 2008 5:15 PM > To: WISPA General List > Subject: Re: [WISPA] Radio Mobile > > > Right, the AP isn't directly at the client, but it says there's only 0.8 > db > of loss due to that. It says I lose 7.4 dB due to obstruction (when I > have > a 1.4 Fresnel zone) and 6.6 due to statistics. > > > ----- > Mike Hammett > Intelligent Computing Solutions > http://www.ics-il.com > > > ----- Original Message ----- > From: "Brian Webster" <[EMAIL PROTECTED]> > To: "WISPA General List" <[email protected]> > Sent: Tuesday, January 01, 2008 3:00 PM > Subject: RE: [WISPA] Radio Mobile > > >> Radio Mobile is not doing a simple free space loss calculation. There >> will >> be a fade margin factored in based on the numbers you use for mode of >> variability. If you open the path profile window then do a "view" >> "details" >> you will get a text window that shows all the calculation details the >> program used to derive the numbers. That is the first place to start to >> look >> for the difference. The other thing you may be seeing is that if you >> don't >> have the antennas aimed directly at each other, in the calculation you >> will >> be getting the gain from something other than the strongest point in the >> pattern. >> >> >> >> Thank You, >> Brian Webster >> www.wirelessmapping.com <http://www.wirelessmapping.com> >> >> >> -----Original Message----- >> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] >> Behalf Of Mike Hammett >> Sent: Tuesday, January 01, 2008 12:03 PM >> To: WISPA General List >> Subject: [WISPA] Radio Mobile >> >> >> How do I figure out how Radio Mobile arrives at it's signal level? On a >> 3 >> km link in 5 GHz, I'm off 15 - 20 db from Eje's power calculator. What >> the >> radio link window says is really close to the input numbers for Eje's >> calculator. Why they're different is that I actually used the right >> antenna >> files and hard fixed the AP at N, S, E, and W. >> >> >> ----- >> Mike Hammett >> Intelligent Computing Solutions >> http://www.ics-il.com >> >> >> >> ------------------------------------------------------------------------- - > -- >> ---- >> WISPA Wants You! Join today! >> http://signup.wispa.org/ >> ------------------------------------------------------------------------- - > -- >> ---- >> >> WISPA Wireless List: [email protected] >> >> Subscribe/Unsubscribe: >> http://lists.wispa.org/mailman/listinfo/wireless >> >> Archives: http://lists.wispa.org/pipermail/wireless/ >> >> >> >> ------------------------------------------------------------------------- - > ------ >> WISPA Wants You! 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