But how fast can 200 or 300MHz go? On Thu, Sep 23, 2010 at 7:41 PM, Brian Webster <bwebs...@wirelessmapping.com > wrote:
> But what if you are able to use spectrum around 200 or 300 MHz? That > certainly goes through trees. > > > > > > Brian > > > > *From:* wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org] *On > Behalf Of *Tom DeReggi > *Sent:* Thursday, September 23, 2010 7:32 PM > *To:* WISPA General List > > *Subject:* Re: [WISPA] Transmit Antenna Height > > > > Yeah, that really sucks. Many areas needing served have thick forest/trees > easilly 70ft tall. > > A 90ft height, just wouldn't allow enough of the signal to have open air, > and the signal would be going through trees most of the full path. > > In 900Mhz, the difference between having the tower side over the tree line > and below the tree line can be the difference between a quarter mile > coverage and a 7 mile coverage in our market. > > All be it, 700Mhz does have better NLOS propogation characteristics than > 900 does. > > > > I would have liked to see that height doubled. > > > > However, admittedly, it will allow much better spectrum re-use in areas > that have a limited number of channels available. > > Spectrum reuse is one of the best ways to serve more people. > > > > > > Tom DeReggi > RapidDSL & Wireless, Inc > IntAirNet- Fixed Wireless Broadband > > > > > > ----- Original Message ----- > > *From:* Fred Goldstein <fgoldst...@ionary.com> > > *To:* WISPA General List <wireless@wispa.org> > > *Sent:* Thursday, September 23, 2010 4:36 PM > > *Subject:* Re: [WISPA] Transmit Antenna Height > > > > This item alone may be the show-stopper, the poison pill that makes it > useless to WISPs in much of the country. > > In places where the routine variation in elevation is more than 75 meters, > there will be houses (subscribers) that are more than 76 meters AAT. I > notice this in the areas I'm studying, both in the east and in the upper > midwest. > > In a place like Kansas, nobody is >75m AAT. But in the woody Berkshires of > Western Massachusetts, the UHF space is needed to get through the trees, and > a significant share of houses are >75m AAT. Also, if you want to cover a > decent radius, the access point needs to be up the hill too. 75 meters > isn't a mountaintop; it's just a little rise. > > It makes no sense to absolutely ban fixed use at a site that is 100m AAT if > the nearest protected-service contour is, say, 50 miles away. A more > sensible rule would be to follow broadcast practice, and lower the ERP based > on height, so that the distance to a given signal strength contour is held > constant as the height rises. Hence a Class A FM station is allowed up to > 15 miles, and if it is more than 300 feet AAT, then it is allowed less than > the 3000 watts ERP that apply at lower heights. > > Maybe the lawyers want to have more petitions to argue over. > > At 9/23/2010 04:07 PM, Rich Harnish wrote: > > > 65. *Decision. *We decline to increase the maximum permitted transmit > antenna height above ground for fixed TV bands devices. As the Commission > stated in the *Second Report and Order*, the 30 meters above ground limit > was established as a balance between the benefits of increasing TV bands > device transmission range and the need to minimize the impact on licensed > services.129 Consistent with the Commission’s stated approach in the *Second > Report and Order *of taking a conservative approach in protecting > authorized services, we find the prudent course of action is to maintain the > previously adopted height limit. If, in the future, experience with TV bands > devices indicates that these devices could operate at higher transmit > heights without causing interference, the Commission could revisit the > height limit. > > 66. While we expect that specifying a limit on antenna height above ground > rather than above average terrain is satisfactory for controlling > interference to authorized services in the majority of cases, we also > recognize petitioners’ concerns about the increased potential for > interference in instances where a fixed TV bands device antenna is located > on a local geographic high point such as a hill or mountain.130 In such > cases, the distance at which a TV bands device signal could propagate would > be significantly increased, thus increasing the potential for interference > to authorized operations in the TV bands. We therefore conclude that it is > necessary to modify our rules to limit the antenna HAAT of a fixed device as > well as its antenna height above ground. In considering a limit for antenna > HAAT, we need to balance the concerns for long range propagation from high > points against the typical variability of ground height that occurs in areas > where there are significant local high points – we do not want to preclude > fixed devices from a large number of sites in areas where there are rolling > hills or a large number of relatively high points that do not generally > provide open, line-of-sight paths for propagation over long distances. We > find that limiting the fixed device antenna HAAT to 106 meters (350 feet), > as calculated by the TV bands database, provides an appropriate balance of > these concerns. We will therefore restrict fixed TV bands devices from > operating at locations where the HAAT of the ground is greater than 76 > meters; this will allow use of an antenna at a height of up to 30 meters > above ground level to provide an antenna HAAT of 106 meters. Accordingly, we > are specifying that a fixed TV bands device antenna may not be located at a > site where the ground HAAT is greater than 75 meters (246 feet). The ground > HAAT is to be calculated by the TV bands database using computational > software employing the methodology in Section 73.684(d) of the rules to > ensure that fixed devices comply with this requirement. > > *130 The antenna height above ground is the distance from the antenna > center of radiation to the actual ground directly below the antenna. To > calculate the antenna height above average terrain (HAAT), the average > elevation of the surrounding terrain above mean sea level must be determined > along at least 8 evenly spaced radials at distances from 3 to 16 km from the > transmitter site. The HAAT is the difference between the antenna height > above mean sea level (the antenna height above ground plus the site > elevation) and the average elevation of the surrounding terrain. > * > 67. In reexamining this issue, we also note that the rules currently do not > indicate that fixed device antenna heights must be provided to the database > for use in determining available channels. It was clearly the Commission’s > intent that fixed devices include their height when querying the database > because the available channels for fixed devices cannot be determined > without this information.131 We are therefore modifying Sections > 15.711(b)(3) and 15.713(f)(3) to indicate that fixed devices must submit > their antenna height above ground to the database. > > 68. We continue to decline to establish height limits for personal/portable > devices. As the Commission stated in the *Second *Report *and Order*, > there is no practical way to enforce such limits, and such limits are not > necessary due to the different technical and operational characteristics of > personal/portable devices. > > -- > Fred Goldstein k1io fgoldstein "at" ionary.com > ionary Consulting http://www.ionary.com/ > +1 617 795 2701 > ------------------------------ > > > > > -------------------------------------------------------------------------------- > WISPA Wants You! Join today! > http://signup.wispa.org/ > > -------------------------------------------------------------------------------- > > WISPA Wireless List: wireless@wispa.org > > Subscribe/Unsubscribe: > http://lists.wispa.org/mailman/listinfo/wireless > > Archives: http://lists.wispa.org/pipermail/wireless/ > > > > > > -------------------------------------------------------------------------------- > WISPA Wants You! 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