Can you clarify a few things....... When you say "hardware" do you mean Tx-Rx, Ants, RF Coax, etc.? Can you explain further "Recommendations for Topology"? (are you trenching?) What do you mean by "incidental radiation with a highly directional antenna."
Incidental radiation is generated by a device that radiates radio frequency energy during the course of its operation although the device is not intentionally designed to generate radio frequency energy, antennas are usually not considered incidental radiators. *In-tunnel coverage is difficult, at best, to predict with certainty. Some important factors in determining tunnel radio coverage are the configuration of the tunnel, the materials used to build the tunnel, and the relative orientation of the receiver to the transmitter. The configuration of the tunnel plays a crucial role in determining the radio coverage. If the tunnel is generally straight and the antenna is located in the tunnel, the signals primary component will be a result of line of sight (LOS) transmission. As the tunnel changes direction, the signal experiences more loss due to reflections and scattering. The more abruptly the tunnel changes direction, the greater the multipath loss is, and the lower the signal level will be. Furthermore, the losses the signal will experience will be driven by the electrical characteristics of the materials used in the tunnel construction. An important factor to consider is multipath fading. In practice, transmitters and receivers are surrounded by objects. These objects constantly reflect and scatter the transmitted signal, causing several waves to arrive at the receiver at different times via different routes. As the signal is refracted and reflected off of various obstacles the power received at any given point varies. As a radio moves from point to point, the signal strength varies due to multipath fading. Depending on the frequency, a user may or may not notice the effects of multipath fading. Lower frequency signals have a longer wavelength (a 100 MHz signal has a wavelength of approximately 9.25 feet, whereas a 800 MHz signal has a wavelength of 1.25 feet) and would require the user to travel a greater distance to notice a discernible difference. Higher frequency signals generally reflect and refract more than the lower frequency signals (another function of a shorter wavelength), which may result in additional transmission paths. Some of the important ant specs to look for are ........ Front to Back Ratio- Beamwidths- Gain- VSWR- Polarization- Antenna Gain Patterns- Average Signal Loss for Radio Paths Obstructed by Common Building Materials Material Type / Loss (decibels) Wall constructed of metal plate 26 Aluminum siding 20.4 Foil insulation 3.9 2.7 x 2.7 square reinforced concrete pillar 12-14 Concrete block wall 13 Sheetrock (3/8 in) 2 sheets 2 ---------------------------------------------------------------- "Robert F. Schaefer" wrote: > Anyone have recommendations wrt hardware and maybe topology for a wireless > tunnel, less than 1 mile in a residential (small houses, not brownstones) > neighborhood? Eventually I'll need to link 5-6 houses together, but right > now I just want to get one link up as proof-of-concept. I have los to > several targets, but at least two are far enough away that I'm concerned > about incidental radiation with a highly directional antenna. It's main > purpose is the tunnel, but after that's stable I would like to open it up to > public access. > > Thanks! > > Bob > > -- > NYCwireless - http://www.nycwireless.net/ > Un/Subscribe: http://lists.nycwireless.net/mailman/listinfo/nycwireless/ > Archives: http://lists.nycwireless.net/pipermail/nycwireless/ -- "NEXTEL-1 IT'S NOT JUST NEXTEL" Note The New address Subscribe to Nextel-1: http://www.groups.yahoo.com/subscribe/NEXTEL-1 "NEXTEL2 FOR iDEN SOFTWARE DEVELOPERS" Subscribe to Nextel2: http://www.groups.yahoo.com/subscribe/NEXTEL2 "WIRELESS FORUM HOMELAND SECURITY GROUP" The Complete Resource for Wireless Homeland Security. Subscribe to WFHSG: http://www.groups.yahoo.com/subscribe/WFHSG -- NYCwireless - http://www.nycwireless.net/ Un/Subscribe: http://lists.nycwireless.net/mailman/listinfo/nycwireless/ Archives: http://lists.nycwireless.net/pipermail/nycwireless/
