On Mon, Mar 06, 2023 at 04:19:00PM -0800, Denis Heidtmann wrote: > wireless towers to service about a 20 mile radius per tower. ... > is 300Mb (MB?) down and up speeds.
This topic veers towards plug-talk instead, but ... ... 20 mile radius from one urban tower is BULLSHIT. Sales droid fail, there will be MANY towers CLOSER. Reaching 20 miles requires a heck of a lot of transmit power. The summed power is proportional to per-customer bit rate, times number of customers, times the SQUARE of the distance ... more or less. In an urban area, the number of customers within a circle is also proportional to the square of the distance ... though almost everybody (Hillsboro, Vancouver, Gresham, Oregon City, Sherwood, and places between) is within 15 miles of the tallest towers in the West Hills. I presume this is a high frequency microwave system. As described, every 15 mile distant user has a largish and stiffly-anchored parabolic dish perched on a high place, aimed PRECISELY at that high-power tower miles away, line of sight. Probably NOT as described. Add "rain fade" and multipath bounces, and you have an EXPONENTIAL dropoff with distance MULTIPLIED by the inverse square. Presuming the single "twenty mile tower" services tens of thousands of customers, it must have MANY phased array panel antennas capable of squirting the summed millions of megabits per second in VERY tight beams in MANY directions simultaneously. And to do all this, both the customer dish and the tower antennas must transmit a LOT OF POWER, especially to cut through rain fade and interference from other services. I live 9 miles from Hillsboro Airport and 11 miles from Portland International Airport, both of which use radar to keep track of many airplanes, by bouncing powerful microwave "searchlights" off them and listening for the very weak echos. Not much power reaches an airplane, and far less bounces back to tickle a finite-sized radar dish. The LOT OF POWER of ALL the wireless data channels will blind those radars - radar will be tuned for different frequencies than "WIFI", but no radar receiver has perfect selectivity. Old airport and aircraft radars weren't designed to reject new services. In the REAL world, Cell service works by dividing a region into patches. As customers become denser, larger patches are carved into many smaller patches with LESS power per transmitter per patch, because (inverse square!) the data beams need not reach as far. Pretty cool idea - until some idiot passenger on a plane turns on their cell phone to reach a cell tower far from the plane, possibly blinding that aircraft's radar, and risking everyone on board. Anyway, I can imagine a RURAL service reaching a handful of customers 20 miles away with LOW bandwidth - and birds getting baked as they perch on the tower. In an urban area, with everyone competing for the same distant tower? Fuggedaboudit. So - my take on this claimed 20 mile radius service is ... bullshit. Probably sales-droid hyperbole and ignorance. Possibly criminal fraud. Please provide quantified details, and the technical name of this service if you can learn that. I will share the info with my buddy Tim, who designs radar systems for Northrup Grumman in Maryland. Tim and I discussed this problem for WiMAX cell/data service, which is designed for much smaller distances in urban areas. He figures WiMAX will eventually convert a pair of passenger jets into aluminum rain, with the larger "raindrops" (like engines and wheels) drilling some deep holes in buildings and their occupants. Tim lives in Annapolis, 16 miles from BWI airport (Baltimore-Washington in Maryland, a Southwest Airlines hub), under the final approach path to runway 33L. My father-in-law Charlie lives in Severna Park, 8 miles from BWI, under the same approach path. When my wife and I visit him (she's there now), we are serenaded by arriving SWA jets as we drift off to sleep. I am glad we don't live under the final approach to PDX. However, we are just a few degrees off final for Hillsboro runways 31L and 31R. Please don't drop Intel and Nike commuter jets on us, as they attempt to turn from base leg to final leg, radar blind at night, and fail to avoid other traffic. I've piloted that approach myself, before I realized that I was a hazard to myself and others. Keith -- Keith Lofstrom [email protected]
