I'm doing some path loss estimates in RadioMobile. Mainly 5.8 GHz stuff. I have a place where I'd like to run a point-to-multipoint sector as an injection feed to multiple APs in the mesh. This would need to run AirMax or Nstreme or NV2 in order to manage the traffic, but that part seems easy enough. If I don't use NV2 and claim the SkyPilot rule, then my ERP is capped at +36 dBm. (So I'm kind of marginal on path loss already.) I can use a 20 dB sector antenna (AM2-60), whose footprint covers all of the APs I'd like to reach, up to 22 kilometers away. The APs are set to have 24 dB panel antennas. So they can run "point to point" ERP upstream, to the extent that it helps the fade margin in that direction. BTW the paths are mostly over water, but elevated by more than 2-3 Fresnel zones.
Now here's the weird part. In RadioMobile, when I adjust the PtMP end's height in half-meter increments, path loss jumps all over the place. To one destination 18.5 km away: At 7 meters, 134.5 dB. At 7.5 meters, 144.7 dB. At 8 meters, 139.3 dB. At 8.5 meters, 134.4 dB. At 10 meters, 137.0 dB. Now to a different destination only 12.5 km away (the closest one), I get: At 7 meters, 137.4 dB. At 7.5 meters, 150.7 dB. At 8 meters, 132.2 dB. At 8.5 meters, 131.7 dB. At 10 meters, 136.5 dB. Well, the obvious answer so far might be to avoid the 7.5 meter height, but now going to a third destination 16.8 kilometers away, I get: At 7 meters, 141.6 dB. At 7.5 meters, 134.3 dB. At 8 meters, 136.6 dB. At 8.5 meters, 139.5 dB. At 10 meters, 151.9 dB. So there's no height that makes everyone happy, and that assumes I actually get a choice of height. Most likely it goes on the power pole wherever they let us attach it. And tweaking the remote ends doesn't make that much difference at all. So here's the question. Is this type of variation likely to exist in the real world, or is this just RadioMobile's propagation model being overly sensitive? Thanks! -- 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/
