Scintillation effects cause the radio signals to be refracted. Scintillation is a real world concern for those building microwave links *ESPECIALLY* if the scintillation off of a warm surface is in the fresnel zone of the link, like in my install over a flat roof. The dish was at least 10 feet off the surface of that roof, but shooting over probably 300 feet of flat rubber membrane. Scintillation every afternoon trashed the link until we raised the dish a few feet.
At 12:27 PM 8/8/2009, you wrote: >LOL... >I believe RickG is trying to point out that the correct word is "Refraction" >and not "Scintillation".. > >Jack U. can add his comments into this.... Heat & Humidity cause Refraction >to radio waves, ...that is why in long links they use Diversity Antenna >Arrays. > >Regards > > >Faisal Imtiaz > >-----Original Message----- >From: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org] On >Behalf Of Mike >Sent: Saturday, August 08, 2009 1:05 PM >To: WISPA General List >Subject: Re: [WISPA] 5.8GHz Link Loss > >Scintillation, for our purposes, is similar to when you see a mirage on a >highway in front of you, usually on a hot day, and not uncommon across >deserts. The wavering of the light waves is the same thing that happens to >radio signals, more-or-less. > >I once had a canopy, with dish mounted on a high roof shooting across a >white flat roof. After the install, the customer would drop lots of >packets. We moved it 4 feet higher to change the angle of incidence and it >stayed stable. That's one reason all of this seems black magic at times. > >Regarding the tropo propagation, as a ham radio operator, at times the uhf >and vhf bands would open from SW FL all the way across the Gulf of Mexico >and we could talk to hams in Texas, Alabama, Louisiana and others at times. >Many times this went on for hours and sometimes days. > > > >At 10:19 AM 8/8/2009, you wrote: > >Which definition of scintillation applies? > > > * Scintillation or twinkling are generic terms for rapid > >variations in apparent brightness or color of a distant luminous object > >viewed through the atmosphere. > > en.wikipedia.org/wiki/Scintillation_(astronomy) > > * scintillate - twinkle: emit or reflect light in a flickering > >manner; "Does a constellation twinkle more brightly than a single > >star?" > > > > >---------------------------------------------------------------------------- >---- >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! 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! 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/
