Ha! I looked up scintillation as well and was wondering the same thing.
Odds are Mike hit it on the head with the RF thermal ducting suggestion. We've seen this on long paths (20miles+) that have little down tilt. The RF signal can be ducted away from the intended target as it gets caught between thermal layers in the atmosphere. Paths with more down tilt between point A and point B appear to be more resilient to RF thermal ducting. I can only assume this is because the RF signal has a better chance of pushing through the thermal duct "wall" err I mean ceiling & floor. Long paths engineered with enough fade margin will typically stay up, but may downshift in modulation to compensate for the reduced signal strength. This is why it is important to eek out every last db of signal when first installing long PtP paths. Best, Brad -----Original Message----- From: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org] On Behalf Of RickG Sent: Saturday, August 08, 2009 10:20 AM To: WISPA General List Subject: Re: [WISPA] 5.8GHz Link Loss Which definition of scintillation applies? Definitions of scintillation on the Web: * (physics) a flash of light that is produced in a phosphor when it absorbs a photon or ionizing particle * twinkle: a rapid change in brightness; a brief spark or flash * a brilliant display of wit * glitter: the quality of shining with a bright reflected light * the twinkling of the stars caused when changes in the density of the earth's atmosphere produce uneven refraction of starlight wordnetweb.princeton.edu/perl/webwn * 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) * Scintillating scotoma is the most common visual aura preceding migraine and was first described by 19th century physician Hubert Airy (1838-1903). en.wikipedia.org/wiki/Scintillation_(medicine) * Scintillation is a fluctuation in the amplitude of a target on a radar display. It is closely related to target glint, or wander, an apparent displacement of the target from its mean position. ... en.wikipedia.org/wiki/Scintillation_(radar) * Scintillation is a flash of light produced in a transparent material by an ionization event. See scintillator and scintillation counter for ... en.wikipedia.org/wiki/Scintillation_(physics) * A flash of light; a spark; The twinkling of a star caused by turbulence in the Earth's atmosphere; The flash of light produced by a phosphor ... en.wiktionary.org/wiki/scintillation * scintillate - give off; "the substance scintillated sparks and flashes" * scintillate - sparkle: reflect brightly; "Unquarried marble sparkled on the hillside" * scintillate - twinkle: emit or reflect light in a flickering manner; "Does a constellation twinkle more brightly than a single star?" * scintillate - physics: fluoresce momentarily when struck by a charged particle or high-energy photon; "the phosphor fluoresced" wordnetweb.princeton.edu/perl/webwn * scintillating - brilliantly clever; "scintillating wit"; "a play full of scintillating dialogue" wordnetweb.princeton.edu/perl/webwn On Sat, Aug 8, 2009 at 9:18 AM, Rubens Kuhl<rube...@gmail.com> wrote: > On Sat, Aug 8, 2009 at 12:33 AM, Ed Spoon - Computer Sales & Services, > Inc.<ed.sp...@cssla.com> wrote: >> So, what causes this crazy loss on all of my 'longer' 5.8 links after >> dark/overnight? Temp drop? Contraction? Condensation? Moonbeams? > > Likely to be scintillation. > > > Rubens > > > ---------------------------------------------------------------------------- ---- > 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/
