unruh wrote:
On 2010-04-18, David Lord <[email protected]> wrote:
Hi
I just noticed that the GPS used as reference for my xtal oscillator
clock source has from midnight last night been losing reach. Previous
24 hr to that logging at 6 minute intervals had all 240 entries
at 377 but now they are mostly at 0 or start increasing for a short
period, last up to 76, then drop back to 0. Any chance this is due
to atmospheric volcanic ash?
I sort of doubt it, unless the ash is conductive.
The ash will change dielectric properties. real and imaginary ( as in lossy )
<from http://www.sepa.org.uk/about_us/news/2010/volcanic_ash_cloud.aspx>
Typical chemical composition of volcanic ash
Volcanoes emit a variety of gases including H2O, CO2, SO2, HCl, NH3, H2S, HF. These gases interact
rapidly with the ash particles of a volcanic plume and especially atmospheric water to form acidic
aerosols.
Volcanic ash may therefore contain potentially harmful substances in the form of water-soluble
materials, mostly acids and salts, which cling to the particles of glass and crystals. The most
common are sulphate, chloride, sodium, calcium, potassium, magnesium and fluoride. Other elements
reported but in lower concentrations include metals such as zinc, cadmium and lead.
Finer ash is able to carry more soluble ions than coarser ash because of its larger surface area;
fine ash and smaller-sized ash travel greater distances from an erupting volcano, typically extend
over very wide areas than larger ash particles and may stay airborne for lengthy periods.
</>
uwe
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