Hi I certainly won't disagree with the data. I have noticed over the years that past a few MHz antennas out in the fresh air always seem to work better than indoor antennas. It could easily be that there is a *lot* of water in your typical roof. Certainly the water is far from pure, so it's going to be pretty low conductivity.
Bob On Mar 15, 2010, at 11:28 PM, Bruce Griffiths wrote: > Below 600C the only significant source of microwave absorption in wood is the > water content: > http://pubs.acs.org/doi/abs/10.1021/ie901336k > > Bitumen has very low microwave loss so if the asphalt doesnt have any > taconite in it its loss should be low. > http://www.nrri.umn.edu/egg/REPORTS/TR200419/CTS0510.pdf > > You could always try the microwave oven test with some samples. > > One thing to consider is the reflection loss from the roof due to its non > unity dielectric constant. > > > Bruce > > Mike Naruta AA8K wrote: >> >> True Bruce. Alas, those trees to the West are matched by >> trees to the East. Power lines run in front of the house >> to the South. And the towers, guy wires, and wire antennae >> are to the North in the back yard. It's like looking up >> a funnel to see the satellites. >> >> I have another Motorola patch under the roof that also works. >> What is the dielectric of wood sheathing and asphalt shingles? >> I may try the cake pans on the inside one; not much snow >> inside the attic. :) >> >> >> Mike - AA8K >> >> >> Bruce Griffiths wrote: >>> A pity that the GPS receiver elevation mask can't generally be made to be >>> azimuth dependent. >>> You could then have a higher elevation limit in the direction of those >>> trees. >>> >>> However, it is possible in principle with an M12+T, M12M T or similar >>> timing receiver which provides the relative timing contribution of each SV >>> to the solution, to back out the contribution of a given SV and compute the >>> corresponding timing correction for software correction of the PPS pulse >>> timing. >>> >>> Bruce >>> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
