[time-nuts] frying pan antenna

[Bob Camp]

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
>>> 
>> 
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> 
> 
> 
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