Re: [time-nuts] Choke Ring Pictures
Microwave absorption of ice is also low as is that of beeswax, rosin and
pitch.
I use a conventional hotplate for melting the latter 3.
Bruce
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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Mike
Perhaps a single antenna element from the phased array in the following
JPL paper would be useful:
http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/12178/1/01-0082.pdf
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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and follow the instructions there.
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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Yes Bruce, I also think that azimuth dependent masking would be useful.
I have been suffering from strong reflections from facing buildings at
50m to 100m, which cause sharp departures from the average PPS TI
(HPZ3801A/ Z38XX app.) values. I can remove the problem by carefully
watching the satellite azimuth/elevation display and sending the
receiver a command to ignore the relevent SV when it passes to the
south (antenna on north facing window ledge). I think that it would be
feasible in somethig like Z83XX and LH to set up an azimuth dependent
mask and monitor the SVs predicted positions to selectively
ignore/include them when they pass out of and into line of site.
I did post in december on this problem but add here a TI stats view to
show the magnitude of the errors seen.
Mike
Le 16/03/2010 03:30, Bruce Griffiths a écrit :
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
Mike Naruta AA8K wrote:
My aluminum frying pan ground plane does a nice job.
The nut welded on for the handle is a convenient
place to attach the lightning ground wire.
Snow accumulation hasn't been a problem yet.
The non-stick underside seems to discourage insects.
You should have seen the look on my wife's face when
I told her that I would like to bolt a frying pan
on the peak of the roof.
Mike - AA8K
WarrenS wrote:
Next on my list of things to try is a smaller open taco maker deep
dish metal pan.
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Bob Camp wrote:
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
there's also an amazing amount of metal and other junk in the usual
composition roof construction. Nails to hold the shingles on, for instance.
But I think the major absorption will be the moisture in the wood sheathing.
By this logic, a thatch roof in a dry climate is the best thing going.
Bruce Griffiths wrote:
Mike
Perhaps a single antenna element from the phased array in the following
JPL paper would be useful:
http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/12178/1/01-0082.pdf
I don't know that Mark's antenna is the right kind of thing for GPS.
the x-pol off axis is pretty high and the construction is dependent on
having the right materials around. You could probably use a HDPE
cutting board instead of teflon and some other foam.
If you want gain in the vertical direction, why not a stacked patch with
air dielectric?
Mark's antenna in the article was eventually intended to be for a
"phased array at the focus of a reflector/reflectarray" application in
space, so fabrication of a stack was more appropriate.
Fascinating Bruce. I had expected more degradation from
the shingles. The indoor antenna was a temporary set up
until I could mount the outdoor one. It works well
enough that I use it as a back-up antenna.
I suppose an advantage to having an older home is the
roof sheathing is composed of wooden boards, rather than
the modern plywood with its bonding resins.
Jim, you are correct about the fasteners. This roof was
stripped and redone two years ago. There are the nails
fastening the boards to the rafters, a layer of tarred
paper, which for some reason roofers like to pierce with
a liberal amount of staples, then the shingles nailed
into place.
I had mounted a Sirius satellite radio antenna under
the roof and discovered a position sensitivity. I
initially went with locations midway between the rafters,
but discovered maximum signal level adjacent to a
rafter. I attribute this to the nailing pattern.
This group is such an interesting resource.
Mike - AA8K
Bruce Griffiths wrote:
Below 600C the only significant source of microwave absorption in wood
is the water content:
There is a tremendous amount of signal degradation from
ordinary building materials. I cannot get a lock at all inside
of my brick, with asphalt shingle house, but I get a quick
lock outside.
The tar paper isn't there as a waterproofing membrane, that
function is handled by the shingles themselves. The tar paper
is installed by the framers, and provides temporary protection
while the house is waiting on the roofers to apply the shingles.
-Chuck Harris
Mike Naruta AA8K wrote:
Fascinating Bruce. I had expected more degradation from
the shingles. The indoor antenna was a temporary set up
until I could mount the outdoor one. It works well
enough that I use it as a back-up antenna.
I suppose an advantage to having an older home is the
roof sheathing is composed of wooden boards, rather than
the modern plywood with its bonding resins.
Jim, you are correct about the fasteners. This roof was
stripped and redone two years ago. There are the nails
fastening the boards to the rafters, a layer of tarred
paper, which for some reason roofers like to pierce with
a liberal amount of staples, then the shingles nailed
into place.
I had mounted a Sirius satellite radio antenna under
the roof and discovered a position sensitivity. I
initially went with locations midway between the rafters,
but discovered maximum signal level adjacent to a
rafter. I attribute this to the nailing pattern.
This group is such an interesting resource.
Mike - AA8K
Bruce Griffiths wrote:
Below 600C the only significant source of microwave absorption in wood
is the water content:
time-nuts mailing list -- time-nuts@febo.com
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and follow the instructions there.
The tar paper is there primarily to reduce air infiltration when the wind
blows. Now days this purpose is served by the white housewrap, the
original brand being Tyvek.
Water that blows past the shingles is stopped by the tarpaper or
housewrap, keeping the sheathing and insulation dry.
From:
Chuck Harris cfharris@erols.com
To:
Discussion of precise time and frequency measurement time-nuts@febo.com
Date:
03/16/2010 10:07 AM
Subject:
Re: [time-nuts] frying pan antenna
Sent by:
time-nuts-bounces@febo.com
There is a tremendous amount of signal degradation from
ordinary building materials. I cannot get a lock at all inside
of my brick, with asphalt shingle house, but I get a quick
lock outside.
The tar paper isn't there as a waterproofing membrane, that
function is handled by the shingles themselves. The tar paper
is installed by the framers, and provides temporary protection
while the house is waiting on the roofers to apply the shingles.
-Chuck Harris
Mike Naruta AA8K wrote:
Fascinating Bruce. I had expected more degradation from
the shingles. The indoor antenna was a temporary set up
until I could mount the outdoor one. It works well
enough that I use it as a back-up antenna.
I suppose an advantage to having an older home is the
roof sheathing is composed of wooden boards, rather than
the modern plywood with its bonding resins.
Jim, you are correct about the fasteners. This roof was
stripped and redone two years ago. There are the nails
fastening the boards to the rafters, a layer of tarred
paper, which for some reason roofers like to pierce with
a liberal amount of staples, then the shingles nailed
into place.
I had mounted a Sirius satellite radio antenna under
the roof and discovered a position sensitivity. I
initially went with locations midway between the rafters,
but discovered maximum signal level adjacent to a
rafter. I attribute this to the nailing pattern.
This group is such an interesting resource.
Mike - AA8K
Bruce Griffiths wrote:
Below 600C the only significant source of microwave absorption in wood
is the water content:
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
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Hi
I have no idea what the ultimate source is, but in the houses I've been able
to directly "sample" a 20 db or more drop outside to inside is not unusual
from about 5 MHz right on up to GPS frequencies. Exactly what the frequency
dependence is I couldn't say. That's accompanied by a rise in noise from all
the stuff flying around on the power lines. Simply put indoors is not a good
place for an antenna.
There will be magical frequencies and locations that won't make sense (up or
down in attenuation). I attribute that to all the metal running around.
Sometimes it helps, mostly it hurts.
Bob
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Chuck Harris
Sent: Tuesday, March 16, 2010 10:03 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] frying pan antenna
There is a tremendous amount of signal degradation from
ordinary building materials. I cannot get a lock at all inside
of my brick, with asphalt shingle house, but I get a quick
lock outside.
The tar paper isn't there as a waterproofing membrane, that
function is handled by the shingles themselves. The tar paper
is installed by the framers, and provides temporary protection
while the house is waiting on the roofers to apply the shingles.
-Chuck Harris
Mike Naruta AA8K wrote:
Fascinating Bruce. I had expected more degradation from
the shingles. The indoor antenna was a temporary set up
until I could mount the outdoor one. It works well
enough that I use it as a back-up antenna.
I suppose an advantage to having an older home is the
roof sheathing is composed of wooden boards, rather than
the modern plywood with its bonding resins.
Jim, you are correct about the fasteners. This roof was
stripped and redone two years ago. There are the nails
fastening the boards to the rafters, a layer of tarred
paper, which for some reason roofers like to pierce with
a liberal amount of staples, then the shingles nailed
into place.
I had mounted a Sirius satellite radio antenna under
the roof and discovered a position sensitivity. I
initially went with locations midway between the rafters,
but discovered maximum signal level adjacent to a
rafter. I attribute this to the nailing pattern.
This group is such an interesting resource.
Mike - AA8K
Bruce Griffiths wrote:
Below 600C the only significant source of microwave absorption in wood
is the water content:
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