Yes, with a scope. The issue was whether or not you could create a
cell phone app using the camera.
*From:* castarritt
*Sent:* Wednesday, December 19, 2018 12:11 PM
*To:* AnimalFarm Microwave Users Group
*Subject:* Re: [AFMUG] Fresnel scope?
I think you did your math assuming the obstruction was at the full
distance of the link, rather than at the half-way point.
If the obstruction is at the half way point of a 2 mile link, and the
60% F1 radius at one mile distance is ~7.5', then 7.5' divided by
5.28' (1/1000th of a mile) gives us ~1.4 mrad. Now look through a
rifle scope with a mil based reticle, and you should be able to judge
the clearance.
On Wed, Dec 19, 2018 at 11:58 AM <[email protected]> wrote:
You made me think a bit.
Consider 11 GHz. One 2 mile link and one 10 mile link.
15’
34’
I presume the online tool is calculating 60% of the first fresnel
zone.
So half that would be the opposite side of a right triangle.
arc tan of 7.5/10560 = .04 deg
arc tan of 17/52800 = .018 deg
So double that for the diameter of the cone based on the distance
and angle you have almost 1 full degree and a third of a degree.
Pretty small circles. May as well call them a dot when viewing
through the camera.
*From:* [email protected]
*Sent:* Wednesday, December 19, 2018 10:12 AM
*To:* AnimalFarm Microwave Users Group
*Subject:* Re: [AFMUG] Fresnel scope?
I toyed around with this idea last night. I think the angle of
view of most phones is too wide. Doing the rangefinder math for
my iPhone 6s a 1 meter dish at 1 km would be less than 4 pixels
across at full resolution (4032x3024). The 5.8 GHz fresnel radius
would be 3.6 m or only 52 pixels. Of course, this would grow
larger if calculated closer to the user—even as the fresnel zone
shrank—but I don’t have the calculus chops to figure out the
ideal size to indicate “this area should be clear no matter how
far away”
December 18, 2018 8:58 AM, [email protected] wrote:
I guess you could run a calibration routine where you take a
photo of some linear feature that exactly fills the frame and
tell the phone how far away it is and how wide it is.
*From:* Brian Webster
*Sent:* Monday, December 17, 2018 10:09 PM
*To:* 'AnimalFarm Microwave Users Group'
*Subject:* Re: [AFMUG] Fresnel scope?
Right and since you know the frequency and total path
distance, if you used a laser range finder to put the spot on
an obstruction you would know that distance and could
calculate the size of the zone at that obstruction distance.
Might be able to do some Pythagorean math on the other side
of an obstruction to determine the width of the “hole”
through to see if it is wide enough for the zone clearance at
that distance? This might be a bit too much for an app that
would work on all phones but I wonder if it would be easier
to make it work on an outboard camera with the known lenses
and rangefinder configuration and just use the phone to run
the calcs.
Thank You,
Brian Webster
www.wirelessmapping.com <http://www.wirelessmapping.com>
www.Broadband-Mapping.com
*From:*AF [mailto:[email protected]] *On Behalf Of
*Chuck McCown
*Sent:* Monday, December 17, 2018 8:40 PM
*To:* AnimalFarm Microwave Users Group
*Subject:* Re: [AFMUG] Fresnel scope?
I guess you could enter the distance of the link and the
camera field of view. With that you could put some circles on
the screen.
*From:*Jeremy
*Sent:*Monday, December 17, 2018 6:13 PM
*To:*AnimalFarm Microwave Users Group
*Subject:*Re: [AFMUG] Fresnel scope?
What about integrating it with one of these laser
rangefinders that are fairly cheap now? The tech exists to
make this product work, but I am not sure if there is a big
enough market to justify the R&D.
On Mon, Dec 17, 2018 at 6:12 PM Chuck McCown
<[email protected]> wrote:
The challenge would be to know the distance to the
obstructions.
*From:*Steve Jones
*Sent:*Monday, December 17, 2018 6:06 PM
*To:*AnimalFarm Microwave Users Group
*Subject:*[AFMUG] Fresnel scope?
Anybody every toyed with making some kind of fresnel
scope for installers?
Like a rangfinder with a red, orange, yellow, and green
opaque overlay that you dial your freq and range and it
adjusts the rings?
Having been doing the installers job for almost a year
and seeing the "gap in the trees" theyve been shooting
through, explains alot of the performance issues.
A phone app would be cool cause you could do a field of
vision screenshot. But i dont know how that could be
calculated with much accuracy given the differences in
cameras
Would be really cool if the adjustable rings could be
used to identify beneficial obstructions for mitigating
destructive multipath.
I cant see the concept being all that complicated, you
would know the magnification, field of vision and
distance from the eye. Making the circles adjust like
miltiple irises would be a might bit complicated though.
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