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 > > 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. > ------------------------------ > > -- > AF mailing list > [email protected] > http://af.afmug.com/mailman/listinfo/af_af.afmug.com > > -- > AF mailing list > [email protected] > http://af.afmug.com/mailman/listinfo/af_af.afmug.com > > ------------------------------ > > -- > AF mailing list > [email protected] > http://af.afmug.com/mailman/listinfo/af_af.afmug.com > ------------------------------ > -- > AF mailing list > [email protected] > http://af.afmug.com/mailman/listinfo/af_af.afmug.com > > > > ------------------------------ > -- > AF mailing list > [email protected] > http://af.afmug.com/mailman/listinfo/af_af.afmug.com > > -- > AF mailing list > [email protected] > http://af.afmug.com/mailman/listinfo/af_af.afmug.com >
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