Author Topic: MOVED - Satellite Dish Wifi  (Read 3357 times)

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Offline MadScientist267

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MOVED - Satellite Dish Wifi
« on: June 19, 2013, 01:51:13 AM »
 Just a couple pics I took recently as my quest for internet connectivity continues....

This *obviously* won't work on a permanent level, but I'm able to drill through houses and get the access point I'm after now with less and less effort....

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From the "target side".

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The gap between the dish and the antenna

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A shot showing the goofy "mounting" position its in. It's designed to be mounted so it's taller than wider, so I had to do some odd tricks to stabilize it. If you look closely at the first pic, you'll see the word "Sony" is laying sideways.

It's not perfect, but gets about 3x better signal than the last wifi attempts, so we're making progress. Other antenna designs are being looked into that aren't so (ahem) obnoxious LOL

Steve
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Offline hiker1

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Re: My whack satellite dish wifi
« Reply #1 on: June 19, 2013, 03:16:46 PM »
cool....ile half to try that !  seems like every where you go in this town theirs wireless !!
new toweres going up every day !   i pay 20 bucks a month for 3mbs --works for me..but you really cant watch any movies--eats it up fast !..   might dig out my old D-LINK.. [usb-flash card]..  and hook that up to a extender cord...then focus the dish on that.............
just do it

Offline frackers

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Re: My whack satellite dish wifi
« Reply #2 on: June 20, 2013, 05:12:26 AM »
I've used a biquad antenna to good effect without the sat dish. Here is an article describing both!!

http://www.engadget.com/2005/11/15/how-to-build-a-wifi-biquad-dish-antenna/
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Offline Seth7

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Re: My whack satellite dish wifi
« Reply #3 on: June 20, 2013, 04:13:24 PM »
I wish there were some tests for various mounting positions .... or even the authors of these Bi-Quad on Sat Dish list the distance from the body of the bracket to the back of the Bi-Quad

It would help with getting an optimal focal position -- i would think ....

I have some 4' internet satellite dish reflectors that id like to use !!!!

even a 12' C-Band dish might be fun ....

Offline frackers

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Re: My whack satellite dish wifi
« Reply #4 on: June 20, 2013, 10:42:31 PM »
The article I referenced assumes you use the original LNB mounting which of course will be at the focus.

If you have lost that then you will be into guesswork although a trick I have used in the past is to wet the dish and see how the sun reflects off the wet surface onto a piece of card to find the correct plane (when the suns image is round and not oval) and at its smallest which will be the focus.
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Offline Seth7

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Re: My whack satellite dish wifi
« Reply #5 on: June 21, 2013, 11:25:29 AM »
Iv thought of doing that in the past ....

the one question i had was this ....

should the light be focused on the feed point ( almost none on the square ears)

or just touching the ends of the bi-quad ....

Offline MadScientist267

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Re: My whack satellite dish wifi
« Reply #6 on: June 21, 2013, 09:34:03 PM »
 Wondered the same thing myself... The focal point of the dish is obviously important, and what I have in the pics above gave me the best results with as far as I was willing to take it that night, but that antenna (a dipole) is WAY closer to the dish than the LNB was. I know very little about antennas, and look forward to building one that can really reach out and hit a nice distance, but its slow going because there's so many variables and I only understand concepts.

The biquad keeps coming up as the answer and looks simple enough to build, and is apparently forgiving somewhat to construction imperfections, but the answers to questions like focal points and the like are hit and miss to locate.

I've also been told that the dipole/dish combination isn't anywhere near ideal because of the radiation pattern a dipole exhibits, which likely explains the obnoxiously close proximity to the dish with what I've done above.

 There's a lot of room for improvement here, so any and all information that anyone either knows the location of or has in the form of personal experience is greatly appreciated.

All of the specs for the dish(es) are available if that helps. I'd also like to try the so-called "dual biquad", as there are 2 radios in this router (WRT54GS running DDWRT).

Steve
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Offline WooferHound

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Re: My whack satellite dish wifi
« Reply #7 on: June 22, 2013, 12:28:03 AM »
This seemed really helpful . . .
http://www.ds3wireless.com/aiming.htm
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Offline hiker1

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just do it

Offline Seth7

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Re: My whack satellite dish wifi
« Reply #9 on: June 22, 2013, 08:11:56 PM »
Wolf's link is about pointing the dish its self ...

and the google search is not definitive ...

the bi-quad has a fairly wide radiation pattern ... that your trying to couple to the dish ....

Finding the best distance from the dish to couple the most signal for the Bi-Quad is a missing factor.




Offline Seth7

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Re: My whack satellite dish wifi
« Reply #10 on: June 22, 2013, 09:47:57 PM »
This has a bunch of useful information .. none of which is helpful to the task im looking for ...

http://www.lecad.fs.uni-lj.si/~leon/other/wlan/biquad/

Offline rossw

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Re: My whack satellite dish wifi
« Reply #11 on: June 22, 2013, 09:48:39 PM »
Finding the best distance from the dish to couple the most signal for the Bi-Quad is a missing factor.

Parabolic dishes (lets just talk about prime-focus for a moment, because they're more intuitive) are not rocket science.

Parabolic dishes have a given FD ratio, which determines exactly where the perfect focus is for a given diameter dish.
You can move in and out from there along the focus axis to maximise the effectiveness of the dish to suit your feed.

Ideally, you want a feed that produces a perfect conical radiation. Reality is that most antennas have different radiation in the H and E plane, so it'll be a compromise.

If your antenna/feed has a radiation angle of (lets say) 30 degrees. If your feed is too close to the dish, you are under-illuminating it and only a part of your parabolic surface is contributing.

If your feed is too far away, you are over-illuminating the dish, and some of your power is going straight past the dish and being wasted..

Perfect illumination sees all the dish being used. The ideal focus can be calculated, but it's still a compromise and fairly easily found by experimentation, measuring the signal strength. It's arguably easier to use the dish in a receive mode with a source quite some distance away (preferably hundreds of wavelengths away), fix the dish and adjust the feed distance for optimum signal strength.

Offline MadScientist267

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Re: My whack satellite dish wifi
« Reply #12 on: June 22, 2013, 09:57:52 PM »
 Thanks for all the input so far - keep it coming, the picture its getting clearer and clearer... ;)

One beautiful aspect to this, while I do indeed have the LNB and arms for both dishes, I too am confused about exactly where the focal point lies, but I have a whole bunch of leftover foam scraps from insulating the van, which make easy targets for simple fabrication of mounting shims and the like.

Looking down the barrel of an LNB however, there is the horn, then a short tube, and then what  I can only imagine is the antenna element. On the triple LNB, these elements are about 2 inches or so behind the weather cap that goes over the horn.

So, does this mean that the focal points are on the elements themselves, or is it closer to the dish, right at the threshold of the horn (which then becomes a waveguide) where focus is no longer an issue?

I'd post a pic but I don't have one handy at the moment, but hopefully in the mean time someone will have seen the internal structure of an LNB feed horn and it will make sense...

Steve
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Offline Seth7

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Re: My whack satellite dish wifi
« Reply #13 on: June 22, 2013, 10:15:05 PM »

Offline MadScientist267

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Re: My whack satellite dish wifi
« Reply #14 on: June 22, 2013, 10:16:45 PM »
 Ah ok posts clashed Ross....

Ok so just as I'm seeing with the dipole, the biquad is going to have yet a different ideal focal length than the dipole and original LNB?

Steve
Wanted: Schrödinger's cat, dead and alive.