Anotherpower.com Forum
Off Grid Living / Camping => Off Grid Living / Alternative Housing => Topic started by: MadScientist267 on June 19, 2013, 01:51:13 am
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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....
[attach=1]
From the "target side".
[attach=2]
The gap between the dish and the antenna
[attach=3]
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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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.............
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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/ (http://www.engadget.com/2005/11/15/how-to-build-a-wifi-biquad-dish-antenna/)
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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 ....
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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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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 ....
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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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This seemed really helpful . . .
http://www.ds3wireless.com/aiming.htm
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heres a few links...https://www.google.com/search?q=homemade+wifi+dish+antenna&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a
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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.
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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/
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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.
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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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This is OT .. but still fun ...
http://www.youtube.com/watch?feature=player_embedded&v=TtzRAjW6KO0#t=0s
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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
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wish there was a chaparalle type feed horn for 2.4Ghz that was DIY ....
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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?
Almost certainly. A dipole has a very wide angle of radiation and will need to be "quite" close to the dish. However, that will also mess with its characteristic impedance and you may not get a good match the the xmitter/receiver if its too far out.
I can't remember the polar radiation pattern from a biquad, but it's going to be somewhat better than a dipole in this purpose, and will want to be further away from the dish surface.
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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
My vote is "yes".
Probably closer so the "sweet spot" covers the element?
All my RF experience is from the old days before they had such high frequencies in common use.
So I could be all wet.
Tom (who learned electrickery on valves not transistors!
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Any one know if a Ku band feed horn would workout ?
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Any one know if a Ku band feed horn would workout ?
It's completely the wrong frequency for any WiFi.
Ku is 12-18GHz, most WIFI is either 2.4 or 5.8GHz
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Several versions of ideas coming from all over the place now, thank you all, and keep the ideas/discussion going if you would por favor... ;)
Some of this has been a waiting game, connectors, cables, designs, ideas, and so on. There's at least one more dipole experiment on the way that I haven't so much as seen yet (good friend down the road is retired and just wanted to help out and see what he could come up with)... I'll be getting my first peek at that tomorrow at some point if all goes well.
I did another quickie dipole of my own the other night, no math, no real planning, just roughly eyeballed the parabola and did a little shaping by using an LED spotlight to attempt to focus the whole thing. With light, it looked plausible more as one might have expected it to look, but when it came down to it, the meters told a different story. My theory is that since there is no sub-structure whatsoever to this thing that it deformed as the tinkering progressed, and well, as you can see, the antenna ended up WAY further away from the reflector than the light test suggested it should be.
This thing ain't even close to ideal, but did do better than just the antenna standing alone without the reflector behind it. Easy enough to test, the reflector can be just picked up and removed without disturbing the rest of it.
These dipole tests aren't about the final product, I'm using them as a learning tool and as baselines to compare design to design. What you see below is about half as potent as the dish version posted that started this thread.
[attach=1]
The view from the target side. Its pretty apparent even from here that the antenna isn't in the butter zone; you can see the "shadow" of the dipole just to either side of the actual antenna.
[attach=2]
A shot from the back. Really all I'm illustrating here is that its just a cut up and deformed wide mouth plastic jug.
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A shot more from directly in front of the van.
[attach=4]
Here it becomes blatantly obvious that the shape of the parabola had become rather distorted and just how far the focal point had been shifted forward. I was probably getting more direct radiating behavior than anything else at this point, but still had a decent signal (the antenna by itself test mentioned above was performed after this shot was taken).
So far, my conclusions are that antennas are strange creatures. There are so many variables that contribute to the performance of any given design, its not even funny... LOL
I'm looking forward to seeing what my buddy down the road here has come up with, as well as trying the biquad and a handful of others I've seen and/or heard about.
Ross, you mentioned other forms of the quad design the other night in IRC... Any chance you'd elaborate? :)
Steve
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Any one know if a Ku band feed horn would workout ?
It's completely the wrong frequency for any WiFi.
Ku is 12-18GHz, most WIFI is either 2.4 or 5.8GHz
Darn decimal point ... wish some places would not list every thing in Mhz ....
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I shouldnt try to read stuff like this when im up an hour past my sleepy time ...
http://www.w1ghz.org/antbook/conf/high_efficiency_prime_feeds.pdf
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Yeah that about made my head explode... You're not the only one LOL
I've been poking around a bit, reading a lot of stuff that resembles the above linked document, and asking lots of questions...
Came up with a cantenna made quick and dirty style and based on just some concepts that I thought would work. I couldn't have been more wrong.
I present to you the CAN'T-enna:
[attach=1]
Error #1: Not long enough, and not the correct diameter. But it is round. :)
[attach=2]
Error #2: I thought a dish like structure would work better than a flat reflector. Bzzzzt.
[attach=3]
Error #3: It was brought to my attention that the inherent oxide layer that forms on aluminum naturally could potentially interfere with the ground connection. Given that this isn't even close to a "real" connector, I think that part of it didn't work out that bad and makes a halfway decent test jig for this type of thing. Its the broken off mounting shaft for a small lever switch.
[attach=4]
Error #4: This isn't the greatest angle to see it either but between this and the above, hopefully one can get the idea that the stub is way too close to the back of the can. It's also smaller gauge than it should be apparently, but given that it's a quick and dirty with just the center conductor tinned, I've stashed away that little tidbit for when I make the real deal.
Designs are on pause ATM, but I'll be getting back into it shortly. I've gathered some parts during this brief hiatus, as well as an eye on another design I'd like to try out.
Stay tuned...
Steve
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Ok, got a little more serious this time, and it paid off... Finally was able to throw a little time at it and see where it went. This is what I came up with.
I went with the bicircle antenna, as it was apparently one of the higher gain antennas for it's simplicity, claims of +14dbA by one guy out on the interwebernets. Probably not too far fetched.. I'm currently putting this up while connected to an AP that has never shown up on the radar before now, so things are looking good.
There's still no dish in the mix, as I'm looking into seeing how far I can get without it since it is rather obnoxious for one, and is also a pain to aim. Less footprint is better up top. ;)
The raw parts:
[attach=1]
3.5 ft of RG58 (I didn't need quite that much, but left a little extra for both error and in case I needed to redo the connection in the antenna due to a meltdown courtesy of the torch... turns out I didn't need it)... The gland/standoff is a small rolled up piece of the sheet with a crimp cut into it at the end for the braid. The elements themselves, 123mm of 2mm solid copper wire, and a reflector made out of the same sheet the standoff was cut from. It's dimensions are 142mm x 102mm, slightly oversized. My understanding is that these are a minimum dimension, and that a little extra is ok, so I made them just slightly bigger than the minimum for the longest wavelength in the band calls for. And of course, someday, I'll need a new scale reference, but for now, the smokes work :)
[attach=2]
Here's the business end after assembly. I was a little bummed that the torch screwed up my nice shiny copper, but such is life.
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A shot from the back where the coax goes in.
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A shot from the top down.
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A shot from the side.
It didn't turn out too bad considering it was my first attempt at one, and I didn't use anything more than the most basic of hand tools to put it together. The trickiest part is getting the rings perched up on top of the standoff just right while applying enough heat to melt and flow the solder, but not make goo out of the cable and it's innards in the process. I ended up using the torch down running with a minimal flame and assisting the iron by heating the side of the tip (it's one of those cheap radio shack 40W deals). That seemed to work out ok.
I intend to at least try this with the dish, but I can say that as it sits right now, I'm reasonably satisfied with the results with it running by itself.
Until next time...
Steve