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Using an Old Satellite Dish as a WLAN Antenna
=m8s=Dark Underlord writes "I was browsing for wireless stuff and came across this link that shows how to use an old satellite dish as an 802.11 antenna." The directions tout the range as being 10 miles given line of sight. We've had other stories about building antennas, but I think these are cooler because of their focused nature, but a Primestar dish is a little tougher to locate than a Pringles can or a floppy disk.
The Original Slashdot Article
Looks like you can pick up a Primestar dish on eBay for about 50 bucks (current auctions here). Shipping looks to be about $20. Anybody know of other sources for acquiring these dishes?
.sig
Aren't you supposed to return the antenna at the end of the contract?
Days ago. And IIRC, it was a /. article that inspired me.
You can't judge a book by the way it wears its hair.
Making a WiFi antenna using a telephone poll. You use the red and green wires to transmit a signal to another WiFi device connected to the red and green wires up to 20 miles away. But what would I know? I'm just a naked chick.
--
So I'm naked. So what?
Primestar dish is a little tougher to locate than a Pringles can or a floppy disk.
Will a DISH Network or DirecTV dish work? I can locate hundreds of these without walking too far. Give me a couple of nights and I can send a bulk shipment you're way for a few thousand dollars.
Now, where did I put my screwdriver?
-- Fighting mediocrity one bad post at a time.
A few years ago I saw one still attached to a pole near an old trailer foundation along the highway. A few minutes of working it loose and we threw it in the trunk. I had plans to buy a receiver on ebay and get C and Ku band channels but never followed through.
Only the State obtains its revenue by coercion. - Murray Rothbard
I tried this a while back, but at the time, even unused sattelite dishes were too expensive. I borrowed a neighbors' dish for the experiment. The hard part was focusing the dish - If you didn't have something sturfy to mount it to, then you would lose the signal pretty easily.
My grandparents have a satelite dish that's about 10 feet in diameter... so should that give access to about 30 miles away? (I know it wouldn't, but it'd be neat to crank the amps)
Karma: Good, or bust!
Where I work our internet connection is via a WISP that uses this "technology". We have a Primestar dish on an elevated pole aimed at a mountaintop 12 miles away. 5Ghz and also a backup 802.11b radio with Yagi antenna that needs an amplifier to go that distance, but does so fairly well. The less-informed employees think the "dish" points to a satellite, not noticing the odd angle it's mounted at :)
http://www.planetc.com/ is the ISP
but it is powerless against slashdotting!
Satellite dishes aren't hard to find; just visit any trailer park or upper-lower/lower-middle class neighborhood, and I guarantee you, there'll be a dish stuck on the corner of every other house. The kids'll be running around half-naked, there'll be a car or two on the lawn, but getting satellite tv still seems to be first priority.
Why bother with the Primestar dish for $50 on Ebay when you can get a real 802.11b/g antenna with 24dB gain for about $65? If memory serves, every 3dB is double, so 24dB is 2^8 or 256 times the signal strength.
I STILL say my dish is better than anything you can get. Damn, I can WiFi to my brother's computer all the way in Zeta-Twelve!
wwc.edu better set up a bunch of these things and stream the site to someone with more bandwith...
SAILING MISHAP
Google Cached Version
http://216.239.53.104/search?q=cache:ltX22XDG3_4J: www.wwc.edu/~frohro/Airport/Primestar/Primestar.ht ml+&hl=en&ie=UTF-8
Hey, guys, this would violate FCC part 15 and other applicable rules. Specifically, we are referring to ERP (effective radiated power).
Have fun if you get nailed!
If you are interested in this, check out the Canteena solution which has a 12 db gain. You can get a *new* shiny antenna for much less than the cost of a used Primestar dish on EBAY. I know the dish in the article boasts 22 db gain with a 10 mile range but, keep in mind that setting up communication that is line of site 10 miles apart is nearly impossible. (Just try using a camera with an 8x telephoto lens to take a non blurry picture, you'll start to get the idea. ) Have fun!
Given the fact this story was just posted on Slashdot..not for long.
Somewhere, tomorrow morning, some poor satellite dish dealer in East Nowhere is going to be very, very happy and not know why.
Please help metamoderate.
"- Sir, you are aware that you have a huge TV antenna duct-taped to the roof of your mini-van?
- Hun, yeah, I do
- And that there seems to be 2 sets of eyes in the back of the mini-van that look like they belong on ghouls
- I think you mean geek sir. And don't mind the flashing leds too, we are having a lan party.
- In a mini-van ?
- Mmh, yeah.
- Ok, drive safe"
*rolls up window and keeps on following the signal*
In Canada, we don't fancy things like socks
In a past life, I used to provide ISP services to a company in Iowa that manufactures dishes used by many of the top names, including DirecTV. I checked their website, www.winegard.com, and it doesn't appear they yet have a consumer distribution channel. But if you want a bunch of dishes, these folks can probably provide them.
FWIW- I toured the plant, and saw sheet metal stamped into dishes. It was impressive.
Imagine the long distance LAN parties.. whoa yah.
Call your buddies up around the neighborhood and your ready.
ogg
Black cat, searing pain, flames...? I must be in Heaven! - Homer Simpson
"I sacrificed a db of gain here by not turning it over, mostly because I'm mounting it on a vent pipe, and didn't want to put that kind of wind load on it. As mentioned above I don't really need the extra signal either."
Wonder if he realizes what that vent pipe is for? Are there any studies on the interference factor from 'methane gas' emmisions on WI-FI?
Maybe it's just the bathtub/sink vent.
sig mind freed
Unless you are actually worried about taking up too much space (and why should we let that get in the way?), why use one of those little mini-dishes? Go all out and find an old 8-ft diameter big dish system. Not only will get a much larger reflector area, but if the control arm and box are still in working order, you can remotely slew over an arc of about 50-60 degrees without modification. This could let you change focus to different nodes from your computer.
Plus it is far more conspicuous, and therefore infinitely more cool.
The atmosphere is opaque to ham radio frequency and so the signal bounces back to earth (that's why you get different levels of signal quality depending on the weather, etc.) while the atmosphere is transparent to the Ghz frequency of Wi-Fi so your signal goes off into space.
Ok I understand the curvature of the Earth thing. But damnit! HAM Radios don't have to be line of site. Why the hell do I have to be within line of site of my friends house to reach his bandwidth!
I'm not sure if you're kidding or not, but I'll tell you the reason anyway.
It has a little to do with output power, but mostly to do with frequency. The higher in frequency you go the more readily the energy is absorbed by "stuff."
Ham operators use HF frequencies (loosely defined as about 7MHz - 30MHz). Those frequencies tend to be reflected and/or refracted by the atmosphere and they can "skip" over great distances. Once the signals reach the ground, they can bounce off the ground and skip again, leading to VERY great distances. If the atmosphere didn't help in this way, ham operators would too be limited to line-of-sight.
All opinions presented here aren't mine.
There are much better solutions. While a pringles can and cantenna might work, assumng you put it right in the focal point, build the cantenna right, and can find the dish, this might be a better way to go:
Try this.
Its a 24dB gain antenna (Thats 256 times power folks), its guaranteed to work, it HAS a feedhorn, and all the calculations have been done for you. Not only that, its a grid antenna so there is almost no wind loading. You might pay 50bux or more for a primestar dish on ebay, plus trying to get the can into the focal point, etc. There is certainly a certain apeal in doing it yourself, but sometimes work for the sake of work is no fun at all.
The best thing? Its only 70 bux, WITH the feedhorn and pigtail.
Right now im using one of those, and two 10 foot C-band dishes to make a big triangle network connection. The C-band to C-band dish connection is over 30km long. (Yea I'm in Canada: 30 kilometers = 18.6411358 miles)
It's easier to fight for one's principles than to live up to them.
For what it's worth, two Linksys WAP11's in bridge mode, and two directional 24dBi gain antennae, and my link is rock solid at 1.1 miles.
I use Linksys WET11 bridges with 24dBi grid antennas made for 2.4GHz (also less than $70 each) and have a rock-solid 11Mbps link a bit over 6 miles away. The trick is to mount your WET11 in a weatherproof box right underneath the antenna, to keep the coax pigtail as short as possible, because signal loss in a long coax is the distance killer. I have only a 3 foot long coax pigtail and run the dc power up the unused pairs of the CAT5 cable to power the WET11. You may have a significant voltage drop at the end of a long CAT5 cable, so you may need to use a +6V or even a +7V DC power supply of adequate amperage to ensure that you still have +5V DC at the end of the CAT5 cable with the WET11 plugged in loading it down. I had to use a +6V, 1.5 amp DC power supply on mine to keep the voltage at +5 volts at the end of my CAT5 cables, or the WET11 wouldn't run.
Charles Miller
The more I learn about the Internet, the more amazed I am that it works at all.
Only the party obtaining the FCC certification is allowed to specify another antenna. You, the user, cannot alter the device even if it meets the requirements of 15.247. Modifying approved transmitters is generally not allowed, with the notable exception of the Amateur Radio Service. A new configuration with higher antenna gain requires a new certification. 47CFR2:
[emphasis added]So unless you have the money to spend on a complete recertification (it's neither cheap nor easy), leave your wifi alone!
Read ALL the regulations, starting with Part 2. The technical limits in Part 15 apply to the "responisble party" who obtains the FCC certification. It has nothing to do with user antenna modifications, which are expressly forbidden by the regulations. Any user modification is forbidden, except for Part 97 use (amateur radio)-- and amateur radio cannot be legally used for public wifi setups.
How the heck do you sight something like this in? You have to be accurate within a few seconds, don't you? A search pattern would take forever with that narrow of a beam, wouldn't it?
The beam isn't that narrow. Let's do a quick mental calculation. A typical direct-to-home Ku-band dish is going to have a beamwidth of about 1 degree (2 degrees, whatever) in order to be able to isolate the right satellite on the arc. That's at Ku-down, which is about 11 GHz. A given antenna will get "wider" as you go down in frequency, so the beam width at 2.4 GHz for this same antenna is much wider. I believe the beam width and frequency scale inversely, so if you go down in frequency by about a factor of 5 (11/2.4) then your beamwidth (however you want to measure it) goes up by the same factor.
So your beamwidth at 2.4 GHz is going to be something like 5-10 degrees. And it's not a super sharp rolloff, so you'll find that signal easy.
Another way of expressing all of the above is to say that an antenna with a certain gain at a high frequency (like Ku band) is going to have a lower gain at a lower frequency, and the corollary of that gain reduction is lobe spreading.
Hey, maybe someone here can point us to a visualization tool for this -- looking at an antenna pattern for a given antenna, crank down the frequency and watch the lobes spread out and drop.
One simple rule for its versus it's
I was looking at the slightly elliptical curve of the dish and it occured to me, the Star Choice dishes (Canadian) are designed to pick up two satellites at once. It could maybe give a wider line of sight if someone modified something like this. I think the feed can would have to be modified for something like this to work. Think something like this might work? or would I be wasting my time?
The FCC doesn't seem to care much about power levels and antennas in the ISM band. Remember, it's kind of a throwback "freebie" given to appease the anarchist crypto parasites and cheap low end consumer equipment for those unable to afford the "protected and scarce" high dollar bands that go up for auction. :-)
The only exception might be certain commercial product vendors who try and sell out of spec equipment to the masses. That is actually worth their time, but some guy with a primestar dish? no way. [ Like linksys getting pressured to take their 2.4Ghz amps off the market because they could interoperate with too many other "unapproved" equipment configurations. Supposedly they can sell them again after making them harder to use with anything but linksys/cisco. arg. ]
There are a number of smaller WISP's that I've come across in the northwest that run 1/2W and 1W amps on their directional point-to-point and point-to-multipoint configurations, but until someone complains that they are interfering, there is no way the FCC is going to proactively come out and bitch.
Wireless users groups across the nation post plans and site configurations using all sorts of unapproved antennas, radios, amplifiers, etc. There is no widespread FCC CRACKDOWN going on. In fact, I challenge anyone to name an incident where a WiFi user (not company) was pressured or forced by the FCC to alter their equipment back into spec. It doesn't happen.
Personally I think this is a good thing. The FCC has done more harm in the 802.11 space than good. Like antenna connectors. Do you know why there is a proliferation of SMA, RP-SMA, N-type, BNC, RP-BNC, MMCX, and any number of other bastardized formats for antennas and equipment? The FCC requires vendors to make their radio's use proprietary connectors to prevent people from easily and usefully extending the range of their equipment with generic antennas. Not that the vendors mind. Nothing like vendor only parts with the associated 400% markup to pad the profit line.
Let the FCC play with the Big Co's and handle licensed spectrum. The ISM bands are where its at.
I've got a reasonably fool proof way of making use of these offset dishes, unless of course you're the more talented fool. The Australian Fox TV dishes are similar, but lend themselves to this technique. Aquire some mirrored perspex or something similar. Cut it into small squares, or just steal a mirrorball. Randomly cover the surface of the dish with these using double sided tape. The thinnner the tape, the better. When you reckon you've got enough, point your dish at the sun so that the focal point, your tin can feed or quad, helical whatever is glowing quite well. Too many little mirrors and you'll melt it. All you want is to be certain that the focal point is exactly where it needs to go. Right on the signal feed. If you know where the feed point is, you also know where the sun is. A pointer of some kind pointing directly into the sun, fixed to the dish so that it throws as little shadow as possible can be used to accurately align the dish with little effort. Mount the dish on your roof. sight along your pointer at the source of the signal. Voila. Dish aligned. Jaycar in Australia sell sheets of tiny mirror squares that are perfect for this job. http://www.freenet-antennas.com in WA has managed some big distances with a modified dish. He doesn't use my alignment method thow.
I used to live in a relatively old area of town, and seem to recall seeing gigantic dishes (which, I assume, were used to pick up broadcast signals, or some archaic form of satellite TV...this is all speculation on my part, of course) ... firstly, does anybody else know what I'm talking about, and secondly, would you be able to use one of those? :)
what sort of signal would you get, do you think?
Some links:
KI7cx dish
Primestar dish
Bi-Quad feed for primestar DIY
10 Euro dish with biquad feed
Modifying Confier Antennas for Wireless Networking
More info: Wireless Leiden
More info about the ARRLs take on that:here. They point out that channels 1-6 fall within the amateur band around 2.4 GHz, and if they get modified within the part 97 allowances for amateurs they could use them instead of the slower packet radio (although I have read about 5-10Mb/s links, but they are more for backbones between the slower areas).
So yes it is posible, just remember that you can't encode/encrypt to obscure the meaning of the data. (Although I have never read anything about putting a passowrd, you might run into trouble because some OSes (i.e. Windows 95B & later ) encrypt the password before sending it).
One Bel (10dB) is a power of ten in intensity. The question I have here is, is that a 22db gain over the stock antenna, or is it a 22db gain over a calibrated 50ohm dipole, as most commercial communications antennas are measured? If the former, what is the gain of the stock antenna?
Mnem
"Enough technical gobbledygook. Tell me how we kill this thing."
I know they're not as desirable as Primestar dishes, but Dish Network and DirecTV dishes work also. I got a couple for free just by asking. Go to the place that you bought your satellite system from (What, you're on cable? Well, get with it!), and ask. My source said that they occasionally would have a spare dish from an installation, and after a few years in business they had a heap of them in the basement, still in the box. They were more than happy to let me walk out with a couple.