Episode 16: Long Hop Wireless

[crumbles]

Best opening line ever:

"Welcome to revision3 episode 16."

In this episode, Patrick and David show off some antennas, attempt 1 and 10 mile wifi links, and learn why more power doesn't always mean more distance.

[jcduerr]

good episode. opening made me rofl

[vahnx]

I did the L of the rofl.

[handyman]

Where is all the links in ep. 16 they said gonna be here??

[stormadvisor]

First off, this is a great show and I can't miss an episode!

I loved the point Patrick made about grounding your external antenna. This is VERY good advice. Especially if you are above any surrounding structure. The big thing about grounding though. Do NOT separate your grounds. Always tie in your radio/Antenna ground to your house ground at the service panel (breaker/fuse box) of your house. This does not mean that you should not put a ground rod in the ground at your antenna. Putting a ground rod there is the right thing to do. But run a wire/strap from there to your service ground.

Here's a url to a good resource: Polyphaser (http://www.polyphaser.com/technical_notes.aspx). I have listened to a rep. from Polyphaser at the Dayton Hamvention (http://www.hamvention.org/) several times and they have good info. You can find good equipment all over the net though (cheaper too). I use them as a resource only because I can't afford their stuff.

[kdepasquale]

I hate to be one of "those" people, but the word "Fresnel" is pronounced "FreNELL" not "Frenzel". Think Fresnel lens (the ones that used to be used in lighthouses).

[buddhabelieves]

Couldn't find any show notes on the iTunes RSS file or on the revision3.com/systm page. I'm working on this seemingly perpetual project to integrate wifi at my office and i'd really like to take advantage of that calculator you were using.

The project seemed well designed at it's inception but i guess i'm figuring out the design caveats as I go along. Adding two Apple airport extremes (The pre-"N" model) as a WEP secured WDS linked Access Points to an already laid out wired network. Two Radio Labs Brand Omni -15db Antennas with 1 Watt Amplifiers. This was designed to cover about 2sq miles of Fair Grounds for an Auto Auction. Mainly having problems getting the second Airport to Pickup and Join the WDS of the Main Base station which is connected to the network.


Thanks for the info,
I'll update this when i get it going.

-Chris

[drandolph]

This might be the first time in Revision3 history but we will update the article for an episode. If you read the post about systm is changing you will notice that I mentioned a few "bugs" for us to still work out with the new work flow. With everyone on the team being so wrapped up in the show and our other projects for Revision3 we totally didn't finish the full article in time but we still wanted to get out the show. Check back with in the next 24 hours and I am sure someone will get the article uploaded to the episode page.

Our bad, :) Dave N' Patrick

[drandolph]

I hate to be one of "those" people, but the word "Fresnel" is pronounced "FreNELL" not "Frenzel". Think Fresnel lens (the ones that used to be used in lighthouses).

When your right, your right but I have a few good old theatre lighting guys that would beg to differ. However you way is the technically right way. Being orginally from the south and working in film and theatre there I think my accent tends to come out and rub off on others.

So y'all have a good one now ya hear?

[eminemdrdre00]

I cant wait for Revision3 episode 17!

[masherscf]

I hate to be one of "those" people, but the word "Fresnel" is pronounced "FreNELL" not "Frenzel". Think Fresnel lens (the ones that used to be used in lighthouses).

I'm glad you did it. I was gonna be one of those people too.


When I was in grad-school, I was building a Linux box to use for my research. I had to do it on the cheap, so I ordered it a piece at a time over the internet. I had the parts shipped right to my office. Lets just say, it's pretty sad when you're on a first-name basis with the UPS guy.

[ascendeddaniel]

I like the idea of Systm exploring wifi tech. I've always considered it black magic, and want to learn more about how rf stuff works. I'd like to see Systm keep exploring this topic and hopefully show us some practical applications of what they learn.

One cool idea is battery powered wireless routers that run meshing software. This allows them to actively extend the range of wifi. A 12V pack of 10 AA Ni-MH will run a wireless router for a several hours, and a router in a car would be portable. DD-WRT (dd-wrt.com) is a great firmware for wireless routers that I use for some of my tinkering. It supports meshing, and could be useful in future experiments.

[drandolph]

Not only did Patrick learn a lot about WiFi but I learn exactly how not to move the human foot. While climbing out on the roof top to adjust the antenna for Patrick my foot slipped into the gutter and tore several ligaments in my left foot and sprained my right foot. So dont say I never suffer for my art.

So if you see me hobbling down the streets of SF be kind and hold a door or buy my an extra round at the bar.

[tempesta]

ahhh ya poor bugger. *winces at description*

I'm watching this right now (for the first time in my life im one of those dual monitor people....i feel like im grown as a man :D )

[ascendeddaniel]

Safety third?

Seriously though, staying safe is very important. At Caltech, we have Health Advocates as in-dorm first responders/medics, of which I am one. We do a lot of stupid stuff, but it's still important to have someone there to remind everyone to wear safety glasses and be there to treat the wounded after.

Hope your foot feels better soon. Glad it wasn't any worse. I'll bet it was still pretty scary though. I'm encouraged that our hosts are willing to put life and limb, or at least limb, on the line for a good show. :)

[chuckyyy]

i have done this and as a geek i know you will want to do this your self so i'll point you in a direction .hutton is your friend and look at the andrews 24 db 2.4 dish or better.


have fun and stay safe

[mikec]

When your right, your right but I have a few good old theatre lighting guys that would beg to differ. However you way is the technically right way. Being orginally from the south and working in film and theatre there I think my accent tends to come out and rub off on others.

So y'all have a good one now ya hear?

Dave my broadcast and theater instructors all pronounced it "FreNELL". Of course I went to school NORTH of the Mason-Dixon line.

[movingrushmore]

Bummer about the foot, but it looks like you've got quite the checklist of equipment in the works too. Can't wait to the see the revised crib. On another note... trying to share wifi with a friend that lives two houses down. The only thing between our house and theirs is another house. We don't have line of sight, but would sharing wifi be doable in this situation?

[vincent12234]

Cool episode, alot of good information about wi-fi Good episode.

[rokk]

First I'd like to say good show, I hope to see many more like this one.

But ...

There are some errors / omitions I'd like to point out:

1. Fresnel zone - while there is an infinite number of fresnel zones, the first one is the most important. Without going into too much details ... Fresnel zone is not a space that needs to be free for your signal to travel unobstructed, but any obstacle in this space could cause your signal to bounce, producing an out-of-phase signal, that could also reach your receiver. If the original signal and the bounced one perfectly align, you actually get better signal strength. In practice, even some obstacles in the 1. fresnel zone won't have much of an impact on signal strength, but if there are too many ...

2. Probably the most important info you need about an antenna is its radiance pattern, not its gain factor.

3. I only saw omni antennas (and one panel?) in the show, if you're going for the long distances, I'd recommend Yagi, Helix or grid type antennas. Personally, I had great results with Yagi types and they're also cheap ...

4. Remember that you need good directional antennas on both ends of the connection (with just one 'good' antenna, you could, for example, only sucessfully transmit, but you couldn't receive anything).

5. In your calculations, you ignored the attenuation of the cables. Most cables have quite a lot of attenuation (even as much as 1.2dB/m and more), so if you use 50m of cables, they better be good. You can get some good quality cables with 0.18dB/m, but they are a lot more expensive. Also, connectors have attenuation, too ...

6. You mentioned that, when doing long distance links, you need a lot of bandwidth ... Bandwidth has nothing to do with how far apart the transmitter and the receiver can be (bandwidth in WiFi is fixed). The distance the signal can travel and still be recognised and the receiving end is dependent on two things: noise and signal attenuation. Attenuation is a physical limitation -- signal strength falls with 1/(d*d), or more realistically 1(d*d*d*d) (d - distance), and there's not much you can do about noise (except maybe change the channel).

I hope I clarified a few things ...

All the best, and good luck with your long-distance link!

[thavok]

Not Sure if anyone knows of a place to gather sensitivity information and what USB adapter works with macbooks. I can't seem to find much on the topic

[captaincrash]

Just wondering how hard it would be for me to set up a wireless gaming network in my small town of about 300 people. The only problem is that this same thing already exists because this is how we get our internet because we're in the middle of nowhere and can't get dsl or cable. Would our signals interfere or overpower mine or could I simply change the frequency of my signal.

[pcguy]

This might be the first time in Revision3 history but we will update the article for an episode. If you read the post about systm is changing you will notice that I mentioned a few "bugs" for us to still work out with the new work flow. With everyone on the team being so wrapped up in the show and our other projects for Revision3 we totally didn't finish the full article in time but we still wanted to get out the show. Check back with in the next 24 hours and I am sure someone will get the article uploaded to the episode page.

Our bad, :) Dave N' Patrick

Anyone know if the article ever made it up to the server?

[pcguy]

I guess that the lack of replies means that I should forget about seeing the show notes for this episode and time soon. Especially since there is a new episode out.

[metatr0n]

My Alfa 500mW USB wireless adapter with a 24dBi parabolic mesh antenna would out perform anything they showed and at a fraction of the cost. I would like to see what kind of distances they could get using a similar setup, as where I live there are no suitable areas for such a test.

[pcguy]

My Alfa 500mW USB wireless adapter with a 24dBi parabolic mesh antenna would out perform anything they showed and at a fraction of the cost. I would like to see what kind of distances they could get using a similar setup, as where I live there are no suitable areas for such a test.

If you do not have a suitable area for a test how do you know:

"My Alfa 500mW USB wireless adapter with a 24dBi parabolic mesh antenna would out perform anything they showed and at a fraction of the cost."

[metatr0n]

If you do not have a suitable area for a test how do you know:

"My Alfa 500mW USB wireless adapter with a 24dBi parabolic mesh antenna would out perform anything they showed and at a fraction of the cost."

The card has a greater power output then the one they showed, plus the antenna is superior, in that it has a design suited for point to point data transfer and has a higher dBi rating.

[blackmaverick]

So what did happen to the show notes for this episode?

[tempesta]

So what did happen to the show notes for this episode?

Patrick Norton. Sledgehammer. Show notes...gone.... :D

[pcguy]

So what did happen to the show notes for this episode?

I Have given up on ever seeing show notes for any systm episodes. Revision3 seems to be trying to be doing more quantity programming rather than quality right now.

:(

[masherscf]

I Have given up on ever seeing show notes for any systm episodes. Revision3 seems to be trying to be doing more quantity programming rather than quality right now.

:(

Wait, I just read this exact thing in another thread. Who was it that posted that. Oh yes, you.

[spress]

This might be the first time in Revision3 history but we will update the article for an episode. If you read the post about systm is changing you will notice that I mentioned a few "bugs" for us to still work out with the new work flow. With everyone on the team being so wrapped up in the show and our other projects for Revision3 we totally didn't finish the full article in time but we still wanted to get out the show. Check back with in the next 24 hours and I am sure someone will get the article uploaded to the episode page.

Our bad, :) Dave N' Patrick


I understand you guys are busy... so am I... I only just today got around to watching Episode 16 (and I'll be going through the rest of the Systm episodes). So... if you expect us to check out the blog and forums, let's get the content up!

I enjoy the show, and am glad they're getting shorter... and conciser!
Make them content rich and then the goofiness will pay!
Thanks.

[roashru]

I also was wondering were are the show notes. I really dont need any help with wifi dxing just wanted to post informative links.

http://home.att.net/~roashru/HPwifiextreme.html A personal web page I made in 2005 with links of commercial suppliers that will sell to consumers.
http://www.usbwifi.orcon.net.nz/ Another good place for wifi dxing info.

802.11B to 802.11B needs line of sight
802.11G to 802.11B needs line of sight
802.11G to 802.11G is OFDM. dosnt need line of sight!

[alaskalonewolf]

Best opening line ever:

"Welcome to revision3 episode 16."

In this episode, Patrick and David show off some antennas, attempt 1 and 10 mile wifi links, and learn why more power doesn't always mean more distance.

Lemme guess, something to do with a tuned parabolic dish, a linear amplifier and some new kick ass software... excuse my drool. That is awesome.

[edorsey]

Using an omni directional antenna does not only just broadcast in all directions, losing considerable power if it is a point to point hop, it also listens in all directions allowing for considerably more interference than a directional antenna.

talking about dB and signal strength, 3 dB of gain is a considerable amount, actually adding 3 dB of gain doubles the signal strength.

Just some random knowledge i thought some people may like to know.