Episode 45 - Practically Free DIY WiFi Antennas [Discussion]

[marilee]

Cut and past your way to better WiFi reception? It costs pennies and takes the fabrication skills of a kindergartner... then bend a 6dBi Omni and a 10dBi directional out of copper wire!

Watch or download the episode here (http://revision3.com/systm/surfer/)

[zboy417]

The WMV Large version of the show is having voice-syncing issues....their mouths don't move with their words

[joey85]

The WMV Large version of the show is having voice-syncing issues....their mouths don't move with their words

I am also having this issue.

[chuckles]

The WMV Large version of the show is having voice-syncing issues....their mouths don't move with their words

Yikes!! It is really out of sync. Working on getting a new encode right now.

-chuckles-

[zboy417]

Yikes!! It is really out of sync. Working on getting a new encode right now.

-chuckles-

Are you going to post when its fixed?

[chuckles]

Are you going to post when its fixed?

Yeah. I'll post an update once I have the fixed version out in the wild.

-chuckles-

[will_stutler]

and here i go thinking it was only me having that issue

thanks for getting on that chuckles

[tokenuser]

The WMV Large version of the show is having voice-syncing issues....their mouths don't move with their wordsI am also having this issue.Me too, and its annoying the crap out of my wife. She feels like she is talking to a bad Japanese overdub.

[zboy417]

Hehe...can we keep the old video as a Systm blooper :D

Also...can we have the Systm theme song in an aif file?
I don't want to copy it from the video, I want the original (it would sound MUCH better :D )

[zboy417]

Just a hope :D...i hope they mension it in next episode and play a clip and make a joke about it :D...
Its a classic words off thing ;)

[chuckles]

Okay. The fixed WMV files have been fixed and replaced.

We apologize for the inconvenience and thank you for your patience..

Happy viewing...

-chuckles-

[will_stutler]

Okay. The fixed WMV files have been fixed and replaced.

We apologize for the inconvenience and thank you for your patience..

Happy viewing...

-chuckles-

thanks a million sir

[philly23]

i was wondering if anyone knew how to replace the internal built in antenna on laptops.... i took my laptop apart and cut the cord now i need to replace it and wanted to improve on the original.

[ddreier]

I'm really glad that they did this, I'm gonna go make one of those 'sardine can' ones for my PC.

Great episode, and absolutly can not wait for next week's.

[sparky42]

Should I put the shiny side of the foil towards or away from the antenna??:D

[blackfeathers]

great episode on diy wifi antennas. very informative.

i was also getting a bit hopeful for patrick being able to finally do an episode without compulsively breaking into yet another voiceover impression, but around 18:11 or so he did not fail to disappoint.

i would probably use a wire template to bend the wires -such as placing nails the required distance apart on a wooden board- in order to keep bends consistent.

nonetheless, a back-to-the-basics straightforward ep. good job.

[dain-denkeler]

Another good source for pigtails is breaking apart old wi-fi routers. Sometimes they have the sma connectors that will snap off of the board, and sometimes they are soldered on, but its worth a shot if you have one laying around collecting dust.

[md2389]

i was wondering if anyone knew how to replace the internal built in antenna on laptops.... i took my laptop apart and cut the cord now i need to replace it and wanted to improve on the original.

Hope you know how to calculate SWR....

[m3wse]

Should I put the shiny side of the foil towards or away from the antenna??:D
Honnestly? it doesn't matter. i thought about this for a second when I first saw it, but both sides of the foil are reflective and card is transparent to radio waves...

Oh, and as I understand it, the magic length for antennas is not actually 1/4 wave, but it is 1/2 wave. Was Patrick wrong? no. The 1/4 wave antennas are half of a 1/2 wave antenna, and the ground plane reflects this (the car roof in the case of a CB whip, which is also why putting them on the front bumper is a bad idea...) and this produces the waves.

As to how it produces the waves, as I understand it antennas work on the principle of resonance. The antenna must be resonant on the correct frequency (hence all the 1/2 wavelength stuff) and the antenna is fed with what is effectively a very high frequency alternating current (this is while transmitting, where length is most critical) and thus you have moving electrons in a wire leading to electromagnetic fields which masquerade as radio waves. When receiving it is pretty much the same thing in reverse.

The one thing Patrick did not explain very well was about the signal bouncing until it gets a full wave. As I understand it, this is exactly what you don't want. The reason for this actually lies in the coaxial cable used to feed the antenna. It has a certain impedance that should match the impedance of the connectors, antenna and of the transmitter/receiver. When the antenna is not resonant, standing waves are set up whereby some of the power does not get radiated out as radio waves and thus ends up being reflected back down the coax, where it then bounces between ends until it is a full wave and gets emitted. The problem with this is that because of the resistance of the coax, the power is wasted. (which is why in an amateur radio setup, the antenna matching unit ideally should be near the antenna because otherwise the coax still wastes power) so in summary, in an ideal world, the antenna perfectly converts the power to radio waves. This is a standing wave ratio or SWR of 1. (1 watt out for every watt coming back) if you have a severe missmatch, you might end up with an SWR of 3 or more (1 watt out for every 3 watts coming back)

Anyway, hope that answers some questions. If you notice any mistakes in my explanation please feel free to correct. I don't claim to be an expert on this...

[laxaloot]

However the lighting of their new set looks like it is lit by old scoops and nothing else. That is not a good thing. Terrible shadows. Otherwise awesome.

[m3wse]

Randolph said in gazette ep 11 that they use scoops made in about 1969... lots of them...

[madguernseyboy]

OK so if I make one of these antennas how do I go about attaching it to the internal Wifi card on my laptop. I am not sure of the type of connector internally but there is two. is it even possible?
http://beta.ivancover.com.nyud.net:8080/wiki/images/thumb/3/34/Eee_wifi_connector.jpg/400px-Eee_wifi_connector.jpg
could you even have two antennas in parallel? therefore normally using the internal antenna on the road and attaching your new systm antenna when you need that extra boost.

thanks
MGB

[m3wse]

not sure you could... or it certainly would me some messy cable routing... these antennas are designed for pcmcia cards and suchlike...

[infango]

hi
some cool wifi antennas :
http://yu1aw.ba-karlsruhe.de/vhf_ant.htm
nad omni antenna :
http://yu1aw.ba-karlsruhe.de/Amos.pdf

is in Czech but there are pictures :D

en translation :
http://yu1aw.ba-karlsruhe.de/AMOS%20eng.pdf
i will make this one after i have tools :D

[zeronome]

Back to WiFi.... I was very surprised to not hear about a pringles can on the show... EPIC wireless antenna

[kickarse]

There's also this one too

http://wireless.gumph.org/articles/homemadeomni.html

and another

flakey(dot info)/antenna/omni/quarter/
(the posting system doesn't like dot info domains, so just change it out for the realy url)

Another good site here...
http://www.fab-corp.com/

[dark_shroud]

Well at least I have a use for the dish I need to take of my roof.

[md2389]

Honnestly? it doesn't matter. i thought about this for a second when I first saw it, but both sides of the foil are reflective and card is transparent to radio waves...

Oh, and as I understand it, the magic length for antennas is not actually 1/4 wave, but it is 1/2 wave. Was Patrick wrong? no. The 1/4 wave antennas are half of a 1/2 wave antenna, and the ground plane reflects this (the car roof in the case of a CB whip, which is also why putting them on the front bumper is a bad idea...) and this produces the waves.

As to how it produces the waves, as I understand it antennas work on the principle of resonance. The antenna must be resonant on the correct frequency (hence all the 1/2 wavelength stuff) and the antenna is fed with what is effectively a very high frequency alternating current (this is while transmitting, where length is most critical) and thus you have moving electrons in a wire leading to electromagnetic fields which masquerade as radio waves. When receiving it is pretty much the same thing in reverse.

The one thing Patrick did not explain very well was about the signal bouncing until it gets a full wave. As I understand it, this is exactly what you don't want. The reason for this actually lies in the coaxial cable used to feed the antenna. It has a certain impedance that should match the impedance of the connectors, antenna and of the transmitter/receiver. When the antenna is not resonant, standing waves are set up whereby some of the power does not get radiated out as radio waves and thus ends up being reflected back down the coax, where it then bounces between ends until it is a full wave and gets emitted. The problem with this is that because of the resistance of the coax, the power is wasted. (which is why in an amateur radio setup, the antenna matching unit ideally should be near the antenna because otherwise the coax still wastes power) so in summary, in an ideal world, the antenna perfectly converts the power to radio waves. This is a standing wave ratio or SWR of 1. (1 watt out for every watt coming back) if you have a severe missmatch, you might end up with an SWR of 3 or more (1 watt out for every 3 watts coming back)

Anyway, hope that answers some questions. If you notice any mistakes in my explanation please feel free to correct. I don't claim to be an expert on this...

And you just happen to be exactly right. Furthermore, if you have a severe enough mis-match, you WILL burn up your hardware.

[kickarse]

Also, if you can help it, the length of the cable and the amount of connectors will help with loss.

[md2389]

Also, if you can help it, the length of the cable and the amount of connectors will help with loss.

Also, the more adapters you use, the more work you will have to do to match impedance. The KISS philosophy definitely applies here.

[dmann]

So, let's pretend that i REEEEEAAAAALLLY dont wanna hack apart my groovy black macbook, but know i will be staying at a nice hotel in July, and as such, it charges way too much for wi-fi.

So, is there a way to use an external USB wifi device to get a signal, that i could then put a nice external antenna on, and grab wi fi from a coffee shop, or cheap motel nearby with an open hot spot?

[zoozabar]

first time poster thought I would show off my try at the windsurfer...

[tarpi]

Hi, I just wanted to say what a great episode!
I am thinking of doing some tinkering with antennas as well but there is something I was wondering.
Has anyone managed to find a realively inexpensive way of measuring some of the microwave parameters on connectors and antennas.
Following these directions is easy, but at these frequencies, its hard to trouble shoot a bad crimp, or a bad solder, or antenna section that is a little bit off in length. All these things can basically ruin the signal strength leaving you in the dark as to what the problem is? Then you have to start from scratch and hope that it works.
So far I've found the low cost 2.4Ghz spectrum analyzer from metageek at
http://www.eeproductcenter.com/rf-micro/review/showArticle.jhtml?articleID=185303180

and for those willing to tinker even more and save some money, Jason Hecker has made even cheaper spectrum analyzer but with 8-bit resolution which is a bummer because the setup is relly slick. http://www.wireless.org.au/~jhecker/specan/

I think before investing money for connectors, crimp tools, and wire strippers, one should have some ways of troubleshooting problems.

Petar

[mapleshade]

first time poster thought I would show off my try at the windsurfer...

I was hoping you used a can, but gave me some ideas for other beer boxes to use. I happened to have some 80lb card stock, so I printed the design right onto it. I have a WRT54G about 30 feet from a laptop with a Linksys B card. I added the default size windsurfer to one antenna at a time, playing with its positioning and only got moderate if any increased signal. Would I benefit from 2 (1 on each antenna)? If I'm not mistaken, the waves radiate out of the top of the antenna; what's the best vertical positioning of the reflector on the antenna?

[albumgeek]

My PC is wired to the router but my G/F is using wireless and she was always getting a bad connection. I didn't have any foil and I was too lazy to go to the store, so I used a coke can and an empty soda bottle for the part that attached to the antenna. After trying it I have to say it works wonders. She is now connected at 54mb/s with full signal strength. Plus as a bonus I reused/recycled some stuff too. Great episode! :D

http://i13.photobucket.com/albums/a267/albumgeek/ParabolicFront.jpg

http://i13.photobucket.com/albums/a267/albumgeek/ParabolicBack.jpg