Quick question about connecting my DIY wifi antenna

nobb · 09-20-2007, 11:57 PM

Hi.

I have been getting slow transfer speeds from my carpc wifi, probably because my garage is far away from my router and my wifi dongle is in the trunk shielded by the car. So I built this wifi antenna:

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

I am using a USB dongle wifi device and I have taken it apart to find that the antenna is built into the circuit board (etched). I just have a question about connecting my DIY antenna to the wifi dongle for best results. Can I just simply solder a standard wire from my antenna to the etched antenna on the dongle? Can the wire just be a single strand (wouldnt the wire also act as an antenna)? Or do I need a wire with a center conductor (connected to the dongle) and conducting outside sheath that surrounds the inner conductor (like a coax cable)? If so, does the sheath need to be connected to anything/grounded?

BarryWoods · 09-21-2007, 01:19 AM

First you need to use microwave grade coax. The stuff they use for tv won't work. It will also kill your wifi card after a while. Google for usb wifi external antenna. That should point you in the right direction.

What kind of coax did you use for the antenna?

nobb · 09-21-2007, 10:00 AM

Why would cable grade coax "kill" my wifi card? I wouldve thought that a thicker, bigger cable would mean less line loss and therefore be better (other than the fact that its not very flexible).

The coax I used for my antenna is from a cable tv (RG6), but I did google up its type and took the velocity factor of my specific cable into consideration when calculating the design required. I did search up usb wifi antenna, but I would rather not have my dongle out in plain sight. I want to have my dongle plugged into my carpc (in trunk) and just run a wire to an antenna.

BarryWoods · 09-24-2007, 11:34 AM

Quote: Originally Posted by nobb

Why would cable grade coax "kill" my wifi card? I wouldve thought that a thicker, bigger cable would mean less line loss and therefore be better (other than the fact that its not very flexible).

The coax I used for my antenna is from a cable tv (RG6), but I did google up its type and took the velocity factor of my specific cable into consideration when calculating the design required. I did search up usb wifi antenna, but I would rather not have my dongle out in plain sight. I want to have my dongle plugged into my carpc (in trunk) and just run a wire to an antenna.

It's called cable attenuation. Rg6 is not microwave rated cable. It's like trying to run a 300watt amp with headphone wires. You're going to lose most of your signal in the first foot of the cable. The two antenna's I've built were from LMR-400. The pigtails from the cards to them are also LMR-400. I have one LMR-240 pigtail as well.

http://binarywolf.com/249/faq.htm
http://www.dxzone.com/catalog/Antennas/WiFi/
http://www.netstumbler.org/f23/

Crawdaddy · 09-24-2007, 11:51 AM

Quote: Originally Posted by BarryWoods

It's called cable attenuation. Rg6 is not microwave rated cable. It's like trying to run a 300watt amp with headphone wires. You're going to lose most of your signal in the first foot of the cable. The two antenna's I've built were from LMR-400. The pigtails from the cards to them are also LMR-400. I have one LMR-240 pigtail as well.

http://binarywolf.com/249/faq.htm
http://www.dxzone.com/catalog/Antennas/WiFi/
http://www.netstumbler.org/f23/

that gentleman knows what he's talking about. I am a hobbyist high-power (even sometimes slightly illegal power) wifi tech, and getting 2.4Ghz rated coax is a must. not even old thinnet coax will keep attentuation levels low enough to make the antenna an antenna. I personally buy all my wifi supplies with the exception of radios and APs from Hyperlink Technologies. They have good prices.

BarryWoods · 09-25-2007, 06:46 PM

I get all my stuff from www.fab-corp.com . They've actually sent stuff to me overnight, that's pretty good from some place by Miami FL to North Pole Alaska.

Crazy_Cabbie · 01-14-2008, 08:17 AM

that coax thing MUST be true, because I JUST soldered an actual 2.4Ghz antenna I around onto the circuit traces I FIGURED were the antenna element and ground, (in a laptop PCMCIA card) and whaddaya know, the thing actually works BETTER!!! what a fluke!!

went from 1 bar/poor signal right up to full/excellent (ap's across the street in a brick building, I'm in the basement...can't wait to see what it does stuck to the car instead of a paint can...)

...if yer gonna be like me, use a $12 ebay special like I did, haha...

nicksmurf111 · 01-23-2008, 10:26 AM

Build your usb dongle inside the antenna mast, and use the thinnest cable to attach between the actual antenna and the card. It will keep the traces from breaking off the pc board. But only use like 2 or 3 inches. This will keep you from loosing power from routing a feed cable through your car. Use a USB extension to you antenna and you will not loose any range.

nobb · 01-23-2008, 11:23 AM

Thanks for the replies. My Wifi dongle is in the trunk (shielded by the trunk, like a Faraday cage). But I didnt want to have the dongle exposed for security reasons, which is why I rather have a tiny inconspicuous antenna exposed instead. I ended up scrapping the antenna idea. I replaced the old Dlink dongle with a cheap chinese dongle I had laying around and my reception increased enough for 54mbps speeds. Good enough for me, no need for an antenna.