Tall Wifi Antenna

**EBFoxbat** · 08-31-2004, 11:34 AM

I'm going to put a 48" Whip antenna on my truck for the CB radio. I don't know much about antenna physics, but I need an antenna for my wifi.

I know I cant use that because its tuned for CB radio range. Can I get anotehr tall antenna tuned fo wifi that is similar in length? I'd like to have one on each side. thanks.

**VWMAN** · 08-31-2004, 11:48 AM

Try this place

http://www.radiolabs.com/products/wi.../wireless.html

**gizmomkr** · 08-31-2004, 11:58 AM

Generally speaking , due to the waveleginth - (WiFi has a mutch shorter waveleginth than CB Frequencies) I think it would be rare to find a wIFi of similar leginth. Even the ones listed on that site are 2 ft max. Most CB whip antenna I see are closer to 6....

**john1701** · 08-31-2004, 08:00 PM

here is some wifi antennas that might interest you,
I have the 8db omni 20 inch mounted on my car.

http://www.hyperlinktech.com/web/ant...0_out_omni.php

**longwoodtrail** · 08-31-2004, 08:05 PM

Is it not possible to create a 6ft antena for 2.4ghz range? What I am trying to ask is, is this outside the parameters for WiFi, or do manufacturers simply not make them?

**ppgt94** · 08-31-2004, 09:29 PM

I got a really nice 9dB wifi antenna from ebay. I think they might be all gone now. The member was Mhzkid or something like that.

**S80** · 09-01-2004, 03:13 AM

Ok. Let's see if I remember this correctly!

The length of an "full length antenna" is determined by the wavelength of the frequency that you will use it for.

To calculate the wavelength you do something like this:

Speed Of Light = 299,792,458 meters per second
Speed Of Light/frequency = wavelength
299,792,458/2.4GHz = 0.125 meters = 4.9 inch

So the optimal length for a 2.4GHz antenna should be 4.9 inches or 12.5cm.
You can also use half length and quarter length antennas. (3.95" or 1.97")

It was a long while since I did this kind of calculations but I think that they are correct!

/Niklas

**erazor** · 09-01-2004, 04:18 AM

So the optimal length for a 2.4GHz antenna should be 4.9 inches or 12.5cm.

but as far as i know you could also make tha antena x * 12,5cm so you can have 25, 50, 100 but an larger antenna means lower signal as said optimal is 12.5

**S80** · 09-01-2004, 04:39 AM

Originally Posted by erazor

but as far as i know you could also make tha antena x * 12,5cm so you can have 25, 50, 100 but an larger antenna means lower signal as said optimal is 12.5

Yes, thats right!

**kiltjim** · 09-01-2004, 11:32 AM

Originally Posted by longwoodtrail

Is it not possible to create a 6ft antena for 2.4ghz range? What I am trying to ask is, is this outside the parameters for WiFi, or do manufacturers simply not make them?

If you look around, you will find extensive equations on building one from coaxial cable. Different cable means different velocity factors.

In thoery, you could build an antenna that is 6 foot in length, but you would need an extremely low velocity factor, or an extremely large gain.

Problems with both: A low velocity factor is going to be pretty hard to find. You would probably end up using something different than coax cable to achieve this.

An extremely high gain antenna is going to limit your effective range. Look
around for better explanations of this, but imagine a balloon. An unsqueezed balloon would be your low gain antenna (~3 dB). So so range all around. Now, squeeze it. The sides are much further from the center, but the top and bottom are now much closer. A huge gain antenna is going to have a horrible range outside of directly horizontal to the car.

Also, the difference in appearance between the CB whip and a rigid WiFi antenna is going to be significant. You are not going to find a whip, it just does not exist.