Will bare wire work?

Will bare wire work?

Postby nashr » Fri Aug 23, 2002 6:12 am

Alright, I apologize for this possibly ridiculous question in advance.

I've read about various homebrew antennas and wondered. What about just plugging an unshielded wire into my wireless card? Would I have to use wire with an appropriate ohm rating? Would it do anything at all for me?

I have a laptop that I pack into my bag and stumble around town with it running. I thought that by running a simple wire from the card out of the bag... perhaps around the shoulder strap.... that perhaps it would improve performance. Thoughts anyone?

Thanks in advance. :confused:
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Postby Thorn » Fri Aug 23, 2002 7:02 am

The question is not whether it will work or not - because it will work - but rather, how well will it work? It won't be great, but it may offer better tx/rx over the card's built-in antenna due to location.

The simplest antenna is the bare center conductor of a piece of coax. In this case it needs to be 1.22" long.
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1.22"

Postby nashr » Fri Aug 23, 2002 7:11 am

Thorn,

Thanks for your feedback and your patience. 1.22", as in inches? I assume that has something to do with wavelength. What about taking a 1-2 foot lenght and looping it around the carrying strap? What's the pro/con for that? Sorry, but this wavelength mathematics just aren't my bag. Thanks again!
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Postby Thorn » Fri Aug 23, 2002 7:36 am

1.22" is a quarter of one wavelength at 2.4GHz, give or take a few hundreds of an inch.

I doubt just wrapping a 1-2' wire around would work very well. It could potentially cause damage due to a high SWR, although the these power levels are probably much too low to cause any real damage.

If you were to wrap a piece of coax around the strap and leave the quarter-wave at the end, it might work. The big problem then becomes choosing the right coax*. It has to be low loss stuff for microwaves**. Then you'll need a pigtail to adapt the coax to the card. If you going to go to the trouble of getting the proper coax and the pigtail, then you're three quarters of the way to an antenna setup anyway. At that point you might just as well order a small extender antenna that's designed to do what you want. There are small desktop extender antennae made which would fit in your laptop bag just fine.

Playing with antennae is fun, if you have the means and the interest - and you WILL have to get to know the math to do it right. If you're just looking for a cheap solution that works correctly, save the blood, sweat, tears and toil, and just spend the money for a rig. It will be much cheaper in the long run.

Good luck!

*Don't use TV coax, it's the wrong impedence.
**Times-Microwave LMR series or equiv.
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Thanks

Postby nashr » Fri Aug 23, 2002 9:21 am

Thank you for the explanation. You've been very helpful. Now to see if there is some sort of non-directional antenna that would be suitable on my back. :)
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Re: Thanks

Postby Thorn » Fri Aug 23, 2002 9:33 am

Originally posted by nashr
Thank you for the explanation. You've been very helpful. Now to see if there is some sort of non-directional antenna that would be suitable on my back. :)


You're welcome, nashr.

BTW, the correct term is "omni-directional" or "omni" for short. Just so you know what to search for. :)

Check out:
http://www.pasadena.net Fungus (the owner) is a member here.
http://www.fab-corp.com Borgman (the owner) is another member - both of these guys offer different deals to other members.
http://www.superpass.com Great antennae from Canada. Great prices, too!

I do know that SuperPass has "desktop extender" omnis- I'm not sure about the others.
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Postby mrplowsupreme » Fri Aug 23, 2002 8:41 pm

Will RG58 A/U 50 ohm cable work?
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Postby Thorn » Sat Aug 24, 2002 7:30 am

It's the right impedience, but I don't know what the dB losses are at 2.4GHz. That would be the deciding factor.
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Postby fordem » Sat Aug 24, 2002 3:06 pm

Originally posted by mrplowsupreme
Will RG58 A/U 50 ohm cable work?


I wouldn't advise it - it's not rated for microwave frequencies
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Cell phone antennas

Postby nashr » Thu Aug 29, 2002 5:44 am

I walked into a Cingular store yesterday and noticed that cell phones operate in a similar freq range. Would an old cell phone antenna work with 802.11b? What about the old "bag phones"; portable phones from pre-cellular days? Anyone?
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Postby ted » Thu Aug 29, 2002 6:59 am

I would say plain no to using any cell phone antennas. Of course, very likely they will work somehow, maybe being better, or maybe worse than a piece of wire. But they are definitely not optimal, and most likely perform badly. The antennas are on these frequencies always tuned and dimensioned for quite narrow frequency band. Those antennas are for either 900 MHz or 1800-1900 MHz and therefore not good for 2400 MHz.

I think it would be not bad idea for you to read antenna FAQ and similar discussions to get an idea what is considered to be a real antenna for WiFi. If you want something that works, you can either see a "cookbook" solution form the antenna discussions, or buy a ready made antenna from some supplier. (you get even info about the suppliers by reading the FAQ and relevant discussions. And do not forget the search facility here.... You see, everybody has been a newbie and had to dig sources of information and doconsiderable self study. It is better to try to research and really learn the stuff than assume that all the questions can be explisitely answered by somebody here.

Btw. I am not trying to be sour to you, but only give some general advice before some of our old-timers gets tired of answering the very fundamental and basic questions n'th time.

Good luck,
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Re: Cell phone antennas

Postby Thorn » Thu Aug 29, 2002 7:01 am

Originally posted by nashr
I walked into a Cingular store yesterday and noticed that cell phones operate in a similar freq range. Would an old cell phone antenna work with 802.11b? What about the old "bag phones"; portable phones from pre-cellular days? Anyone?


nashr,
Cell phones are at 900MHz, far from the 2.4GHz of 802.11b, so a cell phone antenna won't work. So called "bag phones" are just larger model cell phones.
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suggestion to nashr

Postby Firebird » Fri Sep 06, 2002 7:33 pm

Just build yourself one of these babies:
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Re: Re: Cell phone antennas

Postby Thunderforge » Fri Sep 06, 2002 8:22 pm

Originally posted by Thorn


nashr,
Cell phones are at 900MHz, far from the 2.4GHz of 802.11b, so a cell phone antenna won't work. So called "bag phones" are just larger model cell phones.


Anyone know of a winshield mount antenna for 2.4 GHz like the cell phone antennas you see on the back windows of people's cars?
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Postby Firebird » Fri Sep 06, 2002 8:35 pm

Anyone know of a winshield mount antenna for 2.4 GHz like the cell phone antennas you see on the back windows of people's cars?


You mean like this one at fab-corp?

5 dBi Magnetic Mount Omni Antenna
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