2 Computers...1 Antenna?

I have access to wi-fi in my marina. On the boat I have 2 notebook computers an a single external antenna connected to one PCMCIA wi-fi card. Is it possible to both computers share a single antenna if I were to buy another PC card and some kind of a Y adapter to split the antenna?

Reply to
Champ
Loading thread data ...

Want be able the access the web from both at the same time. Have the one antenna mounted on top of the mast. Trying to save the cost and hassle of installing a 2nd antenna and associated wiring. Why mount 2 when 1 will do?

Reply to
Champ

'Want be able the access the web from both at the same time.'

hi, here's what i'd do. connect to the wifi network from one notebook with the PC card with the external antenna. now get a usb wifi card and install this on the same notebook. connect to the second notebook using ad-hoc mode and enable internet sharing on the first notebook ( if win 2k/xp) What this essentially does is that configures the ip address of the usb interface on the first notebook to 192.168.0.1 and enables DHCP. so the second notebook will get an ip address from the first and will be able to browse the network/internet. PS ive also done this with a lifebook running XP and an i-book (mac)

Reply to
outbackwifi

What are you trying to save? The cost of an antenna? Won't either machine pick up the wifi signal?

Reply to
Alan White

Thanks outbackwifi. That's one option for sure, but I should probably have added that I'd like to be able to use either notebook independently without having to having both powered up. (Wife has hers, and I have mine at the nav station.) Needless to say, I'm not too Wi-Fi savvy and maybe it's just not possible, but a simple Y-splitter would be ideal. Of course I don't know if anyone even makes such a thing. Any other thoughts?

Reply to
Champ

I can be done, I've done it, but you won't like what it takes to make it happen. FCC rules and common practice do not allow for synchronizing the two transmitters. Such systems are also not type certified in such a configuration, making them illegal for deployment, but we'll ignore the legal problems for now. We'll have a problem with: 1. Both transmitters on at the same time creating intermodulation products that generate spurious crap that trashes other services. 2. Isolation between transmitter and receiver overloads receiver. 3. Spread spectrum "hash" bleeds into adjacent channels and creates interference on the receive channels. 4. Loss through the combiner. 5. You will not be able to use an antenna mounted.

The usual combiner is a Wilkinson 1/4 wave combiner, which has a loss of about 1dB and an isolation of about 20-30dB. The 1dB loss is not much of a problem, but the 20-30dB isolation is. That's not enough to keep the transmitter junk out of the receiver, or to prevent desensitization. Because the VSWR of most antennas and radios is 2:0 or worse at the band edges, the isolation will be at the lower end of the scale (20dB) or worse. The adjacent channel junk is about 30dB down from the peak power, so the receiver will need to handle: +15dBm - 20dB -30dB = -35dBm of inband junk. That's roughly the overload point of the receiver and will just barely work. What's needed is are two isolating cavity filters each tuned to the two (different) frequencies. Only $100 each.

formatting link
another 2dB RF loss.

The combiner is $48.

formatting link
would not believe how simple the device is inside).

So, if you wanna do it, you'll need to have the two radios on two different channels, $350 in boxes, about $30 in connecting cables, tolerate 3dB (half the power) additional loss, and make sure you have a very low VSWR antenna, which usually eliminates anything with high gain.

Reply to
Jeff Liebermann

Consider a WiFi repeater go to

formatting link
and check out the VP2210 - Outdoor Wi-Fi base station (uses the high antenna for Wi-Fi, and repeats on the boat itself).

While at it, if you have Cell phones, consider ALSO adding a similar Cell-phone repeater at

formatting link
so you can use cell-phones at many places around the boat

I use both on the roof of my RV((up 12 ft)), and repeat the signal for my laptops/PDA and cellphones inside.

Reply to
Peter Pan

The crossover cable idea seems to be about the easist solution. The newest notebook has an ethernet card built in. I guess all I'd need is a 2nd PCMCIA ethernet card for the 2nd computer and the crossover cable. This isn't that big a boat and a 10-12' cable oughta do it. Since you said "might" just run a crossover cable, is this a sure, proven thing? This will really allow both computers to access the web at the same time? As you can tell, this stuff pretty new to me. Thanks for all the info guys!

Reply to
Champ

Depending on where the laptops are located, you might just run a crossover cable between wired etherenet ports on the two laptops, and enable ICS on the one with the WiFi.

Or get a wireless repeater.

formatting link

Reply to
dold

It does break your "don't want to power them both up" desire. The computer in the middle does have to be turned on. ICS absolutley does work. The crossover cable definitely works. Your two laptops will be on a network together. you get very little control over that link. The IP address is fixed. Fuss with it, and it will never work again ;-)

But if you have to buy a PCMCIA card and the cable, then I wouldn't go that way. I would go with a USB-wifi. I see them pretty cheap now. I bought one for $49.95, with two $20 rebates, end cost $9.95. I carry it in my laptop bag to set up adhoc networks to customers that don't have a network. A lot of people have unused ethernet ports, but almost everyone has a USB port. I use AdHoc or a crossover and ICS in this fashion to reach the internet via dialup, so it ought to work for your case.

Since the other card's antenna is on the mast, there probably won't be any interference, if the existing card's internal antenna can be turned off. Otherwise, you can select the channel used on the ad-hoc part (between the two computers), you'll have no control over the channel used by the distant WAP.

Reply to
dold

internet

seems like a trivial prob to me. if you dont want to power up both notebooks at the same time, then take out the card from notebook 'A' and put it into notebook 'B' when you want to use 'B' only!!!

Reply to
outbackwifi

No doubt that would be a easy solution if I NEVER wanted to have both running at the same time, but that's not the case.

Reply to
Champ

Repeater/extender sounds ideal but you would need to find model number of existing AP to be ascertained that you'll get one that will work with it. Then you would actually extend the system so your neighbors might benefit too and become the dock hero - at least until you sail off into the sunset.

Reply to
bumtracks

Reply to
Ed Williams

Has anyone here (not connected with the vendor) tested these "Signal Seeker" USB-connected flat panel devices and determined whether they actually give better performance than cantennas, etc., as claimed?

Reply to
Donald G. Davis

Reply to
Ed Williams

I'd be happy to evalute a pair of them... with the understanding that I keep the pair when the tests are done.

Reply to
Floyd L. Davidson

I'm not the moderator (does this group have one?), but I'm the one who asked, and I'd be glad to take one and test it against the adapters I have available (internal Belkin F5D7000 with cantenna; USB Netgear WG111) and report my comparative results--I'd return the Signal Seeker if it does not work better than each of those, or pay for it and keep it if it does. If you accept this offer, please e-mail me for mailing address.

Reply to
Donald G. Davis

Big Cheese, Jeff. Moderator, Peter Pan. The group settle on anything? Not likely. Best tester? Jeff or Floyd, but I don't think they work for free for a commercial endeavor. Who would test the thing and make it stop looking like you are the only one who likes it? Me.

Reply to
dold

Cabling-Design.com Forums website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.