Re: [Thinkpad] General wireless ISP question(s)

John gives very good advice on this (are you a ham, John), but let me
add a couple of things. LMR-400 coax is good, but LMR-600 is much
better at 2.4GHz. If you're running 50 feet of LMR-400 you will lose
about 3.4dB of signal, which is just over 50%. 50 feet of LMR-600
will lose about 2.2dB, which is a definite advantage. LMR-600 can
be had for under $1/foot if you find a bargain. If you only need a short
run it won't matter so much, but the weak-signal ham part of me says
go for every dB you can. ;-)

The more serious thing to talk about is the danger of playing with microwave
frequency RF. 2.4Ghz is right were microwave ovens operate. 100mW of
power isn't going to cause much of a problem being around it, but the gain
of a dish makes it *very* desireable to stay away from it when operational!
100mW with 21dB of gain is about 11W effective radiated power (erp) and
that is a danger to your eyes. Do NOT stand in front of a dish when its on.
If you get a really horrid headache you need to go to your local ER and
tell them that you were exposed to 13cm RF. Sadly I now know of three
people who have had bad experiences with wifi dish RF problems. Computer
people tend to think of everything in the computer world as safe; all the
electronics uses low voltage, etc. This is true but the RF world is a rather
different world.

Take care.

--STeve Andre'
ham call wb8wsf

On Sunday 22 August 2004 16:45, John Schmidt wrote:
> Hi David,
>
> I've been part of a wireless ISP co-op for the last several years. My own
> link is almost 13 miles to a repeater site. A few bits from my own
> experience:
>
> - You definitely want a high-gain grid-dish type antenna (21 to 24 dBi)
> mounted on the outside of your house, as high as possible. At 2 miles from
> the transmitter, this is not a must, but it's good engineering practice
> (avoids spraying your RF around unnecessarily) and you can use all of the
> "link margin" you can get in the 2.4 GHz band.
>
> - Use high quality co-ax cable (LMR-400 at least) to connect to an access
> point (AP) mounted either inside or outside your house.
>
> - The AP should be one of those that generate a full 100 mW output -- most
> of the consumer models do not do this. Our co-op uses Cisco Aironet radios
> exclusively for 2.4 GHz 802.11b. My own is a UC-4800E which is
> discontinued by Cisco but can still be found on Ebay. It has an external
> antenna connector which is connected to an adapter to fit the dish
> connector (N-type). An Aironet PCI radio card is another good option. Again
> -- make sure to get the 100 mW output model.
>
> - I strongly recommend using a router connected to the AP for your internal
> network. Your internal network can be either wired or wireless.
>
> - Don't forget lightning protection for external antennas. See the NEC
> (National Electrical Code) for requirements. Get a professional installer
> to help if needed.
>
> - If you run a wireless 802.11b network inside the house, set it so the
> channel does not overlap with your outside link. There are 11 channnels
> designated for 802.11b, but only 3 do not overlab -- 1, 6, 11. This is why
> buildings with multiple AP's will only use these channels. Your wireless
> ISP should be using one of these -- use one of the others internally.
>
> Due to the accumulation of RF interference in the 2.4 GHz band, our
> wireless co-op is in the process of transitioning to using Motorola Canopy
> radios on 5.7 GHz for our links. These are more expensive than 802.11b, but
> their protocol is much better for longer links in the presence of
> interference. You might ask your WISP about their plans to deal with the
> continually increasing level of 2.4 GHz noise.
>
> Have fun!
>
> John
>
> At 03:49 AM 8/21/2004 -0500, David Reid wrote:
> >Greetings List,
> >
> >My fingers are crossed, hopefully, I will soon have broadband at my rural
> >home,
> >via a new upstart local wireless broadband provider. I'm just over 2 miles
> >from
> >their current transmitter site, can see the tower they're on from my front
> >porch
> >so I'm hoping that will be an even better advantage.
> >
> >Anyone else on this list, a fulltime wireless customer? I would be
> >interested in
> >your comments about the service, maybe some "out of the box thoughts"
> >
> >Just wondering about a few things,
> >
> >I've seen external antenna's advertised, for instance, Computer Geeks has
> >something that looks like a Pringles Signal finder, advertised as great
> >antenna
> >for increasing reception.
> >
> >Is there any means to connect our "xxx p" wireless thinkpads (I have an
> >A30p) to
> >an external antenna? Do they (ext ant.) really work?
> >
> >In speaking to the owner of this new company, I asked if it were feasable
> > to setup a remote reciever. Much of my office work done outside and
> >throughout the
> >County. If I were on the fringe of the wireless signal area, he stated I
> > could indeed setup a temporary antenna to pick up a signal.
> >
> >I suppose I'd have to have this connected to a small router or hub and
> >hard wire
> >via ethernet cable to my Thinkpad?
> >
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Received on Sun Aug 22 14:38:42 2004