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'[OT:] WIFI Waveguide antenna'
2004\08\02@005115 by Robert B.

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Has anybody had experiences with homebrew wifi antennas?  I built one this
evening similar to the "cantenna" described in various places on the web,
and it works OK, but not up to the level I was hoping for.

The cantenna is located in a room separate from the desktop PC which gets no
wifi signal at its manufacturer-supplied omni-antenna.  The laptop (built-in
wifi) picks up a strong signal where the cantenna is located, but the
desktop hooked to the cantenna in the same location picks up a very weak
signal (~-85db snr).  I used about 15 feet of standard coaxial cable as the
antenna line.. anybody know how to figure the theoretical signal loss
through it?  I'm not sure but I doubt coax was designed for 2ghz+
frequencies.  Does anybody know for certain?

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2004\08\02@005738 by David VanHorn

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At 11:50 PM 8/1/2004, Robert B. wrote:

>Has anybody had experiences with homebrew wifi antennas?  I built one this
>evening similar to the "cantenna" described in various places on the web,
>and it works OK, but not up to the level I was hoping for.
>
>The cantenna is located in a room separate from the desktop PC which gets no
>wifi signal at its manufacturer-supplied omni-antenna.  The laptop (built-in
>wifi) picks up a strong signal where the cantenna is located, but the
>desktop hooked to the cantenna in the same location picks up a very weak
>signal (~-85db snr).  I used about 15 feet of standard coaxial cable as the
>antenna line.. anybody know how to figure the theoretical signal loss
>through it?  I'm not sure but I doubt coax was designed for 2ghz+
>frequencies.  Does anybody know for certain?

Most of the antennas I've seen have used cans that are too small a diameter.
"Waveguide below cutoff".  Also, most small coax is pretty lossy at 2.5 GHz.
I've used RG-174 at 1.5 GHz for GPS, but not more than about 10', and with an amplified antenna.

Look at ham designs for antennas in the 2.3 GHz band and just scale it smaller a bit.

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2004\08\02@011555 by Robert B.

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Wouldn't too small a diameter create a wave guide *above* cutoff?  Or am I
missing something..  My can is about 3.5" wide, making the theoretical
cutoff right around 2500MHz.  Do you think a smaller can might work better?

{Original Message removed}

2004\08\02@013011 by Ian Stewart

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Check out this site
http://www.usbwifi.orcon.net.nz/

Ian
----- Original Message -----
From: "Robert B." <piclistspamKILLspamNERDULATOR.NET>
To: <.....PICLISTKILLspamspam.....MITVMA.MIT.EDU>
Sent: Monday, August 02, 2004 4:50 PM
Subject: [OT:] WIFI Waveguide antenna


> Has anybody had experiences with homebrew wifi antennas?  I built
one this
> evening similar to the "cantenna" described in various places on the
web,
> and it works OK, but not up to the level I was hoping for.
>
> The cantenna is located in a room separate from the desktop PC which
gets no
> wifi signal at its manufacturer-supplied omni-antenna.  The laptop
(built-in
> wifi) picks up a strong signal where the cantenna is located, but
the
> desktop hooked to the cantenna in the same location picks up a very
weak
> signal (~-85db snr).  I used about 15 feet of standard coaxial cable
as the
> antenna line.. anybody know how to figure the theoretical signal
loss
> through it?  I'm not sure but I doubt coax was designed for 2ghz+
> frequencies.  Does anybody know for certain?
>
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2004\08\02@013014 by Robert Ussery

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>-----Original Message-----
>From: pic microcontroller discussion list [@spam@PICLISTKILLspamspamMITVMA.MIT.EDU]
>On Behalf Of Robert B.


>Has anybody had experiences with homebrew wifi antennas?  I built one this
>evening similar to the "cantenna" described in various places on the web,
>and it works OK, but not up to the level I was hoping for.
>
>The cantenna is located in a room separate from the desktop PC which gets
>no
>wifi signal at its manufacturer-supplied omni-antenna.  The laptop (built-
>in
>wifi) picks up a strong signal where the cantenna is located, but the
>desktop hooked to the cantenna in the same location picks up a very weak
>signal (~-85db snr).  I used about 15 feet of standard coaxial cable as the
>antenna line.. anybody know how to figure the theoretical signal loss
>through it?  I'm not sure but I doubt coax was designed for 2ghz+
>frequencies.  Does anybody know for certain?

I built one recently using a USB dongle and some Asian cookware, as
described on:

http://www.usbwifi.orcon.net.nz/

I used a free (after rebate) USB dongle from ecost.com, and a $10 18" wok
lid from "The Cupboard" (a local cookware shop - possibly a chain). I don't
have any hard performance numbers on it yet, but it can operate at much
lower SNR's than my $80 Proxim wireless card, and seems very directional.
Off the top of my head, I'd guestimate that I'm getting about 15-20db gain.
If I get around to it, I'll post a page on my website (I have pics, but no
page yet), and post it to the list.


TTYL!

- Robert

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2004\08\02@014503 by Russell McMahon

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> The cantenna is located in a room separate from the desktop PC which gets
no
> wifi signal at its manufacturer-supplied omni-antenna.  The laptop
(built-in
> wifi) picks up a strong signal where the cantenna is located, but the
> desktop hooked to the cantenna in the same location picks up a very weak
> signal (~-85db snr).  I used about 15 feet of standard coaxial cable as
the
> antenna line..

The coax will be killing you. Coax rated for 2.4 GHZ is horrendously dear.
If you weren't offended by the price wou paid for it, it's not the right
stuff :-). Try a VERY (inconventiently) SHORT length first to get things
sorted and then go from there.

Pringle can's, which are often recommended, are too small in diameter. If
your can is visibly larger dia than a Pringle can you are probably OK.
Actual diameter is not critical as long as it is large enough.

This may be useful
YMMV

       http://www.saunalahti.fi/elepal/antenna2.html

Site which claims to have a workable cantenna
(Be worried that they also mention Pringle's cans :-) )

       http://www.turnpoint.net/wireless/index.html

Commercial Cantenna for $US13.
Picture will give you ideas on what works

       http://www.cantenna.com/



       RM

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2004\08\02@014710 by Richard Prosser

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I can't remember the exact figures but RG174 has a loss of something like
10.5db/100ft at 400MHz and 40dB/100ft at 2GHz. This works out to about
44db/100ft at 2.4GHz So 15 ft will be about  6.6db, assuming matched
operation and good connectors.

Loss increases linearly in db by length and withn the square root of
frequency - roughly although diaelectric losses catch up and increase
linearly above some point dependent on material. Screening losses also go
up linearly with frequency and depend on screen design.

Hence the RG174 loss at 2.4GHz is higher than the value calculated from the
400MHz value.

In a poorly matched condition you could get any result - but it will be
worse.

I think.

RP







At 11:50 PM 8/1/2004, Robert B. wrote:

>Has anybody had experiences with homebrew wifi antennas?  I built one this
>evening similar to the "cantenna" described in various places on the web,
>and it works OK, but not up to the level I was hoping for.
>
>The cantenna is located in a room separate from the desktop PC which gets
no
>wifi signal at its manufacturer-supplied omni-antenna.  The laptop
(built-in
>wifi) picks up a strong signal where the cantenna is located, but the
>desktop hooked to the cantenna in the same location picks up a very weak
>signal (~-85db snr).  I used about 15 feet of standard coaxial cable as
the
>antenna line.. anybody know how to figure the theoretical signal loss
>through it?  I'm not sure but I doubt coax was designed for 2ghz+
>frequencies.  Does anybody know for certain?

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2004\08\02@015123 by David VanHorn

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At 12:15 AM 8/2/2004, Robert B. wrote:

>Wouldn't too small a diameter create a wave guide *above* cutoff?  Or am I
>missing something..  My can is about 3.5" wide, making the theoretical
>cutoff right around 2500MHz.  Do you think a smaller can might work better?

Yes, late night.. :)

You might benefit from pushing it out a bit more.


You can also mount your wi-fi thingy in the focus of a dish. Even those cheap primestar dishes will work, though their focus can be a bit non-obvuous at first.

That way you suffer no feedline losses at all, and AFAIK aren't technically in violation of part 15, as you haven't mechanically altered the antenna.

You can use powered repeaters to extend USB a fair bit, or use "USB-Anywhere" boxes to remote it.

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2004\08\02@015746 by Robert Ussery

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Here's the promised page:
http://users.frii.com/lmalpais/wokwifi/wifi.html

enjoy! Lots of good antenna pics. I still have to test the antenna, but
preliminary results with NetStumbler indicate significant gain improvements
over the raw dongle, and even over high-quality wireless cards.

TTYL!

- Robert

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2004\08\02@015747 by Marc Nicholas

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Or use Ethernet<-->Wifi bridges :-)

I recently purchased a commercial waveguide ("Super Cantenna") and can
vouch that bigger than a Pringles can is definitely where it's at. I'd
also say if you can fab something like this yourself (or appropriate
something), then save your money :-)


 -marc

On Mon, 2 Aug 2004, David VanHorn wrote:

{Quote hidden}

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2004\08\02@082451 by John J. McDonough

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----- Original Message -----
From: "Richard Prosser" <RemoveMERichard.ProsserEraseMEspamEraseMEPOWERWARE.COM>
Subject: Re: [OT:] WIFI Waveguide antenna


> In a poorly matched condition you could get any result - but it will be
> worse.

It seems unlikely that this antenna will be a good match, and the mismatched
result will always be worse, sometimes astonishingly so.  Its pretty easy
for a mismatch to multiply the loss by an order of magnitude or two.  I'm
assuming by "standard coaxial cable" the OP meant RG-59/U, which, while it
isn't as bad as 174, is still pretty awful.  Take awful and multiply it by
10 or 100 and you quickly get to horrible.

--McD

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2004\08\02@083326 by Howard Winter

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Robert,

On Mon, 2 Aug 2004 00:50:16 -0400, Robert B. wrote:

> I used about 15 feet of standard coaxial cable as the
> antenna line.. anybody know how to figure the theoretical signal loss
> through it?

Not unless you tell us what it is!  There's no such thing as "standard" coax - standard for what?  TV?
Satellite?  Ethernet?  Amateur radio?  You want something that has 50ohm impedance, which rules out TV and
Satellite (75 ohm).

Have a look here:  http://www.ocarc.ca/coax.htm  for a calculator to show cable loss.

These are for 15' of various types at 2.4GHz, assuming you have good 50 ohm matching:

RG 174  9.035dB (about 88% attenuation)
RG 58C  6.34dB  (about 77% attenuation)
RG 58   3.87dB  (about 65% attenuation)
RG213   2.173dB (about 40% attenuation)

Which means that whatever you put into one end of an RG174 cable, only an eighth of it would come out of the
other end, which is a Bad Thing!

Now RG213 is big and unwieldy, and isn't justified from these figures, so if I was doing this I'd go for RG58.

Cheers,


Howard Winter
St.Albans, England

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2004\08\02@093305 by David VanHorn

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At 07:34 AM 8/2/2004, Howard Winter wrote:

>Robert,
>
>On Mon, 2 Aug 2004 00:50:16 -0400, Robert B. wrote:
>
>> I used about 15 feet of standard coaxial cable as the
>> antenna line.. anybody know how to figure the theoretical signal loss
>> through it?
>
>Not unless you tell us what it is!  There's no such thing as "standard" coax - standard for what?  TV?
>Satellite?  Ethernet?  Amateur radio?  You want something that has 50ohm impedance, which rules out TV and
>Satellite (75 ohm).

Actually, 75 ohm cable is less lossy up high (in general) and might be a better choice.
Some antennas match better to 75 than to 50, and at the card end, a 1.5-1 VSWR isn't a big deal.  Far more important that the antenna be resonant.  Tough to know up here without specialized equipment.

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2004\08\02@102044 by John Ferrell

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> That way you suffer no feedline losses at all, and AFAIK aren't
technically in violation of part 15, as you haven't mechanically altered the
antenna.
>
I think it has more to do with effective radiated power (ERP). I doubt an
experimenter would be challenged on the subject but a commercial product
would.

It has been a long time ago but I did a lot of experimenting at 1296 mhz.

Some things I learned:
If the transmitter is located at the radiator there are NO feedline losses.
If the antenna is resonant, the RF will get to it.
If the antenna is inside, prototyping is cheap & easy.
 Kitchen grade aluminum and cardboard work well for even finished products.
Hold things together with hot melt glue, tape, staples.
Bigger usually works better than smaller.
The further you get from quarter or half wave radiators the tougher the
problem becomes.
Dr. John Kraus was the last guy to do anything really new with antennas.

Be aware of interferrenc from other 2.5G signals. I have an X10 TV link, a
microwave oven, a cordless phone and a WIFI connection at my house.

John Ferrell
http://DixieNC.US

{Original Message removed}

2004\08\02@104821 by Russell McMahon

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> > That way you suffer no feedline losses at all, and AFAIK aren't
> technically in violation of part 15, as you haven't mechanically altered
the
> antenna.

> I think it has more to do with effective radiated power (ERP). I doubt an
> experimenter would be challenged on the subject but a commercial product
> would.

Definitely ERP in any enlightened administration.
FCC qualify as enlightened ;-)

ERP can be horrendously high for amateur playing. I have heard people talk
about putting amplifiers in front of WiFi cards already rated at 100 mW+
This plus a half decent dish will cause major havoc while not gaining vastly
more than is possible with care and legal gear.

A well designed larger but not huge (around 30") dish will give 18 dB plus
gain and legal limit ERP (figures don't rise to top of brain at moment)(+15
dBm?).
Add equal dish at other end and an OK receiver and short decent coax and
good elevation and you are looking at over 20 mile links. Some report WELL
over. Few people need or can manage what goes with a 20 mile plus link.

Good elevation near ends of link is vital for range due to Fresnel zones.
Falling ground until well clear is highly desirable. Those repeaters aren't
on hilltops by mistake.


       RM

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2004\08\02@111312 by Robert B.

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Sorry, I just pulled a scrap out of the basement.  I'm pretty sure it's RG58
though, and either way it looks like it seriously attenuates my signal :(

To get my desktop out of the dead spot takes at least 15' of some sort of
cable, and I haven't been able to locate anything that doesn't kill the
signal.  I guess it does technically *work* now (I'm typing this email with
the cantenna taped to the door-frame) so maybe I'll just mount it
permanently and suffer through the slow 4Mbs network connection.
{Original Message removed}

2004\08\02@111727 by Robert B.

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These are all good things to know!  I don't have any other 2.4ghz signals
besides the wifi and an occasional microwave.  The microwave was dropped at
one point, so spews out lots of extra radiation in that band when its
operated.  My neighbor's 2.4ghz phone system sometimes mysteriously craps
out whenever I cook a hotdog ;-)

Now that I mention it, I wonder if his phone could be an interference
source.  Too bad my scope only works up to 100MHz :(


{Original Message removed}

2004\08\02@112142 by Robert B.

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Maybe I'll have to give this idea a shot.  By moving the signal receiver to
the dish the signal probably gets a whole lot better at distances from the
host PC.  The USB cable could be up to 16ft, just enough to get the antenna
into the signal area.  And I suppose there wouldn't be anywhere near the
loss problems with a longish USB cable.  Too bad I wasted money on this darn
PCI adapter!


{Original Message removed}

2004\08\02@112350 by Robert B.

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I built mine out of an old tomatoe juice can just under 4" diameter and
about 10" tall, then installed the probe as per the web-calculators
available.  It sounds like I'm probably sniffing at the wrong hydrant, and
should try locating one of those USB dongles at the focal point of a dish,
then run the USB cable back to my PC.


{Original Message removed}

2004\08\02@112559 by Alan B. Pearce

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>The microwave was dropped at one point, so spews out lots
>of extra radiation in that band when its operated.  My
>neighbor's 2.4ghz phone system sometimes mysteriously craps
>out whenever I cook a hotdog ;-)

Sheesh mate. Replace it real quick. hate to think what you are doing to
yourself with this thing. !!!!!!!!

>Now that I mention it, I wonder if his phone could be an
>interference source.

And what is your network doing to his phone ???? :)))))

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2004\08\02@114047 by hael Rigby-Jones

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>-----Original Message-----
>From: pic microcontroller discussion list
>[spamBeGonePICLISTSTOPspamspamEraseMEMITVMA.MIT.EDU] On Behalf Of Robert B.
>Sent: 02 August 2004 16:22
>To: KILLspamPICLISTspamBeGonespamMITVMA.MIT.EDU
>Subject: Re: [OT:] WIFI Waveguide antenna
>
>
>Maybe I'll have to give this idea a shot.  By moving the
>signal receiver to the dish the signal probably gets a whole
>lot better at distances from the host PC.  The USB cable could
>be up to 16ft, just enough to get the antenna into the signal
>area.  And I suppose there wouldn't be anywhere near the loss
>problems with a longish USB cable.  Too bad I wasted money on
>this darn PCI adapter!

Definitely the way to go.  The USB adapters are also dirt cheap, I just
bought an 802.11G dongle (need USB2 to get full bandwidth) for just over £20
($36) in "rip-off Britain" so I suspect the 11mbit/s dongles are virtualy
pennies in the US.

Mike

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2004\08\02@114916 by Alan B. Pearce

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>Definitely the way to go.  The USB adapters are also dirt
>cheap, I just bought an 802.11G dongle (need USB2 to get
>full bandwidth) for just over £20 ($36) in "rip-off Britain"
>so I suspect the 11mbit/s dongles are virtualy
>pennies in the US.

Where did you get that Michael? I have had a look on ebay and they go for
close to twice that for the .11g ones, but about that for .11b. Reason I am
interested is that it seems like a nice way to add wifi to my Linux firewall
that I want to set up, which will have a spare USB plug on it.

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2004\08\02@114918 by David VanHorn

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>
>ERP can be horrendously high for amateur playing. I have heard people talk
>about putting amplifiers in front of WiFi cards already rated at 100 mW+
>This plus a half decent dish will cause major havoc while not gaining vastly
>more than is possible with care and legal gear.

I'm only licensed for 1500W up here.. :)

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2004\08\02@115124 by David VanHorn

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At 10:16 AM 8/2/2004, Robert B. wrote:

>These are all good things to know!  I don't have any other 2.4ghz signals
>besides the wifi and an occasional microwave.  The microwave was dropped at
>one point, so spews out lots of extra radiation in that band when its
>operated.  My neighbor's 2.4ghz phone system sometimes mysteriously craps
>out whenever I cook a hotdog ;-)

I would seriously think about getting that checked.

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2004\08\02@120158 by Robert B.

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I checked around it with a fluorescent tube, and it appears to be a highly
directional leak towards my neighbor's house.  I know its crude, but its the
best I could do.  So I just go in the other room (away from the leak)
whenever something has to nuke for any length of time.  It's really not a
very good microwave, so I probably should just replace it, but I really
didn't think it was all that dangerous.  It sounds like maybe I'm wrong...


{Original Message removed}

2004\08\02@120406 by hael Rigby-Jones

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>-----Original Message-----
>From: pic microcontroller discussion list
>[TakeThisOuTPICLIST.....spamTakeThisOuTMITVMA.MIT.EDU] On Behalf Of Alan B. Pearce
>Sent: 02 August 2004 16:50
>To: TakeThisOuTPICLISTKILLspamspamspamMITVMA.MIT.EDU
>Subject: Re: [OT:] WIFI Waveguide antenna
>
>
>>Definitely the way to go.  The USB adapters are also dirt
>cheap, I just
>>bought an 802.11G dongle (need USB2 to get full bandwidth) for just
>>over £20 ($36) in "rip-off Britain" so I suspect the 11mbit/s dongles
>>are virtualy pennies in the US.
>
>Where did you get that Michael? I have had a look on ebay and
>they go for close to twice that for the .11g ones, but about
>that for .11b. Reason I am interested is that it seems like a
>nice way to add wifi to my Linux firewall that I want to set
>up, which will have a spare USB plug on it.

http://www.ebuyer.co.uk (quickfind code 63002) is the actual device I
bought. However, I have just checked and the product I bought seems to have
gone up to £27.99.  Not unusual for Ebuyer however, they do seem to have a
very "flexible" pricing policy.  Worth keeping an eye on it though as I've
known prices to go down shortly after they've been increased.

There is an alternative device for £22.99 (quickfind code 60710) that is a
little bit larger and has an external antenna which may well be better if
you aren't intending on putting it in front of a dish.
Note that they are described as being of "Ebuyer" brand, but in relality
they simply sell whichever product they can get the cheapest, which may or
may not be in retail packaging.  The one I bought was made by Origo
http://www.origo2000.com/show-prds.php?ID_NUM=80

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2004\08\02@120614 by hael Rigby-Jones

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>-----Original Message-----
>From: pic microcontroller discussion list
>[RemoveMEPICLISTspamspamBeGoneMITVMA.MIT.EDU] On Behalf Of Robert B.
>Sent: 02 August 2004 17:01
>To: spamBeGonePICLIST@spam@spamspam_OUTMITVMA.MIT.EDU
>Subject: Re: [OT:] WIFI Waveguide antenna
>
>
>I checked around it with a fluorescent tube, and it appears to
>be a highly directional leak towards my neighbor's house.  I
>know its crude, but its the best I could do.  So I just go in
>the other room (away from the leak) whenever something has to
>nuke for any length of time.  It's really not a very good
>microwave, so I probably should just replace it, but I really
>didn't think it was all that dangerous.  It sounds like maybe
>I'm wrong...

With the cost of a new microwave oven as low as they are, I don't think I'd
be taking the risk to be honest.  Your neighbour might not be very
understanding if he knew you were slowly cooking him as well :o)

Mike

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2004\08\02@121234 by David VanHorn

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>
>With the cost of a new microwave oven as low as they are, I don't think I'd
>be taking the risk to be honest.  Your neighbour might not be very
>understanding if he knew you were slowly cooking him as well :o)

TOSS IT.

If you're lighting up a tube, you're emitting WAY too much!

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2004\08\03@033738 by Alan B. Pearce

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Thanks for the pointer to ebuyer, Michael. Will have to investigate them
when I'm closer to needing one.

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2004\08\05@084422 by Howard Winter

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David,

On Mon, 2 Aug 2004 08:34:22 -0500, David VanHorn wrote:

> At 07:34 AM 8/2/2004, Howard Winter wrote:
>
>...<
> You want something that has 50ohm impedance, which rules out TV and Satellite (75 ohm).
>
> Actually, 75 ohm cable is less lossy up high (in general) and might be a better choice.
> Some antennas match better to 75 than to 50, and at the card end, a 1.5-1 VSWR isn't a big deal.  Far more
important that the antenna be resonant.  Tough to know up here without specialized equipment.

I think the problems of mismatch may go far beyond the SWR, and the reduction of loss may not matter because
WiFi is a fast duplex system.  It could be that when transmitting stops the ringing caused by the mismatch at
both ends may still be strong enough that when the card switches to receiving it's deafened and doesn't hear
the reply.  This is a guess based on no knowledge of the hang-time parameters of WiFi!

A number of years ago the office I worked in had a 10-base-T network (50-ohm coax daisy-chained, I think) and
I got a call from a secretary saying that if I didn't get there soon and fix it, she'd throw her computer out
of the window!  Performance had degraded to the point where it took 2 minutes to open a file (in WordPerfect
for example).  I connected up a Time Domain Reflectometer and found that there were reflections that shouldn't
have been there.  Traced along the cable and found that someone had added their machine to the network, using
a piece of 75-ohm cable (about 3m long) and this was causing enough reflections to bring the whole network to
its knees!  And this was with everything just wired together, not listening for an incoming signal from the
"aether"  :-)  I've had a healthy respect for impedance matching ever since.

Cheers,


Howard Winter
St.Albans, England

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2004\08\05@085044 by Howard Winter

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Robert,

On Mon, 2 Aug 2004 11:12:27 -0400, Robert B. wrote:

> Sorry, I just pulled a scrap out of the basement.  I'm pretty sure it's RG58
> though, and either way it looks like it seriously attenuates my signal :(

Ah - is it a damp basement by any chance?  Were the connectors already fitted or did you fit them yourself?
If there's water in the cable it *will* really attenuate!

Cheers,


Howard Winter
St.Albans, England

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2004\08\05@085912 by Howard Winter

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Mike,

On Mon, 2 Aug 2004 16:42:52 +0100, Michael Rigby-Jones
wrote:

>  I just bought an 802.11G dongle (need USB2 to get
full bandwidth) for just over £20

Can I ask what make this is and where you got it,
please?

Cheers,


Howard Winter
St.Albans, England

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2004\08\05@090121 by Robert B.

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The cable is bone dry, and there were no connectors fitted so I put them on
myself.  I'll openly admit it's a hacked together job from materials I had
on hand at the time to see if the cantenna would pick up a signal.  The
signal is surprisingly good considering all the problems people have pointed
out with it.  Now that final exams are over I'll be working to properly
match everything, and maybe build one of those USB-dongle dishes just for
comparison.

On a side note, I was testing the ol' deathray microwave to see if it did
interfere with the network, and yeah it brings it down real quick.  My
neighbor's wifi signal (different neighbor than the 2.4ghz phone) is
attenuated significantly as well, but that might be just on my end.  I'll
have to ask him if he's noticed any abnormalities in his network services
around dinner time. ;-)

{Original Message removed}

2004\08\05@090535 by hael Rigby-Jones

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>-----Original Message-----
>From: pic microcontroller discussion list
>[@spam@PICLISTRemoveMEspamEraseMEMITVMA.MIT.EDU] On Behalf Of Howard Winter
>Sent: 05 August 2004 13:59
>To: EraseMEPICLISTspam@spam@MITVMA.MIT.EDU
>Subject: Re: [OT:] WIFI Waveguide antenna
>
>
>Mike,
>
>On Mon, 2 Aug 2004 16:42:52 +0100, Michael Rigby-Jones
>wrote:
>
>>  I just bought an 802.11G dongle (need USB2 to get
>full bandwidth) for just over £20
>
>Can I ask what make this is and where you got it,
>please?
>

Posted this before for Alan:


http://www.ebuyer.co.uk (quickfind code 63002) is the actual device I
bought. However, I have just checked and the product I bought seems to have
gone up to £27.99.  Not unusual for Ebuyer however, they do seem to have a
very "flexible" pricing policy.  Worth keeping an eye on it though as I've
known prices to go down shortly after they've been increased.

There is an alternative device for £22.99 (quickfind code 60710) that is a
little bit larger and has an external antenna which may well be better if
you aren't intending on putting it in front of a dish.
Note that they are described as being of "Ebuyer" brand, but in relality
they simply sell whichever product they can get the cheapest, which may or
may not be in retail packaging.  The one I bought was made by Origo
http://www.origo2000.com/show-prds.php?ID_NUM=80

Regards

Mike

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2004\08\12@015616 by Robert B.

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Hello everybody,

I finally got around to building one of the USB-dongle style antennas, and
let me say WOW it blows away my tin-can waveguide antenna.  The s/n ratio is
much better, and dropped packets are almost non-existant.  The windows icon
thingy went from "Very low" to "Very Good", and the netstumbler readings
increased dramatically, from about -85dB to -60dB.

The basic design utilized a $2.95 wire strainer from my local Wally-world,
along with a linksys Wireless-B (I skimped) USB Network adapter (model
WUSB11).  A little hot glue and a tripod completed the rig.  It's no longer
necessary to string the cable into the next room for acceptable reception,
and from what I can tell the reception is improved dramatically over the
previous design.  I'm even picking up a few other networks in the
neighborhood.

The new antenna is somewhat directional, but picks up an acceptable signal
for about 100 degrees of rotation.  This indicates that perhaps the antenna
is not at the reflectual center of the wire strainer, or the strainer is not
truly parabolic (or both..).  But at any rate I can't complain.  The USB
connection installed easily as well.

Picture of the rig here:  http://www.nerdulator.net/files/wifi.jpg


{Original Message removed}

2004\08\12@194621 by John Ferrell

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You done good!
Just remember, if you see them, they can see you...

John Ferrell
http://DixieNC.US

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