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External antennae for notebooks and others...

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Anonymous
July 2, 2004 4:01:29 PM

Archived from groups: alt.internet.wireless (More info?)

Hi,

I have seen a lot of discussion about this, and have seen a number of
offerings, all of which seem to involve lots of "bodges" ... with pigtails,
and replacement connectors.... etc etc ...

Given that the radio signal appears to be the critical part, and the more
connectors / adapters you add the greater the signal loss, is it possible to
use a USB wifi "dongle" with a metal mesh reflector, and rely on the USB
cable to carry the digital signal ...

Would there be any snags to this approach?

What would be the maximum length of USB cable? And could a Powered USB Hub
increase this ?

Regards

John



---
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Anonymous
July 2, 2004 4:01:30 PM

Archived from groups: alt.internet.wireless (More info?)

On Fri, 2 Jul 2004 12:01:29 +0100, "John Beeston"
<john.Beeston@talk21.com> wrote:

>Given that the radio signal appears to be the critical part, and the more
>connectors / adapters you add the greater the signal loss, is it possible to
>use a USB wifi "dongle" with a metal mesh reflector, and rely on the USB
>cable to carry the digital signal ...

http://www.freeantennas.com
http://www.freeantennas.com/projects/Ez-10/

The nice part is that it doesn't require an pigtails. A USB radio
should work as well. I'll leave it to your ingenuity to figure out
how to do it with a PCMCIA card in a laptop. (ribbon cable
extension?)

>Would there be any snags to this approach?

That depends on your construction abilities. There have been
aluminium foil and cardboard corner reflectors built, that I consider
to be marginal and unstable, but it can't be any worse than a
cardboard pringles can antenna.

>What would be the maximum length of USB cable? And could a Powered USB Hub
>increase this ?

16ft for USB.


--
Jeff Liebermann jeffl@comix.santa-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 AE6KS 831-336-2558
Anonymous
July 2, 2004 5:05:23 PM

Archived from groups: alt.internet.wireless (More info?)

> Given that the radio signal appears to be the critical part, and the more
> connectors / adapters you add the greater the signal loss, is it possible to
> use a USB wifi "dongle" with a metal mesh reflector, and rely on the USB
> cable to carry the digital signal ...

You mean something like this?

http://www.nodomainname.co.uk/cantenna/IMG_0384s.jpg

http://www.nodomainname.co.uk/cantenna3/cantenna3.htm

:) 

> Would there be any snags to this approach?

Not really

> What would be the maximum length of USB cable? And could a Powered USB Hub
> increase this ?

USB cable length is 5m max, you can string 5 active cables together so
lets call that 25m.

David.
Related resources
Anonymous
July 2, 2004 5:39:11 PM

Archived from groups: alt.internet.wireless (More info?)

John Beeston wrote:
> Hi,
>
> I have seen a lot of discussion about this, and have seen a number of
> offerings, all of which seem to involve lots of "bodges" ... with
> pigtails, and replacement connectors.... etc etc ...
>
> Given that the radio signal appears to be the critical part, and the
> more connectors / adapters you add the greater the signal loss, is it
> possible to use a USB wifi "dongle" with a metal mesh reflector, and
> rely on the USB cable to carry the digital signal ...
>
> Would there be any snags to this approach?
>
> What would be the maximum length of USB cable? And could a Powered
> USB Hub increase this ?
>
> Regards
>
> John
>
would this be any good?

http://www.linksys.com/products/product.asp?grid=33&sci...




--
Mike E
Anonymous
July 2, 2004 8:34:36 PM

Archived from groups: alt.internet.wireless (More info?)

"David Taylor" <djtaylor@bigfoot.com> wrote in message
news:MPG.1b4f5fddec65da5e989c9a@news.individual.de...
> > Given that the radio signal appears to be the critical part, and the
more
> > connectors / adapters you add the greater the signal loss, is it
possible to
> > use a USB wifi "dongle" with a metal mesh reflector, and rely on the USB
> > cable to carry the digital signal ...
>
> You mean something like this?
>
> http://www.nodomainname.co.uk/cantenna/IMG_0384s.jpg
>
> http://www.nodomainname.co.uk/cantenna3/cantenna3.htm
>
> :) 
>
> > Would there be any snags to this approach?
>
> Not really
>

Very impressive, but I was thinking of something far simpler ... this
approach still has mentions of brass bits, solder, and pigtails...

But there again, perhaps I do not understand the full complexities...

I was thinking more of a small self contained USB device such as the
linksys WUSB12 or D-Link DWL122 being placed at the focus of a suitable
dish and connected back to the PC using a standard USB extension cable (or
cables)

For the reflector I had something like a SKY satellite dish in mind, as
these are cheap, and easy to install.

John




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Anonymous
July 2, 2004 8:34:37 PM

Archived from groups: alt.internet.wireless (More info?)

John Beeston <john.Beeston@talk21.com> wrote:
> I was thinking more of a small self contained USB device such as the
> linksys WUSB12 or D-Link DWL122 being placed at the focus of a suitable
> dish and connected back to the PC using a standard USB extension cable (or
> cables)

> For the reflector I had something like a SKY satellite dish in mind, as
> these are cheap, and easy to install.

The mini-USB won't properly paint a satellite dish. It might work in a
small can, like the one on David's page.
I used a DWL-122 witha 9" pie plate pretty effectively. I'm going to mount
it in the bottom of a coffee can next.

You need two coffee cans soldered together and cut off to about 6 inches,
and then mount the USB mini about half inch from the bottom end.

http://www.turnpoint.net/wireless/cantennahowto.html provides the
calculator and ideas. I was going to put the miniUSB in there, although
some experimentation to find the right focus and orientation.



--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8-122.5
Anonymous
July 2, 2004 10:22:12 PM

Archived from groups: alt.internet.wireless (More info?)

Clarence, I am interested in your pie plate ... how / where did you mount
the DWL-122?

John


<dold@ExternalXa.usenet.us.com> wrote in message
news:cc40h9$ajh$1@blue.rahul.net...
>
> The mini-USB won't properly paint a satellite dish. It might work in a
> small can, like the one on David's page.
> I used a DWL-122 witha 9" pie plate pretty effectively. I'm going to
mount
> it in the bottom of a coffee can next.
>
> You need two coffee cans soldered together and cut off to about 6 inches,
> and then mount the USB mini about half inch from the bottom end.
>
> http://www.turnpoint.net/wireless/cantennahowto.html provides the
> calculator and ideas. I was going to put the miniUSB in there, although
> some experimentation to find the right focus and orientation.
>
>




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Anonymous
July 2, 2004 11:12:30 PM

Archived from groups: alt.internet.wireless (More info?)

> Very impressive, but I was thinking of something far simpler ... this
> approach still has mentions of brass bits, solder, and pigtails...

Not in the first picture I linked you to. All that's going on there is
a the antenna from a Netgear USB NIC poked up into the cardboard tube
(foil lined).

> I was thinking more of a small self contained USB device such as the
> linksys WUSB12 or D-Link DWL122 being placed at the focus of a suitable
> dish and connected back to the PC using a standard USB extension cable (or
> cables)
> For the reflector I had something like a SKY satellite dish in mind, as
> these are cheap, and easy to install.

It has been done before but it's just as easy to stuff the antenna into
a can and use the can in the place of the LNB.

David.
Anonymous
July 2, 2004 11:14:00 PM

Archived from groups: alt.internet.wireless (More info?)

> 16ft for USB.

or 5 active cables strung together. :) 
Anonymous
July 2, 2004 11:44:57 PM

Archived from groups: alt.internet.wireless (More info?)

Jeff Liebermann <jeffl@comix.santa-cruz.ca.us> wrote:
> The nice part is that it doesn't require an pigtails. A USB radio
> should work as well. I'll leave it to your ingenuity to figure out
> how to do it with a PCMCIA card in a laptop. (ribbon cable
> extension?)

I used a reflector with an Orinoco PCMCIA card.
I was holding the reflector with one hand, and the laptop with the other,
so it wasn't very useful, but NetStumbler definitely showed the effects of
the reflector being in place.
"I'll leave it to your ingenuity to figure out how to do it" in some
worthwhile fashion ;-)

--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8-122.5
Anonymous
July 2, 2004 11:54:45 PM

Archived from groups: alt.internet.wireless (More info?)

John Beeston <john.Beeston@talk21.com> wrote:
> Clarence, I am interested in your pie plate ... how / where did you mount
> the DWL-122?

I used a Marie Calendar's pie tin, which is just a touch too small of a
surface. I used double back tape to affix the mini-USB to a wall, a
window, a cookie sheet, and the pie tin. In each case, I also used
varying thicknesses of material behind the mini-USB, and settled on about
3/4" standoff from the surface.

I have some NetStumbler charts that made sense at the time, but I can't
correlate the charts to the different applications now. azimuth,
elevation, and orientation were all important. Without learnbydestorying's
help, I don't know how the antenna element in the dongle is oriented.

The pie plate was directional enough that I could see that my strongest
signal was coming in through a window, rather than a straight line through
the wall.

The coffee can is the next step, although I haven't decided how to route
the wire. The easiest would be to just run it down the side, inside the
can. Better would be poking a hole in some lined cardboard, like David
Taylor, but Pringles is way too small, so I'm going to play with the coffee
can. I only have one can, and I need two, so I'm a little slow getting
started.

Although Jeff might point out that all of my attempts are so haphazard,
a few inches of length might not be important.

---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8-122.5
Anonymous
July 3, 2004 6:54:23 AM

Archived from groups: alt.internet.wireless (More info?)

On Fri, 2 Jul 2004 19:44:57 +0000 (UTC), dold@ExternalXa.usenet.us.com
wrote:

>Jeff Liebermann <jeffl@comix.santa-cruz.ca.us> wrote:
>> The nice part is that it doesn't require an pigtails. A USB radio
>> should work as well. I'll leave it to your ingenuity to figure out
>> how to do it with a PCMCIA card in a laptop. (ribbon cable
>> extension?)

>I used a reflector with an Orinoco PCMCIA card.
>I was holding the reflector with one hand, and the laptop with the other,
>so it wasn't very useful, but NetStumbler definitely showed the effects of
>the reflector being in place.

Careful. Tuning by signal strength alone is not sufficient. You need
to keep an eye on the S/N (signal to noise) ratio. You can have a
very strong signal, but if multipath, reflections, or interference get
in the way, your S/N ratio and thus your thruput will suffer.

>"I'll leave it to your ingenuity to figure out how to do it" in some
>worthwhile fashion ;-)

The Orinoco/Proxim/Wavelan/Agere/Avaya/Whatever card has a connector
for a pigtail to an external antenna. Methinks that will work better
although it is admittedly more expensive.

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831.336.2558 voice http://www.LearnByDestroying.com
# jeffl@comix.santa-cruz.ca.us
# 831.421.6491 digital_pager jeffl@cruzio.com AE6KS
Anonymous
July 3, 2004 7:13:41 AM

Archived from groups: alt.internet.wireless (More info?)

On Fri, 2 Jul 2004 19:54:45 +0000 (UTC), dold@ExternalXa.usenet.us.com
wrote:

>Although Jeff might point out that all of my attempts are so haphazard,
>a few inches of length might not be important.
>Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8-122.5

Yep. Let's do the math the long way (to illustrate the problem).

The 2.4GHz band is 83MHz wide.
One wavelength at the bottom of the band is:
3x10^8 meters/sec / 2.400x10^9 cycles/sec = 12.50 cm/wavelenth.
and at the top of the band:
3x10^8 meters/sec / 2.483x10^9 cycles/sec = 12.08 cm/wavelenth.
For a half wave dipole, the difference between the top and bottom of
the band is:
6.25 cm - 6.04 cm = 0.21 cm = 2.1 mm.
So, your basic tolerance for a simple (62mm) half wave dipole is plus
or minus 1.0 mm or your antenna falls out of the ISM band. Actually,
it's somewhat tighter than that as being 1.0mm off is sufficient to
screw up the VSWR and induce some entertaining group delay across the
operating bandwidth.

To be fair, the reflector does not need to be that accurate. Rule of
thumb for big dishes is flat within 1/10 wavelength or within 12.5mm
of flat at 2.4GHz. Well, ok... I guess your wrinkled aluminium foil
reflector is close enough.

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831.336.2558 voice http://www.LearnByDestroying.com
# jeffl@comix.santa-cruz.ca.us
# 831.421.6491 digital_pager jeffl@cruzio.com AE6KS
Anonymous
July 3, 2004 6:27:44 PM

Archived from groups: alt.internet.wireless (More info?)

Jeff Liebermann <jeffl@comix.santa-cruz.ca.us> wrote:
> Careful. Tuning by signal strength alone is not sufficient. You need
> to keep an eye on the S/N (signal to noise) ratio. You can have a
> very strong signal, but if multipath, reflections, or interference get
> in the way, your S/N ratio and thus your thruput will suffer.

The NetStumbler screen combines strength and SNR in one graph. There are
occasions where the "red" portion gets a little larger, but I live in the
sticks with no alternate sources of noise. The noise is generally -100dB,
so the SNR is pretty good. I do see it come up, but the best signal
strength is the lowest SNR in coincidence. I haven't tested throughput as
a tuning aid. I think that might be valuable with finely focused antennas
at long distance. Maybe I'll do a little checking with iperf.

> The Orinoco/Proxim/Wavelan/Agere/Avaya/Whatever card has a connector
> for a pigtail to an external antenna. Methinks that will work better
> although it is admittedly more expensive.

I have a few of those. A mag mount for the car, a Conifer that provides a
claimed 11dBi, and a spare "N" adapter that's not being used currently.

Flat pieces of metal are flat pieces of metal. I don't see the difference
in a commercially built antenna and a similar design built at home out of
Radio Shack PC board material. The commercial antenna might be built of
better material for outdoor use, or have plastic housings to make it look
pretty, but the dimensions are all that matter.

My wrinkled aluminum foil works as well as the Conifer, except that the
beam is narrower. I haven't looked at the specs to see if that is supposed
to be true. I started to learnbydestroying to measure the dimensions of
the Conifer, but I couldn't get myself to break the waterproof seal.

The only specs I can find for the Conifer are in Russian.

< http://www.rahul.net/dold/clarence/SMC/EZ10-strength.ht... >
< http://www.is.net.ua/wireless/prod/dl2410.html >
< http://dast.nlanr.net/Projects/Iperf/ >

--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8-122.5
Anonymous
July 3, 2004 10:20:47 PM

Archived from groups: alt.internet.wireless (More info?)

On Fri, 2 Jul 2004 12:01:29 +0100, John Beeston wrote:

> Hi,
>
> I have seen a lot of discussion about this, and have seen a number of
> offerings, all of which seem to involve lots of "bodges" ... with pigtails,
> and replacement connectors.... etc etc ...
>
> Given that the radio signal appears to be the critical part, and the more
> connectors / adapters you add the greater the signal loss, is it possible to
> use a USB wifi "dongle" with a metal mesh reflector, and rely on the USB
> cable to carry the digital signal ...
>
> Would there be any snags to this approach?
>
> What would be the maximum length of USB cable? And could a Powered USB Hub
> increase this ?
>
> Regards
>
> John
>
> ---
> Outgoing mail is certified Virus Free.
> Checked by AVG anti-virus system (http://www.grisoft.com).
> Version: 6.0.713 / Virus Database: 469 - Release Date: 30/06/2004

Check these links:

http://www.usbwifi.orcon.net.nz/
http://www.manuka.orcon.net.nz/usbscoop.jpg
http://www.manuka.orcon.net.nz/roofscan.jpg

HTH
--
Barry
Anonymous
July 5, 2004 1:16:17 AM

Archived from groups: alt.internet.wireless (More info?)

Jeff Liebermann <jeffl@comix.santa-cruz.ca.us> wrote:
> 6.25 cm - 6.04 cm = 0.21 cm = 2.1 mm.
> So, your basic tolerance for a simple (62mm) half wave dipole is plus
> or minus 1.0 mm or your antenna falls out of the ISM band. Actually,
> it's somewhat tighter than that as being 1.0mm off is sufficient to
> screw up the VSWR and induce some entertaining group delay across the
> operating bandwidth.

I'm not building a dipole. I'm using the prebuilt Mini-USB for that.

> To be fair, the reflector does not need to be that accurate. Rule of
> thumb for big dishes is flat within 1/10 wavelength or within 12.5mm
> of flat at 2.4GHz. Well, ok... I guess your wrinkled aluminium foil
> reflector is close enough.

I was referring to the length of the coffee can. The "2 lb" can is 4" in
diameter, and 4" long (IIRC. I don't have the can here). According to
http://www.turnpoint.net/wireless/cantennahowto.html
The can is only 1/2 of a wavelength, and should be at least 3/4.

The wrinkled aluminum foil might be more of a problem with off angle
reflections, but there's also been talk of the ripples in the metal cans
being a bad thing, as opposed to a Pringles can, which is smooth but too
small. The wrinkled foil reference is to my reflector at
< http://www.rahul.net/dold/clarence/SMC/EZ10-strength.ht... >

I hadn't thought about using that reflector for a mini-USB. The reflector
could be smaller, since the dipole is smaller than a WAP.
I still don't know how the antenna is oriented, or even what type of
antenna it is. I don't think it is a patch, because it doesn't seem to
have a front-to-back ratio.

Smooth lined cardboard cans could be better for cantennas. I see that
Country Time Lemonade is 5" diameter and is 9" long. That's plenty long,
but I don't know if it's the proper material. Can I test with an ohmmeter
for conductivity? Is that what I want to measure? That wouldn't be good
for outdoor use, as David Taylor notes after leaving his outside.

http://www.nodomainname.co.uk/cantenna/cantenna.htm
"Unfortunately, I left the whole lot outside one night and it rained
causing the milk tub to get a bit soggy - RIP trust tub!"

--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8-122.5
Anonymous
July 5, 2004 1:36:14 AM

Archived from groups: alt.internet.wireless (More info?)

Barry Jones <bjones01@acm.org> wrote:
> http://www.usbwifi.orcon.net.nz/
> http://www.manuka.orcon.net.nz/usbscoop.jpg
> http://www.manuka.orcon.net.nz/roofscan.jpg

That site is what caused me to buy a mini-USB. Using a mini-USB dongle
allows you to remove the dongle and use it normally in a higher-strength
environment. It seems so much easier than building the can as an antenna,
which requires relatively more expensive cables and an internal card.

I'm going to have to buy another to play with, though, because I gave my
other one away to someone who is just not trying hard enough ;-).


Belkin is pretty cheap at CompUSA this weekend, but I never seem to find
the sale items available at CompUSA.
Standard sized USB $9.99
< http://www.compusa.com/products/product_info.asp?produc... >

Mini-USB $29.99
< http://www.compusa.com/products/product_info.asp?produc... >

--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8-122.5
Anonymous
July 5, 2004 5:03:14 AM

Archived from groups: alt.internet.wireless (More info?)

Jeff Liebermann <jeffl@comix.santa-cruz.ca.us> wrote:
> It's a ceramic patch antenna which is about 7mm x 7mm. See:
> http://www.component.tdk.com/2.4GHAnntena.pdf

There was a picture on one of the .nz web pages, but I wasn't sure if it
was the Dick Smith or the DWL mini-USB. Probably doesn't matter.
http://www.usbwifi.orcon.net.nz/dsewifi.jpg
The top portion of the jpeg-as-web-page shows the naked dongle on a
broomstick above the roof.

>>Smooth lined cardboard cans could be better for cantennas. I see that
>>Country Time Lemonade is 5" diameter and is 9" long. That's plenty long,
>>but I don't know if it's the proper material.

> At RF frequencies, ALL the RF conductivity is on the surface of the
> conductor. You could make it out of a silver plated plastic insulator

I recall skin effect from my days in heavy radar, but I don't know if this
is the proper skin. Silver plated anything is a little on the pricey side
for the homebrew antenna market.

> I'm also disgusted at the prevalence of using cylindrical horns
> instead of a much better and higher gain horn antennas. Basically,

David Taylor speaks of putting a horn on the end of a can.
http://www.nodomainname.co.uk/Antennas/antenna.htm#Can%...
That shows another 6dB or so.

> No. DC conductivity does NOT equate to RF conductivity. RF
> conductivity is all skin effect and is on the surface of the
> conductor. Some skin effect references:

That's in a material that is conductive. I don't know that
the liner in these cardboard tins is conductive, or all the same.

> Ummm... Perhaps a stainless can antenna?
> http://www.cantenna.com/catalogue/SC12.html

I really am interested in the USB dongle. It's so much cheaper than the
802.11b card+pigtail+cantenna. The guys in nz suggest pulling the ceramic
patch off and soldering on a different antenna, but then you've destroyed
the dongle, and need to adhere to stricter design for radiator sizing.

--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8-122.5
Anonymous
July 5, 2004 5:03:15 AM

Archived from groups: alt.internet.wireless (More info?)

On Mon, 5 Jul 2004 01:03:14 +0000 (UTC), dold@ExternalXa.usenet.us.com
wrote:

>There was a picture on one of the .nz web pages,

I think you mean this one.
http://www.usbwifi.orcon.net.nz/usbscoop.jpg
A little reminder... the efficiency of a parbolic reflector is at best
50% assuming a decent feed that doesn't over or under illuminate the
dish. My guess(tm) is that the efficiency of a ceramic patch antenna,
illuminating a chrome plated steel vegetable scoop is close to 10%.
Chrome also makes a lousy RF conductor.

>The top portion of the jpeg-as-web-page shows the naked dongle on a
>broomstick above the roof.

Swell. Tear apart the USB radio, remove the ceramic patch antenna,
and replace it with a coax connector or solder on pigtail. Attach a
real antenna. See:
http://jeffl.ihwy.com/linksys/wusb11/wusb11-2.jpg
The pads in the upper right are where the ceramic patch antenna was
connected. The pattern is perfect for a PC mount SMA connector.
However, I got lazy and soldered some semi-rigid coax to the pads,
with an SMA at the end.

>> At RF frequencies, ALL the RF conductivity is on the surface of the
>> conductor. You could make it out of a silver plated plastic insulator

>I recall skin effect from my days in heavy radar, but I don't know if this
>is the proper skin. Silver plated anything is a little on the pricey side
>for the homebrew antenna market.

Not really. I make my antenna parts for copper water pipe, copper
flashing, and sheet brass. Mostly, I use electroless silver solution
(silver cyanide) to plate the copper and brass. The problem with
electroless silver is that it's not really thick enough at the lower
ham frequencies. I have the calcs if you want them. However, for
2.4Ghz, it's not problem. One skin depth is:

The skin depth is:
depth = 2.6 * K1 / sqrt(freq)
where:
Depth = inches
Freq = Hz
K1 = 0.94 for silver

depth = 2.6 * 0.94 / 49000 = 0.000026 in = 26 micro inches.
(or about 0.3 microns).

Electroless silver is self limiting at 2-3 microns, so this should be
no problem at 2.4GHz where anything over 0.3 microns will suffice. If
you don't mind making a mess, silver plating is fairly easy. The
biggest headache was getting the chemicals shipped to me without a
hazardous substance waver.

Some useful instructions on plating:
http://www.LearnByDestroying.com/crud/silver-plating.tx...
http://www.qsl.net/n9zia/why_silver_plate.html
More on skin effect:
http://www.geocities.com/CapeCanaveral/Hangar/6160/skin...

>David Taylor speaks of putting a horn on the end of a can.
Bah humbug. I was thinking of something more substantial.
http://www.setileague.org/photos/wghorn/ewen2001.jpg (1420MHz)
http://www.setileague.org/photos/wghorn.htm
http://www.barc.org/ao40_antennas/rxantenna.html

>> No. DC conductivity does NOT equate to RF conductivity. RF
>> conductivity is all skin effect and is on the surface of the
>> conductor. Some skin effect references:

>That's in a material that is conductive. I don't know that
>the liner in these cardboard tins is conductive, or all the same.

Neither do I. However, even if they are conductive at DC (as measured
by an ohms-guesser), it's still the surface conductivity and skin
effect that determines the performance at 2.4GHz. One of my better
screwups was instead of painting an aluminium antenna, I cleverly had
it black anodized. Performance stunk until I scraped off the plating
with sandpaper. The same problem occurrs with chrome, and zinc
plating.

>I really am interested in the USB dongle. It's so much cheaper than the
>802.11b card+pigtail+cantenna. The guys in nz suggest pulling the ceramic
>patch off and soldering on a different antenna, but then you've destroyed
>the dongle, and need to adhere to stricter design for radiator sizing.

Sacrifices must be made. Use the force (or a suitable disassembly
tool).


--
Jeff Liebermann jeffl@comix.santa-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 AE6KS 831-336-2558
Anonymous
July 5, 2004 8:56:34 PM

Archived from groups: alt.internet.wireless (More info?)

Jeff Liebermann <jeffl@comix.santa-cruz.ca.us> wrote:
> I think you mean this one.
> http://www.usbwifi.orcon.net.nz/usbscoop.jpg

One of the other ones, but the same gang.

> A little reminder... the efficiency of a parbolic reflector is at best
> 50% assuming a decent feed that doesn't over or under illuminate the
> dish. My guess(tm) is that the efficiency of a ceramic patch antenna,
> illuminating a chrome plated steel vegetable scoop is close to 10%.
> Chrome also makes a lousy RF conductor.

They seemed to have good success. This is a hobby, not a need.
The closest to need is a friend of mine who lives close enough to a
commercial hotspot that he can associate to the hotspot, but never gets the
login web page. He doesn't need much gain, and then he can give up his
dialup access and phone line.

> Swell. Tear apart the USB radio, remove the ceramic patch antenna,
> and replace it with a coax connector or solder on pigtail. Attach a
> real antenna. See:

I really am exploring what can be done with the mini-USB intact. If I want
to pull off the ceramic antenna, I might as well start with a full sized
USB that has an antenna, and follow one of David Taylor's designs.

--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8-122.5
Anonymous
July 6, 2004 9:29:41 PM

Archived from groups: alt.internet.wireless (More info?)

<dold@ExternalXa.usenet.us.com> wrote in message
news:cca9ci$bru$1@blue.rahul.net...

> I really am interested in the USB dongle. It's so much cheaper than the
> 802.11b card+pigtail+cantenna. The guys in nz suggest pulling the ceramic
> patch off and soldering on a different antenna, but then you've destroyed
> the dongle, and need to adhere to stricter design for radiator sizing.
>

I, too, favour the idea of leaving the dongle as is,and simply fitting it to
reflector... a bit like a bulb in a car headlight ... one wonders whether
one of those big old shiny headlamps could be used?

I see concerns about painting / illuminating the reflector. Presumably this
is from the transmit side of the radio .. Is there an issue if the transmit
side is enhanced far less than the receive side?

I guess if there are two such reflector systems in use, the fact that both
had improved reception would be of benefit as long as the noise levels were
not increased too much. Presumably the focussing effect of the reflector
would help reduce any noise not in the direct path?

The various sales descriptions of these dongles refer to omni-directional
antennae.... is this true for both transmit and receive? Is there any simple
way of determining the signal strength pattern on transmit?

John




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Anonymous
July 6, 2004 9:29:42 PM

Archived from groups: alt.internet.wireless (More info?)

On Tue, 6 Jul 2004 17:29:41 +0100, John Beeston wrote:

>
> I, too, favour the idea of leaving the dongle as is,and simply fitting it to
> reflector... a bit like a bulb in a car headlight ... one wonders whether
> one of those big old shiny headlamps could be used?

That sounds like a great idea. Easy to weatherproof, probably a tight
focus, and you could probably mount it so that you can aim it like you aim
a car headlight. Let me know how it works if you try it. My time will come
next summer, when I put up a little hideaway in the back of the property.
<g>

> I see concerns about painting / illuminating the reflector. Presumably this
> is from the transmit side of the radio .. Is there an issue if the transmit
> side is enhanced far less than the receive side?

Supposedly the increased signal to noise ratio helps in the other direction
(actually the receive function of the AP). I would do one side at a time,
and see what you get.

> I guess if there are two such reflector systems in use, the fact that both
> had improved reception would be of benefit as long as the noise levels were
> not increased too much. Presumably the focussing effect of the reflector
> would help reduce any noise not in the direct path?

If you don't use an external amplifier, you don't have to worry about
increased noise. Any increased noise using focussed antennae should be in
proportion to the increased signal. In addition, you'll be blocking out
noise from other sources.

> The various sales descriptions of these dongles refer to omni-directional
> antennae.... is this true for both transmit and receive? Is there any simple
> way of determining the signal strength pattern on transmit?

I've seen some sites listed in this group that have data on the signal
strength patterns of various antennae. The omni's typically have a doughnut
shaped signal strength pattern, oriented horizontally if the antenna is
vertical. One's with higher dbi's presumably have a flatter doughnut.

> John
>
> ---

BTW, the above is not a good sig delimiter. It should be
dash-dash-space-newline. If you can't change the AV's output, you can put a
working delimiter above it, or above your name.


> Outgoing mail is certified Virus Free.
> Checked by AVG anti-virus system (http://www.grisoft.com).
> Version: 6.0.715 / Virus Database: 471 - Release Date: 04/07/2004

Not really interested. We're in a text based world here.

--
Barry
Anonymous
July 6, 2004 10:46:47 PM

Archived from groups: alt.internet.wireless (More info?)

John Beeston <john.Beeston@talk21.com> wrote:
> The various sales descriptions of these dongles refer to omni-directional
> antennae.... is this true for both transmit and receive? Is there any simple
> way of determining the signal strength pattern on transmit?

My plan is to put the USB dongle on a stick, and rotate it 360 degrees
while observing NetStumbler against a reference WAP.

In testing reflectors, I put the "D-Link" label away from the reflector.
Maybe it would be better if it faced the reflector. Or was edge-on, or
nose-on.

Jeff provided a reference to http://www.component.tdk.com/2.4GHAnntena.pdf
Presuming that the DLink is the 3mm CABPB0730A, there are three patterns.
The third is apparently the flat orientation. I don't understand the
distinction between the first two. I see that the graphic of the chip is
oriented differently, but I don't know what it means in terms of the
physical layout.
It also appears that there is a frequency sweet spot that varies depending
on which graph you are looking at. Just gain appears best for the higher
channels. The pattern varies by frequnecy as well, not necessarily
favoring the high channels. Depending on whether you have control of the
WAP, that might be an important tuning aid.

--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8-122.5
Anonymous
July 7, 2004 8:40:54 PM

Archived from groups: alt.internet.wireless (More info?)

dold@externalxa.usenet.us.com wrote:
> I really am exploring what can be done with the mini-USB intact. If I want
> to pull off the ceramic antenna, I might as well start with a full sized
> USB that has an antenna, and follow one of David Taylor's designs.

I looked at Fry's Electronics. The standard sized USB-802.11b adapters are
still around $59. The DLink DWL122 is $19 after rebates. A refurb Netgear
MA111(?) is $29. So the Mini-USB is a lot cheaper than the standard size.
Ripping it open and soldering a pigtail directly to the board, ending in a
radiator inside a can would be a very small and cheap version of the USB
Cantenna http://www.nodomainname.co.uk/cantenna3/cantenna3.htm


--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8-122.5
Anonymous
July 7, 2004 10:52:25 PM

Archived from groups: alt.internet.wireless (More info?)

<dold@ExternalXa.usenet.us.com> wrote in message
news:cch92m$k68$1@blue.rahul.net...
> dold@externalxa.usenet.us.com wrote:
> > I really am exploring what can be done with the mini-USB intact. If I
want
> > to pull off the ceramic antenna, I might as well start with a full sized
> > USB that has an antenna, and follow one of David Taylor's designs.
>
> I looked at Fry's Electronics. The standard sized USB-802.11b adapters
are
> still around $59. The DLink DWL122 is $19 after rebates. A refurb
Netgear
> MA111(?) is $29. So the Mini-USB is a lot cheaper than the standard size.
> Ripping it open and soldering a pigtail directly to the board, ending in a
> radiator inside a can would be a very small and cheap version of the USB
> Cantenna http://www.nodomainname.co.uk/cantenna3/cantenna3.htm
>

But if a similar effect can be achieved by simply placing said device at the
focus of a dish ... why get out the tools?

If you are simply soldering a pigtail to another radiator... have you gained
anything over relying on the built in radiator (ceramic or whatever)?

Would the effectiveness of the new radiator, without the can, be better than
the inbuilt antenna?

John


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Outgoing mail is certified Virus Free.
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Anonymous
July 7, 2004 11:14:42 PM

Archived from groups: alt.internet.wireless (More info?)

John Beeston <john.Beeston@talk21.com> wrote:
> But if a similar effect can be achieved by simply placing said device at the
> focus of a dish ... why get out the tools?

That's a question best answered by empirical study.

> If you are simply soldering a pigtail to another radiator... have you gained
> anything over relying on the built in radiator (ceramic or whatever)?

> Would the effectiveness of the new radiator, without the can, be better than
> the inbuilt antenna?

That's possible, even likely. You could attach a 3dBi rubber ducky in
place of the -1dBi ceramic. (I don't know if it's -1dBi. That's what Jeff
indicated, but I don't see a spec on the web page for the DWL-122.)

Then you'd have something that looks like the $99 Linksys.
http://www.linksys.com/products/product.asp?grid=33&sci...

--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8-122.5
Anonymous
July 8, 2004 9:42:45 AM

Archived from groups: alt.internet.wireless (More info?)

On Wed, 7 Jul 2004 18:52:25 +0100, "John Beeston"
<john.Beeston@talk21.com> wrote:

>But if a similar effect can be achieved by simply placing said device at the
>focus of a dish ... why get out the tools?

Who said that it works? The ceramic patch antenna sprays RF in almost
all directions. Some of it illuminates the dish, but the rest goes
off to places where you don't want it to go (spillover). It's not too
bad for on receive, but it's hell on transmit where perhaps only 20%
of the RF coming out of the patch antenna makes it to the dish. Also,
dishes are at best 50% efficient, so we have more losses involved.
There's also no guarantee that the dish will have anywhere near the
theoretical gain defined by its aperature size (basically the diameter
of the dish sets the theoretical maximum gain). Start reading here:
http://www.w1ghz.org/antbook/contents.htm
and be sure to at least read Chapter 4 at:
http://www.w1ghz.org/antbook/chap4.pdf
which covers the basics of dish illumination.

>If you are simply soldering a pigtail to another radiator... have you gained
>anything over relying on the built in radiator (ceramic or whatever)?

I don't really understand the question. The basics are:
1. Antennas do not generate any additional signal. They only
redirect what is available.
2. Antenna gain is simply redirecting that RF in one direction, at
the expense of stealing RF that usually would go in another direction.
3. Antenna gain, efficiency, bandwidth, and beamwidth can all be
traded for each other. You don't gain in one of these, without losing
in the others. (Kinda like: good, fast, cheap...pick two).

>Would the effectiveness of the new radiator, without the can, be better than
>the inbuilt antenna?

Probably. The built in patch antenna is only slightly direction.
Shoving it inside a can which forces all the RF to spew from the mouth
of the can, instead of in all directions, is probably a net gain
assuming that there are no disgusting reflections, vswr from the
proximity of the metal can, or detuning of something on the radio. It
also assumes that the surface of the can is low loss material (RF skin
effect). Lots of assumptions, but a bit of careful construction
should yield some gain.


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831.336.2558 voice http://www.LearnByDestroying.com
# jeffl@comix.santa-cruz.ca.us
# 831.421.6491 digital_pager jeffl@cruzio.com AE6KS
Anonymous
July 8, 2004 9:55:29 AM

Archived from groups: alt.internet.wireless (More info?)

On Wed, 7 Jul 2004 19:14:42 +0000 (UTC), dold@ExternalXa.usenet.us.com
wrote:

>John Beeston <john.Beeston@talk21.com> wrote:
>> But if a similar effect can be achieved by simply placing said device at the
>> focus of a dish ... why get out the tools?

>That's a question best answered by empirical study.

Ahem. That's a question I can easily model using one of the NEC2
tools. My favorite for this month is 4NEC2 version 5.39. Methinks
TDK and others have NEC2 decks for their patch antennas (somewhere).
I can use that to simulate the feed, and illuminate the can, dish,
pizza platter, vegetable sieve, or garbage can of choice and produce a
suitable model. My extensive experience with empirical (also known as
cut-n-try or seat-of-the-pants) engineering is that it ALWAYS ends up
worse than what theory and modelling predicts.

>That's possible, even likely. You could attach a 3dBi rubber ducky in
>place of the -1dBi ceramic. (I don't know if it's -1dBi. That's what Jeff
>indicated, but I don't see a spec on the web page for the DWL-122.)

The ceramic patch antennas vary from -4dBi to +2dBi depending mostly
on physical size. The really tiny ones found on small USB radios tend
to be the lower gains. The smaller R-SMA connector antennas are just
1/2 wave coaxial antennas with a gain of about +1.5dBi (thanks to the
use of cheezy coax). The slightly longer rubber antennas found on
Linksys radios are only slightly better due to better coax.
Incidentaly, these are measurements from my antique test equpiment
pile and are subject to more errors than I care to admit. However,
methinks they're close enough for comparison purposes.

>Then you'd have something that looks like the $99 Linksys.
>http://www.linksys.com/products/product.asp?grid=33&sci...

Yep. That antenna is better than the ceramic patch antenna. I
haven't disected any of the latest USB radios yet, but I suspect that
there are pads sufficient to mount an SMA or MMCX connector in place
of the patch antenna, or simply attach a pair of 6.3cm wires to form a
dipole and keep it simple.

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831.336.2558 voice http://www.LearnByDestroying.com
# jeffl@comix.santa-cruz.ca.us
# 831.421.6491 digital_pager jeffl@cruzio.com AE6KS
Anonymous
July 12, 2004 12:38:52 PM

Archived from groups: alt.internet.wireless (More info?)

In article <apnpe09d67nkk8s6quttp9onrpkosjtdvp@4ax.com>,
jeffl@comix.santa-cruz.ca.us says...
> Yep. That antenna is better than the ceramic patch antenna. I
> haven't disected any of the latest USB radios yet, but I suspect that
> there are pads sufficient to mount an SMA or MMCX connector in place
> of the patch antenna, or simply attach a pair of 6.3cm wires to form a
> dipole and keep it simple.
>
Good discussion thread and info!
Are you saying that a "dipole" works as a dipole without a balanced
feed?
Anonymous
July 12, 2004 1:03:30 PM

Archived from groups: alt.internet.wireless (More info?)

On Mon, 12 Jul 2004 08:38:52 GMT, John S <none@none.none> wrote:

>In article <apnpe09d67nkk8s6quttp9onrpkosjtdvp@4ax.com>,
>jeffl@comix.santa-cruz.ca.us says...
> > Yep. That antenna is better than the ceramic patch antenna. I
>> haven't disected any of the latest USB radios yet, but I suspect that
>> there are pads sufficient to mount an SMA or MMCX connector in place
>> of the patch antenna, or simply attach a pair of 6.3cm wires to form a
>> dipole and keep it simple.

>Good discussion thread and info!
>Are you saying that a "dipole" works as a dipole without a balanced
>feed?

Yep. The purpose of a balun (balanced to unbalanced transformer) is
to prevent the coax cable from radiating and ruining the pattern. In
the case of the dipole attached to the USB radio, there's no coax
cable and no room for a balun. If you're thinking of attaching some
small coax cable to the board, building a dipole at the end of the
coax cable, and the perfect pattern is deemed desirable, you can get
the same effect by simply wrapping the end of the coax shield with
some lossy material. This will absorb any RF or VSWR that tries to
use the coax as a re-radiator. I've used 1/4" magnetic recording tape
for the purpose, but have never bothered to test how well it works (or
if it works in the first place). Anyway, don't worry about balanced
vs unbalanced.

Incidentally, Proxim has the antenna measurements of their popular
Gold/Silver Proxim/Orinoco/Agere/Avaya/Wavelan/Lucent card at:
http://www.proxim.com/support/all/orinoco/technotes/ant...
http://www.geocities.com/lincomatic/orinocoant.html
The interesting part is the note that the reference point in the
measurement of -26dB is equal to an antenna gain of 0dBi. Looking at
the pattern, my guess is that the measured gain varies between 0dBi
and -15dBi. (A simple dipole is +2.15dBi). And this is one of the
better performing radios...


--
Jeff Liebermann jeffl@comix.santa-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 AE6KS 831-336-2558
!