Homemade Antenna Choice, Jeff, et al, can you give me your best guess?

Jeff, can you please give me your best guess on which of
these home-to-be-built antennas is likely to yield the
highest gain using a linksys usb dongle -have two to choose
from WSUB100 Range Plus or USB54GSC (which is better?). Will
be used under multiple OS's both windows 7, XP; Linux These
radios are quite large like 3-4 inches in length, what is the
location of the pickup point for signals under the case? If
you don't have time, the most important questions are the
antenna ones.


Antenna 1(A1): kitchen collander with fine "screendoor" mesh
(deeper curve than true parabola ), 27cm diameter 11 depth ;
focal point at 4.14cm Dongle will be attached through fitted
hole in center of the "dish" or possibly attached to wooden
dowel also attached through hole in center of "dish" to allow
for focal point adjustment.


Antenna 2(A2): Umbrella size 86cm dia. ; 18.4 cm deep ;
focal point 25 cm with aluminum foil glued to top of umbrella
with some loss?? (how much? )from metal struts that support
umbrella shape. Also some loss from metal center post of
umbrella which extends just enough to hold wood or plastic
dowel to hold the usb dongle. This is also not a true
parabola but much shallower in curve than Antenna 1.

Other factors to consider: wire mesh A1 vs mostly solid alum
foil A2, shallowized parabola vs deepened parabola, metal
pole in center of A1 vs no metal pole in A2

Also additional question is Mylar-the kind you see in metal
baloons any better than heavy gauge alum foil for this, or
does not matter?

I have not built either of these yet awaiting input from this
group. Which one should I build and why?

Thanks for any on topic useful replies.

On Tue, 1 Nov 2011 20:10:39 +0000 (UTC), Foxybaby
<(E-Mail Removed)> wrote:

>Jeff, can you please give me your best guess on which of
>these home-to-be-built antennas is likely to yield the
>highest gain using a linksys usb dongle -have two to choose
>from WSUB100 Range Plus or USB54GSC (which is better?).

I avoid using USB dongles unless they have an external antenna
connector. Neither of the two you've mentioned has an external
antenna connector. I have no idea which of the two is "better" since
I've never used either.

The problem with putting a reflector behind a USB dongles is that
you'll get different gains between xmit and receive. In receive, the
reflector picks up the aperature area of the dish and sends alost all
of it to the USB dongle. However, in transmit, the USB dongle sprays
RF in every direction, including directions where it misses the
reflector. This RF is lost, going to places unknown. I ran through
the calcs in a previous rant, but am too lazy to find it right now.
Bug me if you want numbers. As I vaguely recall, there was about a
10dB difference between xmit and receive. See dish illumination
issues under:
<http://www.w1ghz.org/antbook/contents.htm>
<http://www.w1ghz.org/antbook/chap6-0.pdf> (see spillover).

Methinks you'll be better off with a wireless client bridge, which
talks to the computer via ethernet, and usually has an external
antenna. The nice feature of this arragement is that it will work
with any OS that talks ethernet and that there are no flaky USB
drivers to deal with.

>Will
>be used under multiple OS's both windows 7, XP; Linux

I haven't checked, but I've had "issues" with USB dongles under Linux
in the past. Make sure it's well supported before buying.

>These
>radios are quite large like 3-4 inches in length, what is the
>location of the pickup point for signals under the case?

It's usually on the pointed end opposite the USB connector.
Something like this:
<http://802.11junk.com/jeffl/pics/wireless/DWL-122/index.html>

>If
>you don't have time, the most important questions are the
>antenna ones.

I'm always busy, never have time, and am lazy.

>Antenna 1(A1): kitchen collander with fine "screendoor" mesh
>(deeper curve than true parabola ), 27cm diameter 11 depth ;
>focal point at 4.14cm Dongle will be attached through fitted
>hole in center of the "dish" or possibly attached to wooden
>dowel also attached through hole in center of "dish" to allow
>for focal point adjustment.

I prefer my veggies raw instead of steamed.
<http://802.11junk.com/jeffl/antennas/Salad-Dish/index.html>
Like the above salad bowl, the colander is closer to a sphere than a
parabola. The result can be seen with the shiny bowl and a light as a
ring of light. No energy in the middle, along the center axis, then a
ring with all the power, After the ring, nothing. It's nowhere near a
point, so therefore, lousy gain.

>Antenna 2(A2): Umbrella size 86cm dia. ; 18.4 cm deep ;
>focal point 25 cm with aluminum foil glued to top of umbrella
>with some loss?? (how much? )from metal struts that support
>umbrella shape. Also some loss from metal center post of
>umbrella which extends just enough to hold wood or plastic
>dowel to hold the usb dongle. This is also not a true
>parabola but much shallower in curve than Antenna 1.

Much better. If you can get it close to a parabola, you'll have a
fine receive antenna, and a lousy transmit antenna due to reasons
previously mentioned. The struts will have little effect if they're
reasonably thin. If the wood is dry, there's little attenuation.

>Other factors to consider: wire mesh A1 vs mostly solid alum
>foil A2, shallowized parabola vs deepened parabola, metal
>pole in center of A1 vs no metal pole in A2

I don't understand the question.

>Also additional question is Mylar-the kind you see in metal
>baloons any better than heavy gauge alum foil for this, or
>does not matter?

RF travels on the surface of conductors. At 2.4GHz, the skin depth is
much smaller than the aluminized mylar plating. Making the aluminum
layer any thicker just adds weight and does nothing for gain. Try the
same plating thickness at lower RF frequencies and it won't work.

>I have not built either of these yet awaiting input from this
>group. Which one should I build and why?

What are you trying to accomplish? Why are you using a USB dongle?

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com (E-Mail Removed)
# http://www.LearnByDestroying.com AE6KS

> http://www.data-alliance.net/-strse-...USB/Detail.bok

While I agree with Jeff that USB sucks, this is a decent USB wifi
dongle. The antenna is external via reverse SMA. It is quite cheap
through Data Alliance and these guys ship fast. I got this one and the N
version, though the 036H is the better long distance unit.

While it's fun to build antennas, there are some cheap wifi antennas
that are pretty good. Try the Laird PA24-16. The radiation pattern
doesn't have a lot of lobes. It is about $35 if you look around.

I built the wifi biquad a few years ago for yucks. It worked OK. There
are some tips on this list on how to build it since many of the websites
do it incorrectly.

I like these panel antennas. They are easy to transport. All the
elements are under a radome, so other than water infiltration problems,
they are well suited for outdoors. Avoid units that come with a pigtail.
It is better to have a connector on the back.

Given construction tolerances, antennas that depend upon aperture rather
than elements re-radiating the signal will work better. That is, a yagi
looks good on paper, but a lot depends on how tightly all the dimensions
are controlled. These panel antennas just sum a lot of smaller antennas,
so the bandwidth is broader and the design is more tolerant to
manufacturing tolerances. Some of these panel antenna are air isolated,
and some are just etched PCB. I would imaging the antenna with air
spacing works better, though I don't know if there is a list of how who
builds what.

Jeff Liebermann <(E-Mail Removed)> wrote in
news:(E-Mail Removed):

>On Tue, 1 Nov 2011 20:10:39 +0000 (UTC), Foxybaby
><(E-Mail Removed)> wrote:
>
>>Jeff, can you please give me your best guess on which of
>>these home-to-be-built antennas is likely to yield the
>>highest gain using a linksys usb dongle -have two to choose
>>from WSUB100 Range Plus or USB54GSC (which is better?).
>
>I avoid using USB dongles unless they have an external
>antenna connector. Neither of the two you've mentioned has
>an external antenna connector. I have no idea which of the
>two is "better" since I've never used either.

Thanks much for your reply.
I don't have a choice, money is tight and I got these two at
an estate sale for $1 each.

>
>The problem with putting a reflector behind a USB dongles is
>that you'll get different gains between xmit and receive.
>In receive, the reflector picks up the aperature area of the
>dish and sends alost all of it to the USB dongle. However,
>in transmit, the USB dongle sprays RF in every direction,
>including directions where it misses the reflector. This RF
>is lost, going to places unknown. I ran through the calcs
>in a previous rant, but am too lazy to find it right now.
>Bug me if you want numbers. As I vaguely recall, there was
>about a 10dB difference between xmit and receive. See dish
>illumination issues under:
><http://www.w1ghz.org/antbook/contents.htm>
><http://www.w1ghz.org/antbook/chap6-0.pdf> (see spillover).

Did not know that. Read one source that said a deeper curve
than parabola will attenuate some of the x-mit losses?

<snip for newserver requirements>

>>Will
>>be used under multiple OS's both windows 7, XP; Linux
>
>I haven't checked, but I've had "issues" with USB dongles
>under Linux in the past. Make sure it's well supported
>before buying.
>
>>These
>>radios are quite large like 3-4 inches in length, what is
>>the location of the pickup point for signals under the
>>case?
>
>It's usually on the pointed end opposite the USB connector.
>Something like this:
><http://802.11junk.com/jeffl/pics/wir...122/index.html
>>
>
>>If
>>you don't have time, the most important questions are the
>>antenna ones.
>
>I'm always busy, never have time, and am lazy.

Haha, you're not lazy far as I can tell

>
>>Antenna 1(A1): kitchen collander with fine "screendoor"
>>mesh (deeper curve than true parabola ), 27cm diameter 11
>>depth ; focal point at 4.14cm Dongle will be attached
>>through fitted hole in center of the "dish" or possibly
>>attached to wooden dowel also attached through hole in
>>center of "dish" to allow for focal point adjustment.
>
>I prefer my veggies raw instead of steamed.
><http://802.11junk.com/jeffl/antennas/Salad-Dish/index.html>
>Like the above salad bowl, the colander is closer to a
>sphere than a parabola. The result can be seen with the
>shiny bowl and a light as a ring of light. No energy in the
>middle, along the center axis, then a ring with all the
>power, After the ring, nothing. It's nowhere near a point,
>so therefore, lousy gain.
>
>>Antenna 2(A2): Umbrella size 86cm dia. ; 18.4 cm deep ;
>>focal point 25 cm with aluminum foil glued to top of
>>umbrella with some loss?? (how much? )from metal struts
>>that support umbrella shape. Also some loss from metal
>>center post of umbrella which extends just enough to hold
>>wood or plastic dowel to hold the usb dongle. This is also
>>not a true parabola but much shallower in curve than
>>Antenna 1.
>
>Much better. If you can get it close to a parabola, you'll
>have a fine receive antenna, and a lousy transmit antenna
>due to reasons previously mentioned. The struts will have
>little effect if they're reasonably thin. If the wood is
>dry, there's little attenuation.
>
>>Other factors to consider: wire mesh A1 vs mostly solid
>>alum foil A2, shallowized parabola vs deepened parabola,
>>metal pole in center of A1 vs no metal pole in A2
>
>I don't understand the question.

I mean the backing on the umbrella will be mostly continuous
alum foil., whereas backing on the collander is mesh with
holes. Also umbrella has metal pole in center that I will cut
partially but there will still be a metal post at the center,
so losses from that, probably minimal.

>
>>Also additional question is Mylar-the kind you see in metal
>>baloons any better than heavy gauge alum foil for this, or
>>does not matter?
>
>RF travels on the surface of conductors. At 2.4GHz, the
>skin depth is much smaller than the aluminized mylar
>plating. Making the aluminum layer any thicker just adds
>weight and does nothing for gain. Try the same plating
>thickness at lower RF frequencies and it won't work.

I guess I don't have to worry about removing the thin nylon of
the umbrella as the waves will go right through it and reflect
on the foil on the other side, right?

>
>>I have not built either of these yet awaiting input from
>>this group. Which one should I build and why?
>
>What are you trying to accomplish? Why are you using a USB
>dongle?

Just trying to get any reasonable surfing connection to a
hotspot. I have another old computer running xp with an alfa
radio and half parabola behind it (quite large) that is
getting me about 100kb/s on what I think (but do not know) is
a pretty distant AP, not sure exactly who owns it
specifically, but they leave it wide open, I think it's a
major COM company.

I just tried a flood lite reflector about the same size and
shape as the collander and it's not strong enough only getting
1-2 bars, 86 reading on Inssider. BTW just started using
Inssider, cuz heard Netstumber does not work under Win7. I
don't like the readout on Inssider-too hard to read from a
distance for positioning of the antenna, unlike Netstumbler
which gives a very clear graphical readout from a distance
(maybe u can switch to graph view on Inssidder?)

The Alfa AWUS036H I suggested is Linux compatible. Kismet as well.
Granted $25 can't compete with $1, but the unit works well.

I really think you can't skimp on the usb dongle. I suppose you can save
some money rolling your own antenna if you have more time than money, or
you just want the experience.

> http://martybugs.net/wireless/biquad/

This is probably the best page for biquad construction. Per Jeff's
suggestion, I used round loops rather than squares. The deal is you need
the proper circumference. The shape isn't as important, and it is easier
to get the circumference correct with a round loop. Marty does the
construction properly by using a coaxial feed. Jeff ran NEC2 on the
other scheme and it had a funny radiating pattern.

The reflector doesn't have to be copper, but soldering to anything else
is a lot of work. In fact, soldering to heavy copper clad isn't all that
easy unless you have a high wattage soldering iron or you have a small
propane torch. Building your own antenna is cheap IF you already own the
tools or have access to them. Otherwise you are buying hacksaws, copper
pipe, etc.

You can use the biquad to feed a dish for more gain. You can often get a
dish for free on Craigslist. The Dish or Direct TV dishes probably are
too small to be useful since the dish doesn't see the all the RF from
the biquad. You can get larger 24x36 elliptical dishes for free if you
stake out Craigslist.

A bit harder to find are the old MDS antennas that were sold for
"wireless cable". They use a parabolic reflector.

All that said, the Laird PA241-16 antenna I suggested is far less work,
and the difference between off the shelf and home built might be $10
when the dust settles.

miso <(E-Mail Removed)> wrote in
news:j8q7t4$lg$(E-Mail Removed):

>> http://www.data-alliance.net/-strse-...WUS036H-1000mW
>> -USB/Detail.bok
>
>While I agree with Jeff that USB sucks, this is a decent USB
>wifi dongle. The antenna is external via reverse SMA. It is
>quite cheap through Data Alliance and these guys ship fast.
>I got this one and the N version, though the 036H is the
>better long distance unit.
>
>While it's fun to build antennas, there are some cheap wifi
>antennas that are pretty good. Try the Laird PA24-16. The
>radiation pattern doesn't have a lot of lobes. It is about
>$35 if you look around.
>
>I built the wifi biquad a few years ago for yucks. It worked
>OK. There are some tips on this list on how to build it
>since many of the websites do it incorrectly.
>
>I like these panel antennas. They are easy to transport. All
>the elements are under a radome, so other than water
>infiltration problems, they are well suited for outdoors.
>Avoid units that come with a pigtail. It is better to have a
>connector on the back.
>
>Given construction tolerances, antennas that depend upon
>aperture rather than elements re-radiating the signal will
>work better. That is, a yagi looks good on paper, but a lot
>depends on how tightly all the dimensions are controlled.
>These panel antennas just sum a lot of smaller antennas, so
>the bandwidth is broader and the design is more tolerant to
>manufacturing tolerances. Some of these panel antenna are
>air isolated, and some are just etched PCB. I would imaging
>the antenna with air spacing works better, though I don't
>know if there is a list of how who builds what.
>

Read too many complaints about that outfit you mention,
located on the Mexico border. If you buy wifi equipment stick
with suppliers that guarantee and test their products:

http://www.wirelessforums.org/alt-in...reless/review-
suppliers-some-good-ones-some-lemons-wifi-radios-68636.html

On Wed, 2 Nov 2011 04:05:47 +0000 (UTC), Foxybaby
<(E-Mail Removed)> wrote:

>I don't have a choice, money is tight and I got these two at
>an estate sale for $1 each.

Good price. Hopefully, they'll work.

>Did not know that. Read one source that said a deeper curve
>than parabola will attenuate some of the x-mit losses?

Yes, but within limits. Visualize your USB dongle at the focus of a
parabolic antenna. If the f/D (focal length divided by Diameter)
ratio is large, you have a shallow dish, with the USB dongle well
above the reflector surface. the result is that the dish only
collects a small part of the RF belched by the USB dongle. However,
if the f/D is small, you have a deep dish, where the dongle is located
deep into the dish. More of the RF it belches is collected by the
reflector. However, there's a limit. Let's pretend that the dongle
is in line with the edge of the dish. Half of the RF belched by the
dongle hits the dish, and the other half goes off in useless
directions. So, even with such a dish, you have a 3dB difference
between tx and rx. The steep sides of the deep dish also don't
contribute much to the gain of the antenna. So, the gain actually
drops as the f/D decreases. There's an optimum value of f/D. See the
graph at:
<http://www.antenna-theory.com/antennas/reflectors/dish3.php>

Since you're cost limited, I suggest you try one of these:
<http://www.freeantennas.com>
Cardboard, covered with aluminum foil, works well enough.

Also, note that it's fairly easy to build an antenna with gain up to
about 8-10dBi. Any more gain and the construction tolerances become
more than what you can do with cardboard, baleing wire, and duct tape.

>I mean the backing on the umbrella will be mostly continuous
>alum foil., whereas backing on the collander is mesh with
>holes. Also umbrella has metal pole in center that I will cut
>partially but there will still be a metal post at the center,
>so losses from that, probably minimal.

The holes in the colander are too small to have any effect. The
non-parabolic pattern will cause some gain loss. The marginal
parabolic shape of the umbrella, as aggrivated by the non-parabolic
shape of the foil between the umbrella ribs will cause some gain loss.
I'm not interested in modeling either design.

>I guess I don't have to worry about removing the thin nylon of
>the umbrella as the waves will go right through it and reflect
>on the foil on the other side, right?

I think the nylon is RF transparent. However, if it's been painted or
silk screened with something containing carbon or metallic powder,
you'll have a problem. Find a small piece and put it in the microwave
oven. If it gets hot, you loose. If it says cool, you win.

>Just trying to get any reasonable surfing connection to a
>hotspot.

Ummm... I'm not really interested in helping you do that, especially
since it seems you haven't obtained permission.

>BTW just started using
>Inssider, cuz heard Netstumber does not work under Win7.

Nestumbler is ancient and has not been updated for about 5 years.
Inssider is a good replacement. There are others. Bug me if you need
a list.

--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On 11/1/2011 10:05 PM, arnie wrote:
> miso<(E-Mail Removed)> wrote in
> news:j8q7t4$lg$(E-Mail Removed):
>
>>> http://www.data-alliance.net/-strse-...WUS036H-1000mW
>>> -USB/Detail.bok
>>
>> While I agree with Jeff that USB sucks, this is a decent USB
>> wifi dongle. The antenna is external via reverse SMA. It is
>> quite cheap through Data Alliance and these guys ship fast.
>> I got this one and the N version, though the 036H is the
>> better long distance unit.
>>
>> While it's fun to build antennas, there are some cheap wifi
>> antennas that are pretty good. Try the Laird PA24-16. The
>> radiation pattern doesn't have a lot of lobes. It is about
>> $35 if you look around.
>>
>> I built the wifi biquad a few years ago for yucks. It worked
>> OK. There are some tips on this list on how to build it
>> since many of the websites do it incorrectly.
>>
>> I like these panel antennas. They are easy to transport. All
>> the elements are under a radome, so other than water
>> infiltration problems, they are well suited for outdoors.
>> Avoid units that come with a pigtail. It is better to have a
>> connector on the back.
>>
>> Given construction tolerances, antennas that depend upon
>> aperture rather than elements re-radiating the signal will
>> work better. That is, a yagi looks good on paper, but a lot
>> depends on how tightly all the dimensions are controlled.
>> These panel antennas just sum a lot of smaller antennas, so
>> the bandwidth is broader and the design is more tolerant to
>> manufacturing tolerances. Some of these panel antenna are
>> air isolated, and some are just etched PCB. I would imaging
>> the antenna with air spacing works better, though I don't
>> know if there is a list of how who builds what.
>>
>
> Read too many complaints about that outfit you mention,
> located on the Mexico border. If you buy wifi equipment stick
> with suppliers that guarantee and test their products:
>
> http://www.wirelessforums.org/alt-in...reless/review-
> suppliers-some-good-ones-some-lemons-wifi-radios-68636.html
Yeah, you complained the last time I mentioned Data Alliance. Hey, two
orders, no problems. I order at night, it is shipped in the morning, and
I get the item in 2 day. I should be so lucky with most vendors.

I suspect you are fronting for the competition.

OK, so they are only A when top of the line is A+.
> http://www.bbb.org/tucson/business-r...es-az-20025847

Do you have some problem with Mexicans?

>> What are you trying to accomplish? Why are you using a USB
>> dongle?

I have opened a couple of dongles, cut the antenna foil and installed an
N connector. You need to plan mechanical support for the N connector,
but they both worked better than anything I had. Now I have an Alfa
AWUS036H and it works better than the inexpensive dongles I modified.
At one time I connected a modified dongle directly to the MFJ Yagi
and ran a USB cord into my boat. That worked well for a couple of years.
Mikek

The AWUS036H is magic.