Salad Bowl USB antenna
Jeff Liebermann
http://802.11junk.com/jeffl/antennas/Salad-Dish/index.html
It's a stainless steel salad bowl, about 1 ft across.
I haven't done any real testing yet. It's sorta directional, shows
some gain, and is cheap (about $9 in parts) to make.
Punch 1 3/8" dia hole in the bottom with a Greenlee or Walsco chassis
punch. Do NOT try it with a rotary hole saw. It will grab and make a
mess. Start with a 1/8" pilot hole. Enlarge to a 3/8" hole for the
chassis punch. Then, use the 1 3/8" chassis punch.
In the hole, insert the 1" threaded to non-threaded PVC grey
electrical adapters. Do NOT use the white PVC equivalents as they use
a tapered, rather than straight, thread which is very difficult to
crank tight. The washers are 1 1/2" to 1" reducing adapters. The
flat bottom is a bit flimsy and should probably be reinforced with
something (old CDROM disk?).
The center feed extension and handle are 1" PVC pipe. Any length will
work. 3/4" pipe could have been used if the plastic case were removed
from the USB device. However, 1" will work with other dongles.
The wireless USB dongle (or Wi-Spy) is connected to a USB extension
cable and shoved into the pipe. Adjust the position so that it's
close to the focus of the dish. It's NOT a parabola, so some trial
and error will be needed. My current guess (probably wrong) puts the
USB tip at 3" above the base.
A 1/2 wave (62mm) disk should probably be installed in front of the
center pipe to block the direct path and to reflect some of the wasted
RF back to the reflector. Next revision.
--
Jeff Liebermann je...@comix.santa-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Chuck Olson
"Jeff Liebermann" <je...@comix.santa-cruz.ca.us> wrote in message
news:3tdb125cqpqjinplt...@4ax.com...
Thanks, Jeff for another educational post. You can check the focus of the
dish visually since it's highly reflective - - just put a band of colored
tape or mark a 1/2" wide colored ring with a felt tip pen on the end of the
tubing and position your eyeball about 20 ft away while someone moves the
tubing in or out until you see the widest area of that color reflected in
the dish - - your 3" is probably pretty close.
Chuck
Jeff Liebermann
>Thanks, Jeff for another educational post. You can check the focus of the
>dish visually since it's highly reflective - - just put a band of colored
>tape or mark a 1/2" wide colored ring with a felt tip pen on the end of the
>tubing and position your eyeball about 20 ft away while someone moves the
>tubing in or out until you see the widest area of that color reflected in
>the dish - - your 3" is probably pretty close.
Good idea. I'll try that later tonight (paying work cometh first).
The way I tried it was to temporarily remove the center (white) PVC
pipe and use my mini-maglite flashlight, with the reflector removed.
It simulates a hemispherical illuminator pattern similar to the
typical USB dongle. The pattern of light on the wall was interesting.
There was some semblence of a focused beam in the correct direction.
However, the steep sides of the bowl caused an annular ring to appear
to the sides. The bowl has some nasty side lobes. Ideally, the dish
should be more parabolic. However the lack of a controlled feed
illumination pattern from the USB dongle makes almost any style of
reflector a problem. I suspect a simple corner reflector, the same
size as the salad bowl, would do better.
do...@xrexxsalad.usenet.us.com
> Yet another antenna abomination.
> http://802.11junk.com/jeffl/antennas/Salad-Dish/index.html
> It's a stainless steel salad bowl, about 1 ft across.
A non-modeled abomination from Jeff?
> Punch 1 3/8" dia hole in the bottom with a Greenlee or Walsco chassis
> punch. Do NOT try it with a rotary hole saw. It will grab and make a
> mess. Start with a 1/8" pilot hole. Enlarge to a 3/8" hole for the
> chassis punch. Then, use the 1 3/8" chassis punch.
Speaketh thou from experience? tossed your salad? ;-)
> In the hole, insert the 1" threaded to non-threaded PVC grey
> electrical adapters. Do NOT use the white PVC equivalents as they use
> a tapered, rather than straight, thread
[...]
> The center feed extension and handle are 1" PVC pipe. Any length will
> work. 3/4" pipe could have been used if the plastic case were removed
> from the USB device. However, 1" will work with other dongles.
> The wireless USB dongle (or Wi-Spy) is connected to a USB extension
> cable and shoved into the pipe. Adjust the position so that it's
> close to the focus of the dish. It's NOT a parabola, so some trial
> and error will be needed. My current guess (probably wrong) puts the
> USB tip at 3" above the base.
You should be able to tell by taking the top off a mini-maglite (lantern
mode), and sliding that to the end of the pipe, and then illuminating the
widest band in the bowl.
> A 1/2 wave (62mm) disk should probably be installed in front of the
> center pipe to block the direct path and to reflect some of the wasted
> RF back to the reflector. Next revision.
That would add another tunable element. The dongle would be inside the
pipe, about 31mm from the disk, and the disk positioned 31mm past the focal
point discovered earlier.
--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8,-122.5
Jeff Liebermann
do...@XReXXSalad.usenet.us.com wrote:
>A non-modeled abomination from Jeff?
I didn't even try. I know garbage when I build it. Still, the basic
design has some merits. If not a salad bowl, perhaps a wok, colander,
or snow saucer? Eventually, I'll do a model although I know it will
be horrible.
The real problem is the hemispherical pattern of the USB wireless
dongle. It radiates in all directions roughly equally. The high f/D
ratio deep dish is idea for such a feed, but there's still
approximately half the power that radiates from the dongle that
doesn't hit the reflector. I figure an efficiency of no better than
25% with the current kludge.
>Speaketh thou from experience? tossed your salad? ;-)
Yeah. The first problem was that I my drill press didn't have
sufficient reach to drill the center hole. So, I bought a genuine ACE
Hardware 1 3/8" hole saw (made for metal) and guide drill for $19
(ouch). I stuffed it into my Milwaukee Hole Hawg, put a 4x4 under it,
and proceeded to try and drill a hole. Any semblance to a safety
hazard is purely coincidental. Instead of a hole, I managed to rip an
ugly gouge with very sharp and rough edges. I spent some time doing
the blacksmith routine on the salad bowl but eventually gave up. I
went to the hardware store, bought another salad bowl, borrowed a
proper 1 3/8" chassis punch from a machine shop, and punched the hole
quite easily.
>You should be able to tell by taking the top off a mini-maglite (lantern
>mode), and sliding that to the end of the pipe, and then illuminating the
>widest band in the bowl.
I did that. See my other post in this thread. I can't do it with the
PVC pipe attached because it's not optically transparent. So, I just
removed it and waved it around the general area. The result was odd.
I had something resembling a focused blob on the wall, which means
it's somewhat of a parabola. However, I also had an annular ring from
reflections off the steep vertical sides of the bowl. This dish is
gonna have one hell of a side lobe problem.
>That would add another tunable element. The dongle would be inside the
>pipe, about 31mm from the disk, and the disk positioned 31mm past the focal
>point discovered earlier.
Yep. That what I was going to try first. My guess is that the 1/2
wave (62mm) diameter reflector will need to be considerably closer to
the USB dongle than 1/4 wave. Something like this:
http://802.11junk.com/jeffl/antennas/HandHeld/index.html
but with a dish instead of a flat plate reflector.
--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558 je...@comix.santa-cruz.ca.us
# http://802.11junk.com je...@cruzio.com
# http://www.LearnByDestroying.com AE6KS
frankd...@gmail.com
where is the dongle located ?
would it help if the dongle was held out in front of some type of
refector such as in the Primestar wi fi dish antenna setup ?
http://www.wwc.edu/~frohro/Airport/Primestar/Primestar.html
Jeff Liebermann
> where is the dongle located ?
Shoved up the center tube from the back of the salad bowl.
> would it help if the dongle was held out in front of some type of
>refector such as in the Primestar wi fi dish antenna setup ?
>http://www.wwc.edu/~frohro/Airport/Primestar/Primestar.html
I don't think so. A reflector of some sorts needs to be installed in
front. However, if it were a can, the illumination angle would be
perhaps 60 degress, which would be insufficient to illuminate the
entire dish. Also, because the focus is only about 3" from the base,
there's no room for a proper can (waveguide) feed.
do...@xrexxsalad.usenet.us.com
> On Mon, 13 Mar 2006 21:16:04 +0000 (UTC),
> do...@XReXXSalad.usenet.us.com wrote:
> >A non-modeled abomination from Jeff?
> I didn't even try. I know garbage when I build it. Still, the basic
> design has some merits. If not a salad bowl, perhaps a wok, colander,
> or snow saucer? Eventually, I'll do a model although I know it will
> be horrible.
If you use a wok, you'll then be required to post your pic on the New
Zealand site, which is filled with unmodeled abominations, some of which,
one would think, _can't_ work, like the tuna fish can. ;-)
http://www.usbwifi.orcon.net.nz/
They really enjoy the wok reflectors. You've added a good tuning mechanism
and a much sturdier support.
They have soft clamps held by c-clamps at the edge of the dish, poking in
the right general vicinity. http://www.usbwifi.orcon.net.nz/68.jpg
And they claim to have found a wok that is parabolic. That one has a
sturdier mount through the back.
> >You should be able to tell by taking the top off a mini-maglite (lantern
> >mode), and sliding that to the end of the pipe, and then illuminating the
> >widest band in the bowl.
> I did that. See my other post in this thread. I can't do it with the
> PVC pipe attached because it's not optically transparent. So, I just
> removed it and waved it around the general area.
The other post wasn't there when I started typing, and I saw it as soon as
I finished posting ;-(
I was thinking of the maglite tip sticking out the end of the PVC a little,
just to find the proper depth, and then readjusting the PVC to cover the
spot you had just identified.
Now here's an application for me:
http://www.usbwifi.orcon.net.nz/cellbear.jpg
mi...@sushi.com
dish. I got two dishes for about $50 with shipping on ebay. I'm sure if
you had connections, the price would be free.
do...@xrexxsalad.usenet.us.com
> There is a break even point where you are better off just buying an old
> dish. I got two dishes for about $50 with shipping on ebay. I'm sure if
> you had connections, the price would be free.
There's a house near here that has a PrimeStar dish on the side of the
house. The feedhorn is gone, but the dish is still there.
Not sure why. Since PrimeStar is long since gone, most of the dishes are
on rooftops because of lack of effort on the part of the occupant.
Those are larger and bulkier that Jeff's salad bowl, though.
The salad bowl probably cost $3.49.
Rico
>Yet another antenna abomination.
> http://802.11junk.com/jeffl/antennas/Salad-Dish/index.html
>It's a stainless steel salad bowl, about 1 ft across.
Now that's a big salad. Given a yound niece of mine, I can understand why
you might have such a bowl laying around unused. She (age 3) won't eat
veggies for anything.
>
>I haven't done any real testing yet. It's sorta directional, shows
>some gain, and is cheap (about $9 in parts) to make.
>
>Punch 1 3/8" dia hole in the bottom with a Greenlee or Walsco chassis
>punch. Do NOT try it with a rotary hole saw. It will grab and make a
>mess. Start with a 1/8" pilot hole. Enlarge to a 3/8" hole for the
>chassis punch. Then, use the 1 3/8" chassis punch.
>
>In the hole, insert the 1" threaded to non-threaded PVC grey
>electrical adapters. Do NOT use the white PVC equivalents as they use
>a tapered, rather than straight, thread which is very difficult to
>crank tight. The washers are 1 1/2" to 1" reducing adapters. The
>flat bottom is a bit flimsy and should probably be reinforced with
>something (old CDROM disk?).
>
>The center feed extension and handle are 1" PVC pipe. Any length will
>work. 3/4" pipe could have been used if the plastic case were removed
>from the USB device. However, 1" will work with other dongles.
>
>The wireless USB dongle (or Wi-Spy) is connected to a USB extension
>cable and shoved into the pipe. Adjust the position so that it's
>close to the focus of the dish. It's NOT a parabola, so some trial
>and error will be needed. My current guess (probably wrong) puts the
>USB tip at 3" above the base.
>
>A 1/2 wave (62mm) disk should probably be installed in front of the
>center pipe to block the direct path and to reflect some of the wasted
>RF back to the reflector. Next revision.
>
Cool, thanks for the idea.
fundamentalism, fundamentally wrong.
mi...@sushi.com
connection on homes too. I've never bothered to knock on a door and
offer to remove one, but that would be a plan if you want to do it on
the cheap.
http://www.lazygranch.com/images/ttr/brock/starband3.jpg
I found this old Starband on a hill in the Nevada desert. I suppose I
could have relieved them of it, but who knows if it is some project in
the works. In any event, the dishes are pretty cheap on the used
market. This particular site had microflects on it, so maybe the
starband as a poor mans reflector.
images/ttr/brock/reflectors.jpg
I've built some biquad antennas. Quite a bang for the buck, and very
simple.
Jeff Liebermann
>There is a break even point where you are better off just buying an old
>dish. I got two dishes for about $50 with shipping on ebay. I'm sure if
>you had connections, the price would be free.
Methinks I forgot to mention why I used a salad bowl and plastic pipe
instead of similar sized dish, such as an 18" pizza dish. The idea
was to provide some gain and directionality for a USB dongle or Wi-Spy
spectrum analyzer without butchering the dongle by adding a pigail or
SMA connector.
The problem is that the USB dongles antenna pattern is roughly
hemispherical (equal signal strength in all directions). With a
fairly flat (small f/D ratio) dish, such as an 18" DBS dish, only a
small part of the RF coming from the USB adapter hits the dish and is
reflected in the desired direction. The rest goes off in useless
directions. I worked out the numbers in a previous posting to
alt.internet.wireless, but am too lazy to find it again.
The deep dish salad bowl is slightly better. My guess is about 40% of
the RF coming from the USB dongle hits the dish. With an added
reflector in front of the USB dongle, this might be improved to
perhaps 50%. Not bad for $9 in parts and only one big hole to drill.
The right way to do this would be to attach a connector or pigtail to
the USB dongle and build a proper antenna. However, I wasn't looking
for the right way, just the cheapest and easiest.
Primestar dish with a Pacific Wireless feed:
http://802.11junk.com/jeffl/antennas/Misc/slides/primestar.html
Yet another nice biquad construction article:
http://www.vallstedt-networks.de/?Fotogalerien/quad2
Dish with biquad feed:
http://www.weijand.nl/wifi/
stan...@gmail.com
ideas at => www.usbwifi.orcon.net.nz . These arose 2004 as a student
project & have since been outstandingly well received ( site has ~ 3/4
million visitors at ~ 1000 daily), with numerous global success
stories. We highly recommend the ~15dB boutique version for both
function & form => www.usbwifi.orcon.net.nz/btique.jpg , BUT the ~ 9dB
"bendy plastic" appraach => www.usbwifi.orcon.net.nz/plaspara.jpg is a
breeze to organise & costs peanuts. Stainless steel salad bowls are
better used for culinary purposes!
In all cases it's almost ESSENTIAL to use Netstumbler on a laptop ( or
WiFoFoFum on a WiFi PDA) to do a signal audit & allow anntena tweaking
& "sweet spot" positioning.
A key part of the project was to allow WiFi to be used in "$1 a day"
countries - hence the POORMAN title. Stan
Jeff Liebermann
>Greetings form sunny New Zealand! Yes- guilty as charged with our WokFi
>ideas at => www.usbwifi.orcon.net.nz . These arose 2004 as a student
>project & have since been outstandingly well received ( site has ~ 3/4
>million visitors at ~ 1000 daily), with numerous global success
>stories.
Nicely done. I'm probably one of those visitors. As you seem to have
a monopoly on antennas made from cooking utensils, I made sure I
wasn't copying one of your ideas.
>We highly recommend the ~15dB boutique version for both
>function & form => www.usbwifi.orcon.net.nz/btique.jpg , BUT the ~ 9dB
>"bendy plastic" appraach => www.usbwifi.orcon.net.nz/plaspara.jpg is a
>breeze to organise & costs peanuts. Stainless steel salad bowls are
>better used for culinary purposes!
Ah, but the salad bowl construction includes a handle and USB mounting
contrivance in the basic design. Although the gain is probably less
than your boutique vegetable washer version, the construction is much
simpler and does not require cannibalizing a desk lamp for a mounting.
I'll do some gain measurements when it stops raining.
>In all cases it's almost ESSENTIAL to use Netstumbler on a laptop ( or
>WiFoFoFum on a WiFi PDA) to do a signal audit & allow anntena tweaking
>& "sweet spot" positioning.
Agreed. For the salad bowl design, the primary purpose was to provide
some added gain and directionality for the Wi-Spy spectrum analyzer.
http://www.metageek.net
It has a built in level meter with a much faster response than
Netstumbler. However, I'm not so certain that either the USB dongle
of the converted wireless mouse receiver used in Wi-Spy are anywhere
near accurate. They both convert a 0-255 RSSI count to dBm using some
manner of lookup table. I'll try to make some measurements and see
what happens.
>A key part of the project was to allow WiFi to be used in "$1 a day"
>countries - hence the POORMAN title. Stan
Well, if cheap is what you want, permit me to suggest a slight
modification. Cease looking for a parbolic dish and just use a flat
plate reflector. The difference in gain between a parabola and flat
plate of identical size in quite small. The arguement over the
Hawking small dish antenna gain versus a flat disk reflector resulted
in some calcs at:
Hawking Dish
| http://802.11junk.com/jeffl/antennas/HawkDish08/index.html
Same thing with flat plate reflector:
| http://802.11junk.com/jeffl/antennas/FullWavePlateReflector/index.html
7.7dBi for the dish. 8.3dBi for the flat plate. With small antennas
(i.e. reflectors about 1 wavelength diameter), a flat plate actually
has slightly more gain than a dish.
do...@xrexxsalad.usenet.us.com
I love the experiment and go site, with so many possibilities and attempts.
Some are a little goofy, like the tuna can, but the CD cover is new to
me... which gives rise to my only complaint with the site.
The opening page has little tiny jpg images that I can't resolve, and
clicking through each is tedious, unless I realize that one of them is new.
The btique is a perfect example. That is cute, but there's no reference to
the building details, although I recall having seen them on an earlier
browse through the images.
Are the images arranged by date? Why isn't there at least a comment for
each one? Why did you chose jpg images instead of pages with text and
images?
That CDROM cover seems pitched at less than a 90 degree angle. Is there
experimental detail on that? If I make one of those, I would be inclined
to have a fold-down flap with the FP noted, and cut at the right shape to
mark the proper opening angle.
stan...@gmail.com
site just evolved from our "work in progress/lab notes", & was
originally intended just to keep class members attuned to each others
efforts. We'd considered a total revamp, & may well yet do so, but
significant issue were
1. Hosting - presently still with a free NZ host (Orcon), which gives
super fast access within NZ . Now many mirrors of course
2. Appreciation of non English speaking/reading users
3. Appreciation of VERY basic PC gear in many "$1 a day" countries
precluding media rich info.
Asian scoops are in fact usually cheaper than a similar
Aluminium/Stainless bowl or metal sheet in many countries, & certainly
offer less wind resistance. They're neater too of course, & their use
I confess appealed greatly to our Kiwi sense of humour! Stan