Salad Bowl USB antenna

Yet another antenna abomination.
http://802.11junk.com/jeffl/antennas...ish/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 (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

"Jeff Liebermann" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Yet another antenna abomination.
> http://802.11junk.com/jeffl/antennas...ish/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 (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

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

"Chuck Olson" <(E-Mail Removed)> hath wroth:

>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.

--
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

Jeff Liebermann <(E-Mail Removed)> wrote:
> Yet another antenna abomination.
> http://802.11junk.com/jeffl/antennas...ish/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

On Mon, 13 Mar 2006 21:16:04 +0000 (UTC),
(E-Mail Removed) 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...eld/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 (E-Mail Removed)
# http://802.11junk.com (E-Mail Removed)
# http://www.LearnByDestroying.com AE6KS

Jeff,

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/P...Primestar.html


Jeff Liebermann wrote:
> On Mon, 13 Mar 2006 21:16:04 +0000 (UTC),
> (E-Mail Removed) 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...eld/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 (E-Mail Removed)
> # http://802.11junk.com (E-Mail Removed)
> # http://www.LearnByDestroying.com AE6KS

On 13 Mar 2006 21:33:56 -0800, (E-Mail Removed) wrote:

> 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/P...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.

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

Jeff Liebermann <(E-Mail Removed)> wrote:
> On Mon, 13 Mar 2006 21:16:04 +0000 (UTC),
> (E-Mail Removed) 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


--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8,-122.5

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.


Jeff Liebermann wrote:
> Yet another antenna abomination.
> http://802.11junk.com/jeffl/antennas...ish/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 (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

(E-Mail Removed) wrote:
> 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.

--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8,-122.5