I would like to build a cantenna that uses a usb adapter as the active
element so that I can avoid the problem of losses in a long run of
coax cable and just use cat5 instead. But I haven't been able to find
much info on best dimensions and usb adapter placement within the can.
What is the best diameter can and how long should it be? Should the
usb adapter poke through the back of the can in the middle or into the
side of the can like in a regular cantenna? If through the side, how
far from the back of the can?
I plan to use an inexpensive Zonet ZEW2501 usb adapter.
Has anyone built something similar and how did it perform?
bjs555 <aaa@bbb.com> wrote:
> I would like to build a cantenna that uses a usb adapter as the active
> element so that I can avoid the problem of losses in a long run of
> coax cable and just use cat5 instead. But I haven't been able to find
Are you talking about a game adapter at the end of cat 5, or a USB dongle
at the end of USB cable? cat 5 can go a lot farther. The USB should go 5
meters without an active repeater.
A friend was using a 6" diameter coffee can, which I found to have lower
gain than the 4" diameter two coffee can setup, but the larger can was
easier to point at an access point about two blocks away.
On Wed, 21 Sep 2005 22:53:42 -0400, bjs555 <aaa@bbb.com> wrote:
>I would like to build a cantenna that uses a usb adapter as the active
>element so that I can avoid the problem of losses in a long run of
>coax cable and just use cat5 instead. But I haven't been able to find
>much info on best dimensions and usb adapter placement within the can.
>What is the best diameter can and how long should it be? Should the
>usb adapter poke through the back of the can in the middle or into the
>side of the can like in a regular cantenna? If through the side, how
>far from the back of the can?
>
>I plan to use an inexpensive Zonet ZEW2501 usb adapter.
>
>Has anyone built something similar and how did it perform?
>
>Thanks for any help.
A simple USB directional unit I made on the below page.
Thank you both for the info and links. What I have in mind is the same
as Clarence Dold's coffee can. I want to use a USB dongle. But he
doesn't give any dimensions or formulas for determining them on his
page. I suppose I could just experiment some but I'd prefer to have a
calculated starting point. What kind of antennas do the dongles use?
Are there different types? Is there a way to solder a pigtail onto a
dongle?
Well, just reread your reply and I see that you are in fact Clarence
Dold and that you used the formulas in another link you gave to decide
where to poke the hole.
bjs555 <aaa@bbb.com> wrote:
> Thank you both for the info and links. What I have in mind is the same
> as Clarence Dold's coffee can. I want to use a USB dongle. But he
> doesn't give any dimensions or formulas for determining them on his
My coffee cans are 4" inside diameter. Plug that in to the turnpoint
calculator, and it will tell you that a wire radiator should be 1.7 inches
from the closed end of the can (measure inside). I made the assumption
that a USB dongle antenna should be at that same point.
The other dimension of interest is the length of the antenna element inside
the can. If I were putting the USB dongle in front of a simple reflector,
I would want it 31mm from the reflector. This suggests that the antenna
element of the dongle should be 31mm away from the wall of the can. The
antenna is at the tip of the dongle. Simply inserting the dongle inside
the can is conveniently near that dimension.
Here are some of the cans that I tried. I liked two 12 oz. Yuban cans the
best, but my friend likes the 3lb Yuban can, because it's easier to point.
According to the calculator, the 3lb can would be more efficient at
frequencies below the 2400 MHz of WiFi, but it works well for him.
The 12oz is even too large, but I couldn't get my hand inside a smaller can
to put the dongle in place. If this were a permanent setup, maybe you
could make it fit into a smaller can, but I was only playing, and I carry
the dongle with me, and don't normally use the can.
This looks like a possibility. But I'd rather leave the dongle intact
like you did.
His site has a great name ... Learn by Destroying ... I do, but too
often by accident ... haha. If I keep the site name in mind, I know
I'll feel better next time it happens.
>bjs555 <aaa@bbb.com> wrote:
>> What kind of antennas do the dongles use? Is there a way to solder a
>> pigtail onto a dongle?
>
>Previously:
>Jeff Liebermann <j...@comix.santa-cruz.ca.us> wrote:
>
> http://members.cruzio.com/~jeffl/pics/wireless/DWL-122/
> I removed the PIFA antenna, attached an SMA connector, and made some
> bench tests for sensitivity, power out, and such.
Well done! It's encouraging to read that you got a connection a mile
away with it!
One thing that bothers me about soldering a pigtail onto a circuit
board is that it may cause an impedance mismatch. What kind of circuit
is typically used to drive an antenna? A power transistor with low
output impedance? Some pictures I've seen show a dongle with an
antenna made of pc board traces. Where would I cut into the traces to
add a pigtail?
Thank you.
On Thu, 22 Sep 2005 23:13:40 +1000, "Pierre" <rainsford@ihug.com.au>
wrote:
>Not a Cantenna but very easy to make with good gain.
>
>http://homepages.ihug.co.nz/~redwood4
>
>Peter
>
>"bjs555" <aaa@bbb.com> wrote in message
>news:kbd4j1lpkbqejd6j20huqn44vk9hqogdh3@4ax.com.. .
>> Well, just reread your reply and I see that you are in fact Clarence
>> Dold and that you used the formulas in another link you gave to decide
>> where to poke the hole.
>>
>> Thanks !!! :)
>
"bjs555" <aaa@bbb.com> wrote in message
news:kbd4j1lpkbqejd6j20huqn44vk9hqogdh3@4ax.com...
> Well, just reread your reply and I see that you are in fact Clarence
> Dold and that you used the formulas in another link you gave to decide
> where to poke the hole.
>
> Thanks !!! :)
Nice photos. There is no author noted on the page, but since you're at the
same ISP: The TITLE of the page is "new document", when I save the bookmark.
--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8,-122.5
On Thu, 22 Sep 2005 09:13:21 -0400, * <aaa@bbb.com> wrote:
>Well done! It's encouraging to read that you got a connection a mile
>away with it!
You can go further but that would require more antenna gain.
>One thing that bothers me about soldering a pigtail onto a circuit
>board is that it may cause an impedance mismatch.
True. I would have used a smaller diameter semi-rigid coax cable for
the sole purpose of reducing the amount of exposed center conductor.
That appears as inductance and will create a substantial mismatch loss
if not properly compensated. If you look carefully at the
motherboards on the WRT54G series of router, you'll see a matching
section next to the TNC antenna connectors. That's specifically to
compensate for the exposed center conductor in the cheezy TNC
connectors or the coax cable to circuit board connection.
| http://www.linksysinfo.org/modules.p...showpage&pid=6
Note the small parts on the leads going from the diversity switch IC
to the antenna connectors or coax. Those are the compensation
network.
>What kind of circuit
>is typically used to drive an antenna?
On Thu, 22 Sep 2005 09:01:17 -0400, * <aaa@bbb.com> wrote:
>This looks like a possibility. But I'd rather leave the dongle intact
>like you did.
Unsolder 3 solder connections and an SMA connector. You can solder
the antenna back if you don't like it. No big deal. Unfortunately,
it's on a neighbors roof and I can't find the photos I took. Maybe
I'll do another.
>His site has a great name ... Learn by Destroying ... I do, but too
>often by accident ... haha. If I keep the site name in mind, I know
>I'll feel better next time it happens.
That reminds me.... If you don't know how to solder, find someone that
will do it for you. It's way too easy to destroy these small devices.
I think I've found a problem with this article on biquad antennas.
| http://homepages.ihug.co.nz/~redwood4/
The general construction is great but there's a problem with the way
the biquad wire ground connections were soldered to the outer copper
sleeve. The way a biquad works is that it's two full wave loops in
parallel. The only dimension that's really critical is the length of
the loops. They can be any shape including a circle, but the total
length is what determines resonance. In the photos, he soldered the
ground wires to the sleeve leaving about a 2mm length of tubing
between the ground points. Aesthetically, that looks very nice, but
the extra 2mm of loop length will cause a slight tendency to detune
the antenna lower in frequency. I'm not sure exactly how critical
this is. I'll play with an NEC2 model first to see what happens. My
guess(tm) is that the loop has to be shortened about 1-2mm to
compensate or the ground ends need to be soldered together.
I also take offense to the use of oversize coax and the large amount
of exposed center conductor at both ends of the oversized coax.
Losses at 2.4GHz hare high, but insignificant for short pieces of
coax. I would have used semi-rigid coax. The transition between the
huge center coax support for the biquad and my suggested semi-rigid
coax will be a big problem. There's no way to keep the center
conductor short. Therefore, methinks it would have been best to use a
single piece of .141 semi-rigid for *BOTH* the center support and the
pigtail. The .141 coax is stiff enough if the copper wire used in the
two loops is reduced in diameter. This will slightly affect the
bandwidth of the antenna, but not catastrophically.
In other words, change everything (one of my bad habits).
Otherwise, it's a very nice construction job and article on building a
biquad. However, I would like to have seem some test results and
comparisons with known antennas.
Thanks for the excellent information. I'm a circuit slob going back a
number of years but this RF stuff is like magic to a low speed guy.
Speaking of soldering, I used to be able to solder anything to
anything but somehow my fingers got thicker as I matured and surface
mount componets now strike fear in my heart :)
I haven't gone very far into this project yet but my dongles (Zonet
ZEW2501) arrived today and I ran a few quick and dirty table top tests
using Netstumbler. I made a crude corner reflector by doubling up and
folding in half a piece of aluminum foil and could see improvements of
about 5 dB by placing it near the dongle and varying the position. A
Trendnet TEW226PC pcmcia card that I already had seems to work
slightly better but I can't put it on the end of a cable like I can
the usb dongle.
This is fun. Maxwell is probably smiling.
Bruce
On Thu, 22 Sep 2005 11:10:03 -0700, Jeff Liebermann
<jeffl@comix.santa-cruz.ca.us> wrote:
>On Thu, 22 Sep 2005 09:01:17 -0400, * <aaa@bbb.com> wrote:
>
>>This looks like a possibility. But I'd rather leave the dongle intact
>>like you did.
>
>Unsolder 3 solder connections and an SMA connector. You can solder
>the antenna back if you don't like it. No big deal. Unfortunately,
>it's on a neighbors roof and I can't find the photos I took. Maybe
>I'll do another.
>
>>His site has a great name ... Learn by Destroying ... I do, but too
>>often by accident ... haha. If I keep the site name in mind, I know
>>I'll feel better next time it happens.
>
>That reminds me.... If you don't know how to solder, find someone that
>will do it for you. It's way too easy to destroy these small devices.
>
>I think I've found a problem with this article on biquad antennas.
>| http://homepages.ihug.co.nz/~redwood4/
>The general construction is great but there's a problem with the way
>the biquad wire ground connections were soldered to the outer copper
>sleeve. The way a biquad works is that it's two full wave loops in
>parallel. The only dimension that's really critical is the length of
>the loops. They can be any shape including a circle, but the total
>length is what determines resonance. In the photos, he soldered the
>ground wires to the sleeve leaving about a 2mm length of tubing
>between the ground points. Aesthetically, that looks very nice, but
>the extra 2mm of loop length will cause a slight tendency to detune
>the antenna lower in frequency. I'm not sure exactly how critical
>this is. I'll play with an NEC2 model first to see what happens. My
>guess(tm) is that the loop has to be shortened about 1-2mm to
>compensate or the ground ends need to be soldered together.
>
>I also take offense to the use of oversize coax and the large amount
>of exposed center conductor at both ends of the oversized coax.
>Losses at 2.4GHz hare high, but insignificant for short pieces of
>coax. I would have used semi-rigid coax. The transition between the
>huge center coax support for the biquad and my suggested semi-rigid
>coax will be a big problem. There's no way to keep the center
>conductor short. Therefore, methinks it would have been best to use a
>single piece of .141 semi-rigid for *BOTH* the center support and the
>pigtail. The .141 coax is stiff enough if the copper wire used in the
>two loops is reduced in diameter. This will slightly affect the
>bandwidth of the antenna, but not catastrophically.
>
>In other words, change everything (one of my bad habits).
>
>Otherwise, it's a very nice construction job and article on building a
>biquad. However, I would like to have seem some test results and
>comparisons with known antennas.
On Thu, 22 Sep 2005 15:43:24 -0400, bjs555 <aaa@bbb.com> wrote:
>Thanks for the excellent information.
Not so fast. I'm having 2nd thoughts about my guesswork on how to
solder the biquad elements. I gotta do an NEC2 model before I can be
sure. I might actually be wrong. (What a horrible thought).
>I'm a circuit slob going back a
>number of years but this RF stuff is like magic to a low speed guy.
Yep. It's magic. That's the excuse I use to justify my exhorbitant
consulting fees. If it were easy or obvious, I couldn't be able to
charge as much.
>Speaking of soldering, I used to be able to solder anything to
>anything but somehow my fingers got thicker as I matured and surface
>mount componets now strike fear in my heart :)
It's exposure to too much RF. When I got started in radio, I had a
full head of hair, steady hand, positive attitude, and full bank
account. After about 40 years of RF exposure, my hair is falling out,
my hand is shaking, my attitude is totally cynical, and my bank
account is depleted. Obviously, this could only be caused by RF
exposure. Who do I sue?
>I haven't gone very far into this project yet but my dongles (Zonet
>ZEW2501) arrived today and I ran a few quick and dirty table top tests
>using Netstumbler.
Good start. See what it does before you destroy it. Take some
pictures and post them somewhere. I'll suggest where to hack and cut.
>I made a crude corner reflector by doubling up and
>folding in half a piece of aluminum foil and could see improvements of
>about 5 dB by placing it near the dongle and varying the position.
5dB gain is not bad depending upon size.
>A
>Trendnet TEW226PC pcmcia card that I already had seems to work
>slightly better but I can't put it on the end of a cable like I can
>the usb dongle.
I was in a local coffee shop about a month ago and saw someone with a
ribbon cable extension from their PCMCIA card slot to the wireless
card hanging on the back of the laptop. Whatever works, I guess.
Jeff Liebermann <jeffl@comix.santa-cruz.ca.us> wrote:
> I think I've found a problem with this article on biquad antennas.
> | http://homepages.ihug.co.nz/~redwood4/
....
> In the photos, he soldered the ground wires to the sleeve leaving about a
> 2mm length of tubing between the ground points. Aesthetically, that
> looks very nice, but the extra 2mm of loop length will cause a slight
> tendency to detune the antenna lower in frequency.
I thought about that bit. I'm not sure that the redwood image isn't stolen
directly from Marty. The picture shows the biquad with 30.5 mm sides, and
a gap in the center, but the text on this page, Marty's and Trevor's
indicates that the legs are equal length.
Trevor isn't clear on this point. He speaks of a 244mm piece of wire, but
leaves a 1.5mm gap at the end. His shows the two legs right together at
the copper tube. Marty and redwood show it spread a bit, as if it would go
directly to the center pin if it continued.
You're suggesting that the ends soldered to the tube need to be just a
little shorter, so that the distance from corner past the tube where the
leg is connected into the (not connected) center conductor is 30.5cm?
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8,-122.5
As the builder of the redwood variant, perhaps I should comment.
Length was originally a bit longer and I had made a few of differing
lengths, mounted them and did some rather crude but bottom line effective
tests using a simple field strength meter (diode type!). It was the length
shown which is the same as the martybugs variety that gave the best result.
Admittedly we tend to use the lower channels, 1,6 rather than the higher end
at 11 at our locations.
The coax, point is made....Cheap and available. In New Zealand, one does not
have quite the abilities to get small lengths of more suitable coax. It was
a bit of a gamble but the best we could readily find locally.
Like Jeff, I have been involved with RF as an amateur and professionally off
and on for over 45 years so am very aware of all the optimum theory and
parts but when you are working to a very limited budget in a place well
removed from mainstream and without your usual facilities (I base in
Melbourne, Australia), you tend to work by the seat of your pants. The real
trick is that it is reasonably reproducible to a point that works. The
biquad is comparatively wideband, more so than a stub in a can! so has a bit
more tolerance anyway.
I leave it open for the average person to produce something so simply
effective using only handyman tools and easily obtained items. Hopefully
some will take the idea and experiment further and produce something even
better, such is most of the experimental nature of handling RF and antennas
et al.
One for you, Jeff, it certainly beats tuning a 10Ghz etched filter with
silver paint and a scalpel under a microscope while watching a spec ani.!
That was in the '80s and culminated in our setting the inaugural 10 Ghz VK
DX two way record! The eyesight was a lot better then too.
Peter
<dold@XReXXusbXa.usenet.us.com> wrote in message
news:dgv5ls$hhi$1@blue.rahul.net...
> Jeff Liebermann <jeffl@comix.santa-cruz.ca.us> wrote:
> > I think I've found a problem with this article on biquad antennas.
> > | http://homepages.ihug.co.nz/~redwood4/
> ...
> > In the photos, he soldered the ground wires to the sleeve leaving about
a
> > 2mm length of tubing between the ground points. Aesthetically, that
> > looks very nice, but the extra 2mm of loop length will cause a slight
> > tendency to detune the antenna lower in frequency.
>
> I thought about that bit. I'm not sure that the redwood image isn't
stolen
> directly from Marty. The picture shows the biquad with 30.5 mm sides, and
> a gap in the center, but the text on this page, Marty's and Trevor's
> indicates that the legs are equal length.
>
> Trevor isn't clear on this point. He speaks of a 244mm piece of wire, but
> leaves a 1.5mm gap at the end. His shows the two legs right together at
> the copper tube. Marty and redwood show it spread a bit, as if it would
go
> directly to the center pin if it continued.
>
> You're suggesting that the ends soldered to the tube need to be just a
> little shorter, so that the distance from corner past the tube where the
> leg is connected into the (not connected) center conductor is 30.5cm?
>
> ---
> Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8,-122.5
>
I've been doing some more experimenting (nothing destroyed yet, but
soon no doubt).
I mentioned earlier that I got about 5 dB improvement with a quick and
dirty corner reflector. I rummaged around the kitchen and found a
spaghetti strainer that's roughly a parabola. It seemed to work about
as well as the corner reflector, but it was harder to hold in position
since I don't yet have an extension usb cable for my dongle. That
brings me to a whole set of questions about what is the best way to
have the antenna at some distance from the computer that's cabled to
the access point. But first a bit more about signal strength.
Unsurprisingly, I found that my signals lose a lot of strength going
through the brick walls of my apartment building. Maybe because they
hold water. I'd like to be able to use my notebook both inside and
outside my apartment. Is there a way to have both an inside and
outside antenna connected to the access point? Kind of like a
diversity antenna but with a separation of many feet rather than a few
inches. If I buy one of the access points with two antennas, can I
hook up an inside antenna to one connector and an outside antenna to
the other? Is there anything that can be done for a router with only
one antenna connector (parallel antennas - signals somehow isolated
and combined where needed - half-baked)? What is the best cable to
use? How far can I go? RF cable seems rather thick and difficult to
work with. Can I get away with thin cable?
Another thing I will try soon is poking a hole in a can of beans
(after dinner :) and slipping it onto the external antenna of my
Netgear MR814 router. I figure I can just twist the can to get azimuth
control and tilt the whole router up and down to vary altitude. I
don't know how well the external antenna will feed into this crude
waveguide but it seems easy to try.
Here are some thoughts/questions about cabling to the access point and
wireless client:
I'd prefer not to use coax to the antennas since the coax is lossy and
hard to snake around. I bought the Zonex ZEW2501 dongles thinking that
I could put them in a can and use a long usb cable to put them
anywhere I wanted. But now I see that there's a limit of 5 meters to
usb cable length. Damn, I want to go about 10 meters. Etherenet cables
can run 100 meters so they would be fine. I could perhaps mount the
whole router inside a reflector and take care of one side of the link
that way. But what could I do about the dongles? I bought two Netgear
MR814 routers hoping I could use one as a client in place of the
dongle, but the routers don't seem to offer a client mode. Any way to
force it? Another (probably bad) idea is to use a junk computer
running Internet Connection Sharing. I haven't thought that through
completely but perhaps someone has done that or has better ideas.
bjs555 <aaa@bbb.com> wrote:
> I mentioned earlier that I got about 5 dB improvement with a quick and
> dirty corner reflector. I rummaged around the kitchen and found a
> spaghetti strainer that's roughly a parabola. It seemed to work about
> as well as the corner reflector, but it was harder to hold in position
> outside my apartment. Is there a way to have both an inside and
> outside antenna connected to the access point?
My understanding is that this works, as long as the client can only see one
antenna at a time. Jeff Liebermann expands on this in a posting in this
group that you might find via a google search. My somewhat similar test is
that my connection would toggle back and forth between the good connection
and the poor connection when I had one stock antenna and one reflector.
> the other? Is there anything that can be done for a router with only
> one antenna connector (parallel antennas - signals somehow isolated
The pattern is pretty wide. My reflector works better to the sides than
the bare antenna did.
> Another thing I will try soon is poking a hole in a can of beans
> (after dinner :) and slipping it onto the external antenna of my
That likely won't work. The radiator portion of the antenna would have to
be inside the can. Having it part in and part out would be unhelpful.
> anywhere I wanted. But now I see that there's a limit of 5 meters to
> usb cable length. Damn, I want to go about 10 meters. Etherenet cables
5 meters of USB cable, but active repeaters can couple cables together. I
bought a five meter cable with an active repeater lump at one end that was
the same price as the 5 meter cable without the repeater.
--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8,-122.5
>> Is there a way to have both an inside and outside antenna connected
>> to the access point?
>
>My understanding is that this works, as long as the client can only see one
>antenna at a time. Jeff Liebermann expands on this in a posting in this
>group that you might find via a google search. My somewhat similar test is
>that my connection would toggle back and forth between the good connection
>and the poor connection when I had one stock antenna and one reflector.
Interesting. I'll search for the posts. If I go with dual antennas, do
I need a splitter like this?: http://www.hyperlinktech.com/web/signal_splitters.php
Maybe I'll have to get used to working with coax after all. How far
can it run before losses get unreasonable? Is 400 series cable the
right kind to use?
>> Another thing I will try soon is poking a hole in a can of beans
>> (after dinner :) and slipping it onto the external antenna of my
>
>That likely won't work. The radiator portion of the antenna would have to
>be inside the can. Having it part in and part out would be unhelpful.
Afraid of that. Thanks for the tip. Saved me some time.
Your Netgear router looks just like mine. I'll try the windsurfer. I
picked up two of the 802.11b Netgears for $15 each (after $20 rebate)
at tigerdirect.com. Couldn't resist the price.
>> anywhere I wanted. But now I see that there's a limit of 5 meters to
>> usb cable length. Damn, I want to go about 10 meters. Etherenet cables
>
>5 meters of USB cable, but active repeaters can couple cables together. I
>bought a five meter cable with an active repeater lump at one end that was
>the same price as the 5 meter cable without the repeater.
bjs555 <aaa@bbb.com> wrote:
> Interesting. I'll search for the posts. If I go with dual antennas, do
> I need a splitter like this?:
I was only referring to a dual-antenna WAP, like my SMC7004WFW. I don't
know about splitting a single antenna.
> Your Netgear router looks just like mine. I'll try the windsurfer. I
> picked up two of the 802.11b Netgears for $15 each (after $20 rebate)
> at tigerdirect.com. Couldn't resist the price.
Netgear WGB511 802.11g Wireless Networking Kit
WGR614v4 Router and WG511 CardBus card that I have.
<http://www.amazon.com/exec/obidos/tg/detail/-/B000117DGW/qid=1105746394/sr=8-7/ref=pd_csp_7/002-3005537-5404050?v=glance&s=pc&n=507846>
The price fluctuates a lot. There aren't any rebates today. I think I was
around $30 for the pair. I'm a rebate junkie.
--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8,-122.5
A can with a USB adapter is on my list of "things to do."
I have had more experience with a 12 inch mixing bowl as on the New
Zealand site.
Works beyond amazingly well and very simple to use.
You sort of point the dish in a direction rather than aiming it.
The dimensions that seem to be optimal is a 12 inch bowl.
The dongle antenna is 7 inches from the base of the bowl.
I have tried various dongle brands.
Last week I tried g vs b.
Jeff Lieberman has explained that g receivers are newer electronics
with more sensitivity.
The Gigafast b is very good. However the link strength is too low for
Netstumbler use - link quality is very high at low signal strength. You
use the utility that comes with the adapter.
The Trendnet brand works well with Netstumbler.
Signal strenth measurement seems to be higher whereas Link quality is
not so off the scale.
Maybe Jeff can comment on this - is it just measurement diffirences on
the scale by the diffirent brands ?
Reception seemed better in some cases than the Gigafast but not in some
cases.
I tried a G Inexq - not really much diffirence but perhaps as Jeff
suggested in fringe reception ?
Most of these dongles seem to use a more oddball chipset - the Zydas
brand .
As a general note - it seems to be a rather good chipset and for
general use for beginners among the easiest to set up . Perhaps others
have comments good or bad as well.
I tried a D-Link dongle and was not impressed compared to the Zydas.
Has anyone tried a Linksys/ Network Everywhere USB adapter - has a more
standard Prism chipset ?
According to the New Zealand website 12 inches seems to be their
optimum.
Has anyone built one of the satellite dish ( Primestar) antennas with a
dongle adapter ?
Would a larger size help in reception.
What would be the focal length to use to build one.
hard to use on a car seat though.
Have fun.
All I can tell you that without the serving bowl reception is not much
in comparison. dold@XReXXusbXa.usenet.us.com wrote:
> bjs555 <aaa@bbb.com> wrote:
> > Interesting. I'll search for the posts. If I go with dual antennas, do
> > I need a splitter like this?:
>
> I was only referring to a dual-antenna WAP, like my SMC7004WFW. I don't
> know about splitting a single antenna.
>
> > Your Netgear router looks just like mine. I'll try the windsurfer. I
> > picked up two of the 802.11b Netgears for $15 each (after $20 rebate)
> > at tigerdirect.com. Couldn't resist the price.
>
> Netgear WGB511 802.11g Wireless Networking Kit
> WGR614v4 Router and WG511 CardBus card that I have.
> <http://www.amazon.com/exec/obidos/tg/detail/-/B000117DGW/qid=1105746394/sr=8-7/ref=pd_csp_7/002-3005537-5404050?v=glance&s=pc&n=507846>
> The price fluctuates a lot. There aren't any rebates today. I think I was
> around $30 for the pair. I'm a rebate junkie.
>
> --
> ---
> Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8,-122.5
On Fri, 23 Sep 2005 11:24:39 -0400, bjs555 <aaa@bbb.com> wrote:
>I've been doing some more experimenting (nothing destroyed yet, but
>soon no doubt).
Actually, you already have but don't realize it. You need to match
the antenna feed to the dish and that's rough with a USB dongle.
>I mentioned earlier that I got about 5 dB improvement with a quick and
>dirty corner reflector. I rummaged around the kitchen and found a
>spaghetti strainer that's roughly a parabola.
I have some not very nice comments to make about using a reflector
with a USB dongle feed. The basic problem is that the original PIFA
or circuit board antenna has roughly a hemispherical antenna pattern.
That means that transmissions from the dongle will go in all
directions and only some of which will hit the dish, reflect toward
the receiver, and provide useful gain. That also means that you will
observe different apparent gains in transmit and receiver. Receive
will be largely unaffected by the dongle feed pattern and will yield
reasonable results. Transmit gain will suck as much of the power goes
in useless directions.
My suggestion is to replace the built in PIFA or whatever antenna in
the USB dongle with a proper coax connector (SMA) or coax pigtail and
use a dish that has a properly matched feed.
Incidentally, the same problem with feed "overspray" or "spillover"
happens with foil reflectors hung on vertical omnidirectional antennas
as in www.FreeAntennas.com. However, the effect is much smaller than
the 15dB loss in the pizza dish reflector because reflector captures
most of the RF from the vertical and redirects it in a useful
direction. For example, if the reflector covered a 120 degree azimuth
wedge (looking down on the antenna), two thirds of the transmitted RF
will go to places unknown, while one third will hit the reflector.
That's about 5dB loss which isn't bad considering that even the best
dish antennas and feeds have about a 3dB illumination loss.
Also note that different parts of the dish provide different amounts
of gain. This is best demonstrated by blocking parts of the dish and
seeing how it affects the gain. Try this with an absorbent material
(black foam or wet towel) and not with a reflector like aluminum foil.
The flat part of the dish, near the middle contributes the most to the
antenna gain. Unfortunately, that tends to be blocked by the feed (or
USB dongle) so offset feeds are used (as in DBS dish antennas) to
avoid blocking the center. Gain derived from the "sides" of the dish
is much less, especially on a deep dish (f/D < 0.35). As the dish
gets deeper, the edges of the dish approach being inline with the
antenna direction, and therefore capture very little signal relative
to the surface area. It's also more difficult to design a proper feed
for a deep dish.
This begs the question "Why are all these people building their own
reflector antennas"? Easy. Even with all the problems mentioned, a
suitable reflector type antenna is a major improvement over the stock
antennas. Even the worst implementation will give about 6dB of gain
which is the equivalent of 4 times the range. However, squeezing the
maximum gain out of the system does require a proper design and
testing.
No. That antennas are turned on only one at a time. That means you
only get the gain of one antenna and cannot combine the signals to get
more gain. Just use one antenna port.
>Maybe I'll have to get used to working with coax after all. How far
>can it run before losses get unreasonable? Is 400 series cable the
>right kind to use?
LMR-400 coax is a good coax for long runs. 6.8dB/100ft loss at
2.4GHz. You will also lose about 0.5dB per connector pair so even a
zero length coax extension will have 1dB of loss. Add a pigtail and
you add 2 more connectors. How far you can go requires that I
calculate the fade margin. I've done this about 20 times. Use Google
Groups advanced search to look for "fade margin".
For a rule of thumb, 6dB loss will cut your range in half. 12dB will
cut it to 1/4th.
On Fri, 23 Sep 2005 22:33:21 +1000, "Pierre" <rainsford@ihug.com.au>
wrote:
>As the builder of the redwood variant, perhaps I should comment.
Oh-oh.
>Length was originally a bit longer and I had made a few of differing
>lengths, mounted them and did some rather crude but bottom line effective
>tests using a simple field strength meter (diode type!).
I could never get consistent results using a field strength meter
(diode hanging on my DVM with two resistors and a cap to filter the
rectified DC). I now have a very old but useful spectrum analyzer.
However, it only goes to 1.2GHz so I use an MMDS downconverter for a
test receiver. My signal source is a 2.4GHz WISP transmitter located
on a mountain top about 3 miles away. Line of sight and minimal local
reflections. Also saves on the cost of a signal source.
>It was the length
>shown which is the same as the martybugs variety that gave the best result.
>Admittedly we tend to use the lower channels, 1,6 rather than the higher end
>at 11 at our locations.
Note that the VSWR curve is quite flat over the entire band. That
allows considerable creativity and variation in construction. I'm
tempted to compromise this broad bandwidth by using a smaller diameter
wire. That will make it much easier to build.
The problem is that the above model is directly from the original
Trevor Marshall implementation without any of the fine details, such
as the coax cable feed diameter thrown into the puzzle. I'll try to
add these in the next few days and see what breaks. I really don't
know (yet) if it will have a significant effect. I'm also going to
change the quad antennas to a loop as putting corners on the antenna
is a waste of effort and actually quite difficult to do accurately.
The only critical dimension is the length of each loop, not the shape.
But first, I gotta learn how to use the 4NEC2 optimizer.
>The coax, point is made....Cheap and available. In New Zealand, one does not
>have quite the abilities to get small lengths of more suitable coax. It was
>a bit of a gamble but the best we could readily find locally.
Well, it's not so much the choice of coax that I'm complaining about.
It's the effects of the transitions. You could have used a smaller
diameter coax for the center feed if you had a better way to support
the biquad elements. Methinks I can do that by using smaller diameter
copper wire for the elements. A piece of RG-174 should work if
stiffened with some solder slopped on the outside braid. Make your
own semi-rigid coax. That should also solve the problem with the
rather sharp right angle turn required where it exits the reflector.
In addition, it will eliminate one coax diameter transition and
eliminate the long exposed center conductor where it hits the radio
circuit board.
>The real
>trick is that it is reasonably reproducible to a point that works. The
>biquad is comparatively wideband, more so than a stub in a can! so has a bit
>more tolerance anyway.
I won't say anything nice about my attempt at building a biquad inside
a 6" outdoor box:
| http://802.11junk.com/jeffl/pics/ant...ad2/index.html
Major mistake was using nylon insulators. They're hygroscopic and
caused the antenna to screw up badly after about 3 days.
>I leave it open for the average person to produce something so simply
>effective using only handyman tools and easily obtained items. Hopefully
>some will take the idea and experiment further and produce something even
>better, such is most of the experimental nature of handling RF and antennas
>et al.
Yep. Learn by Destroying. One does not understand antennas until one
builds a few that don't work as expected.
Idea for you. Go to stationary store and find some foam board. It
comes in various thicknesses but most commonly about 1/4" thick. 1/2
wave aluminum foil reflector on one side of the board. Copper tape a
biquad or patch antenna on the other side. Maybe 4 folded dipoles
playing vertical collinear. Pile additional layers to get the correct
thickness. Shove coax through foam and make connection with glue or
aluminum duct tape.
>One for you, Jeff, it certainly beats tuning a 10Ghz etched filter with
>silver paint and a scalpel under a microscope while watching a spec ani.!
>That was in the '80s and culminated in our setting the inaugural 10 Ghz VK
>DX two way record! The eyesight was a lot better then too.
Congrats and nicely done. I've built filters out of copper pipe
fittings but never tried to do anything at 10GHz (other than use
converted commercial equipment). I did machine an interdigital filter
at X-band but I never could get it to work right.
Thanks for your reply. If I understand you correctly, that would mean
that a dish type reflector is more effective on a receiver than a
transmitter. Picturing the radio waves as rays of light, the rays
would be nearly parallel at a receiver very far from a transmitter.
Thus, nearly all the captured rays would go to the focus of the
reflector. For a reflector a few inches from the transmitter, however,
many rays would "spill out" and wouldn't contribute to the transmitted
beam. So it seems to make more sense to put a reflector on a client
antenna rather than an access point antenna. Is this verified by
experiment? (I know, why don't I do it - not fully set up yet.)
Another question:
I did some searching for IC RF amps starting from the page you gave in
an earlier post. I found this Maxim data sheet: http://pdfserv.maxim-ic.com/en/ds/MAX2240.pdf
which shows an application circuit at the top. In the circuit, the
signal is shown ac coupled to the antenna through a 10 pF cap. Is that
typical? Would I connect an external antenna at the RF out end of the
cap? Do I cut any traces to an existing antenna? Are compensation
circuits (not sure these apply to RF) sometimes used?
Also, at this page: http://www.nodomainname.co.uk/ma401/ma401.htm
the author describes a way to add an external antenna to a particular
wifi card by removing an inductor and adding 2 150 pF caps. Why is he
doing that?
You gave some pictures of a dongle that you modified for an external
antenna. Where did you connect to the circuit?
Sorry for asking so many questions but I find this topic so
interesting. And thanks for the antenna theory references.
Cheers,
Bruce
On Sat, 24 Sep 2005 08:44:09 -0700, Jeff Liebermann
<jeffl@comix.santa-cruz.ca.us> wrote:
>On Fri, 23 Sep 2005 11:24:39 -0400, bjs555 <aaa@bbb.com> wrote:
>
>>I've been doing some more experimenting (nothing destroyed yet, but
>>soon no doubt).
>
>Actually, you already have but don't realize it. You need to match
>the antenna feed to the dish and that's rough with a USB dongle.
>
>>I mentioned earlier that I got about 5 dB improvement with a quick and
>>dirty corner reflector. I rummaged around the kitchen and found a
>>spaghetti strainer that's roughly a parabola.
>
>I have some not very nice comments to make about using a reflector
>with a USB dongle feed. The basic problem is that the original PIFA
>or circuit board antenna has roughly a hemispherical antenna pattern.
>That means that transmissions from the dongle will go in all
>directions and only some of which will hit the dish, reflect toward
>the receiver, and provide useful gain. That also means that you will
>observe different apparent gains in transmit and receiver. Receive
>will be largely unaffected by the dongle feed pattern and will yield
>reasonable results. Transmit gain will suck as much of the power goes
>in useless directions.
>
>See:
>| http://groups.google.com/group/alt.i...3ed746dc7446e7
>for details. I ran the numbers for an 18" pizza dish in:
>| http://groups.google.com/group/alt.i...7ddbbf5aa01dd7
>That's probably a worst case example as the deep dish rice dryer seems
>a be a better shaped reflector.
>
>Some not so light reading:
>| http://www.w1ghz.org/antbook/contents.htm
>See Part 4 on dish and feed basics.
>| http://www.w1ghz.org/antbook/chap4.pdf
>Just look at the figures and read the captions if you don't want to
>dive to deep.
>
>My suggestion is to replace the built in PIFA or whatever antenna in
>the USB dongle with a proper coax connector (SMA) or coax pigtail and
>use a dish that has a properly matched feed.
>
>Incidentally, the same problem with feed "overspray" or "spillover"
>happens with foil reflectors hung on vertical omnidirectional antennas
>as in www.FreeAntennas.com. However, the effect is much smaller than
>the 15dB loss in the pizza dish reflector because reflector captures
>most of the RF from the vertical and redirects it in a useful
>direction. For example, if the reflector covered a 120 degree azimuth
>wedge (looking down on the antenna), two thirds of the transmitted RF
>will go to places unknown, while one third will hit the reflector.
>That's about 5dB loss which isn't bad considering that even the best
>dish antennas and feeds have about a 3dB illumination loss.
>
>Also note that different parts of the dish provide different amounts
>of gain. This is best demonstrated by blocking parts of the dish and
>seeing how it affects the gain. Try this with an absorbent material
>(black foam or wet towel) and not with a reflector like aluminum foil.
>
>The flat part of the dish, near the middle contributes the most to the
>antenna gain. Unfortunately, that tends to be blocked by the feed (or
>USB dongle) so offset feeds are used (as in DBS dish antennas) to
>avoid blocking the center. Gain derived from the "sides" of the dish
>is much less, especially on a deep dish (f/D < 0.35). As the dish
>gets deeper, the edges of the dish approach being inline with the
>antenna direction, and therefore capture very little signal relative
>to the surface area. It's also more difficult to design a proper feed
>for a deep dish.
>
>This begs the question "Why are all these people building their own
>reflector antennas"? Easy. Even with all the problems mentioned, a
>suitable reflector type antenna is a major improvement over the stock
>antennas. Even the worst implementation will give about 6dB of gain
>which is the equivalent of 4 times the range. However, squeezing the
>maximum gain out of the system does require a proper design and
>testing.
But there is an RF cable, it's from the Compaq WL110 card via a small
pigtail to an N type connector and then via a bit of RG195 coax which is
then stripped back to make the feed into the cardboard can.
I'm not sure I'd go so far as to call it a "proper" feed but a quick and
dirty bodge. Scraping the laquer off the foil liner and soldering to
self adhesive copper tape really is a bodge! :)
Good man - you show no fear of opening and improving these cards and
dongles. Thanks for the good pics and tips on your web pages.
Well, could the cable be eliminated completely if you soldered a wire
directly to the RF outpoint point on the circuit board and duct taped
the whole card to the outside of the cantenna with the wire poking
through? I wouldn't know what to do about the ground braid. Maybe I'm
all wet.
Bruce
On Sat, 24 Sep 2005 17:56:42 GMT, David Taylor <djtaylor@bigfoot.com>
wrote:
>> I'm thinking now that the best approach might be a something like
>> this:
>> http://www.nodomainname.co.uk/cantenna3/cantenna3.htm
>> where a proper feed is made into the waveguide without using RF
>> cables.
>
>But there is an RF cable, it's from the Compaq WL110 card via a small
>pigtail to an N type connector and then via a bit of RG195 coax which is
>then stripped back to make the feed into the cardboard can.
>
>I'm not sure I'd go so far as to call it a "proper" feed but a quick and
>dirty bodge. Scraping the laquer off the foil liner and soldering to
>self adhesive copper tape really is a bodge! :)
>
>David.
Jeff Liebermann <jeffl@comix.santa-cruz.ca.us> wrote:
> Incidentally, the same problem with feed "overspray" or "spillover"
> happens with foil reflectors hung on vertical omnidirectional antennas
> as in www.FreeAntennas.com. However, the effect is much smaller than
> the 15dB loss in the pizza dish reflector because reflector captures
> most of the RF from the vertical and redirects it in a useful
> direction. For example, if the reflector covered a 120 degree azimuth
> wedge (looking down on the antenna), two thirds of the transmitted RF
> will go to places unknown, while one third will hit the reflector.
> That's about 5dB loss which isn't bad considering that even the best
> dish antennas and feeds have about a 3dB illumination loss.
I don't think your math is accurate. If you consider the 3dB beamwidth to
be 50 degrees, then the 50 degrees of "overspray" is headed in the right
direction. The EZ-12 looks like 120 degrees, so the effect should be 50 %
of the radiated power going in the right direction.
Comparing your NEC plot of a BiQuad to the NEC plot of the EZ-12 looks like
a minimal difference. The EZ-12 has a 3dB beamwidth of 50 degrees, your
biquad is 60. The charts are based differently, but it looks like you have
11.1 dB of gain, the Ez-12 11.41.
And the EZ-12 is, as the name implies, easy to build.
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8,-122.5
Jeff Liebermann <jeffl@comix.santa-cruz.ca.us> wrote:
> I have some not very nice comments to make about using a reflector
> with a USB dongle feed. The basic problem is that the original PIFA
> or circuit board antenna has roughly a hemispherical antenna pattern.
> That means that transmissions from the dongle will go in all
> directions and only some of which will hit the dish, reflect toward
> the receiver, and provide useful gain.
Does the wire in a biquad transmit all of it's power toward the copper
plate?
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8,-122.5
usb adapter cantenna 
Linear Mode
