Range on a pair of Belkin 54G routers in wireless bridge mode?

What's the expected range on a pair of Belkin 54G routers in wireless bridge
mode?

I've seen someone mention on at least one web tech support forum that they
were having troubles staying connected 100% of the time, but they then went
on to say that they were trying to bridge 400 feet, from one building to
another building. Can I expect similar results?

What frequencies are used in Belkin's bridge-to-bridge mode? I assume it
may not be standard because Belkin's bridge mode only works with other
Belkin WAP's.

Also can I replace one of the stock omni-directional antennas with a
cantenna to use along the bridge line of sight? If the bridge mode
frequency is different than standard 802.11b's 2.412 GHz or so, I'll need to
know that to calculate my can radius and quarter-wavelength distance, yada
yada yada...


--
bill evans
(E-Mail Removed)
Hartselle, AL

Freeman Dyson: "It's best not to limit our thinking. We can always
air-condition the Earth."








Bill Evans

"Bill Evans" <WHEvansIII-(E-Mail Removed)> wrote:
>What's the expected range on a pair of Belkin 54G routers in wireless bridge
>mode?
>
>I've seen someone mention on at least one web tech support forum that they
>were having troubles staying connected 100% of the time, but they then went
>on to say that they were trying to bridge 400 feet, from one building to
>another building. Can I expect similar results?

Probably. (I have no experience specifically with Belkin
equipment, but unless there is something very unusual about it
there won't be any real difference as far as range goes.)

However, 400 feet from one building to another, works if and
only if certain things happen to be true. You simply will not
get good results going through walls, and some walls (metal) are
absolutely killers. Hence you will do much better if you can
place both units in a window, for example. Or even outside if
you manage that. And the higher the elevation the better,
because reflections from vehicles on the ground can cause
signals to fade too.

Hence worst case is two units at ground level with a two or more
walls between them, and best case is both units sitting in a 4th
story window with an unobstructed view of each other.

With that said, I have one unit sitting in the window at ground
level, which works fairly well to a repeater about 400 yards
away. Moreover there are two houses blocking a direct view!
Near as I can tell the signal is bouncing off a building on the
opposite side of the street (none of them have metal siding or
anything obvious, so I'm not really sure just what the signal is
bounding off).

The same AP is just barely useable through one wall, on the
ground floor of the building directly across the street! I put
a repeater in a second story window, and it wasn't all that good
either! But when I moved it from one side of the window to the
other, a matter of about 20 inches, it became rock solid!

The moral of the story is that you'll have to try it and see
what you get. Under the right circumstances it can certainly be
done.

>What frequencies are used in Belkin's bridge-to-bridge mode? I assume it
>may not be standard because Belkin's bridge mode only works with other
>Belkin WAP's.
>
>Also can I replace one of the stock omni-directional antennas with a
>cantenna to use along the bridge line of sight? If the bridge mode
>frequency is different than standard 802.11b's 2.412 GHz or so, I'll need to
>know that to calculate my can radius and quarter-wavelength distance, yada
>yada yada...

They all use the same set of channels. A cantenna optimized for
channel 11 might not work as well on channel 1, but I'd guess
that the difference would be slight. Certainly an antenna cut
for say channel 8 will do equally well for everything from 6 to
10, at a minimum.

The typical construction of a cantenna is not adaquate for
outdoor use, except perhaps in a very dry climate where there is
also not much wind. But for mounting inside, they make a
significant difference, both in signal strength at the desired
location but also to reduce signal strength in undesired
directions.

--
Floyd L. Davidson <http://web.newsguy.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) (E-Mail Removed)

On Thu, 03 Feb 2005 01:58:43 -0900, (E-Mail Removed) (Floyd L.
Davidson) wrote:

>They all use the same set of channels. A cantenna optimized for
>channel 11 might not work as well on channel 1, but I'd guess
>that the difference would be slight. Certainly an antenna cut
>for say channel 8 will do equally well for everything from 6 to
>10, at a minimum.

This might help. I ran Trevor Marshall's model of a can antenna
through 4NEC2 to get some numbers:
http://www.LearnByDestroying.com/pic...400/index.html
The gain and vswr are fairly flat across the band (2400-2483.5).
However, there are some differences that I'm guessing (this is a
guess, not a calculation) that will yield about 1.5dB difference in
gain and reflected power loss difference between the center (chnl 6)
and the edges (chnl 1 and 11).

However, also note that the design uses a conical 1/4 wave feed and
not the usual 1/4 wave single wire to obtain additional bandwidth.
I've been meaning rework it a single wire and see what happens. I'm
fairly sure that the bandwidth will be much narrower and band edge
losses will be much higher.

>The typical construction of a cantenna is not adaquate for
>outdoor use, except perhaps in a very dry climate where there is
>also not much wind. But for mounting inside, they make a
>significant difference, both in signal strength at the desired
>location but also to reduce signal strength in undesired
>directions.

Agreed. The big advantage of the can antenna is that it is cheap and
easy to build. Everything else about it is wrong or can be done
better. I've compared the coffee can flavour[1] of cantenna with my
rather sloppily constructed biquad panel implimentation. In general,
the biquad is superior in all measurements and crude tests. It's also
much smaller, I think easier to build (there's some debate here), and
much easier to package.
http://martybugs.net/wireless/biquad/
I don't have an easy way to measure absolute gain accurately, but I
can easily measure relative gain difference between antennas. The
single biquad has about 3dB more gain than my 1lb coffee can
implimentation.

[1] Rumor has it that caffinated coffee cans have more "punch" than
decaf.

One reason that the coffee can type of antenna is fairly popular is
that it was the first of the do it thyself antennas and therefore has
some kind of "image" that it is better than a commercial antenna.
Never mind that almost any type of external antenna will be better
than what's delivered with the stock AP's and client radios.
Argh. phone call...


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

Jeff Liebermann <(E-Mail Removed)> wrote:
> This might help. I ran Trevor Marshall's model of a can antenna
> through 4NEC2 to get some numbers:

I don't see any cantenna references on Trevor's site.

> However, also note that the design uses a conical 1/4 wave feed and
> not the usual 1/4 wave single wire to obtain additional bandwidth.

Are you talking about the cone in front of the can, or something different
about the feed wire itself?

http://www.nodomainname.co.uk/Antennas/antenna.htm "Can with Conical Horn".

> the biquad is superior in all measurements and crude tests. It's also
> much smaller, I think easier to build (there's some debate here), and
> much easier to package.

http://www.turnpoint.net/wireless/cantennahowto.html
Is pretty easy to build. I don't see how a BiQuad could be easier than
that. My USB-dongle coffee can wouldn't even require any soldering in the
one-can configuration. I'd have to look at the numbers to see how much
gain I got from the second can.
http://www.rahul.net/dold/clarence/u...42-800x600.jpg

The USB-dongle in a pill bottle takes the prize for ease of concealment in
an outdoor setup. I can't locate the reference page, but they just put the
USB dongle into a pill bottle, and arranged it over a light on a metal
building doorway. It looked like a motion sensor, and the metal building
provided some reflector, giving them a shot to another building that wasn't
too far away, and was unreachable with any antenna inside the metal shop.


> http://martybugs.net/wireless/biquad/
> I don't have an easy way to measure absolute gain accurately, but I
> can easily measure relative gain difference between antennas. The
> single biquad has about 3dB more gain than my 1lb coffee can

http://martybugs.net/wireless/antennacomp.cgi doesn't agree.

Of course, that's not a 1lb coffee can. When I fussed around with the
calculators, and some trials, I found that two one pound coffee cans
soldered together made the best antenna of the cans I tried.


> [1] Rumor has it that caffinated coffee cans have more "punch" than
> decaf.

I lose any hope of a serious conversation with you, sometimes.

> One reason that the coffee can type of antenna is fairly popular is
> that it was the first of the do it thyself antennas and therefore has
> some kind of "image" that it is better than a commercial antenna.

No, I think that would be the difficult-to-build Pringles can.
It generally comes out poorly when compared to the cantenna.

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

On Thu, 3 Feb 2005 18:36:46 +0000 (UTC), (E-Mail Removed)
wrote:

>Jeff Liebermann <(E-Mail Removed)> wrote:
>> This might help. I ran Trevor Marshall's model of a can antenna
>> through 4NEC2 to get some numbers:

>I don't see any cantenna references on Trevor's site.

http://www.nec2.org/coffee.txt

>> However, also note that the design uses a conical 1/4 wave feed and
>> not the usual 1/4 wave single wire to obtain additional bandwidth.

>Are you talking about the cone in front of the can, or something different
>about the feed wire itself?
>http://www.nodomainname.co.uk/Antennas/antenna.htm "Can with Conical Horn".

No. It's the feed element. In most coffee can antennas, it's just a
1/4 wave piece of wire. In his implimentation, it's a conical shape.
Here's a photo from his site of a 5.6Ghz version:
http://trevormarshall.com/feedcone.jpg
It's kinda hard to see on the 4NEC2 similation, but if you look at:

http://www.LearnByDestroying.com/pic...ometry-01.html
yu'll sorta see the conical feed in red.

>Is pretty easy to build. I don't see how a BiQuad could be easier than
>that.

Like I said, it's arguementative. I find that tweaking the coffee can
for maximum gain is more difficult than the biquad, which usually
works the first try. I post a photo of a biquad that I'm currently
building that's held together with solder and hot melt glue.

>My USB-dongle coffee can wouldn't even require any soldering in the
>one-can configuration. I'd have to look at the numbers to see how much
>gain I got from the second can.
>http://www.rahul.net/dold/clarence/u...42-800x600.jpg

Notice I didn't say anything about planting USB radios inside cans.
The original comments were related to a wireless (transparent) bridge,
which methinks a USB radio is generally incapeable.

>The USB-dongle in a pill bottle takes the prize for ease of concealment in
>an outdoor setup. I can't locate the reference page, but they just put the
>USB dongle into a pill bottle, and arranged it over a light on a metal
>building doorway. It looked like a motion sensor, and the metal building
>provided some reflector, giving them a shot to another building that wasn't
>too far away, and was unreachable with any antenna inside the metal shop.

Pill bottle? Well, someone showed up with an antenna made from a
large aluminium funnel, a TNC connector, and some mangled coax. At
first, I thought it was a joke, until he showed me some comparison
tests, vswr measurements, and antenna patterns. I vaguely recall
about 8dBi gain. The moral is that you can build an antenna out of
just about anything. Pill bottle?>

>> http://martybugs.net/wireless/biquad/
>> I don't have an easy way to measure absolute gain accurately, but I
>> can easily measure relative gain difference between antennas. The
>> single biquad has about 3dB more gain than my 1lb coffee can
>
>http://martybugs.net/wireless/antennacomp.cgi doesn't agree.
>
>Of course, that's not a 1lb coffee can. When I fussed around with the
>calculators, and some trials, I found that two one pound coffee cans
>soldered together made the best antenna of the cans I tried.

That seems to be the consensus. Actually, I think it is a 1lb coffee
can (100mm x 185mm) for the Trevor Marshall design. Reducing the
numbers in the table, I see random rubbish indicative of significant
errors, probably from reflections. Reducing the tables to differences
between the can and biquad 1 and 2, I find that the two biquads are
anywere between 4dB better, to 4dB worse than the cantenna. That's an
8dB variation in results which methinks is rather inconsistant.
That's what I expect from a random test range. Reflections from the
ground are always a problem with street level tests.

>> [1] Rumor has it that caffinated coffee cans have more "punch" than
>> decaf.
>I lose any hope of a serious conversation with you, sometimes.

Seriously, there is hope. However, I have problems resisting the
temptation to interject some humor in an otherwise dull and overly
technical topic.

>No, I think that would be the difficult-to-build Pringles can.
>It generally comes out poorly when compared to the cantenna.

Yep. Remind me to send you my hacked version of Ivor's antenna design
spreadsheet.
http://www.ivor.it/wireless/cantenna.html
It has some problems that I'm trying to fix. However, it's close
enough to demonstrate what happens with different lengths of can
antennas. Methinks you'll be rather amazed at the effects of the can
length. As I recall, the problem with the Pringles can was that it
was close to the exact wrong length for the worst possible
performance. There's also an issue of skin effect conductivity. The
aluminized paper is probably not the greatest. Neither is whatever is
used to plate the insides of a tin can. I build my stuff from copper
sheet roof flashing. When it works, I silver plate it.

Drivel: Gotta run to the local hospital for part 2 of a radioactive
treadmill test. It was LOTS of fun demonstrating how radioactive I
was (100mR/hr) after yesterdays test to my friends and customers.
Those with a clue were tempted to run for their lives after they heard
my geiger counter clicking. 24 hrs later, I'm still doing about
8mR/hr. Normal background is about 0.1mr/hr. Wheeeee...

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

Jeff Liebermann <(E-Mail Removed)> wrote:
> On Thu, 3 Feb 2005 18:36:46 +0000 (UTC), (E-Mail Removed)
> wrote:

>>I don't see any cantenna references on Trevor's site.
> http://www.nec2.org/coffee.txt

I still don't see any on Trevor's site ...

> No. It's the feed element. In most coffee can antennas, it's just a
> 1/4 wave piece of wire. In his implimentation, it's a conical shape.
> Here's a photo from his site of a 5.6Ghz version:
> http://trevormarshall.com/feedcone.jpg

Wow! Okay, that might be difficult to construct, but I still don't see
anything on his site about cantenna. That cone is used in a flat slotted
waveguide http://www.trevormarshall.com/waveguides.htm

> Like I said, it's arguementative. I find that tweaking the coffee can

Ah, tweaking. Given how hard it is for the home hobbyist to get a
reasonable test range, tweaking is just out of the question in a coffee
can. That's why you use a calculator and poke your hole, and take what you
get... Unless you drink enough coffee to have a steady supply of cans.
And then, where is the tweaking? Assuming that someone got it right,
that's it. Poke a hole in the place that you're told to poke it.

> That seems to be the consensus. Actually, I think it is a 1lb coffee
> can (100mm x 185mm) for the Trevor Marshall design. Reducing the

Using the calculator at
http://www.turnpoint.net/wireless/cantennahowto.html
I decided that a pair of Stagg's Chilli cans were the best size for a wire
cantenna, but it was too small for me to fit my USB dongle.
The Staggs is 85mm x 220mm. I use that with my Orinoco.
For the USB, the 4" coffee can was a usable size, similar to Trevor's.

> Yep. Remind me to send you my hacked version of Ivor's antenna design
> spreadsheet.
> http://www.ivor.it/wireless/cantenna.html
> It has some problems that I'm trying to fix. However, it's close

I played with that, and didn't find any difference from turnpoint, for the
sizes I had on hand. Some commentary on one of the sites made me think
that the differences were from measuring on the outside of the can, which
didn't take into account the raised bottom. I measured the inside.

> enough to demonstrate what happens with different lengths of can
> antennas. Methinks you'll be rather amazed at the effects of the can
> length.

How long do you think it should be? Doubling was good for the chili and
the coffee. The chili really needs to be a little longer, and the coffee
could stand to be shorter, if the goal is one wavelength. Adjusting that
would be rather difficult with cans. You'd have to prototype, and then
build the right one. A rolled copper sheet suddenly gets a lot more
attractive.


This weekend, I'm going to poke a hole in the bottom of a 3lb coffee can
for my USB, mounted 31mm tip from bottom, kind of like the sardine can at
http://www.usbwifi.orcon.net.nz/sardusb.jpg but bigger and more shielded.

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

On Thu, 3 Feb 2005 20:53:56 +0000 (UTC), (E-Mail Removed)
wrote:

>>>I don't see any cantenna references on Trevor's site.
>> http://www.nec2.org/coffee.txt
>
>I still don't see any on Trevor's site ...

He didn't post an exaustive analysis. That's what I wanted to do (and
never finished). See:
http://www.nec2.org/wlan.htm
which proclaims:
"Another model that you might simulate is the ubiquitous Coffee
Can feed. Lower gain than the BiQuad, it also tends to radiate
significant sidelobes. I produced an optimum design for a Coffee
Can Antenna, with about 9dB of gain. You can copy the NEC model
from this link."

>That cone is used in a flat slotted
>waveguide http://www.trevormarshall.com/waveguides.htm

Yeah, that's what I said. The photo is for a 5.6GHz model, not
2.4Ghz. It's not like the cone is some strange oddity. See:

http://www.jefflaplante.com/catalog/...products_id/51
for where to buy a 2.4GHz version $15. I suspect this is overkill for
a coffee can antenna, but it does improve the bandwidth.

>Ah, tweaking. Given how hard it is for the home hobbyist to get a
>reasonable test range, tweaking is just out of the question in a coffee
>can.

I beg to differ. You just have to know some tricks. For example,
it's always necessary to use a reference antenna with known and
controlled characteristics. I have such a beast that I've spent some
time getting to play. I can easily measure the *relative* gain of the
antenna as compared to the reference antenna. If I make the
assumption that my test antenna is accurate, then I can easily
calculate the absolute gain. I also make an effort to compare the NEC
computah models with my measurements. I consider a 3dB total
variation to be good enough. My test range is across a valley
plastered with RF aborbing trees. My house is conveniently located on
the side of a hill so that reflections are minimal. If I'm concerned
about reflections, I just place a "tube" or "box" of RF absorbent foam
around the beam path. It will also work with omnis, but I usually
want to also characterize the mounting structure, so I'm usually
forced to live with the ground and mounting hardware reflections. I
would NEVER do the test on street level with a reflecting surface in
the beamwidth or fresnel zone.

>That's why you use a calculator and poke your hole, and take what you
>get... Unless you drink enough coffee to have a steady supply of cans.
>And then, where is the tweaking? Assuming that someone got it right,
>that's it. Poke a hole in the place that you're told to poke it.

I never follow instructions. I would poke the hole in the bottom of
the can and adjust the distance between the back of the can and a
dipole or bi-conical feed element. For the more common side mounted
derrangement, I would use a much smaller connector (SMA) with a thread
mount instead of the usual N connector. The hole would be a slot in
the side of the can. The SMA connector would be sandwitched between
two copper or brass washers. That will allow it to be moved back and
forth without leaving any (ungrounded) gapeing holes.

Quiz time: The driven element is 1/4 wave long. (Actually, it's about
0.95 * 1/4 wave due to end dispersion). So, from where do you measure
the 1/4 wave? From tip to where the wire enters the shielded part of
the connector, or from the tip to the metal can base ground? Yes,
it's that critical if you want low VSWR.

Incidentally, a short discussion about modeling coffee can antennas in
the NEC-LIST mailing list (on robomod.net) nailed me to the proverbial
wall for posting an NEC2 model without first doing a sanity check on
the model. It has some problems resulting in a potentially lousy gain
correlation with reality. So, now I gotta fix the model as well as
the spreadsheet generator. Grumble...

>> Yep. Remind me to send you my hacked version of Ivor's antenna design
>> spreadsheet.
>> http://www.ivor.it/wireless/cantenna.html
>> It has some problems that I'm trying to fix. However, it's close
>
>I played with that, and didn't find any difference from turnpoint, for the
>sizes I had on hand. Some commentary on one of the sites made me think
>that the differences were from measuring on the outside of the can, which
>didn't take into account the raised bottom. I measured the inside.

Ok, you answered my question correctly. You measure the 1/4 wave feed
element from tip to where it shielding on the connector starts.
That's fairly easy to measure with a small diameter SMA connector.
It's a mess of trigonometry for a big fat N connector, where the
effective shielding starts somewhat into the TFE part of the connector
resulting in an unexpectantly long feed element. It's *NOT* measured
to the base of the connector or the inside of the can which would
result in too short a feed element. It's not magic, but it's also not
trival to calculate. Therefore, I tweak and measure, also known as
optimize.

>> enough to demonstrate what happens with different lengths of can
>> antennas. Methinks you'll be rather amazed at the effects of the can
>> length.
>
>How long do you think it should be?

It appears to be cyclic. Some lengths are good but a half wave longer
causes the pattern to go really weird. I'm tryin got figure out if
it's for real or merely a figament of my calculation. 4NEC2 version
5.5 just appeared, which should fix the problems modelling patches
(that I found). Stay tuned.

>Doubling was good for the chili and
>the coffee. The chili really needs to be a little longer, and the coffee
>could stand to be shorter, if the goal is one wavelength. Adjusting that
>would be rather difficult with cans. You'd have to prototype, and then
>build the right one. A rolled copper sheet suddenly gets a lot more
>attractive.

Too expensive for initial prototypes. Use 0.090" thick aluminium
roofing flashing. If you're careful, you can build a telscopeing tube
for the ultimate in tweaking. Also, get some aluminium foil duct tape
to hold the seams together. For something that needs to be soldered,
use some copper tape. Only the inside is electrically important. You
can get very sloppy on the outside. I usually plant some copper tape
around connectors and joints for a better connection ground. The
dissimilar metals won't be a problem as long as the antenna stays dry.

If you feel ambitious, you might wanna dry building a horn antenna,
instead of a can, which has a noticeably higher gain per unit volume
than the can.
http://www.seattlewireless.net/index.cgi/CardboardHorn
http://users.skynet.be/chricat/horn/...avascript.html
Ugh. Cardboard? Well, I guess that will work.

The copper flashing I use is expensive and is mostly for building
horn, slot, patch, panel, or grounded backplane (i.e. biquad)
antennas. I buy it by the roll from the roofing supply. I think the
last roll cost me about $150.

>This weekend, I'm going to poke a hole in the bottom of a 3lb coffee can
>for my USB, mounted 31mm tip from bottom, kind of like the sardine can at
>http://www.usbwifi.orcon.net.nz/sardusb.jpg but bigger and more shielded.

Sigh. Best-o-luck. I don't think the sides of the sardine can are
high enough or the ground plane big enough to offer much help with the
antenna pattern. You might wanna compare the gain with something much
simpler, like a chunk of box cardboard, wrapped in aluminium foil,
with a hole poked in the middle. One of these daze, I'll rip my
DWL-122 apart, replace the PIFA antenna with an SMA connector or
install a real dipole antenna, and so some numbers. (Yet another
project).

If you're serious about the can antenna, you might consider shoving an
ABS (white plastic) 3/4" pipe across the diameter of the can, and
cramming the dongle into the pipe. I think it will fit, but don't
have a USB dongle type radio handy to test.

Aren't antennas fun? This should be interesting....
--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 AE6KS 831-336-2558

Jeff Liebermann <(E-Mail Removed)> wrote:
> On Thu, 3 Feb 2005 20:53:56 +0000 (UTC), (E-Mail Removed)
> wrote:

>>Ah, tweaking. Given how hard it is for the home hobbyist to get a
>>reasonable test range, tweaking is just out of the question in a coffee
>>can.

> I beg to differ. You just have to know some tricks. For example,

I meant physically. Moving the mount around in the coffee can is a bit
problematic, compared to the slide feed on the biquad.

> mount instead of the usual N connector. The hole would be a slot in
> the side of the can. The SMA connector would be sandwitched between
> two copper or brass washers. That will allow it to be moved back and
> forth without leaving any (ungrounded) gapeing holes.

Tsk-tsk. A while back you suggested that not fully soldering around the
base of an N-connector would have serious consequences. Now you're going to
have a slot to play with, presumably with no solder at all?

> Quiz time: The driven element is 1/4 wave long. (Actually, it's about
> 0.95 * 1/4 wave due to end dispersion). So, from where do you measure
> the 1/4 wave? From tip to where the wire enters the shielded part of
> the connector, or from the tip to the metal can base ground? Yes,
> it's that critical if you want low VSWR.

That doesn't look like a difficult measurement, that's a huge measurement.
You have the tip, you have the end of the solder bucket, you have the lump
of nylon surrounding the solder bucket, the lump of metal holding the
nylon, the side of the can, and the end of the threaded portion of the
N-connector. Which are you saying is the right place? I would say the top
of the metal, but the nylon would allow some radiation below there, so
somewhat lower. Turnpoint says "the total length of both the brass tube
and wire sticking out past the connector is 1.21 inches", so that's what I
did.

> Ok, you answered my question correctly. You measure the 1/4 wave feed
> element from tip to where it shielding on the connector starts.
> That's fairly easy to measure with a small diameter SMA connector.
> It's a mess of trigonometry for a big fat N connector, where the
> effective shielding starts somewhat into the TFE part of the connector
> resulting in an unexpectantly long feed element. It's *NOT* measured
> to the base of the connector or the inside of the can which would
> result in too short a feed element. It's not magic, but it's also not
> trival to calculate. Therefore, I tweak and measure, also known as
> optimize.

But when you get done, you tell the world... Isn't that what 1.21" is?

>>How long do you think it should be?

> It appears to be cyclic. Some lengths are good but a half wave longer
> causes the pattern to go really weird. I'm tryin got figure out if
> it's for real or merely a figament of my calculation. 4NEC2 version
> 5.5 just appeared, which should fix the problems modelling patches
> (that I found). Stay tuned.

Waiting patiently.

I'm thinking about shopping the stores for slightly different coffee cans,
to make a tight slide. Otherwise, it's cut and try. I thought about stove
vent tubing, since that does slide together, but I'd like something I can
solder when I get done.

>>This weekend, I'm going to poke a hole in the bottom of a 3lb coffee can
>>for my USB, mounted 31mm tip from bottom, kind of like the sardine can at
>>http://www.usbwifi.orcon.net.nz/sardusb.jpg but bigger and more shielded.

> Sigh. Best-o-luck. I don't think the sides of the sardine can are
> high enough or the ground plane big enough to offer much help with the

Oh, certainly. I think the sardine can is just about silly. I did use a
9" pie plate with some good effect, but I was mounted flat 31mm in front of
the plate. I didn't think about poking through from the back.

I'm going for a 3lb coffee can. That wasn't as good as the 1lb can for the
side mounting, but it's what I have on hand ;-)

> If you're serious about the can antenna, you might consider shoving an
> ABS (white plastic) 3/4" pipe across the diameter of the can, and
> cramming the dongle into the pipe. I think it will fit, but don't
> have a USB dongle type radio handy to test.

That would be as a slide mount, coming in from the side, instead of just
poking the USB connector through? The can I used positions that antenna
about in the center, so I thought that might be good. I did notice that
this style of mounting allows the dongle to wobble off vertical, so the PVC
(ABS is black) pipe would help with that, as well as allowing some
adjustment. Tugging on the cable moves the dongle enough to make a big
difference in the gain.
http://www.rahul.net/dold/clarence/u...42-800x600.jpg

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

On Sat, 5 Feb 2005 21:07:34 +0000 (UTC), (E-Mail Removed)
wrote:

>Tsk-tsk. A while back you suggested that not fully soldering around the
>base of an N-connector would have serious consequences. Now you're going to
>have a slot to play with, presumably with no solder at all?

Grounding is good. More grounding is better. Tighten the nut on the
connector and squash it between two brass washers. Good enough
ground.

>That doesn't look like a difficult measurement, that's a huge measurement.
>You have the tip, you have the end of the solder bucket, you have the lump
>of nylon surrounding the solder bucket, the lump of metal holding the
>nylon, the side of the can, and the end of the threaded portion of the
>N-connector. Which are you saying is the right place? I would say the top
>of the metal, but the nylon would allow some radiation below there, so
>somewhat lower. Turnpoint says "the total length of both the brass tube
>and wire sticking out past the connector is 1.21 inches", so that's what I
>did.

The feed element starts from where it extends beyond the shield on the
connector. However, with a wide connector like an "N", it's kinda a
guess as to where to start measureing. Looking at the connector from
different angles, the difference between measuring perpendicular to
perhaps a 45degree angle is about 2mm. Doesn't seem like much until
you consider that at 2.4GHz, the difference for a 1/4 wave element
between each of the band is:
3.0*10^8 m/sec / 2.400 * 10^9 cycles/sec /4 = 31.25mm
3.0*10^8 m/sec / 2.4835 * 10^9 cycles/sec /4 = 30.20mm
So, a difference of 1.05mm will move you from one end of the band to
the other. Can you say critical? This is why tweaking is important
and a way of life with microwaves.

>But when you get done, you tell the world... Isn't that what 1.21" is?

There are far too many effects to guarantee that 1.21" will be the
exact correct length. For example:
Differences in N connector construction
Variations on can diameter affecting connector projection size.
Aspect ratio (dia/length) of 1/4 wave element.
end dispersion effects.
The variations will be slight, but when 1.05mm will move you from one
end of the band to the other, methinks it's important to consider
them.

>> It appears to be cyclic. Some lengths are good but a half wave longer
>> causes the pattern to go really weird. I'm tryin got figure out if
>> it's for real or merely a figament of my calculation. 4NEC2 version
>> 5.5 just appeared, which should fix the problems modelling patches
>> (that I found). Stay tuned.
>
>Waiting patiently.

Well, I could have done it this weekend, but I prefered to do other
things. I'll get to it eventually. I promise. Really.

>I'm thinking about shopping the stores for slightly different coffee cans,
>to make a tight slide. Otherwise, it's cut and try. I thought about stove
>vent tubing, since that does slide together, but I'd like something I can
>solder when I get done.

I don't think you'll need to do much soldering. Copper roofing
flashing would be a good start. Please realize that it doesn't have
to be round. A rectangular waveguide section will work just fine. As
I previously suggested, make a rectangular horn antenna instead out of
flat copper sheet. Soldering is easy (with a really big iron). If
you wanna avoid soldering, use flanges and fill the gaps with copper
tape. However, I suggest you build your prototype out of aluminium
0.009" roofing flashing and use hot melt glue to hold things together.
Aluminium duct tape for filling in the seams. This isn't fabulous,
but will get you close to the final dimensions so that the final
copper version doesn't degenerate to cut-n-try. Also, be prepared to
silver plate the final design.

>> If you're serious about the can antenna, you might consider shoving an
>> ABS (white plastic) 3/4" pipe across the diameter of the can, and
>> cramming the dongle into the pipe. I think it will fit, but don't
>> have a USB dongle type radio handy to test.

>That would be as a slide mount, coming in from the side, instead of just
>poking the USB connector through?

Yes. I think it's an easier way of mounting the dongle. Shove it
into the pipe, pack it in place with some styrofoam peanuts, and no
glue required for mounting.

>The can I used positions that antenna
>about in the center, so I thought that might be good. I did notice that
>this style of mounting allows the dongle to wobble off vertical, so the PVC
>(ABS is black) pipe would help with that, as well as allowing some
>adjustment.

Sorry. Y'er right. The black is ABS while the white and grey are
PVC. I've had minor problems with the grey PVC pipe detuning the
antennas, but no problems with the white PVC. Fiberglass would be the
best, but unless you wanna pay boating supply prices, PVC is cheaper.
To be sure, shove a piece of plastic pipe in the microwave oven and
see if it gets hot. If it does, forget that idea. Don't bother with
the black plastic ABS pipe as I know it melts in the microwave oven.

>Tugging on the cable moves the dongle enough to make a big
>difference in the gain.
>http://www.rahul.net/dold/clarence/u...42-800x600.jpg

Hot melt glue it in place. I'm a big user of "adhesive technology"
and "surface mounting" aids, formerly known as bondo and duct tape.
Whatever works. The previous generation was bubble gum and hay
baleing wire.


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831.336.2558 voice http://www.LearnByDestroying.com
# (E-Mail Removed)
# (E-Mail Removed) AE6KS

"Floyd L. Davidson" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> "Bill Evans" <WHEvansIII-(E-Mail Removed)> wrote:
>>What's the expected range on a pair of Belkin 54G routers in wireless
>>bridge
>>mode?
>>
>>I've seen someone mention on at least one web tech support forum that they
>>were having troubles staying connected 100% of the time, but they then
>>went
>>on to say that they were trying to bridge 400 feet, from one building to
>>another building. Can I expect similar results?
>
> Probably. (I have no experience specifically with Belkin
> equipment, but unless there is something very unusual about it
> there won't be any real difference as far as range goes.)
>
> However, 400 feet from one building to another, works if and
> only if certain things happen to be true.


Guys, after receiving my pair of Belkin 54g routers, much to my chagrin I
found that they had no removable antenna mounts! Having no experience with
Belkin and tons with Linksys routers, I assumed they all had antennas that
would screw off.

So I'm going to have to do any potential replacement of a stock antenna on
the wifi NIC.


> You simply will not
> get good results going through walls, and some walls (metal) are
> absolutely killers. Hence you will do much better if you can
> place both units in a window, for example. Or even outside if
> you manage that. And the higher the elevation the better,
> because reflections from vehicles on the ground can cause
> signals to fade too.
>


Oh I've been there, done that with a cantenna on a Linksys router.

My original question was focusing primarily on the range in BRIDGE MODE.
That range may be identical to the unit's nominal range talking to an
average wifi NIC.


> Hence worst case is two units at ground level with a two or more
> walls between them, and best case is both units sitting in a 4th
> story window with an unobstructed view of each other.
>
> With that said, I have one unit sitting in the window at ground
> level, which works fairly well to a repeater about 400 yards
> away. Moreover there are two houses blocking a direct view!
> Near as I can tell the signal is bouncing off a building on the
> opposite side of the street (none of them have metal siding or
> anything obvious, so I'm not really sure just what the signal is
> bounding off).
>
> The same AP is just barely useable through one wall, on the
> ground floor of the building directly across the street! I put
> a repeater in a second story window, and it wasn't all that good
> either! But when I moved it from one side of the window to the
> other, a matter of about 20 inches, it became rock solid!
>
> The moral of the story is that you'll have to try it and see
> what you get. Under the right circumstances it can certainly be
> done.
>
>>What frequencies are used in Belkin's bridge-to-bridge mode? I assume it
>>may not be standard because Belkin's bridge mode only works with other
>>Belkin WAP's.
>>
>>Also can I replace one of the stock omni-directional antennas with a
>>cantenna to use along the bridge line of sight? If the bridge mode
>>frequency is different than standard 802.11b's 2.412 GHz or so, I'll need
>>to
>>know that to calculate my can radius and quarter-wavelength distance, yada
>>yada yada...
>
> They all use the same set of channels. A cantenna optimized for
> channel 11 might not work as well on channel 1, but I'd guess
> that the difference would be slight. Certainly an antenna cut
> for say channel 8 will do equally well for everything from 6 to
> 10, at a minimum.
>
> The typical construction of a cantenna is not adaquate for
> outdoor use, except perhaps in a very dry climate where there is
> also not much wind. But for mounting inside, they make a
> significant difference, both in signal strength at the desired
> location but also to reduce signal strength in undesired
> directions.
>


Long.story.short: I'm going to go diagonally from one end of a 200' (deep
and wide) building to the other with five Belkin 54g's, four acting as
bridges off of the main master unit acting as DHCP server and router for the
entire network.

At that extreme corner, I have a wood exterior wall. 200' away from that is
a concrete block building with an A-frame roofline I can put a cantenna up
in to get a good L.O.S. back to the main building. Now I'm trying to decide
which PCI (or possibly USB) wifi NIC to order.

Obviously I'm looking for one with great specs (high end on transmit power,
etc.) and a removable antenna to allow me to go up 8-10' to get above the
concrete blocks for the best L.O.S. with the least bulk in between the two
devices.



--
bill evans
(E-Mail Removed)
Hartselle, AL

Freeman Dyson: "It's best not to limit our thinking. We can always
air-condition the Earth."