parabolic antenna and beam width

[Guest]

Archived from groups: alt.internet.wireless (More info?)

Hi all,
I purchased two LinkSys WRT54GS wifi routers to set up a wireless bridge
between two houses, the distance is about 340 meters, there are some oak
trees in the line of sight.

I am considering to buy two parabolic antennas from Stella Doradus, but
I am not sure how much gain I need to setup a stable wifi bridge:
<http://www.stelladoradus.com/2.4para.shtml>

I noticed that the antennas with higher gain have smaller beam width, so
I think it is harder to 'point' them in the right direction and they are
less proof to movements (wind, etc.). Is that correct?

I am considering to get the 24 SD19 one, with 19 dBi gain, will it be
enough for my needs?

If I get an antenna with higher gain, just to be on the safe side, will
I have problems to 'point' it in the right direction or will the radio
signal be too 'strong'?
Please excuse my ignorance about this subject ...

What low loss cable do you recommend? Is the LMR400 a good one?

I think the Linksys wifi router has a RP-TNC connection, but I am not
sure about the Stella Doradus antenna, any idea?

Where can I buy a couple of short cables (e.g. 30 cm) already with the
right connectors installed at the ends?

Thanks a lot.

 

[Guest]

Archived from groups: alt.internet.wireless (More info?)

I dont think you can use the wrt54gs as a bridge, it is an Access
point and wont talk to another AP.
You need something like the WAP54g that can function as a bridge, AP,
AP client or repeater.



"meATprivacyDOTnet" <me@privacy.net> wrote in message
news:30mcquF318d9pU1@uni-berlin.de...
> Hi all,
> I purchased two LinkSys WRT54GS wifi routers to set up a wireless
bridge
> between two houses, the distance is about 340 meters, there are some
oak
> trees in the line of sight.
>
> I am considering to buy two parabolic antennas from Stella Doradus,
but
> I am not sure how much gain I need to setup a stable wifi bridge:
> <http://www.stelladoradus.com/2.4para.shtml>
>
> I noticed that the antennas with higher gain have smaller beam
width, so
> I think it is harder to 'point' them in the right direction and they
are
> less proof to movements (wind, etc.). Is that correct?
>
> I am considering to get the 24 SD19 one, with 19 dBi gain, will it
be
> enough for my needs?
>
> If I get an antenna with higher gain, just to be on the safe side,
will
> I have problems to 'point' it in the right direction or will the
radio
> signal be too 'strong'?
> Please excuse my ignorance about this subject ...
>
> What low loss cable do you recommend? Is the LMR400 a good one?
>
> I think the Linksys wifi router has a RP-TNC connection, but I am
not
> sure about the Stella Doradus antenna, any idea?
>
> Where can I buy a couple of short cables (e.g. 30 cm) already with
the
> right connectors installed at the ends?
>
> Thanks a lot.

 

[Guest]

Archived from groups: alt.internet.wireless (More info?)

On Thu, 25 Nov 2004 16:42:21 +0100, meATprivacyDOTnet <me@privacy.net>
wrote:

>I purchased two LinkSys WRT54GS wifi routers to set up a wireless bridge
>between two houses,

Send them back and get either a pair of WAP54G bridge radios, or a
single WAP54G to talk to your WRT54GS. Wireless routers don't talk to
each other (unless you're planning to use WDS).

>the distance is about 340 meters, there are some oak
>trees in the line of sight.

Trees are evil.

>I am considering to buy two parabolic antennas from Stella Doradus, but
>I am not sure how much gain I need to setup a stable wifi bridge:
><http://www.stelladoradus.com/2.4para.shtml>
>
>I noticed that the antennas with higher gain have smaller beam width, so
>I think it is harder to 'point' them in the right direction and they are
>less proof to movements (wind, etc.). Is that correct?
>
>I am considering to get the 24 SD19 one, with 19 dBi gain, will it be
>enough for my needs?

Well, I'll be happy to do the math for you, as I've done several times
in this newgroup. However, I need to know coax cable type and length,
and type and length of optional pigtail. See:
http://www.ydi.com/calculation/som.php
for the basic calcs. See:

http://www.google.com/groups?selm=5m54q0dmt6cmvvb496p921t9eqbm022vnt%404ax.com
for an example of how I grind the numbers.

>If I get an antenna with higher gain, just to be on the safe side, will
>I have problems to 'point' it in the right direction or will the radio
>signal be too 'strong'?

No. There's no such thing as too strong in such a system. The signal
level required to overload the receiver front end is fairly
substantial. I can calculate that if you'd like, but I don't think it
will be an issue at 340 meters.

>What low loss cable do you recommend? Is the LMR400 a good one?

LMR400 is a good choice. However, if the cable run is rediculously
long, heavier cable such as LMR600 may be necessary. By the time you
get to fat cable, methinks it's best to simply mount the radio on the
roof near the antenna.
http://www.sveasoft.com/articles/armored/
(About 6 page. See tiny "next" in lower right corner of page).

>I think the Linksys wifi router has a RP-TNC connection, but I am not
>sure about the Stella Doradus antenna, any idea?

WRT54GS uses R-TNC. The data sheets on the dish at:
http://www.stelladoradus.com/2.4.ghz.parabolic.antennas.php
show a male N connector.

>Where can I buy a couple of short cables (e.g. 30 cm) already with the
>right connectors installed at the ends?

That would depend on what country you were located. In the US, I buy
from:
http://www.fab-corp.com
No experience with international vendors.


--
Jeff Liebermann jeffl@comix.santa-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 AE6KS 831-336-2558

 

[Guest]

Archived from groups: alt.internet.wireless (More info?)

Yes, the gain of antenna comes from squashing the radiated energy into a
smaller beam, so
higher gains go hand in and with smaller beamwidths, and the beamwidth to
the -3dB points
will be approx (1.2 * wavelength / dish diameter) radians (where 2 * 3.142
radians equals 180 degrees).

Link bandwidth will drop with signal strength.
Signal strength will drop with increasing distance - 1/r^2 as the beam
spreads out, and 1/r due to attenuation through
the atmosphere - I've seen a theoretical model somewhere on the net (I can't
find it now); the 1/r term is significant at 2.4GHz as this corresponds to
water absorption.

I'm not sure what attenuation you will get in your environment, but you
could try plotting a graph of signal level against range or log(range), and
extrapolating from that.

I can't comment on the cable - but I'd keep it as short as possible to
minise losses.
Maplin (UK) do various connectors, including TNC (not connected to cable):-

http://www.maplin.co.uk/family.aspx?menu=227&menuname=RF+Connectors&worldid=2&doy=25m11


At a range of about 4 metres I'm getting a signal strength of -34dBm, giving
a
link rate of 54Mbd.I still get a link rate of 54Mbd even if I drop the
received signal
to -55to -60dBm (by badly positioning the antenna - down the back of a
radiator)

At a range of about 50 metres through 2 brick walls and a silver birch I get
around -70dBm,which my Linksys thinks it can manage 1Mbd through.

hope this helps.
Colin


"meATprivacyDOTnet" <me@privacy.net> wrote in message
news:30mcquF318d9pU1@uni-berlin.de...
> Hi all,
> I purchased two LinkSys WRT54GS wifi routers to set up a wireless bridge
> between two houses, the distance is about 340 meters, there are some oak
> trees in the line of sight.
>
> I am considering to buy two parabolic antennas from Stella Doradus, but I
> am not sure how much gain I need to setup a stable wifi bridge:
> <http://www.stelladoradus.com/2.4para.shtml>
>
> I noticed that the antennas with higher gain have smaller beam width, so I
> think it is harder to 'point' them in the right direction and they are
> less proof to movements (wind, etc.). Is that correct?
>
> I am considering to get the 24 SD19 one, with 19 dBi gain, will it be
> enough for my needs?
>
> If I get an antenna with higher gain, just to be on the safe side, will I
> have problems to 'point' it in the right direction or will the radio
> signal be too 'strong'?
> Please excuse my ignorance about this subject ...
>
> What low loss cable do you recommend? Is the LMR400 a good one?
>
> I think the Linksys wifi router has a RP-TNC connection, but I am not sure
> about the Stella Doradus antenna, any idea?
>
> Where can I buy a couple of short cables (e.g. 30 cm) already with the
> right connectors installed at the ends?
>
> Thanks a lot.

 

[Guest]

Archived from groups: alt.internet.wireless (More info?)

On Thu, 25 Nov 2004 22:23:41 -0000, "nospam" <me@privacy.net> wrote:

>Yes, the gain of antenna comes from squashing the radiated energy into a
>smaller beam, so
>higher gains go hand in and with smaller beamwidths, and the beamwidth to
>the -3dB points
>will be approx (1.2 * wavelength / dish diameter) radians (where 2 * 3.142
>radians equals 180 degrees).

Let's see how close we get with the antenna in question:
http://www.stelladoradus.com/pdfs/2.4/parabolic/grid/24%20SD27.pdf
It's interesting that the chart at:
http://www.stelladoradus.com/2.4.ghz.parabolic.antennas.php
claims 10 degress for the SD27, while the data sheet says 8 degrees.

wavelength = 3x10^8 meters/sec / 2400x10^6 Hz = 0.125 meters
Dish diameter = 91 cmd
1.2 * 0.125 / 0.91 = 0.164 radians
0.164 radians * 180 / Pi = 9.4 degrees.
Yep, it works.

Argh. I'm late. More later...

>Link bandwidth will drop with signal strength.
>Signal strength will drop with increasing distance - 1/r^2 as the beam
>spreads out, and 1/r due to attenuation through
>the atmosphere - I've seen a theoretical model somewhere on the net (I can't
>find it now); the 1/r term is significant at 2.4GHz as this corresponds to
>water absorption.
>
>I'm not sure what attenuation you will get in your environment, but you
>could try plotting a graph of signal level against range or log(range), and
>extrapolating from that.
>
>I can't comment on the cable - but I'd keep it as short as possible to
>minise losses.
>Maplin (UK) do various connectors, including TNC (not connected to cable):-
>
>http://www.maplin.co.uk/family.aspx?menu=227&menuname=RF+Connectors&worldid=2&doy=25m11
>
>
>At a range of about 4 metres I'm getting a signal strength of -34dBm, giving
>a
> link rate of 54Mbd.I still get a link rate of 54Mbd even if I drop the
>received signal
>to -55to -60dBm (by badly positioning the antenna - down the back of a
>radiator)
>
>At a range of about 50 metres through 2 brick walls and a silver birch I get
>around -70dBm,which my Linksys thinks it can manage 1Mbd through.
>
>hope this helps.
>Colin
>
>
>"meATprivacyDOTnet" <me@privacy.net> wrote in message
>news:30mcquF318d9pU1@uni-berlin.de...
>> Hi all,
>> I purchased two LinkSys WRT54GS wifi routers to set up a wireless bridge
>> between two houses, the distance is about 340 meters, there are some oak
>> trees in the line of sight.
>>
>> I am considering to buy two parabolic antennas from Stella Doradus, but I
>> am not sure how much gain I need to setup a stable wifi bridge:
>> <http://www.stelladoradus.com/2.4para.shtml>
>>
>> I noticed that the antennas with higher gain have smaller beam width, so I
>> think it is harder to 'point' them in the right direction and they are
>> less proof to movements (wind, etc.). Is that correct?
>>
>> I am considering to get the 24 SD19 one, with 19 dBi gain, will it be
>> enough for my needs?
>>
>> If I get an antenna with higher gain, just to be on the safe side, will I
>> have problems to 'point' it in the right direction or will the radio
>> signal be too 'strong'?
>> Please excuse my ignorance about this subject ...
>>
>> What low loss cable do you recommend? Is the LMR400 a good one?
>>
>> I think the Linksys wifi router has a RP-TNC connection, but I am not sure
>> about the Stella Doradus antenna, any idea?
>>
>> Where can I buy a couple of short cables (e.g. 30 cm) already with the
>> right connectors installed at the ends?
>>
>> Thanks a lot.
>

--
Jeff Liebermann jeffl@comix.santa-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 AE6KS 831-336-2558

 

[Guest]

Archived from groups: alt.internet.wireless (More info?)

On 11/25/04 5:31 PM, Airhead wrote:
> I dont think you can use the wrt54gs as a bridge, it is an Access
> point and wont talk to another AP.
> You need something like the WAP54g that can function as a bridge, AP,
> AP client or repeater.

Hi,
I am going to use an alternative firmware to get the bridging
functionality for the LinkSys WRT54GS router.

Check this out:
<http://www.sveasoft.com/>

BTW, does anyone know any another (possibly free) alternative firmware
with bridging functionality for that router?

Thanks.

 

[Guest]

Archived from groups: alt.internet.wireless (More info?)

On 11/25/04 10:12 PM, Jeff Liebermann wrote:

> Send them back and get either a pair of WAP54G bridge radios, or a
> single WAP54G to talk to your WRT54GS. Wireless routers don't talk to
> each other (unless you're planning to use WDS).

Actually I am planning to use an alternative firmware (e.g.
<http://www.sveasoft.com/>) to get the bridging feature.

Can I use WDS instead? I don't think so, since I only need to do a
dedicated wifi bridge between the two LinkSys WRT54GS routers. Is that
correct?

> Trees are evil.

Yes, I know that, but they are not a lot. Will higher gain antennas help
with them?

> Well, I'll be happy to do the math for you, as I've done several times
> in this newgroup. However, I need to know coax cable type and length,
> and type and length of optional pigtail. See:
> http://www.ydi.com/calculation/som.php

I found some pigtails in my country (Italy): the length is 30 cm, the
cable type is RG-316. Is it a good one?

> No. There's no such thing as too strong in such a system. The signal
> level required to overload the receiver front end is fairly
> substantial. I can calculate that if you'd like, but I don't think it
> will be an issue at 340 meters.

Great, then I'll get the parabolic antennas with the higher gain I can
find, just to be on the safe side. I should be able to configure the
radio signal power on the LinkSys WRT54GS router.

> LMR400 is a good choice. However, if the cable run is rediculously
> long, heavier cable such as LMR600 may be necessary. By the time you
> get to fat cable, methinks it's best to simply mount the radio on the
> roof near the antenna.
> http://www.sveasoft.com/articles/armored/
> (About 6 page. See tiny "next" in lower right corner of page).

Great article, I think I'll do that, so I only need two pigtails
(probably 30 cm or so), it looks like there are no LMR400 pigtails
around, is it hard to make a pigtail out of that cable type?

> That would depend on what country you were located. In the US, I buy
> from:
> http://www.fab-corp.com

That looks a great online shop, but shipping fees are pretty high.
I found this one at a good price:
<http://cgi.ebay.it/ws/eBayISAPI.dll?ViewItem&item=5733635092>
Does it look good to you?

Thanks a lot.

 

[Guest]

Archived from groups: alt.internet.wireless (More info?)

"meATprivacyDOTnet" <me@privacy.net> wrote in message
news:30rne0F33142iU1@uni-berlin.de...
| On 11/25/04 10:12 PM, Jeff Liebermann wrote:
|
| > Send them back and get either a pair of WAP54G bridge radios, or a
| > single WAP54G to talk to your WRT54GS. Wireless routers don't talk to
| > each other (unless you're planning to use WDS).
|
| Actually I am planning to use an alternative firmware (e.g.
| <http://www.sveasoft.com/>) to get the bridging feature.
|
| Can I use WDS instead? I don't think so, since I only need to do a
| dedicated wifi bridge between the two LinkSys WRT54GS routers. Is that
| correct?
|
| > Trees are evil.
|
| Yes, I know that, but they are not a lot. Will higher gain antennas help
| with them?
|

To an extent yes but the link budget (path loss) is hard to estimate.
Signal levels can vary by season, if the leaves have dew (ie wet/dry)

| > Well, I'll be happy to do the math for you, as I've done several times
| > in this newgroup. However, I need to know coax cable type and length,
| > and type and length of optional pigtail. See:
| > http://www.ydi.com/calculation/som.php
|
| I found some pigtails in my country (Italy): the length is 30 cm, the
| cable type is RG-316. Is it a good one?

Don;t know much about the RG-316 but I do know that with any coax the
quality can vary considerably.
|

 

[Guest]

Archived from groups: alt.internet.wireless (More info?)

On Sat, 27 Nov 2004 17:13:50 +0100, meATprivacyDOTnet <me@privacy.net>
wrote:

>Actually I am planning to use an alternative firmware (e.g.
><http://www.sveasoft.com/>) to get the bridging feature.

OK. I don't know much about the various alternative firmwares.

>Can I use WDS instead?

To do what? The only description of what you intended to accomplish
is to "bridge" between the two houses.

>I don't think so, since I only need to do a
>dedicated wifi bridge between the two LinkSys WRT54GS routers. Is that
>correct?

Again, to do what? Are you going to have wireless clients running
around each end, that need to access the internet through the bridge
radios? Will there be wired clients on both ends? Can you tolerate
the 50% reduction in thruput caused by WDS?

>Yes, I know that, but they are not a lot. Will higher gain antennas help
>with them?

Sure, higher gain antennas will help drill through folliage. However,
if the signal is completely blocked by the trees, even the largest
antennas will result in an unsable connection.

>I found some pigtails in my country (Italy): the length is 30 cm, the
>cable type is RG-316. Is it a good one?

No. The outer diameter is 0.098". This very small coax is made for
connecting between circuit boards and external panel mount connectors.
Loss is 0.60dB/ft. At 30cm (about 10") it's not going to make much
difference. However, the pigtail I'm referring to is the one between
your WRT54G and the LMR-400 coax cable from the rooftop antenna. With
coax that small, one mistake and you're gonna rip the coax out of the
connectors. I suggest pigtails from something stronger like LMR-100A
which is 0.150" dia (and 0.35dB/ft).

>> No. There's no such thing as too strong in such a system. The signal
>> level required to overload the receiver front end is fairly
>> substantial. I can calculate that if you'd like, but I don't think it
>> will be an issue at 340 meters.

>Great, then I'll get the parabolic antennas with the higher gain I can
>find, just to be on the safe side. I should be able to configure the
>radio signal power on the LinkSys WRT54GS router.

Yes, but you'll probably want and need the strongest signal possible.
The connection speed is totally dependent on the signal strength (and
s/n ratio). If you loose signal strength, the error rate will
increase, which causes the bridge radios to drop their data rate to
reduce errrors.

>> http://www.sveasoft.com/articles/armored/
>> (About 6 page. See tiny "next" in lower right corner of page).

>Great article, I think I'll do that, so I only need two pigtails
>(probably 30 cm or so), it looks like there are no LMR400 pigtails
>around, is it hard to make a pigtail out of that cable type?

The reason you need a pigtail is that LMR-400 is very stiff. It will
literally tear apart a connector or drag the WRT54G across the table.
You need a short piece of something between the LMR-400 and the radio
to allow some movement if necessary. You can get an R-TNC connector
on the end of a piece of LMR-400 coax. You can also get an N to R-TNC
adapter. However, both tof these methods, which do not require a
pigtail, will cause problems with connector alignment, damage, and
moving boxes.

It's not difficult to crimp your own connectors. RF-Industries makes
most of the connectors. About $5-$8/ea from Digikey. The crimping
tools are available for about $35.
http://www.hyperlinktech.com/web/cable_tools.php
Plan on ruining a few while learning to use the crimpers. Also, be
sure to get the cable stripper. I do mine by hand, with a pocket
knife, but I'll admit that the stripper does a better job.

>I found this one at a good price:
><http://cgi.ebay.it/ws/eBayISAPI.dll?ViewItem&item=5733635092>
>Does it look good to you?

For $12, it's a bargain. That's less than what the connectors usually
cost me. The LMR-195 is much more flexible than LMR-100A but somewhat
more attenuation (0.55dB/ft).

--
Jeff Liebermann jeffl@comix.santa-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 AE6KS 831-336-2558

 

[Guest]

Archived from groups: alt.internet.wireless (More info?)

On 11/25/04 11:57 PM, Jeff Liebermann wrote:

> Let's see how close we get with the antenna in question:
> http://www.stelladoradus.com/pdfs/2.4/parabolic/grid/24%20SD27.pdf
> It's interesting that the chart at:
> http://www.stelladoradus.com/2.4.ghz.parabolic.antennas.php
> claims 10 degress for the SD27, while the data sheet says 8 degrees.
>
> wavelength = 3x10^8 meters/sec / 2400x10^6 Hz = 0.125 meters
> Dish diameter = 91 cmd
> 1.2 * 0.125 / 0.91 = 0.164 radians
> 0.164 radians * 180 / Pi = 9.4 degrees.
> Yep, it works.
>
> Argh. I'm late. More later...

So will this be a good antenna for a 350 meters link?

Don't forget a couple of trees in the LOS ...

Thanks.

 

[Guest]

Archived from groups: alt.internet.wireless (More info?)

On Sat, 27 Nov 2004 17:25:55 +0100, meATprivacyDOTnet <me@privacy.net>
wrote:

>On 11/25/04 11:57 PM, Jeff Liebermann wrote:
>
>> Let's see how close we get with the antenna in question:
>> http://www.stelladoradus.com/pdfs/2.4/parabolic/grid/24%20SD27.pdf
>> It's interesting that the chart at:
>> http://www.stelladoradus.com/2.4.ghz.parabolic.antennas.php
>> claims 10 degress for the SD27, while the data sheet says 8 degrees.
>>
>> wavelength = 3x10^8 meters/sec / 2400x10^6 Hz = 0.125 meters
>> Dish diameter = 91 cmd
>> 1.2 * 0.125 / 0.91 = 0.164 radians
>> 0.164 radians * 180 / Pi = 9.4 degrees.
>> Yep, it works.
>>
>> Argh. I'm late. More later...

>So will this be a good antenna for a 350 meters link?

Probably. My seat of the pants guess is that 24dBi on both ends is
probably needed to drill through two trees. However I'm a
practitioner of the black art of calculation and always grind the
numbers before passing judgement. You haven't supplied a few key
pieces of missing information, so I can't grind any numbers.

From a previous posting:

Well, I'll be happy to do the math for you, as I've done several
times in this newgroup. However, I need to know coax cable type
and length, and type and length of optional pigtail. See:
http://www.ydi.com/calculation/som.php
for the basic calcs. See:

http://www.google.com/groups?selm=5m54q0dmt6cmvvb496p921t9eqbm022vnt%404ax.com
for an example of how I grind the numbers.

>Don't forget a couple of trees in the LOS ...

Don't forget the cable lengths (each end). I can usually give a good
guess as to the penetration through trees based on some foliage
attenuation models and personal experience. For that, I need a photo
with the fresnel zone marked on the image, as well as a photo of the
cross section of the intended path. As a general rule of thumb, if
you have soaking wet or frozen broadleaf trees, nothing will work. If
it's needles or very dry (desert) shrubbage, it can be penetrated.
Absolutely nothing goes through a trunk.


--
Jeff Liebermann jeffl@comix.santa-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 AE6KS 831-336-2558

 

[Guest]

Archived from groups: alt.internet.wireless (More info?)

On 11/28/04 12:44 AM, Jeff Liebermann wrote:

> Again, to do what? Are you going to have wireless clients running
> around each end, that need to access the internet through the bridge
> radios? Will there be wired clients on both ends? Can you tolerate
> the 50% reduction in thruput caused by WDS?

Let me explain better.

I would like to use the LinkSys boxes to setup the wifi bridge between
the two buildings.

Then I'll attach (wired, not via radio) the computers of each building
to the LAN ports of each WRT54GS or to a network switch connected
(wired) to the WRT54GS.

So, no wireless clients will be connected to the WRT54GS boxes (except
for themselves).

I want the computers of both building to be on the same network (e.g.
192.168.0.1/255.255.255.0).

I also want to share the broadband connection: one of the building has a
high speed connection to the Internet using a Cisco router.

What is the best way to realize such wifi bridge?

Set one WRT54GS in AP mode and the other one in client mode?

This should be possible with the Sveasoft Satori (public) firmware, but
it looks like there are a couple of problems with that:
- You have to disable lookback interface on the client WRT54GS, not sure
why and if it causes any problem.
- Only one (wired) client can be connected to the client WRT54GS,
otherwise things won't work well: this is a big limitation for me.

Can anyone confirm this?

It looks like the Sveasoft Alchemy (pre-release) firmware handles the
bridge feature in a different way, but the firmware is not public yet
and I cannot test it ...

That's why I thought to give WDS a try.

Here is the WDS definition:

<http://www.broadbandbuyer.co.uk/BuyersGuide/FAQDetail.asp?TextID=340&SetID=80>
---
WDS (Wireless Distribution System) is a Wireless Access Point mode that
enables wireless bridging in which WDS APs communicate only with each
other only (without allowing for wireless clients or stations to access
them), and/or wireless repeating in which APs communicate both with each
other and with wireless stations (at the expense of half the throughput).
---

It looks like it may be a good way to get a wireless bridge between two
WRT54GS boxes and have the full bandwidth available, since I am not
going to connect any wireless client to the LinkSys boxes.

Do you think that will work?

> Sure, higher gain antennas will help drill through folliage. However,
> if the signal is completely blocked by the trees, even the largest
> antennas will result in an unsable connection.

I can see a little bit through the foliage, hopefully eve the radio
signal will be able to pass through ...

> No. The outer diameter is 0.098". This very small coax is made for
> connecting between circuit boards and external panel mount connectors.
> Loss is 0.60dB/ft. At 30cm (about 10") it's not going to make much
> difference. However, the pigtail I'm referring to is the one between
> your WRT54G and the LMR-400 coax cable from the rooftop antenna. With
> coax that small, one mistake and you're gonna rip the coax out of the
> connectors. I suggest pigtails from something stronger like LMR-100A
> which is 0.150" dia (and 0.35dB/ft).

I'll be putting each WRT54GS device in an almost sealed box next to the
antenna, all I need is pigtail between the device and the antenna, no
need for the LMR-400 coax cable.

> The reason you need a pigtail is that LMR-400 is very stiff. It will
> literally tear apart a connector or drag the WRT54G across the table.
> You need a short piece of something between the LMR-400 and the radio
> to allow some movement if necessary. You can get an R-TNC connector
> on the end of a piece of LMR-400 coax. You can also get an N to R-TNC
> adapter. However, both tof these methods, which do not require a
> pigtail, will cause problems with connector alignment, damage, and
> moving boxes.
>
> It's not difficult to crimp your own connectors. RF-Industries makes
> most of the connectors. About $5-$8/ea from Digikey. The crimping
> tools are available for about $35.
> http://www.hyperlinktech.com/web/cable_tools.php
> Plan on ruining a few while learning to use the crimpers. Also, be
> sure to get the cable stripper. I do mine by hand, with a pocket
> knife, but I'll admit that the stripper does a better job.

Thanks for the great explanation, I haven't seen a LMR-400 coax cable
yet, I had no idea it was so stiff ...

> For $12, it's a bargain. That's less than what the connectors usually
> cost me. The LMR-195 is much more flexible than LMR-100A but somewhat
> more attenuation (0.55dB/ft).

Actually it looks like the opposite is true: the LMR-100A is thinner and
has more attenuation than the LMR-195:
<http://www.mtwirefree.net/w3eme/coax.htm>
<http://www.timesmicrowave.com/cgi-bin/calculate.pl>

Unless I am missing something, the eBay pigtail seems very good, I think
I am going to get a couple of them.

Thanks.

 

[Guest]

Archived from groups: alt.internet.wireless (More info?)

On 11/28/04 12:14 AM, Jeff Liebermann wrote:

> Don't forget the cable lengths (each end). I can usually give a good
> guess as to the penetration through trees based on some foliage
> attenuation models and personal experience. For that, I need a photo
> with the fresnel zone marked on the image, as well as a photo of the
> cross section of the intended path. As a general rule of thumb, if
> you have soaking wet or frozen broadleaf trees, nothing will work. If
> it's needles or very dry (desert) shrubbage, it can be penetrated.

Except for the pigtail, there will be no cable at each installation,
since I'll put the LinkSys box next to the antenna.

What would be the best way to get you some pics?

Thanks a lot for your advise.

 

[Guest]

Archived from groups: alt.internet.wireless (More info?)

On Sun, 28 Nov 2004 18:28:16 +0100, meATprivacyDOTnet <me@privacy.net>
wrote:

>Except for the pigtail, there will be no cable at each installation,
>since I'll put the LinkSys box next to the antenna.

OK, I can work with that and a bit of guesswork.

>What would be the best way to get you some pics?

Email. Addresses in signature are real. Don't send Bcc: or I'll have
to fish it out of the spam trap.



--
Jeff Liebermann jeffl@comix.santa-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 AE6KS 831-336-2558

 

[Guest]

Archived from groups: alt.internet.wireless (More info?)

On Sun, 28 Nov 2004 18:28:16 +0100, meATprivacyDOTnet <me@privacy.net>
wrote:

>Except for the pigtail, there will be no cable at each installation,
>since I'll put the LinkSys box next to the antenna.

Ok. Let's run the initial numbers. I'll throw in the trees when I
see them. See:
http://www.ydi.com/calculation/som.php
What you're looking for is an absolute minimum of 10dB fade margin.
The system will work with 0dB of fade margin, but not be particularly
stable. A passing bird would cause the signal to disappear. At 10dB,
if set to 802.11g only (ignore 802.11b), will probably be running at
12Mbps connection speed (and about half that in thruput). Any
interference will make it worse.

I use these number for receiver sensitivity at various connection
speeds. They're from a D-Link DI-624 data sheet and appear to be
rather typical. You're WRT54GS will be close.
* 54Mbps OFDM, 10% PER, -68dBm)
* 48Mbps OFDM, 10% PER, -68dBm)
* 36Mbps OFDM, 10% PER, -75dBm)
* 24Mbps OFDM, 10% PER, -79dBm)
* 18Mbps OFDM, 10% PER, -82dBm)
* 12Mbps OFDM, 10% PER, -84dBm)
* 11Mbps CCK, 8% PER, -82dBm)
* 9Mbps OFDM, 10% PER, -87dBm)
* 6Mbps OFDM, 10% PER, -88dBm)
* 5.5Mbps CCK, 8% PER, -85dBm)
* 2Mbps QPSK, 8% PER, -86dBm)
* 1Mbps BPSK, 8% PER, -89dBm)

Using my crystal ball and some guesswork:
Distance = 0.211 miles (340 meters)
TX power = +15dBm
RX sens = -84dBm (at 12Mbits/sec OFDM)
TX ant gain = 17dBi (medium size dish)
RX ant gain = 17dBi (same at other end)
TX coax loss = -3dB (1ft LMR-195 plus a mess of connectors)
RX coax loss = -3dB (same at other end)
which yields a fade margin of 36dB which is quite good. That would
give you a max possible 26dB for foliage loss, which is reasonable for
a small broadleaf not very dense tree. A really bad approximation is
about 1dB per meter attenuation through the "typical" tree (whatever
that means) minus the trunk, heavy branches, and water logged leaves
(banana, tropical, etc). If you increase the antenna gain to 24dBi,
your fade margin will be 50dB, leaving 40dB for foliage loss. That's
enough to go through most "typical" trees.

This should give you some clues on trees:
http://www.wlanantennas.com/wlan_faq_radioprop.htm

Yeah, methinks it will work at 340 meters with 17dBi dishes.


--
Jeff Liebermann jeffl@comix.santa-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 AE6KS 831-336-2558

 

[Guest]

Archived from groups: alt.internet.wireless (More info?)

On 11/29/04 1:58 AM, Jeff Liebermann wrote:

> To the best of my knowledge (i.e. I might be wrong), the stock WRT54GS
> (Linksys firmware) does not have a client mode. The WAP54G certainly
> does. Looks like Sveasoft Satori 4.0 does:
> http://www.linksysinfo.org/modules.php?name=News&file=article&sid=72
> The problem with this derrangement is that it will bridge exactly one
> MAC address. That's fine if your remote site only has one computah,
> but that's never the case. You can do it by enabling the VPN
> termination on your unspecified Cisco router and gettting a VPN router
> at the other end. Messy, but possible. Not recommended.

I have multiple computers at the remote site, so the single MAC address
will be an issue for me.
I got the WRT54GS instead of the WAP54G because it has better hardware
(fast CPU, more memory, SpeedBoster, etc.) and I thought the alternative
firmware would add all the WAP54G features ...

> Yes, WDS will work. See:
> http://www.orinocowireless.com/support/techbulletins/TB-046.pdf
> for one of the better writeups on WDS. Go down to "Performance
> Evaluations" and try to predict what you'll get. Since Orinoco used
> 802.11b, your numbers will be about 4 times better if you have lots of
> signal to play with. Note that item #3 on Page 10, where both clients
> are wired to the access points with a single radio in each access
> point, yields the worst thruput. Yeah, it will work if you don't mind
> running at the speed of a snail.

It looks like there is an error on page 10, item #3 should read "Both
clients WIRELESSLY connected to each AP ..." instead of "Both clients
WIRED connected to each AP ...", at least according to the diagram on
page 11.

My setup would be like item #1 ("Both clients wired connected to each
AP"), that yiedls the best throughput.
I think that's close to the actual maximum 802.11b throughput: it looks
like you don't loose any bandwidth using WDS to setup a wireless bridge
between two APs and using wired clients.

> You're probably safe with LMR-100 or LMR-195. I would not go with the
> really tiny stuff.

Why most people use LMR-100A instead of LMR-195 (less loss) for pigtails?

> Reminder: Think about where the water will go if it gets inside or
> drips down the coax. It most assuredly will.

Will drilling a hole in the bottom of the sealed box help?

> Incidentally, you may find these handy as most commercial antennas use
> N pigtails. An N to R-TNC adapter would eliminate the added pigtail.
> http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=5734622202

That looks great.
What would be the approximate signal loss of such adapter?

If it is lower than an additional pigtail, as I think, why people keep
using the pigtail?

BTW, does anyone sell high gain parabolic antennas with a RP-TNC
connector, instead of the common N type connector?

Thanks a lot.

 

[Guest]

Archived from groups: alt.internet.wireless (More info?)

On Mon, 29 Nov 2004 11:33:37 +0100, meATprivacyDOTnet <me@privacy.net>
wrote:

>> Yes, WDS will work. See:
>> http://www.orinocowireless.com/support/techbulletins/TB-046.pdf

>It looks like there is an error on page 10, item #3 should read "Both
>clients WIRELESSLY connected to each AP ..." instead of "Both clients
>WIRED connected to each AP ...", at least according to the diagram on
>page 11.

Egads, your correct. My appologies. I've never tried to use WDS to
replace a transparent bridge and have no clue what might happen. My
sense of smell tells me that something is wrong, because if it did
work, then everyone would be using it to replace "workgroup bridges"
and "game adapters" to connect multiple devices. The key part of a
transparent bridge is that the boxes have a (proprietary) bridging
protocol, that distributes the MAC address to "port number" table to
BOTH ends of the bridge to keep traffic down to a minimum. Without
this protocol, the bridges will be sending a substantial amount of
traffic that goes nowhere. I'm not sure if WDS can do that.

>My setup would be like item #1 ("Both clients wired connected to each
>AP"), that yiedls the best throughput.
>I think that's close to the actual maximum 802.11b throughput: it looks
>like you don't loose any bandwidth using WDS to setup a wireless bridge
>between two APs and using wired clients.

I think the problem isn't the bandwidth through the bridge. It's what
the bridge decides about traffic that should go across the bridge. In
a transparent bridge, if Radio #1 doesn't have a list of MAC addresses
of devices that are accross the bridge, it might send everything (as
in a hub). I'm not sure how it works and might be wrong, but it's
worth testing. I don't have a single box in the office that does WDS
so I can't setup a test for at least a few days.

>Why most people use LMR-100A instead of LMR-195 (less loss) for pigtails?

I don't know. All of the commerically made R-TNC to N pigtails I have
are LMR-100. It's quite stiff and I guess if I could have bought
LMR-195, I would have ordered it. For short lengths, the difference
in loss is negligible. I guess it's "traditional"?

>> Reminder: Think about where the water will go if it gets inside or
>> drips down the coax. It most assuredly will.

>Will drilling a hole in the bottom of the sealed box help?

Yes. I posted a rant on the subject or waterproofing in this
newsgroup in the past. Basically, the only form of sealed
waterproofing that really works is a pressurized box. If there's a
path to the atmosphere, water will condense inside. I do use
pressurized boxes and coax runs for commercial towers, but that's
overkill home use, where access is fairly trivial. I also conformal
coat the boards, which is also overkill (and messy). Two small holes
in the bottom of the box will be sufficient to drain off anything that
accumulates. The heat from the board will be sufficient to prevent
condensation on the board, but not on all the other hardware which
will tend to corrode. Use stainless as much as possible.

>> Incidentally, you may find these handy as most commercial antennas use
>> N pigtails. An N to R-TNC adapter would eliminate the added pigtail.
>> http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=5734622202

>That looks great.
>What would be the approximate signal loss of such adapter?

I could look it up, but my guess is 1dB. I use a rule of thumb of
0.5dB per connector pair and 1dB for adapters. (That's about 10%
power loss for the adapter). It's probably made by RF Industries.
Download the catalog (9MBtyes)
http://www.rfcoaxconnectors.com
and see if you can find a PT-4000-135 (R-TNC male to N female).

Hmmm... I notice that they offer pigtails in LMR-195.

>If it is lower than an additional pigtail, as I think, why people keep
>using the pigtail?

Did you read my previous explanation? The problem is that LMR-400 is
usually used for runs between the access point and the antenna. No
pigtail required at the antenna, but if you installed an R-TNC
connector on the LMR-400, the stiff coax would lift the radio off the
table or otherwise be a mechanical problem. In extreme cases, it
could rip the connector out of the radio (as on a PCMCIA card). You
could possibly get away with it using a R-TNC connector, but an SMA
connector on the end of an LMR-400 coax cable will surely break off.

>BTW, does anyone sell high gain parabolic antennas with a RP-TNC
>connector, instead of the common N type connector?

I don't think so and I have a guess as to why. The problem is that
most of the antenna manufacturers cut costs by using the absolute
cheapest coax possible for their pigtails. RG-8/u and RG-58a/u are
common. The reason they can get away with that is the difference in
loss between quality and junk coax over a 1ft distance is
insignificant. Anything will work. I don't think anyone makes an
R-TNC crimp connector for RG-8/u junk coax, only N connectors.


--
Jeff Liebermann jeffl@comix.santa-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 AE6KS 831-336-2558

 

[Guest]

Archived from groups: alt.internet.wireless (More info?)

On 11/29/04 4:16 AM, Jeff Liebermann wrote:

> Yeah, methinks it will work at 340 meters with 17dBi dishes.

Thanks for the calculations: I'll try to get the 24 dBi parabolic
antennas anyway, just to be on the safe side.

I'll try to send you a couple of pics of the trees as soon as I have a
chance.

Thanks again for your very useful advice.

 

[Guest]

Archived from groups: alt.internet.wireless (More info?)

Jeff Liebermann <jeffl@comix.santa-cruz.ca.us> wrote:

> I think the problem isn't the bandwidth through the bridge. It's what
> the bridge decides about traffic that should go across the bridge. In

If the bridges are each connected to switches, won't the switches make much
of that decision for them, only letting them see data for destinations seen
on that port on the switch?

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

 

[Guest]

Archived from groups: alt.internet.wireless (More info?)

On Mon, 29 Nov 2004 21:57:17 +0000 (UTC),
dold@XReXXparab.usenet.us.com wrote:

>Jeff Liebermann <jeffl@comix.santa-cruz.ca.us> wrote:
>
>> I think the problem isn't the bandwidth through the bridge. It's what
>> the bridge decides about traffic that should go across the bridge. In

>If the bridges are each connected to switches, won't the switches make much
>of that decision for them, only letting them see data for destinations seen
>on that port on the switch?

Duh... yes. I forgot that most wireless routers have built in 4 port
switches. The switches (actually multi-port bridges) will take care
of bridging function. I'm not sure how it would work with more than
two WDS routers, but that's not an issue here. I still smell
something is wrong, but my previous guess was not it. Thanks.


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831.336.2558 voice http://www.LearnByDestroying.com
# jeffl@comix.santa-cruz.ca.us
# 831.421.6491 digital_pager jeffl@cruzio.com AE6KS

 

[Guest]

Archived from groups: alt.internet.wireless (More info?)

On 11/29/04 6:42 PM, Jeff Liebermann wrote:

> I think the problem isn't the bandwidth through the bridge. It's what
> the bridge decides about traffic that should go across the bridge. In
> a transparent bridge, if Radio #1 doesn't have a list of MAC addresses
> of devices that are accross the bridge, it might send everything (as
> in a hub). I'm not sure how it works and might be wrong, but it's
> worth testing. I don't have a single box in the office that does WDS
> so I can't setup a test for at least a few days.

I'll give WDS a try as soon as I have a chance and post back to the
newsgroup with the results.

> I don't know. All of the commerically made R-TNC to N pigtails I have
> are LMR-100. It's quite stiff and I guess if I could have bought
> LMR-195, I would have ordered it. For short lengths, the difference
> in loss is negligible. I guess it's "traditional"?

I read a couple of messages about LMR-100A fitting better the connectors
than LMR-195, due to the cable size. Is that correct?

> I could look it up, but my guess is 1dB. I use a rule of thumb of
> 0.5dB per connector pair and 1dB for adapters. (That's about 10%
> power loss for the adapter). It's probably made by RF Industries.
> Download the catalog (9MBtyes)
> http://www.rfcoaxconnectors.com
> and see if you can find a PT-4000-135 (R-TNC male to N female).

I downloaded the catalog, but couldn't find that adapter, anyway I think
your guess is pretty good.

> Did you read my previous explanation? The problem is that LMR-400 is
> usually used for runs between the access point and the antenna. No
> pigtail required at the antenna, but if you installed an R-TNC
> connector on the LMR-400, the stiff coax would lift the radio off the
> table or otherwise be a mechanical problem. In extreme cases, it
> could rip the connector out of the radio (as on a PCMCIA card). You
> could possibly get away with it using a R-TNC connector, but an SMA
> connector on the end of an LMR-400 coax cable will surely break off.

Thanks for the further explanation, I got it now.
Since I am going to put the antenna next to the AP, I'll get the R-TNC
male to N female adapter, no additional pigtail needed for me.

> I don't think so and I have a guess as to why. The problem is that
> most of the antenna manufacturers cut costs by using the absolute
> cheapest coax possible for their pigtails. RG-8/u and RG-58a/u are
> common. The reason they can get away with that is the difference in
> loss between quality and junk coax over a 1ft distance is
> insignificant. Anything will work. I don't think anyone makes an
> R-TNC crimp connector for RG-8/u junk coax, only N connectors.

That sounds reasonable.
It looks like Stella Doradus uses RG-213/u (60 cm) cable for the antenna
pigtail:
<http://www.stelladoradus.com/2.4.ghz.parabolic.antennas.php>

Is it a good one?
BTW, what does the 'u' stand for?

Thanks again.

 

[george]

Archived from groups: alt.internet.wireless (More info?)

"Jeff Liebermann" <jeffl@comix.santa-cruz.ca.us> wrote in message
news:cshcq0h4cbvrjkt21km3t97jshc1rkg6il@4ax.com...
>> http://www.sveasoft.com/articles/armored/
> (About 6 page. See tiny "next" in lower right corner of page).

I got chills when I saw the picture of the plate being drilled without being
clamped and just being hand held. My friend did *major* damage to his hand
doing that while using an seemingly innocent small drill press when the
workpiece caught and spun.



>
> >I think the Linksys wifi router has a RP-TNC connection, but I am not
> >sure about the Stella Doradus antenna, any idea?
>
> WRT54GS uses R-TNC. The data sheets on the dish at:
> http://www.stelladoradus.com/2.4.ghz.parabolic.antennas.php
> show a male N connector.
>
> >Where can I buy a couple of short cables (e.g. 30 cm) already with the
> >right connectors installed at the ends?
>
> That would depend on what country you were located. In the US, I buy
> from:
> http://www.fab-corp.com
> No experience with international vendors.
>
>
> --
> Jeff Liebermann jeffl@comix.santa-cruz.ca.us
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060 AE6KS 831-336-2558

 

[Guest]

Archived from groups: alt.internet.wireless (More info?)

George <george@nospam.invalid> wrote:
>>> http://www.sveasoft.com/articles/armored/

> I got chills when I saw the picture of the plate being drilled without being
> clamped and just being hand held. My friend did *major* damage to his hand
> doing that while using an seemingly innocent small drill press when the
> workpiece caught and spun.

And such a nice picture of the same metal plate _clamped_ to the drill
press on the previous page.

I did the opposite of your friend. A 1/2" handheld drill motor spun me
around when it caught in a heavy steel plate. No long term damage, but I
was young and invincible then.

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

 

[Guest]

Archived from groups: alt.internet.wireless (More info?)

On Tue, 30 Nov 2004 11:23:41 +0100, meATprivacyDOTnet <me@privacy.net>
wrote:

>I read a couple of messages about LMR-100A fitting better the connectors
>than LMR-195, due to the cable size. Is that correct?

Well, the connectors and cable diameters for LMR-100A and LMR-195 are
completely different. Hopefully, someone didn't just mix up the crimp
connectors and crimp tools.
http://www.timesmicrowave.com/telecom/pdf/LMRGuide.pdf

>That sounds reasonable.
>It looks like Stella Doradus uses RG-213/u (60 cm) cable for the antenna
>pigtail:
><http://www.stelladoradus.com/2.4.ghz.parabolic.antennas.php>
>Is it a good one?

RG-213/u is double shielded RG-8/u. For a 1ft run, it's fine.

>BTW, what does the 'u' stand for?

RG means "radio guide" as in something that guides radio waves to
whever they're going. The various numbers were originally the page
numbers of some lost military catalog of coax cables. The /A /B /U
are the different types of jackets. I think /u means
non-contaminating jacket. Like any other significant numbering
system, the military dumped the whole RG mess in about 1945 in favour
of the C17 numbering system which nobody uses.

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831.336.2558 voice http://www.LearnByDestroying.com
# jeffl@comix.santa-cruz.ca.us
# 831.421.6491 digital_pager jeffl@cruzio.com AE6KS

 

[Guest]

Archived from groups: alt.internet.wireless (More info?)

On Tue, 30 Nov 2004 21:37:39 +0000 (UTC),
dold@XReXXparab.usenet.us.com wrote:

>George <george@nospam.invalid> wrote:
>>>> http://www.sveasoft.com/articles/armored/
>
>> I got chills when I saw the picture of the plate being drilled without being
>> clamped and just being hand held. My friend did *major* damage to his hand
>> doing that while using an seemingly innocent small drill press when the
>> workpiece caught and spun.

>And such a nice picture of the same metal plate _clamped_ to the drill
>press on the previous page.

>I did the opposite of your friend. A 1/2" handheld drill motor spun me
>around when it caught in a heavy steel plate. No long term damage, but I
>was young and invincible then.

Bah. For a really fun time, try running a gasoline engine powered
post hole digger. If you want a fun carousel ride, you've found the
right contraption. Stick the auger into a rock and around you go.
These do have a "dead mans switch" on the handles, but I figured out
that one would be dead by the time it works.


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831.336.2558 voice http://www.LearnByDestroying.com
# jeffl@comix.santa-cruz.ca.us
# 831.421.6491 digital_pager jeffl@cruzio.com AE6KS