Range for two WRT54GL bridged

Hello:

I am thinking of setting up two Linksys WRT54GL routers, in a bridged
configuration so that they talk wirelessly to each other directly. My
question is, what is the estimated range if these two routers are
connected wirelessly, with their default antennas that they come with?
In our case, we will have a direct line of sight between them, but the
distance is about 800 feet. I am trying to figure out if the default
antennas might be enough or if we'll need to purchase new antennas.

Thank you very much for all feedback,
--
Chris

> In our case, we will have a direct line of sight between them, but the
> distance is about 800 feet. I am trying to figure out if the default
> antennas might be enough or if we'll need to purchase new antennas.

Get a pair of directional antennas. Make sure they're firmly mounted as to
stay aimed at each other. You don't need the second antenna on the WRT54
series, at least not for a point-to-point link like this. Antennas are
cheap and you'll get better data rates.

(E-Mail Removed) wrote:
> Hello:
>
> I am thinking of setting up two Linksys WRT54GL routers, in a bridged
> configuration so that they talk wirelessly to each other directly. My
> question is, what is the estimated range if these two routers are
> connected wirelessly, with their default antennas that they come with?
> In our case, we will have a direct line of sight between them, but the
> distance is about 800 feet. I am trying to figure out if the default
> antennas might be enough or if we'll need to purchase new antennas.
>
> Thank you very much for all feedback,

Just out of curiosity, how are you getting power there? I had an outbuilding
that was about 1000FT from the house, but had an underground power cable to
it from the house. I used powerline networking as the bridge (one router
output to the others wan input, same ssid, created a huge covered area)

On 5 Sep 2006 12:28:31 -0700 (E-Mail Removed) wrote:

| I am thinking of setting up two Linksys WRT54GL routers, in a bridged
| configuration so that they talk wirelessly to each other directly. My
| question is, what is the estimated range if these two routers are
| connected wirelessly, with their default antennas that they come with?
| In our case, we will have a direct line of sight between them, but the
| distance is about 800 feet. I am trying to figure out if the default
| antennas might be enough or if we'll need to purchase new antennas.

At 800 feet I'd say it's next to impossible on the provided antennae,
and probably difficult on anything but the highest gain external
antenna (e.g. might work but be quite slow). For this kind of distance
I'd go for a 1 meter minimum parabolic dish on each end. Look for one
that has at least 24dbi gain.

Are there any objects in between? Walls? Trees? People?

Will you be using the default firmware, or an alternate firmware?

My understanding is the WRT54GL by default is an access point and I
learned the hard way an access point is not supposed to talk to another
access point. I don't know if the included software can be told to do
otherwise (either AP to AP or BR to BR, or just AP to BR) or if you
need to get some better software. I'm curious what you manage to get
working (at a shorter distance when testing, not at 800 feet as I think
that will fail with the default antennas) and how. I'd like to do the
same thing (at 20 feet) with the firmware it comes with so I can start
using it before building custom firmware images.

I also am curious how a 2-antenna device would be connected to external
antennas. Since I don't know what the WRT54GL is actually doing with
each RF port (especially on transmit ... both at the same time, or just
the one that seemed to be more reliable for the intended peer device).

--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
| first name lower case at ipal.net / spamtrap-2006-09-05-(E-Mail Removed) |
|------------------------------------/-------------------------------------|

On Tue, 5 Sep 2006 16:48:28 -0400 Bill Kearney <(E-Mail Removed)> wrote:

|> In our case, we will have a direct line of sight between them, but the
|> distance is about 800 feet. I am trying to figure out if the default
|> antennas might be enough or if we'll need to purchase new antennas.
|
| Get a pair of directional antennas. Make sure they're firmly mounted as to
| stay aimed at each other. You don't need the second antenna on the WRT54
| series, at least not for a point-to-point link like this. Antennas are
| cheap and you'll get better data rates.

Which antenna is the 1st and which antenna is the 2nd?

What to do with the one not connected to the directional antenna?
1. Terminate it?
2. Leave it open?
3. Leave the original ducky on it?

--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
| first name lower case at ipal.net / spamtrap-2006-09-05-(E-Mail Removed) |
|------------------------------------/-------------------------------------|

(E-Mail Removed) hath wroth:

>I am thinking of setting up two Linksys WRT54GL routers, in a bridged
>configuration so that they talk wirelessly to each other directly. My
>question is, what is the estimated range if these two routers are
>connected wirelessly, with their default antennas that they come with?
>In our case, we will have a direct line of sight between them, but the
>distance is about 800 feet. I am trying to figure out if the default
>antennas might be enough or if we'll need to purchase new antennas.

Well, let's do the math. See:
http://wireless.wikia.com/wiki/Wi-Fi#Link_Calculations
for the procedure.

The rubber ducky antennas have about 2dBi gain on a good day.
Since there's no feed line, the coax cable losses are zero.
I'll assume line of sight and no Fresnel Zone infringement, which is a
rather dubious assumption. Since everyone seems to crank up the power
on the WRT54G/GS/GL boxes, I'll assume 100mwatts of tx power. This is
going to be a stretch so I'll use the 2nd slowest 802.11g wireless
connection speed of 12Mbits/sec OFDM, which should give 6Mbits/sec
thruput.

TX power = +20 dBm
TX coax loss = 0 dB
TX ant gain = 2 dBi
Distance = unknown
RX ant gain = 2 dBi
RX coax loss = 0 dB
RX sens = -84 dBm (at 12 Mbits/sec)
Fade margin = 20 dB

Plugging into:
http://www.terabeam.com/support/calculations/som.php
with various guesses for the distance until I get 20 dB of fade margin
(SOM). I get a range of about 0.15 miles or:
0.15 miles * 5280 ft/mile = 800 ft.

2.4Ghz 0.8 Fresnel Zone at midpoint of an 800ft span is a radius of
about 7.2ft.
http://www.terabeam.com/support/calc...esnel-zone.php
That's a nice way of saying that your antennas have to be at least 8
ft off the ground or you will have additional losses. Also, no junk
within a radius of 7.2ft of the line of sight at midpoint.

It should work if everything is perfect. The numbers only get worse,
never better. You gotta have good line of sight, no junk in the
Fresnel Zone, no interference from other users, and lots of luck.
Personally, methinks it's going to be a stretch at 800ft with the
stock rubber ducky antennas. I would attach a pair of directional
gain antennas instead of trying to do it with the stock antennas.
--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Thank you very much for the info. I will post the results if & when we
get this up.

Best,
--
Chris


Jeff Liebermann wrote:
> (E-Mail Removed) hath wroth:
>
> >I am thinking of setting up two Linksys WRT54GL routers, in a bridged
> >configuration so that they talk wirelessly to each other directly. My
> >question is, what is the estimated range if these two routers are
> >connected wirelessly, with their default antennas that they come with?
> >In our case, we will have a direct line of sight between them, but the
> >distance is about 800 feet. I am trying to figure out if the default
> >antennas might be enough or if we'll need to purchase new antennas.
>
> Well, let's do the math. See:
> http://wireless.wikia.com/wiki/Wi-Fi#Link_Calculations
> for the procedure.
>
> The rubber ducky antennas have about 2dBi gain on a good day.
> Since there's no feed line, the coax cable losses are zero.
> I'll assume line of sight and no Fresnel Zone infringement, which is a
> rather dubious assumption. Since everyone seems to crank up the power
> on the WRT54G/GS/GL boxes, I'll assume 100mwatts of tx power. This is
> going to be a stretch so I'll use the 2nd slowest 802.11g wireless
> connection speed of 12Mbits/sec OFDM, which should give 6Mbits/sec
> thruput.
>
> TX power = +20 dBm
> TX coax loss = 0 dB
> TX ant gain = 2 dBi
> Distance = unknown
> RX ant gain = 2 dBi
> RX coax loss = 0 dB
> RX sens = -84 dBm (at 12 Mbits/sec)
> Fade margin = 20 dB
>
> Plugging into:
> http://www.terabeam.com/support/calculations/som.php
> with various guesses for the distance until I get 20 dB of fade margin
> (SOM). I get a range of about 0.15 miles or:
> 0.15 miles * 5280 ft/mile = 800 ft.
>
> 2.4Ghz 0.8 Fresnel Zone at midpoint of an 800ft span is a radius of
> about 7.2ft.
> http://www.terabeam.com/support/calc...esnel-zone.php
> That's a nice way of saying that your antennas have to be at least 8
> ft off the ground or you will have additional losses. Also, no junk
> within a radius of 7.2ft of the line of sight at midpoint.
>
> It should work if everything is perfect. The numbers only get worse,
> never better. You gotta have good line of sight, no junk in the
> Fresnel Zone, no interference from other users, and lots of luck.
> Personally, methinks it's going to be a stretch at 800ft with the
> stock rubber ducky antennas. I would attach a pair of directional
> gain antennas instead of trying to do it with the stock antennas.
> --
> Jeff Liebermann (E-Mail Removed)
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060 http://802.11junk.com
> Skype: JeffLiebermann AE6KS 831-336-2558