Need external antenna for WRT54GL

[Mike]

I have a WRT54GL flashed with dd-wrt and I was wondering what would be good
directional antenna to buy. Should I buy 2 antennas for each output or just
one? Which is the best output to use if I only need 1 antenna?

[DTC]

Mike wrote:
> I have a WRT54GL flashed with dd-wrt and I was wondering what would be good
> directional antenna to buy. Should I buy 2 antennas for each output or just
> one? Which is the best output to use if I only need 1 antenna?

http://www.linksysinfo.org for antenna info.

Best output is the 100 mW (20 dBm) and run a 16 dBi gain omni antenna.
This will meet the 4 watt (36 dBm) maximum ERIP. Also, the Linksys
does not deal well running at more power at its max of 250 mW.

Opps...you want a directional antenna. Still keep the output at
100 Mw and use a 36 dBi antenna.

[seaweedsteve]

On Mar 1, 2:50 pm, DTC <m...@nothingtoseehere.zzx> wrote:

> Opps...you want a directional antenna. Still keep the output at
> 100 Mw and use a 36 dBi antenna.

Got any links for a 36 dbi antenna? I imagine you're just passing the
legal numbers on!

Anyway, to answer the questions, many directional antennas will work
well but the question is; what is your intended use? Is it to be
mounted indoors or outdoors? Go to a dealer's site and select indoors
or outdoors and then look for a gain pattern to tell how tightly
focused the antenna is.

I imagine many people just go for the highest gain, but that could be
a mistake for many reasons. For one thing, the gain patter is grows
narrower as the gain goes up and you lose coverage and intensify
interference.

I had an application where I needed to connect to various clients
located over a 60-80 degree range horizontally and a 40 degree range
vertically. It was more important to get everybody covered than to
have the highest gain.

I settled on a small 12 dbi panel antenna with a wide 60 degree beam
width. It has served us well and even connects at longer distances
(600 meters) with line of sight.
http://www.hyperlinktech.com/web/hg2412p.php

Panel antennas are commonly used and range from 12 - 19 dbi. This is
a good middle ground but again, check the pattern against your needs.

Parabolic reflectors are also commonly used. There's a nice little 14
dbi reflector antenna called a "Backfire" that comes recommended:
http://www.hyperlinktech.com/web/hg2414d.php

If you need long distance (caution: 8 degree beam width is tricky to
aim - pinpoint precision), you can go with a larger, high gain
parabolic grid antenna:
http://www.hyperlinktech.com/web/hg2424g.php

If you are going with interior antennas, then your options or more
limited, typically panels, which should work fine. Hawking has an
interesting corner antenna that is worth looking at. (No links.)

Whatever you choose, use low loss coax cable to connect, specifically
LMR400 for anything over 10-12 feet. Don't settle for cable over a
foot that does not have a number. Don't buy the cheap department
store (or Ebay) antennas that come with six feet of crappy cable
attached. This cable eats up most or all of the gain.

If you just need an improved directional signal inside your house,
consider putting a reflector on your stock antenna(s):
http://users.picknowl.com.au/~gloaming_agnet/ant2.html This can
really work.

Finally, you do not need two antennas, you can use one side of your
Linksys and disconnect the other, disabling it in the router
interface. I used the right side as you face the router, but may be
mistaken on that.

Cheers,
Steve

[Jeff Liebermann]

DTC <me@nothingtoseehere.zzx> hath wroth:

>Mike wrote:
>> I have a WRT54GL flashed with dd-wrt and I was wondering what would be good
>> directional antenna to buy. Should I buy 2 antennas for each output or just
>> one? Which is the best output to use if I only need 1 antenna?

You only need or want one directional antenna. The diversity switch
will do weird things if you have two different types of antennas or
tow directional antennas with divergent patterns.

As to which is the most appropriate directional antenna, I dunno. You
haven't mentioned what you're trying to accomplish. Different
antennas do different things.

>http://www.linksysinfo.org for antenna info.
>
>Best output is the 100 mW (20 dBm) and run a 16 dBi gain omni antenna.
>This will meet the 4 watt (36 dBm) maximum ERIP. Also, the Linksys
>does not deal well running at more power at its max of 250 mW.
>
>Opps...you want a directional antenna. Still keep the output at
>100 Mw and use a 36 dBi antenna.

Some detail. The maximum output power varies with the antenna gain
for a directional antenna and point to point system according to this
handy table:

Ant Tx Pwr EIRP EIRP
dBi dBm dbm watts
6 30 36 4
9 29 38 6.3
12 28 40 10
15 27 42 15.8
18 26 44 25.1
21 25 46 39.8
24 24 48 63.1
27 23 50 100
30 22 52 158.5
33 21 54 251.2
36 20 56 398.1
39 19 58 631
42 18 60 1000

However, for an omnidirectional antenna, you're limited to +36dBm EIRP
or 1 watt into a 6dBi omni antenna.


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[DTC]

seaweedsteve wrote:
> On Mar 1, 2:50 pm, DTC <m...@nothingtoseehere.zzx> wrote:
>
>> Opps...you want a directional antenna. Still keep the output at
>> 100 Mw and use a 36 dBi antenna.
>
> Got any links for a 36 dbi antenna? I imagine you're just passing the
> legal numbers on!

I'll have to look up the link to the pdf as its not obvious on the
Andrew's website. Its part of the terrestrial microwave line. They run
around $3,400 to start, not counting radome or shipping.