Edmund <nomail@hotmail.com> hath wroth:
>After I have successfully made some wifi antenna's I now want
>to make a high gain omni for a hotspot.
>What is the highest gain I could get with what design?
>There are some commercial types sold as 12 dB gain???
>but what I found on the internet to make yourself is
>7 dB tops.

Commercial omni antennas can be found as high as 15dBi gain:
http://www.fab-corp.com/product.php?...cat=250&page=1
http://www.hyperlinktech.com/web/hg2415u_pro.php

Past about 8dBi, omni antennas become very tricky to build. The
problem is that construction is rather critical. It's also very
difficult to test the results.

Besides maximizing the gain, there's the problem of downtilt. The
above 15dBi antenna has a vertical beamwidth of 8 degress and almost
no downtilt. If you mount that on a tall building, it's useful for
talking to the horizon, but not to users below the antenna. In
general, an end fed vertical colinear antenna will have some uptilt of
the beam. Mount the antenna on a horizontal yardarm, and there's even
more uptilt. Unless the antenna construction includes some provisions
for downtilt, you may end up sending all your signal into the sky
instead of the ground (where the users are located).
| http://www.terabeam.com/support/calc...a-downtilt.php

Unless you really need all around coverage at the horizon, I suggest
you think about sector antennas.
http://www.superpass.com/2400-2483M.html
http://www.hyperlinktech.com/web/ant...out_sector.php
If you wanna build your own, see:
http://pe2er.nl/wifisector/
http://www.qsl.net/yu1aw/vhf_ant.htm
http://www.brest-wireless.net/wiki/materiel:amos

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