linksys oddities with directional antenna

I have a linksys WRT54GS using DD-WRT firmware with a high gain
directional antenna to another access point some distance away
(800-1000 feet).

When I plug ethernet into the WRT54GS, I can communicate without issue.

When I attempt to use a wireless connection into the WRT54GS, it 'sorta
works sometimes', it's as if the box is deciding that there's a better
signal here, and it broadcasts/receives over the stock omni antenna,
instead of other the high gain antenna to talk to the other access
point.


Any suggestions? I'm thinking I may just have to buy an additional
access point, and ethernet connect it to the roof mounted (high gain
antenna), and force the roof mounted one to only use the high gain
antenna, and to ignore the stock omni.

(E-Mail Removed) wrote:

> I have a linksys WRT54GS using DD-WRT firmware with a high gain
> directional antenna to another access point some distance away
> (800-1000 feet).
>
> When I plug ethernet into the WRT54GS, I can communicate without issue.
>
> When I attempt to use a wireless connection into the WRT54GS, it 'sorta
> works sometimes', it's as if the box is deciding that there's a better
> signal here, and it broadcasts/receives over the stock omni antenna,
> instead of other the high gain antenna to talk to the other access
> point.
>
> Any suggestions? I'm thinking I may just have to buy an additional
> access point, and ethernet connect it to the roof mounted (high gain
> antenna), and force the roof mounted one to only use the high gain
> antenna, and to ignore the stock omni.

I was told here that that was exactly the behaviour to expect, so I was
surprised after installing Talisman to find that it works fine for me. How
is your local WRT54 configured? Mine is in WDS mode, which I'm pretty sure
you need to do this.
--
derek

(E-Mail Removed) hath wroth:

>I have a linksys WRT54GS using DD-WRT firmware with a high gain
>directional antenna to another access point some distance away
>(800-1000 feet).
>
>When I plug ethernet into the WRT54GS, I can communicate without issue.
>
>When I attempt to use a wireless connection into the WRT54GS, it 'sorta
>works sometimes', it's as if the box is deciding that there's a better
>signal here, and it broadcasts/receives over the stock omni antenna,
>instead of other the high gain antenna to talk to the other access
>point.

That's exactly what's happening. The diversity reception is not
designed to play load balancer between your distant link and your
local wireless laptops. The algorithm involved is that the antenna
that received that last valid packet is selected. The access point
will continue using that antenna until it gets a high packet error
rate, at which time it will try the other antenna. That works quite
well for reducing the effects of momentary reflections but is useless
for doing a balancing act between two radically different wireless
clients.

I once read a much better explanation somewhere on the web but can't
find it right now.

The algorithm seems to be (I'm not sure) etched in silicon and vary
with chipset vendor. Some chipsets are more aggressive on switching
antennas, while others stay glued to their favorite antenna. I don't
know which end the Broadcom chipset in the WRT54G fits. My guess is
toward the tenacious end because every time I've tried a similar
arrangement, I have a similar problem.

>Any suggestions? I'm thinking I may just have to buy an additional
>access point, and ethernet connect it to the roof mounted (high gain
>antenna), and force the roof mounted one to only use the high gain
>antenna, and to ignore the stock omni.

Yep, that's the right way to do it and should work just fine. However,
there are some ugly alternatives:

1. If you have 3 dB surplus gain or tx power in your outdoor wireless
link, you can attach a power splitter to the antenna. Disable
diversity and select just one antenna. Each antenna (indoor or
outdoor) gets half the tx power. Be prepared to deal with a mess of
cables and connectors.
http://www.hyperlinktech.com/web/sig..._2400_2way.php

2. A variation of the above is to "leak" some RF near the WRT54G
using do-it-thyself leaky coax (Radiax). I made a custom pigtail out
of about a 1 meter piece of LMR-240, where I had gouged out 1/4 wave
electrical slots in the shield with a Dremel tool and knife. It
leaked just enough RF to allow using a laptop in the room where the
WRT54G was located.

--
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