I got my own wireless network (for 20 users working on 802.11g mode with WPA2 PSK encryption, inet connection DSL 4Mbit/512kbit) for about 2 years.
I started with Linksys WRT54GS v.1.1 working as AP and router. After some time I decidec to split AP and router into 2 devices - 2x WRT54GS.
I read on this and other forums that Broadcom wifi chips has not so good radio performance (sensitvity, signal quality especially on higher output power levels etc.) so I tried to swap it with AP based on Atheros wifi chips.
I bought ASUS wl-500gP and Ubiquiti SR2 400mW card (AR5412) for top performance (and now even Ubiquiti XR2 AR5414).
Unfortunetally every time I swap AP form Linksys to ASUS+Atheros I got worse performance/compatibility with user cards (based on Atheros and Ralink chipsets). For last year I tried openwrt WR RCx then 0.9 and now Kamikaze (lots of releases including 7.06 and 7.07) and probably every madwifi release ported to openwrt with no success. What is the problem?
The SR2 has excellent output power and sensitivity (the signal levels form my users  reported by Atheros/madwifi are a lot better than those reported by Broadcom/'wl') BUT users with Ralink based cards has connecting problems (frequent 'deauthenticated due to local deauth request' in logread etc) and users with Atheros based cards has a lot worse performance (poor real troughput, rather no problem with deauth) compared with Linksys ...
When using Linksys I can fix AP tx rate to some value (eg. 'wl rate 18') because automatic rate gives worse effect.
With older madwifi (and 'sample' rate estimator) it was possible (eg. 'iwconfig ath0 rate 18M') but now with both 'minstrel' and 'sample' estimators it doesn't work at all and automatic modes gives poor performance...
After swap to Linksys the problem always dissapear and my network works SMOOTH without any disconnects, strange log errors etc. at pretty good (but not top) performance (only some far users with low recieving signal has moderate perf.)...

It seems that Broadcom 'wl' driver has VERY good compatibility with diffrent user chipsets (tested also with Realtek and Intel wifi chips) - I never noticed any incompatibility (disconnecting problems,poor performance) with any wifi chipset I ever used with Linksys. The only problem is moderate radio sensitivity, and limited output power (mostly by signal quality)
The Atheros is problematic with madwifi and with Mikrotik too. I tested multiple versions of Mikrotik system with diffrent Atheros based cards - Ubiquiti SR2 , XR2 , Senao MNP 8602 on Routerboard 112 and WRAP 2C boards - I always got 'extensive data loss' etc)
Anyone has similar experience?

The SR2 and XR2 draw way too much power for the WL-500gP.   I wouldn't use anything over a 200mW card in the gP and that may be pushing it.   

If you want the benefits of the Ubiquiti cards you need to get something built for powering them, like a Gateworks board.   

The Ubiquiti cards have an amp that adds 10dBm to the output power reported by madwifi.  You might be able to get them to work okay if you set the transmit power to something between 6 and 10 dBm. 

The SR2 and XR2 are more sensitive to noise because of the internal amp.   The more recent versions of MADWIFI seem to work better with noise trouble.   

I have more experience with the SR5 cards from Ubiquiti and get excellent speed and connection strength when used on Gateworks boards.

(Last edited by lschweiss on 27 Aug 2007, 20:23)

Thaks for your reply lschweiss,

I know the Ubiquiti cards very well and I know about +10dB offset (which is one of many advantages of this cards).
The problem isn't related to underpowered SR2/XR2 with ASUS wl-500gP because I tested it with WRAP 2C also with the same results. More, I used SR2 and ASUS wl-500gP with success on max power (26dBm, 400mW) but with older madwifi release (i don't remember which one) - I was able to fix Tx rate (by 'iwconfig ath0 rate 11M') and it was rock stable and it offered great performance! unfortunetally the storm killed my AP so I had to swap it with new one and ofcource I uploaded the latest openwrt (7.07) and madwifi (r2568) releases (I though that new=better).
It was mistake. It is no more possible to fix Tx rate - you can execute 'iwconfig ath0 rate 11M' but tx rate still jumps over the different speeds (even though 'wlanconfig ath0 list' reports 11M..). The automatic rate estimators (even new 'minstrel') aren't good for interference enviroment.