I'm using iwconfig to set the parameters of my network card - all is working ok apart from after a few minutes the bit rate setting will drop to being 24 Mb/s from 54 (or there abouts). If i do a 'iwconfig wlan0 rate auto' then it opens up the higher speeds but resets back to 24 after a few minutes.
What else do i need to set or is there a way to make the setting stick? I tried iwconfig wlan0 rate 54 which sets it ok but same happens as before.....any ideas?

Cheers

I'm curious as to what your signal strength is. (link quality and noise level as well)

It could be auto-negotiating down for a good reason.

iwconfig by itself should list all adapters and their respective performance levels.

When the interface is down it doesn't drop down - iwconfig just now gives me -
Link Quality=82/100 Signal level:-201 dBm Noise level:-256 dBm
and a bit rate of 36 - not the best but it varies slightly.
When the interface is up and I'm connected, the link quality is good but it always drops to 24 after a few minutes, this happens with no data transfers happening.

My hardware is RT2500 based card using the native drivers - no encryption

Which distribution? My recent experiences and readings are telling me that sometimes bad firmware can cause this behavior.

Absolutely, though you might have some difficulty flashing the firmware on the card under linux, my aironet card has all the necessary utilities though.

Though I was interested in seeing the link quality settings when the adapter is up.

I can compare against my own and get a rough idea of what you are seeing.

Here's an output when the rate is set higher - throughput is definetaly better

Bit Rate:48 Mb/s
RTS thr=2312 B Fragment thr=2312 B
Encryption keyff
Link Quality=78/100 Signal level:-210 dBm Noise level:-256 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:0 Missed beacon:0

and after a few minutes it goes to -

Bit Rate:24 Mb/s
RTS thr=2312 B Fragment thr=2312 B
Encryption keyff
Link Quality=78/100 Signal level:-212 dBm Noise level:-253 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:0 Missed beacon:0

and as I was doing this it done a few strange things - dropped to 2,1 then lost connection and reconnected at 38 Mb/s - now sitting at 48!!
Think this may be a driver problem?? weird though