i am trying to set up a wireless-n (b/g compatible) wireless network, because even though all my Macs/Apple TV are wireless-n enabled, i want to be able to access the local network on my iPhone, so need to use the b/g compatible mode. the wireless network has been set up on an airport express connected via ethernet to a netgear router. i have another airport express and a time capsule around the house to extend the network (as wireless signals seem to reach much less distance in my current home than i usually experience).

the problems i am experiencing are intermittent slow wireless speeds, which i am presuming is to do with interference from other devices. so i am getting a lot of 'rebuffering stream' messages when connecting to shared iTunes libraries (ports TCP 3689 and UDO 5353 are open), and apple TV keeps dropping/freezing when watching films.

i tried copying a 200MB file from one Mac to another connected to the b/g compatible network and on my first attempt it seemed like the transfer was going to take over an hour, so very very slow. then i tried the same file on a wireless-n only (5GHz) network and it took less than a minute. I then tried out a wireless-n only (2.4GHz) network, but both the second airport express and the time capsule couldn't connect to the network to extend it, and kept flashing orange. Finally I tried a b/g compatible network again and this time it looked like the transfer would take a few minutes (so much quicker than before), but like I've said the problem is intermittent.

so i am wondering what i can do to get the b/g compatible mode working better. i have tried using different channels and still i experience the same problems. i used this equipement in another house in b/g compatible mode without any difficulties

i would be grateful for some help in troubleshooting this issue. i have reset all airport devices and the router to factory settings and still i have the same issue.