I am aware that running a mix of 802.11g and 802.11n devices will cause WiFi speed to reduce when the g device is active. As I intend to purchase some devices that I can only find with 802.11g I want to check the impact and also see whether the separate SSID feature in the 2820n would avoid the speed loss.

However my first test was to see how bad this is with a mix of g and n devices on the same SSID and I am actually having a hard time to find that much difference. I am using a laptop with an Intel Ultimate-N 6300 (connecting at 300Mbps) and a netbook with a general 802.11g device and testing with various file copies. The laptop copies at around 10MB per second irrespective of whether the netbook is using WiFi or not.

So can anyway provide any information about how bad mixing g and n devices is and whether the 2820n's separate SSID feature or three aerials makes any difference?

Using mixed speed via different SSIDs is a good thing. I do the same on my network. However I use two separate Wifi access point to achieve this. If you do this on one device, like the 2820, you use the same set of Wifi radios for the SSIDs and for the network type 802.1 b/g/n. You will not see any performance improvement, although network segregation can be a good thing.

To sum it up, I doubt that you will see any speed improvements.

Thanks for the reply - I thought that may be the case.

I'll dig out my spare WiFi unit and use that for the slower connections.