Upgraded to fibre this morning and getting a consistent 76/18 via Ethernet, via WiFi it's 34/18 while 50cm from the router.

Running 3.6.8_sb_232201
WAN1 disabled
Bandwidth management and QoS turned off
Using 11n only
WPA2
WPS & WDS disabled
Green Field, 20/40, Auto, MSDU enabled, Long preamble disabled, TX Burst enabled
Bandwidth management disabled

Is there something else I'm missing?

Thanks.

some solved the issue with the 2830 by applying a new install using the *rst* file extension and configure every back from the begin (manually the settings)
Then don't use green field and try different channels .. to my 2830 channel one has better signal
Also try different encryption from wpa mixed to wpa 2 only

Thanks babis, will give it a go at the weekend.

Applied the .rst file. Looks like the wifi performance is limited to around 40Mb/s which is a shame given the free wifi router supplied by Plusnet will happily provide over 70Mb/s out of the box.

Using WPA2 only, speed on each channel setting:
Auto 39.5
1 41.3
2 41.5
3 38.6
4 41.7
5 16.3
6 17.2
7 15.5
8 39.0
9 38.7
10 37.8
11 39.0
12 37.1
13 41.4

It's a shame as I like the other features of the 2830. Are there any other SOHO Drayteks that can cope with downloading at > 70Mb/s over wifi?

i am not sure what speeds other models should get

try different combinations example wpa/wpa2 mixed, then try without security to see if is better ... turning the left / right antennas about 45 degree should help better
Perhaps if you have any old device, slow down the network? so try again with n only

Fairly confident I've tried most things that would have an impact, from the "bouncing off the rev limiter" nature of the 4 or 5 speed tests I've tried it looks like the limit of the hardware rather than any config setting.

Slightly moot point now as I've now set up a TP-Link TL-WA901ND AP and it's providing 76Mb/s out of the box.