Hey, looks a little like my problem mentioned here:

http://forum.tp-link.com/showthread.php?93978-VR900-5Ghz-channel-width-40Mhz-and-80Mhz-not-working

I am pretty sure that VR900 has some firmware problems, I event tried to downgrade to old firmware versions without any success. Also, I open a support request with TP-Link.

Some review on internet report good speeds on VR900 devices, maybe they are lying or (and it is even worst) some devices have a hardware problem that causes wifi poor performance.

This is so weird, it just happend i ahve no idea why, i sent email to TP-Link support to use my warranty, hope this will help ....

Try solution I show on:

http://forum.tp-link.com/showthread.php?93978-VR900-5Ghz-channel-width-40Mhz-and-80Mhz-not-working

Maybe it can help you.

I've no Problems to get Wifi-Rates between 76 and 136 MB with my VR900v using my Medion-Tablet.

My Suggestion would be, that you should anlayze your WLAN surrounding with an Wifi Analyser like the app with same Name from Keuwlsoft.
Maybe you have RFI or too much Access-Points in your surrounding (with bad channel choice) so that the effective Signal/Noise Ration won't
allow better automatic WLAN-Settings.

If this is your Problem, than you should think about a better placement of your Archer.

But the second Test I would do before, is the disabling of 802.11b and the configuration of a fixed channel (1-6-11 is the conservative channel
selection since amercans won't habe channel 12 and 13, 1-5-9-13 or 1-7-13 the european channel selections).
But please look at a Wifi Analyser which Channel is not overloaded or disturbed because of a wrong configuration of your neighbour.

In the beginning my Archer choosed Channel 4 which is only usable when all Wifi-Components in the surrounding have very good narrow-band
bandpass-filtering. But there are a lot of components which won't have such filtering and would disturb my WLAN (from channel 1 or 7)

My experience is, that as long as neither you nor your neigbours produce drastic heavy load, it would be better to have a good working crash-
collisions detection (using the same channel as your neigbour) as to have interferences because of choosing a different channel but in overlap
with an other AP in your surrounding.

But last possibility (if you won't find a detectable signal from your Archer with the Wifi Analyser) could be, that the WiFi of your Archer (or in
the most cases I know from other APs the pigtails between the internal WiFi-Module and the Antenna-Connectors) is broken.

With best regards

Thomas G.M. Mainka

PS: If you want my answer in German this would be no Problem since I'm a German and my english is very bad... (But this is an english Forum)

This has recently happened to me.
At first I thought it was my provider (Vodafone Ireland).
According to reports I should be able to get 70mb/s on my line. I am profiled to 40mb/s as there are stability issues. Last few days the wifi signal had dropped down to 1-4mb/s.
I had decided to ring them this morning, but had to change over to their supplied modem Product type HG658c Hardware version HG658BZV VER.A. Once I had done that the speed went up to 41mb/s.
I have set the wifi channel on the best for me using a wifi scanner, so I know that's not the issue. I will see if the same thing happens tonight as yesterday during the day the speed was fine according to my son who downloaded an Infinite Warfare update yesterday.

This is actually a replacement VR900 as the first one had issues connecting. Not a very happy camper.
Will report back later.

thank link of canuto