Slow wlan speed

[noric]

Hello,
I'm having some wlan speed problems with my RT-N66U and Merlin fw 374.40.
I used to connect my laptop through its stock 1x1 wifi card and I used to get the expected 150Mbps on the 2.4GHz band (with channel bonding). This meant actual 7MB/s, which is to be expected (AFAIK).

I have now switched to a 3x3 Intel 6300 nic to improve lan transfer speed. But to my surprise this hasn't happened. The link speed is low: usually about 200Mbps but sometimes drops to about 100Mbps. Moreover, the actual transfer speed hasn't improved at all: about 7MB/s.
This was tested doing a lan transfer to both the router's hdd and a gigabit lan desktop. Note that the transfer speed between the desktop and the router's hdd is about 19MB/s (the router's cpu is the cap here).

This is not a problem of wireless coverage, because signal power actually improved with the Intel 6300 (from 50 to 40 dBm). Anyway, I've also tried staying very close to the router, to no avail.

I've tried to force the wifi to 20MHz (btw the 2.4GHz band isn't crowded at all) and nothing changed.
I've tried managing the nic's options in device manager but nothing changed.

This was tested on both Ubuntu and windows XP.

Could anyone please provide some advice to troubleshoot this? I'm out of ideas at the moment...
Thanks

 

[ColinTaylor]

Do you have the antennas connected correctly?

https://communities.intel.com/thread/24022

 

[noric]

Do you have the antennas connected correctly?

https://communities.intel.com/thread/24022

Yes, that's how i connected them.
I've added a third antenna (my laptop came with two), but I had tried that one with my previous wifi card and it worked as (if not better than) the two stock ones.
I've tried to only use two antennas (it should at least reach 300Mbps), but instead it's stuck at about 144Mbps.
Should I try to install a more modern windows sytem? Just to rule out xp/linux.

 

[ColinTaylor]

I've tried to only use two antennas (it should at least reach 300Mbps), but instead it's stuck at about 144Mbps.
Should I try to install a more modern windows sytem? Just to rule out xp/linux.

It's always worth trying a different OS or driver if you can.

You say that with 2 antennas it's stuck at 144Mbps, that would suggest that you're connecting at the maximum speed possible with 20MHz.

Also bear in mind that it's normal for the link speed to adapt to the lowest value necessary to transmit or receive the data.

I'd also suggest that you don't do speed tests to the router's HDD. As you already know, that can give you false results.

Beyond that I can't really give you any more suggestions. Sorry.

 

[noric]

It's always worth trying a different OS or driver if you can.

You say that with 2 antennas it's stuck at 144Mbps, that would suggest that you're connecting at the maximum speed possible with 20MHz.

Also bear in mind that it's normal for the link speed to adapt to the lowest value necessary to transmit or receive the data.

I'd also suggest that you don't do speed tests to the router's HDD. As you already know, that can give you false results.

Beyond that I can't really give you any more suggestions. Sorry.

I have already tried different drivers, on xp.
With two antennas I should reach 300Mbps, because I use 40MHz. Anyway the transfer speed is always 7MB/s, slower than it should.
I'm testing to my desktop pc, not to the router's hdd.
With my previous wifi card I was stable at 150Mbps, I don't understand why the new one is so unstable. There is obviously something wrong.

Edit: I forgot to say that the 5GHz band is slow too.

 

[noric]

Same behaviour on windows Seven.

Defective card or wrong router settings? I would need to test with another router...