Wifi slow and unstable on my slackware

I have this card

06:00.0 Network controller: Atheros Communications Inc. AR9565 Wireless Network Adapter (rev 01)

My laptop is distant 34ft from router i have set those options

iwconfig wlan0 mode Ad-Hoc
iwconfig wlan0 rate 54M

and i have set module options

options ath9k nohwcrypt=1

This is an example of slowness using slackyd

Repository: personal [serverhttp]
`- Downloading FILELIST.TXT [100 % @ 150.7 KB/s]    
`- Downloading PACKAGES.TXT [100 % @ 52.4 KB/s]    
`- Downloading CHECKSUMS.md5 [100 % @ 27.8 KB/s]    
`- Downloading MANIFEST.bz2 [100 % @ 111.1 KB/s]    
>> Uncompressing MANIFEST.bz2: done.

serverhttp is on my lan,and with cabled nic i reach 6MB/S On wpa,i used

ctrl_interface=/var/run/wpa_supplicant
ctrl_interface_group=root
eapol_version=1                           
ap_scan=1                             
fast_reauth=1   
update_config=1

network={
    ssid="Slackware"
    psk="***"
    proto=RSN
    key_mgmt=WPA-PSK
    pairwise=CCMP
}

and finally iwconfig

wlan0     IEEE 802.11bgn  ESSID:"Slackware"  
          Mode:Managed  Frequency:2.427 GHz  Access Point: *******   
          Bit Rate=6.5 Mb/s   Tx-Power=16 dBm   
          Retry short limit:7   RTS thr:off   Fragment thr:off
          Power Management:off
          Link Quality=38/70  Signal level=-72 dBm  
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:128  Invalid misc:468   Missed beacon:0

Distro is slackware,some suggestion for speed? Thanks