OpenWrt Forum Archive

Topic: TX power limit to 50mw??

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Post #1
gmoncada
12 Mar 2009, 07:33

I just flashed my Avila Gateworks with OpenWrt 8.09 RC + EMP8602+S 802.11a+b+g Atheros - AR5414 chipset.

and I'm confused abut Tx-Power it reports.

root@Gateworks:/# iwconfig ath0
ath0      IEEE 802.11g  ESSID:"linksys"  Nickname:""
          Mode:Managed  Frequency:2.437 GHz  Access Point: 00:0F:66:74:E8:08
          Bit Rate:36 Mb/s   Tx-Power:17 dBm   Sensitivity=1/1
          Retry:off   RTS thr:off   Fragment thr:off
          Encryption key:off
          Power Management:off
          Link Quality=8/70  Signal level=-88 dBm  Noise level=-96 dBm
          Rx invalid nwid:11096  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:0   Missed beacon:0

the card can support a txpower of 600mw but in iwlist only support 50mw

root@Gateworks:/# iwlist ath0 txpower
ath0      8 available transmit-powers :
          0 dBm         (1 mW)
          5 dBm         (3 mW)
          7 dBm         (5 mW)
          9 dBm         (7 mW)
          11 dBm        (12 mW)
          13 dBm        (19 mW)
          15 dBm        (31 mW)
          17 dBm        (50 mW)
          Current Tx-Power:17 dBm       (50 mW)

Are those TXpower values REAL or FAKE? If they are REAL how can I limit the Tx power to 600mW?

Post #2
kode54
12 Mar 2009, 07:49

Why do you need so much power? Do you even have any wireless adapters capable of transmitting back at that power level? (Yes, the clients do need just as much range as the access point.)

Post #3
gmoncada
12 Mar 2009, 07:58

thanks for the reply...


i dont need much power, i only need 23dbm
how i can modify the Txpower settings?

best regars!

Post #4
skysky
7 Dec 2009, 10:16

Hi

I have that problem too.

I have a 1000 mW atheros. But I see max 14 dBm in "iwlist ath0 txpower".

Is there any limitation?

Thanks

Post #5
jow
7 Dec 2009, 12:07

Hi.

Iiirc certain atheros cards have a tx power offset, means that the values you see in iwlist are added to a base power level on the card - maybe this is the reason why you don't see higher values? You should research the specifics of your card, maybe there is some information in the datasheet.

~ JoW

Post #6
skysky
8 Dec 2009, 22:18

Thanks jow.
You are right.
That's the reason. I couldn't find any thing in its datasheet, but I tested a 600mw atheros card on mikrotik and I saw this behavior there too.
I saw an interesting thing there. It shows the txpower of my card for example like this :

27 (17)
24 (14)

It seems that in this card there's a 10dBm offset.

But I don't know how it detects that offset.

Thanks again

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