1 2 Previous Next 27 Replies Latest reply: Apr 14, 2013 9:14 PM by wallarug RSS

RT3070 wireless adapter adjust tx power??

wallarug Level 14

I seem to be unable to adjust the tx power above 20dbm.  I have tried: 'iwconfig wlan0 txpower 22' but this does not change the txpower.

 

I have also disabled the power-management.

 

The adapter claims that it can hit 5800mW of power which aquates to about 37dBm.

 

Does anyone know how I can get the txpower up? (I can put it down, just not up)

 

root@raspberrypi:~# lsusb

Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

Bus 001 Device 002: ID 0424:9512 Standard Microsystems Corp.

Bus 001 Device 003: ID 0424:ec00 Standard Microsystems Corp.

Bus 001 Device 004: ID 148f:3070 Ralink Technology, Corp. RT2870/RT3070 Wireless Adapter

root@raspberrypi:~# iwconfig wlan0 txpower 30

Error for wireless request "Set Tx Power" (8B26) :

    SET failed on device wlan0 ; Invalid argument.

root@raspberrypi:~#

  • 1. Re: RT3070 wireless adapter adjust tx power??
    wallarug Level 14

    adding to this, how can I tell if my card supports AP mode?  I tried iw list but this is what I got:

     

    root@CMDoverwatch:~# iw list

    Wiphy phy0

            Band 1:

                    Capabilities: 0x172

                            HT20/HT40

                            Static SM Power Save

                            RX Greenfield

                            RX HT20 SGI

                            RX HT40 SGI

                            RX STBC 1-stream

                            Max AMSDU length: 3839 bytes

                            No DSSS/CCK HT40

                    Maximum RX AMPDU length 65535 bytes (exponent: 0x003)

                    Minimum RX AMPDU time spacing: 2 usec (0x04)

                    HT RX MCS rate indexes supported: 0-7, 32

                    TX unequal modulation not supported

                    HT TX Max spatial streams: 1

                    HT TX MCS rate indexes supported may differ

                    Frequencies:

                            * 2412 MHz [1] (20.0 dBm)

                            * 2417 MHz [2] (20.0 dBm)

                            * 2422 MHz [3] (20.0 dBm)

                            * 2427 MHz [4] (20.0 dBm)

                            * 2432 MHz [5] (20.0 dBm)

                            * 2437 MHz [6] (20.0 dBm)

                            * 2442 MHz [7] (20.0 dBm)

                            * 2447 MHz [8] (20.0 dBm)

                            * 2452 MHz [9] (20.0 dBm)

                            * 2457 MHz [10] (20.0 dBm)

                            * 2462 MHz [11] (20.0 dBm)

                            * 2467 MHz [12] (20.0 dBm) (passive scanning, no IBSS)

                            * 2472 MHz [13] (20.0 dBm) (passive scanning, no IBSS)

                            * 2484 MHz [14] (20.0 dBm) (passive scanning, no IBSS)

                    Bitrates (non-HT):

                            * 1.0 Mbps

                            * 2.0 Mbps (short preamble supported)

                            * 5.5 Mbps (short preamble supported)

                            * 11.0 Mbps (short preamble supported)

                            * 6.0 Mbps

                            * 9.0 Mbps

                            * 12.0 Mbps

                            * 18.0 Mbps

                            * 24.0 Mbps

                            * 36.0 Mbps

                            * 48.0 Mbps

                            * 54.0 Mbps

            max # scan SSIDs: 4

            max scan IEs length: 2257 bytes

            Coverage class: 0 (up to 0m)

            Supported Ciphers:

                    * WEP40 (00-0f-ac:1)

                    * WEP104 (00-0f-ac:5)

                    * TKIP (00-0f-ac:2)

                    * CCMP (00-0f-ac:4)

            Available Antennas: TX 0 RX 0

            Supported interface modes:

                     * IBSS

                     * managed

                     * AP

                     * AP/VLAN

                     * WDS

                     * monitor

                     * mesh point

            software interface modes (can always be added):

                     * AP/VLAN

                     * monitor

            interface combinations are not supported

            Supported commands:

                     * new_interface

                     * set_interface

                     * new_key

                     * new_beacon

                     * new_station

                     * new_mpath

                     * set_mesh_params

                     * set_bss

                     * authenticate

                     * associate

                     * deauthenticate

                     * disassociate

                     * join_ibss

                     * join_mesh

                     * remain_on_channel

                     * set_tx_bitrate_mask

                     * action

                     * frame_wait_cancel

                     * set_wiphy_netns

                     * set_channel

                     * set_wds_peer

                     * connect

                     * disconnect

            Supported TX frame types:

                     * IBSS: 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0

                     * managed: 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0

                     * AP: 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0

                     * AP/VLAN: 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0

                     * mesh point: 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0

                     * P2P-client: 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0

                     * P2P-GO: 0x00 0x10 0x20 0x30 0x40 0x50 0x60 0x70 0x80 0x90 0xa0 0xb0 0xc0 0xd0 0xe0 0xf0

            Supported RX frame types:

                     * IBSS: 0xd0

                     * managed: 0x40 0xd0

                     * AP: 0x00 0x20 0x40 0xa0 0xb0 0xc0 0xd0

                     * AP/VLAN: 0x00 0x20 0x40 0xa0 0xb0 0xc0 0xd0

                     * mesh point: 0xb0 0xc0 0xd0

                     * P2P-client: 0x40 0xd0

                     * P2P-GO: 0x00 0x20 0x40 0xa0 0xb0 0xc0 0xd0

     

    Any ideas?

  • 2. Re: RT3070 wireless adapter adjust tx power??
    shabaz Level 15

    In practice the wifi adapter is unlikely to support such a high output (5800mW would require more than 1A at

    5V USB supply) (is this a normal USB stick type of wifi adapter?). 20dBm is more likely though. A a bit odd why it claims 5800mW specifically. Maybe they meant 580mW (which is still really huge for wifi).

  • 3. Re: RT3070 wireless adapter adjust tx power??
    wallarug Level 14

    Here is the link to the product:

    http://www.ebay.com/itm/KINAMAX-High-Power-5800mW-802-11b-g-n-150Mbps-Wi-Fi-Wireless-Network-Adapter-/150904547616?ssPageName=ADME:X:RTQ:US:1123

     

    I know that this is on ebay but I did my background research and every website said 5800mW with 58dBm antenna.

  • 4. Re: RT3070 wireless adapter adjust tx power??
    shabaz Level 15

    It sounds like they are relying on a directional antenna which makes sense (no need to radiate a huge power everywhere). So, they are possibly implementing 20dBm output with a 17dBi antenna (this would be extremely directional). It looks like there are antenna topologies for 17dBi for such frequencies, e.g. this one.

  • 5. Re: RT3070 wireless adapter adjust tx power??
    wallarug Level 14

    Going on what you said before:

    In practice the wifi adapter is unlikely to support such a high output (5800mW would require more than 1A at

    5V USB supply) (is this a normal USB stick type of wifi adapter?). 20dBm is more likely though.

    I think you are somewhat right.

     

    Maybe Linux limits the amount of Watts (current in this case) that you can pull out of the USB port.

     

    I did a quick google search:

    http://en.wikipedia.org/wiki/DBm

     

    Have a look at the table halfway down the page:

    dBm levelPowerNotes
    80 dBm100 kWTypical transmission power of FM radio station with 50-kilometre (31 mi) range
    62 dBm1.5 kW = 1,500 WMaximum legal power output of a U.S. ham radio station.[3]
    60 dBm1 kW = 1,000 WTypical combined radiated RF power of microwave oven elements
    50 dBm100 WTypical thermal radiation emitted by a human body

    Typical maximum output RF power from a ham radio HF transceiver

    40 dBm10 WTypical PLC (Power Line Carrier) transmit power
    37 dBm5 WTypical maximum output RF power from a handheld ham radio VHF/UHF transceiver
    36 dBm4 WTypical maximum output power for a Citizens' band radio station (27 MHz) in many countries
    33 dBm2 WMaximum output from a UMTS/3G mobile phone (Power class 1 mobiles)

    Maximum output from a GSM850/900 mobile phone

    30 dBm1 W = 1,000 mWTypical RF leakage from a microwave oven

    DCS or GSM 1,800/1,900 MHz mobile phone. EIRP IEEE 802.11a (20 MHz-wide channels) in either 5 GHz Subband 2 (5,470–5,725 MHz) provided that transmitters are also IEEE 802.11h-compliant, or U-NII-3 (5,725–5,825 MHz). The former is EU only, the latter is US only.

    29 dBm794 mW
    28 dBm631 mW
    27 dBm500 mWTypical cellular phone transmission power

    Maximum output from a UMTS/3G mobile phone (Power class 2 mobiles)

    26 dBm400 mW
    25 dBm316 mW
    24 dBm251 mWMaximum output from a UMTS/3G mobile phone (Power class 3 mobiles)

    1,880–1,900 MHz DECT (250 mW per 1,728 kHz channel). EIRP for Wireless LAN IEEE 802.11a (20 MHz-wide channels) in either the 5 GHz Subband 1 (5,180–5,320 MHz) or U-NII-2 & -W ranges (5,250–5,350 MHz & 5,470–5,725 MHz respectively). The former is EU only, the latter is US only.

    23 dBm200 mWEIRP for IEEE 802.11n Wireless LAN 40 MHz-wide (5 mW/MHz) channels in 5 GHz subband 4 (5,735–5,835 MHz, US only) or 5 GHz subband 2 (5,470–5,725 MHz, EU only). Also applies to 20 MHz-wide (10 mW/MHz) IEEE 802.11a Wireless LAN in 5 GHz Subband 1 (5,180–5,320 MHz) if also IEEE 802.11h compliant (otherwise only 3 mW/MHz → 60 mW when unable to dynamically adjust transmission power, and only 1.5 mW/MHz → 30 mW when a transmitter also cannot dynamically select frequency).
    22 dBm158 mW
    21 dBm125 mWMaximum output from a UMTS/3G mobile phone (Power class 4 mobiles)
    20 dBm100 mWEIRP for IEEE 802.11b/g Wireless LAN 20 MHz-wide channels in the 2.4 GHz ISM band (5 mW/MHz).

    Bluetooth Class 1 radio. Maximum output power from unlicensed AM transmitter per U.S. Federal Communications Commission (FCC) rules 15.219.[4]

    19 dBm79 mW

     

    This would give three reasons as to why I can't put more than 20dBm into the device:

    1) It is sort of illegal

    2) The maximum normal output of wireless devices is normally only 100mW (20dBm)

    3) You cannot draw 5.8Watts out of a USB port on the raspberry pi (I think 5volt * 500mW = 2.5W would be the maximum before you need a powered hub or blow it up)

  • 6. Re: RT3070 wireless adapter adjust tx power??
    shabaz Level 15

    Agree : )

  • 7. Re: RT3070 wireless adapter adjust tx power??
    obcd Level 1

    1. You are probably right about this. Even some channels are blocked, depending upon the country settings.

    2. There do exist high power devices. I have an alpha wifi stick that claims to be high power.

    It will drain more than the allowed 500mA from your usb port.

    Most pc's only care about the total current used on all usb ports, so on a pc this can work.

    Wifi communication is bidirectional. It's useless to have a high power stick if the access point is unable to transmit in high power as well.

    For some cheap adapters without external antenne, sending more power could extend the usable range a little. High power devices usually will have a good antenna as you don't want the RF radiation to interfer with the surrounding chips.

  • 8. Re: RT3070 wireless adapter adjust tx power??
    wallarug Level 14

    NEW QUESTION:

     

    Where can I find the db.txt file?

     

    This will allow me to change the allowed txpowers for each country.

  • 9. Re: RT3070 wireless adapter adjust tx power??
    msilveus Level 3

    Hi Fergus,

     

    The easiest why to find files is to install locate using 'sudo apt-get install locate' Once you have it installed run 'sudo updatedb' afterwards run 'locate db.txt' to get a list of every file named db.txt. You can then add updatedb as a cron job and have it automatically update the file list db and then locate we stay up to date.

     

    Mike

  • 10. Re: RT3070 wireless adapter adjust tx power??
    wallarug Level 14

    Couldn't find it.  Any one know where the information about wireless power is stored?  I read about a file called db.txt but I could not find it.

  • 11. Re: RT3070 wireless adapter adjust tx power??
    wallarug Level 14

    Any idea what any of this means?

     

    [    2.645344] usb 1-1.3: Product: 802.11 n WLAN

    [    2.653229] usb 1-1.3: Manufacturer: Ralink

    [    3.753010] udevd[137]: starting version 175

    [    5.219718] cfg80211: Calling CRDA to update world regulatory domain

    [    6.202215] usb 1-1.3: reset high-speed USB device number 4 using dwc_otg

    [    6.483273] ieee80211 phy0: Selected rate control algorithm 'minstrel_ht'

    [    6.484945] Registered led device: rt2800usb-phy0::radio

    [    6.485093] Registered led device: rt2800usb-phy0::assoc

    [    6.485224] Registered led device: rt2800usb-phy0::quality

    [    6.485359] usbcore: registered new interface driver rt2800usb

    [    8.919891] cfg80211: World regulatory domain updated:

    [    8.927372] cfg80211:     (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp)

    [    8.935303] cfg80211:     (2402000 KHz - 2472000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)

    [    8.942959] cfg80211:     (2457000 KHz - 2482000 KHz @ 20000 KHz), (300 mBi, 2000 mBm)

    [    8.950748] cfg80211:     (2474000 KHz - 2494000 KHz @ 20000 KHz), (300 mBi, 2000 mBm)

    [    8.958288] cfg80211:     (5170000 KHz - 5250000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)

    [    8.966107] cfg80211:     (5735000 KHz - 5835000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)

     

    ...From startup prompt.  It is stopping /etc/network/interfaces from controlling the card.

  • 12. Re: RT3070 wireless adapter adjust tx power??
    wallarug Level 14

    Anyone know why I can't get an IP address with my RPi as an Access Point?

     

    http://www.raspberrypi.org/phpBB3/viewtopic.php?f=36&t=31404

  • 13. Re: RT3070 wireless adapter adjust tx power??
    wallarug Level 14

    This topic has sort of gone dead but...

     

    I have found a way that you can stop the Linux OS (using BT5 in a Virtual machine for a start) from limiting tx power...

     

    What I want to know though is:

    1.  Is it telling me the truth that you can put 1.1A@ 5 volts into a Kinamax TS-9900 without blowing it up?

     

         NOTES:

         -  It 'claims' to have a txpower of 5800mW with a 58dBi Antenna.

         Transmission Power: 5800mW @ 38dBm ± 1dBm - http://forum.lowyat.net/topic/2414082/all

     

     

    2.  What are the signs that it is not copeing with the 1.1A of power?  Fire?  Smoke?  Burning Electronics Smell?  Heat?

  • 14. Re: RT3070 wireless adapter adjust tx power??
    mcb1 Level 15

    These are very ambitious figures.

    I doubt its posible to get 58dBi out of that antenna design.

     

    I have a 32km wireless link, that has a 24dBi grid pack antenna on the roof, and the TX power is 29dBm, and we are limited to 2MBps, although it probably will do more.

     

    With 2.4GHz, interference and close objects can cause the biggest loss of performance, despite the power settings.

     

     

    Mark

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