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I want to decrease the signal strength of my wireless card (to minimize interference, among other factors), so I tried the following command:

iwconfig wlan0 txpower 1

Running iwconfig again confirms the change (initially it displayed 19 dBm):

wlan0    IEEE 802.11bgn  Mode: Master  Tx-Power=1 dBm
         Retry long limit:7  RTS thr:off  Fragment thr:off
         Power Management:off

However, in practice there does not seem to be any change: if I move my phone around, which is connected to this wireless hotspot, it has excellent signal even several meters away, just like when Tx-Power indicated 19 dBm.

Even if I try setting the power to something like 0.0001, the output of iwconfig displays 0 dBm, but in practice it does not seem to minimize signal strength.

I assumed that Tx-power would regulate how the hotspost signal might be seen by other devices, but I may be wrong.

Is there another way to verify whether this value is actually taken into account? Or is there a reason why iwconfig might be lying about the actual Tx-power used?

Note: intended usage is to have my phone 10 cm away from the hotspot, using only a low-speed connection.

1 Answer 1

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Your hotspot's wifi driver would need to support this, which is only actually implemented for some chipsets, others do not change the transmission power.

If you really want to tether your phone over a very short range, use bluetooth tethering. Its a short range network and you need to pair devices instead of having a common password for all.

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    But is there a way to know if my driver supports it? Setting txpower to 1 or 0 results in no error message, and iwconfig later reports as if it had worked. dmesg also does not report any errors. I'm fine if the driver does not support it, but I'd like it to tell me, or at least be coherent with the output of iwconfig. Maybe there are several layers which are not communicating properly?
    – anol
    Mar 12, 2015 at 7:48
  • I do not know. I just had the same problem. Experimented with it and it changed nothing at all.
    – allo
    Mar 13, 2015 at 7:37

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