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Safe tx power level fora wrt54g v4

Discussion in 'Cisco/Linksys Wireless Routers' started by jacksradio, Mar 21, 2006.

  1. jacksradio

    jacksradio Network Guru Member

    I was wondering if the power level on a WRT54G v4 router can be increased safely to 100mw? If not, what is the maximum safe level without additional heat sinking?

    The reason I am asking is this: my router is in the garage....(don't ask) and I am having trouble staying connected when I am in the house approx 25-30 feet away. The computer will connect and show excellent signal strength for a short period of time.( it varies) and then it will drop connection and when it tries to re-establish the network address it never does. I usually have to go into ipconfig and release/renew and sometimes that does not work. Sometimes I have to uninstall the card and the re-install. Meanwhile, the computer see's the network at full strength but says it has limited or no connectivity.

    When I have the computer in the garage, this never happens, so I am thinking that, although the software is reporting full strength in the house, it actually is not and I need increase the power setting a small bit.

    I would appreciate any advice.

  2. jchuit

    jchuit Network Guru Member

    The best way to increase range is to improve the antenna.

    I say around 100 mwatt is the safe max output power, but keep in mind that the wireless client will get a stronger signal, but transmits with the same power.

    For more info about the max output power, read this topic:

    If the Tarifa firmware, you can (status->wireless page) see the R. signal strength rssi (Rx signal) and the tssi (Tx signal), this is an indicator for the quality of the wireless communication.

  3. vincentfox

    vincentfox Network Guru Member

    I believe the factory setting is 28 mW for a good reason.

    Do you have a 200 mW card in your client machine? If it's a standard unit I would be surprised if the client is more than about 32 mW.

    So there is really nothing to gain by increasing it, except gaining the ILLUSION of improving signal as evidenced by the number of bars in the client utility, which really only shows you how strong of a signal it RECEIVES.

    Since networking has to be 2-way, this is pretty much useless.

    A higher-gain antenna increases ability to receive weak signals as well as transmit farther along it's direction of maximum gain. Buy a better antenna. Or build a reflector like at http://www.freeantennas.com/
  4. jacksradio

    jacksradio Network Guru Member

    So let me see if I understand correctly...You are thinking my problem lies in the fact that the client is not communicating with the router instead of the other way around. Interesting. What can be done on the client end of things to improve this. I don't think attaching a corner reflector to my laptop is a viable option.

  5. Toxic

    Toxic Administrator Staff Member

    The ETSI standard in the EU is 100mW max. i wouldn't suggest anymore for internal use. it could damage your health.
  6. RonWessels

    RonWessels Network Guru Member

    On the client end of things? If your laptop has built-in wireless, there's almost certainly nothing that can be done to improve the antenna. I don't know if there are any CardBus notebook wireless adapters that have detachable (and therefore upgradeable) antennas. Or you could research which notebook wireless adapter has the highest transmit power and try that.

    You could also put reflectors on your router's antennas to turn them into directional antennas, which would improve the reception from your laptop. Or otherwise upgrade the router's antennas, again to improve reception.
  7. Toxic

    Toxic Administrator Staff Member

    well i have seen a few places on the net about improving wireless power levels usin software tweaks in the driver *.inf file.

    i have played about with it and got some gain by setting a new line on the power level to show an increase over 100% level.

    ie 115% etc. it did seem to give better signal strength from the router in site survey mode. the PC Card was showing a much better RSSI level.
  8. vincentfox

    vincentfox Network Guru Member

    I think you are missing my point JacksRadio. Transmit and receive need to be symmetrically enhanced to achieve meaningful improvements in WiFi.

    An antenna increases receive AND transmit ability. Envision a person using a cone to enhance communications. They can hold the cone up to their mouth and shout through it to throw their voice further in a direciton. Or they can hold it up to their ear and hear whispers much further away.

    Increasing only transmit power is like giving someone a bullhorn. Sure they can now scream louder, but you have done nothing to enhance their hearing.

    Yes in difficult situations I would put directional reflector antenna on both ends. It's often not practical on the client end. But at least you can put it on the AP. The reflector on the AP will let it hear a laptop further out. It's a focusing device that concentrates signal, whether they are incoming or outgoing. A reflector on the AP will typically take a "low" signal up to "good". Or push the range further out.

    It's the best thing you can do. Spend a bit making a reflector as documented at http://www.freeantennas.com/ and report back. The simplest is I think the corner reflector, try that first.
  9. jchuit

    jchuit Network Guru Member

    What happens when we increase transmit power.

    The best way to increase range is a good antenna, but what happens, if we increase the radiated power.

    What happens when we double the transmit power, lets say, we have an ap and a client at a remote location:

    The WRT54G has two types of wireless datastreams:
    1. beacons, ack's, broadcast, rts/cts, etc......
    2. Data between ap and client and back again.

    Most in category 1 is transmitted in the 1-2 Mbit/s datastream.
    All in category 2 is transmited in the most fast possible speed.

    Cat 1 will get a bigger range if we increase the transmit power and thus more radio energy is emited into the free air.

    This is bad, some remote clients like to associate but can't reach the accespoint and can give interference.

    Cat 2 will increase the wireless speed until it is 54/s Mbit.

    The remote client normaly would hear a 24Mbit/s speed, this dataspeed will now double to 48Mbit/s, this means the total amount of radio energy emited will not increase, this because the radio transmits twice as fast.

    Of course is this not the case when the accespoint is very close near the client. This effect saturates at 54 Mbit/s.

    In this case: The total amount of radio energy needed for the transmission of the data depends on the distance and the amount of data.


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