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What are the benefits (if any) of a higher tx power?


michael_kent123
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I was recently watching a video by Vivek Ramachandram on how to increase the tx power of the Alfa card.

Question: what is the benefit of this?

Does it allow the Alfa to "see" networks that are further away?

Does it allow for packet injection over a further distance?

Does it give a benefit for arpspoofing e.g. being able to transmit the fake MAC of the router over a greater distance?

Can someone please articluate the benefits of tx power 30 over, say, tx power 20.

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Think of the wifi adapter as a megaphone, measured in decibels. The non-deaf people around you are the various wifi radios nearby, beit clients or APs. The tx power is the volume knob on the megaphone, and the effect it would have on the people around you is the same effect it would have on the radios nearby.

So with a higher transmission power your outbound signal travels further and is more likely to overpower the other signals (at the same frequency).

- You can inject packets more reliably because when you and the legitimate transmitter send the data at the same time, your signal is more likely to overpower the legitimate one and because of this end up being the signal actually heard by the receiver.

- You can transmit your data over a greater distance.

- It has no effect on your receiving capability, so you won't pick up any more packets than you did previously.

You want to ARP spoof once you MITM'd a connection. Having a higher transmission power means you can appear 'closer' to the client making it want to prefer your signal over the legitimate one and even allowing you to overpower the legitimate signal because you're 'louder'. Once you're in between you can pull out your usual bag of tricks and go play as you would otherwise, which might involve arp spoofing.

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Thanks - this is a helpful explanation.

There is a thread in the Pineapple section on the best Alfa for Pineapple. I am wondering what the best Alfa is for those of us who want to use it for arpspoofing, packet injection, etc.

In terms of tx power, a poster seems to be suggesting that one Alfa model can provide 2 dBi. I don't understand this if you can only alter the tx power to 30 (using iw reg set BO).

Thanks again!

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Think of the wifi adapter as a megaphone, measured in decibels. The non-deaf people around you are the various wifi radios nearby, beit clients or APs. The tx power is the volume knob on the megaphone, and the effect it would have on the people around you is the same effect it would have on the radios nearby.

So with a higher transmission power your outbound signal travels further and is more likely to overpower the other signals (at the same frequency).

- You can inject packets more reliably because when you and the legitimate transmitter send the data at the same time, your signal is more likely to overpower the legitimate one and because of this end up being the signal actually heard by the receiver.

- You can transmit your data over a greater distance.

- It has no effect on your receiving capability, so you won't pick up any more packets than you did previously.

You want to ARP spoof once you MITM'd a connection. Having a higher transmission power means you can appear 'closer' to the client making it want to prefer your signal over the legitimate one and even allowing you to overpower the legitimate signal because you're 'louder'. Once you're in between you can pull out your usual bag of tricks and go play as you would otherwise, which might involve arp spoofing.

Is there any reason therefore not to increase the tx power to 30? It seems to only do good things.

More specifically, if one created a "soft" or fake AP, a higher tx power would presumably overcome the "real" signals from the genuine AP?

Edited by michael_kent123
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The other issue I wanted to ask is about increasing power via antennas. I know nothing about antenna theory. I have a 9 dBi antenna for the Alfa.

What is the most powerful indoor antenna I can get for the Alfa (i.e. not having to attach it to the side of a house).

Does the antenna affect only tx power or also the ability to receive better?

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The dBi value for an antenna I believe relates to the reception strength of an antenna, but I'm sure people will correct me on that if that's not true. Obviously a really shitty antenna will suck at transmitting too, but I thought the main focus was reception.

The reason for not defaulting to 30 as tx power rating is the legality of it all. It's like wondering why people aren't driving X mph on the highway when their cars are capable of it - the government has, in their wisdom, decided that X is the limit and if you go over it and get caught, you'll get a piece of their mind. In reality I've yet to hear of anybody getting even so much as a fine for transmitting their wifi signal at 30 when the local legal limit was less.

Generally speaking, most people wouldn't know what to change if you hit them over the head with a clue stick - they turn on the device, throw it in a corner and try to forget about the thing as quickly as possible. As long as the internets are available, they couldn't care less. It basically means that if you do know what to do and how to do it, there's a good chance your signal will always win from theirs. What you do from that point on is up to you. It might simply be that you want better reception throughout your home...

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Just because you can crank up the power doesn't mean the hardware can do it properly. Bumping the power over stock usually starts producing quite a bit of noise. Also like Cooper said, your local communication governing body has limits on the effective power you can transmit at. Bumping the volume to 11 with certain antenna can and often do go over those limitations. You might be able to get away with it most of the time, but sometime one of those vans might be close enough to drop the banhammer on you. The fines really do suck.

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It can also shorten the lifetime of your hardware. Imagine the stock setting being 10 lets call it. This would be the equivilant of letting your car idle at 1,000 rpm. Now if you bump that up to 30 imagine you just redlined your car at 6,000 rpm, it won't last as long!

It may not kill your device in days or even weeks if you crank it up but it will push it harder and it can cause hardware failures.

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It can also shorten the lifetime of your hardware.

While this is true for overclocking in general, what you're really doing is operating the device at the designed limits for a specific region that isn't the region you're currently in. If doing this runs your card outside of its normal operating spec (normal for the hardware, not normal for the local rules) you have a truly shitty card.

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While this is true for overclocking in general, what you're really doing is operating the device at the designed limits for a specific region that isn't the region you're currently in. If doing this runs your card outside of its normal operating spec (normal for the hardware, not normal for the local rules) you have a truly shitty card.

Not necessarily. A device was engineered, tested, and certified to work at a specific wattage, this is usually what it comes set at and isn't modifiable. Since we are running open software on the pineapple we have access to code most people never see, so we do have the ability to fry the card by running it way above spec. It's the same as running dd-wrt/open-wrt on a linksys wrt54g. Maxing out the power makes them run terrible, but holy shit the range you could get!

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Not necessarily. A device was engineered, tested, and certified to work at a specific wattage, this is usually what it comes set at and isn't modifiable. Since we are running open software on the pineapple we have access to code most people never see, so we do have the ability to fry the card by running it way above spec. It's the same as running dd-wrt/open-wrt on a linksys wrt54g. Maxing out the power makes them run terrible, but holy shit the range you could get!

I actually learned all this from putting dd-wrt on an old Lynksys router and it did fry about 5 months later after regular use at nearly full power. Just use a little sense when your changing these settings, if you don't have a reason to send packets 1/2 mile then you can probably keep the power somewhere around half and be content with it!

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