Sabrent High-Power WiFi

[Dave Rickey]

I recently purchased a Sabrent 1000mw USB WiFi adapter, to help get decent WiFi connections in my rig. Standard WiFi adapters have a 50mw transmitter, which means that you only get a moderate range increase by using larger, higher-gain antennas. Past 6dBi your antenna is letting you receive signals from routers that your transmitter is not strong enough to reach (unless the router also has a high-dBi antenna, something you can't control). Higher transmitter power lets you punch a signal through to a router you otherwise could not reach, the combination of a 12dBi omni-directional antenna and a 1000mw transmitter allows good connections out to as far as 1/4 of a mile (unobstructed). A directional antenna (pringles can or Yagi) could potentially reach a mile, but requires more complicated mounting.

I've been more than happy with it, from my rig I easily get connected at 5 bars anywhere that claims free wifi, and from my chair in the living room I am getting 5 bars to a neighbor 4 blocks away (through several houses). Sabrent is not the only high-power wifi adapter available (or even the most powerful, Alfa makes a 2000mw model), it was just the cheapest ($20) when I decided to buy one. I have eventual plans to mount a 12dBi antenna on my Winegard mast, allowing me to get more range when I'm urban boondocking.

I would add that the Sabrent model linked comes with a bootable Linux CD that includes utilities for hacking WEP and WPA security on wireless networks, and even cracking the administrative password for the router itself. Actually using this CD for this purpose is illegal in one way or another in nearly every state.

--Dave

[DriVer]

Quote:

Originally Posted by Dave Rickey I would add that the Sabrent model linked comes with a bootable Linux CD that includes utilities for hacking WEP and WPA security on wireless networks, and even cracking the administrative password for the router itself. Actually using this CD for this purpose is illegal in one way or another in nearly every state.

Dave, I bet you're right about the legal issues with the software. I wouldn't want to go down that route.

[Dave Rickey]

BTW: On transmitters through an omni-directional antenna, the inverse-square law applies, to double the range you have to increase the power by a factor of four. So a 1000mw transmitter has a bit more than 4 times the range of a 50mw, while the 2000mw model would only gain about a third more than that (which is why I didn't bother with it, 3 times the cost for only a marginal increase in range).

The point is, if you've already upgraded your antenna and it's not doing enough for your wifi quality, consider a high-power transmitter model. They're a *lot* cheaper than they used to be, not any more than standard models in many cases.

--Dave

[davecampbell]

1000 mW is absolutely foolish, it interferes with others reception and 1000 mW ought to buy you 10 MILES LOS.

The problem is that 1000mW transmit power is only half the story, Youre blasting your sent signal all over town and interfering with others networks, but you havent improved the RECEIVER any or much. It takes both.

[Dave Rickey]

1000mw pumped through a parabolic antenna, with another on the other end, might reach 10 miles. We're talking about 1W of transmitted RF carrying a dense digital signal, it doesn't have a lot of reach (in comparison, a typical CB is 40W, and a typical FM station is 10,000W, both carrying a considerably simpler signal).

Yes, it's only half the story, that's why I described this as something you use when you've already upgraded your antenna, and that's not doing enough. In combination with a 12-15dBi omni-directional antenna, it could give a range of 1/4 mile, more would require a stronger signal and antenna on the router side. At most locations, the "free WiFi" is not using anything more than the same routers people buy from WalMart for home networks. They have single dipole antennae that simply can't pick up a 50mw transmitter.

--Dave

[John Hilley]

Quote:

Originally Posted by Dave Rickey I recently purchased a Sabrent 1000mw USB WiFi adapter, to help get decent WiFi connections in my rig. Standard WiFi adapters have a 50mw transmitter, which means that you only get a moderate range increase by using larger, higher-gain antennas. Past 6dBi your antenna is letting you receive signals from routers that your transmitter is not strong enough to reach (unless the router also has a high-dBi antenna, something you can't control). Higher transmitter power lets you punch a signal through to a router you otherwise could not reach, the combination of a 12dBi omni-directional antenna and a 1000mw transmitter allows good connections out to as far as 1/4 of a mile (unobstructed). A directional antenna (pringles can or Yagi) could potentially reach a mile, but requires more complicated mounting. I've been more than happy with it, from my rig I easily get connected at 5 bars anywhere that claims free wifi, and from my chair in the living room I am getting 5 bars to a neighbor 4 blocks away (through several houses). Sabrent is not the only high-power wifi adapter available (or even the most powerful, Alfa makes a 2000mw model), it was just the cheapest ($20) when I decided to buy one. I have eventual plans to mount a 12dBi antenna on my Winegard mast, allowing me to get more range when I'm urban boondocking. I would add that the Sabrent model linked comes with a bootable Linux CD that includes utilities for hacking WEP and WPA security on wireless networks, and even cracking the administrative password for the router itself. Actually using this CD for this purpose is illegal in one way or another in nearly every state. --Dave

You would also be illegal anywhere in the US using an antenna with more than 6dBi gain. The maximum EIRP for mobile WiFi is 4 watts. Every 3dBi doubles the effective power, thus 3dBi is 2X and 6 dBi is 4X. With the 1,000mW (1 watt) transmitter 6dBi (4X) gives you 4 watts.

[Midniteoyl]

Funny how it says "For WarDriving'

[Dave Rickey]

Quote:

Originally Posted by John Hilley You would also be illegal anywhere in the US using an antenna with more than 6dBi gain. The maximum EIRP for mobile WiFi is 4 watts. Every 3dBi doubles the effective power, thus 3dBi is 2X and 6 dBi is 4X. With the 1,000mW (1 watt) transmitter 6dBi (4X) gives you 4 watts.

Higher dBi in the antenna does not change transmitted power, you push 1 watt in, 1 watt comes out. Actually, it can slightly reduce your effective output power compared to a straight single-dipole antenna because of phase interference in the antenna. Another reason why you may need to push more power when using high-dBi omni-directional antenna.

Different rules for directional antenna, of course. A pringles can is shaping the waveform from a dipole, and removing interference from the return signal. A Yagi is essentially a series of dipoles spaced just far enough apart to reinforce each other from/to the direction of aim. But neither will actually increase transmitter power, if you don't push watts in, you don't get watts out.

--Dave

[AZgl1500]

Dave, I think you are confusing the issue with the way you have stated your case.

Assuming a 1 watt RF output power.

A dipole has an ERP factor of 1.0 or a radiated power of 1 watt patterned into pretty much a figure 8 pattern . The dipole antenna is the assumed reference antenna for all other antennas.

A Yagi, according to the antenna chapters in the book I learned from, uses phasing between all of the other dipole elements to emphasize "forward radiated power" with the sacrifice of "rear radiated power". A Yagi antenna with a gain of 3 dB will give the user an effective "forward radiated power" of 3 dB above (more than) the single dipole.

So, that being the case, it would be the same as IF the user's transmitter is putting out 2.0 watts into a single dipole.

Antenna theory is way and beyond the scope of this forum, but please do not confuse the issue with saying that even with a 15 dBi antenna they will only get 1 watt "effective forward radiated power (ERP)". That could not be farther from the truth. It will effectively radiate a signal towards the front of the 15 dBi antenna that is the equivalent of a full 32 watts pushed into a single dipole. The Yagi does this by constricting the Figure 8 pattern of a dipole into an extremely narrow forward lobe with almost no radiated power in all other directions. This also makes the necessity of having it pointed correctly very difficult. The beam width is very narrow.

For sake of comparison:

Gain: Ref Pwr: Effective Radiated Power:

03 dB, 1 watt = 2 watts ERP
06 dB, 1 watt = 4 watts ERP
09 dB, 1 watt = 8 watts ERP
12 dB, 1 watt = 16 watts ERP
15 dB, 1 watt = 32 watts ERP

As others have mentioned, this will create the equivalent of an "alligator" signal saturating the receiving router's receiver. At the same time, this "alligator" will be nearly impossible for other users in the RV camp to even notice their signal packets. (due to the lack of side signals as a result of the Yagi's narrowed radiation pattern) That will increase packet collisions making the whole of the camp's internet service just about useless.

off topic: sort of. Yagi is always capitalized, it is a man's name and proper respect to Mr. Yagi should be given.

[John Hilley]

Good explanation AZgl1500. Not to confuse things even more, but the FCC requires transmitters and antennas to be complient as pairs and certified thus by the manufacturer. Legally you can't just pair any transmitter with just any antenna you choose. Lucky for those that don't understand what they are doing, the FCC doesn't have many enforcement engineers and WiFi isn't high on their list for enforcement.