What Kind Of Antenna Should I Get

What Kind Of Antenna Should I Get

Postby tommy8834 » Fri Jul 26, 2002 11:11 pm

Hi,

I want to buy an antenna but I don't know which one to choose. It seems like there are so many different types of antenna's being sold. Can anyone tell me the difference between the Omni antenna, Panel antenna, Parabolic antenna, Sectors antenna, and the Yagi antenna's? I have a friend that has a wireless AP and I would like to connect to his access point and share his bandwidth. He lives around 6 blocks down the street and I really don't have a line of sight to his house but I could probably put the antenna on my roof and point it towards his house. Please let me know which antenna type I should use and please describe each type of antenna. I would also like to know what kind of antenna is the strongest and if I should build my own or not (If I build my own, I would like a really powerful one, any instructions on how to build one online?). Also, what is dbi and what does it mean if I get a 24db antenna versus a 5dbi antenna. I heard that 36db is the highest I can get without breaking FCC law or something like that. If not, I would really like to build a 50dbi antenna if instructions were provided. Any help would be greatful. I would really like to get one soon.

Thanks.
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Postby Thorn » Sun Jul 28, 2002 9:44 am

Look, this stuff is pretty complicated, and your questions are indicating a complete lack of knowledge. I'll try to help here, but please don't expect that there are any easy answers on this stuff.

A lot of this stuff is in the NetStumber FAQ threads. Look there for more details. BTW, this area is actually for FAQs, As some of these things are applicable to this as a FAQ, could you in the future, please post questions for direct help in the HELP Area?

Antenna differences:Omni antenna is omnidirectional. In other words, the signal is transmitted and received equally in all directions. Panel antenna, Parabolic antenna, Sectors antenna, and the Yagi antennae are all directional antennae. They all have different applications, which is highly dependant on the particular setup.

Trying so decide the antenna needed to a link to you friend's AP is impossible with so little information. Sorry. To figure it, you need a more exact distance (a "block" varies too much), terrain, tree info, building types, etc. Even then it will only be a wild guess.

If you want to build antennae, get the ARRL book, and scan the sites listed here for plans.

36dB legal is the highest for a Point-to-MultiPoint setup under FCC laws. 48dB is the highest for a Point-to-Point. A 50dBi antenna would be illegal under any circumstances, since you would be transmitting at a something like five times the legal limit, assuming you were pushing 15dB to a 50dBi antenna. About the highest omni you can use is 15 dBi and the highest directional is about 24dbi. FYI, FCC fines run ubout $10k (yes, 10,000 dollars) per incident. Don't do it.

Good luck, read the FAQs here. Once your questions start to get specific, you will start to get specific answers.
Thorn
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Antenna Types

Postby mshimek » Thu Aug 01, 2002 12:25 pm

Selection of antenna type is subject to many variables. One might select a panel antenna due to it's mounting characteristics and physical appearance, such as a long hallway in a building or on the side of a building. One might select a yagi for it's wide beamwith, using it in a campus setting were you might want to "spray" your signal on a distant buiding or group of users in a distant building, but mounted out of sight on the roof. A panel antenna might be good for this also. Dish, Grid, and Parabolic antennas are mainly used in Point to Point bridging applications, where lots of gain is needed to a single point target. Omni antennas, are used in situations where signal is needed in an area around the location of the AP, in a campus or neighborhood internet sharing situation. There are many antennas to chose from, and each has it's place in the puzzle.
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