puzzled by indoor antennas

[delxu]

I am puzzled by some introduction about indoor antennas.

Some vendors introduce indoor antenna box which contain a power amlifier and an omni-directional antenna, it can cover as large as 30,000 square feet, and can cover up to 4 floors!

I know the more power the antenna send out, more it can reach, but the problem is how the weak signal sended by the wireless adapter in a PDA or notebook computer can reach the antenna and be recognized without any error? since the data transmission is bi-directional!

I am just puzzled by the alleged cover range some vendor claim!

[medaica]

There are 2 methods to extend range at the base using passive antenna:
(1) bi-directional amplifier connected to a single antenna. This device senses transmit power from the radio and feed it to the PA. When none exists, the PA is powered down and the LAN goes on line to amplify receive signal (in opposite direction).
(2) separate antennas, PA and LNA for transmit and receive path respectively.

802.11 radios are meant to be low cost products thus the internal PA and LNA are optimised for price vs performance. Performance increase can be realized if married with a good external linear power amplifier and very low noise amplifier (with pre-selector filter). Note that if you don't have a good PA and LNA you will not get the theoretical range extension that corresponds to the gain of these devices.

[delxu]

Originally posted by medaica
There are 2 methods to extend range at the base using passive antenna:
(1) bi-directional amplifier connected to a single antenna. This device senses transmit power from the radio and feed it to the PA. When none exists, the PA is powered down and the LAN goes on line to amplify receive signal (in opposite direction).
(2) separate antennas, PA and LNA for transmit and receive path respectively.

802.11 radios are meant to be low cost products thus the internal PA and LNA are optimised for price vs performance. Performance increase can be realized if married with a good external linear power amplifier and very low noise amplifier (with pre-selector filter). Note that if you don't have a good PA and LNA you will not get the theoretical range extension that corresponds to the gain of these devices.

Thanks.
I know there is a bi-directional amplifier in that antenna box. I am only wondering that how can the signal from a simple 11b adapter (with only 2.2 dbi patch antenna inside) can pass through 3 floors and reach the indoors antenna box? It might be totally absorbed by the 3 concrete floors


=================================
antenna box|
_____=____|


4th floor
=================================


3rd floor
=================================


2nd floor
=================================


1st floor |PC with 11b adapter|
=================================

[Uncle Ken]

The vendors' claims are for the access points, not the clients. The fact is that the access point may blast its signal throughout 4 floors, but you are correct that clients with weak signals probably won't be heard over that distance. Vendor's claim can still be valid, while not revealing the whole truth -- or, hadn't you ever noticed that with vendors?

[Toyboy]

Originally posted by medaica
There are 2 methods to extend range at the base using passive antenna:
(1) bi-directional amplifier connected to a single antenna. This device senses transmit power from the radio and feed it to the PA. When none exists, the PA is powered down and the LAN goes on line to amplify receive signal (in opposite direction).
(2) separate antennas, PA and LNA for transmit and receive path respectively.

802.11 radios are meant to be low cost products thus the internal PA and LNA are optimised for price vs performance. Performance increase can be realized if married with a good external linear power amplifier and very low noise amplifier (with pre-selector filter). Note that if you don't have a good PA and LNA you will not get the theoretical range extension that corresponds to the gain of these devices.

medaica, can you recommend some specific amps and antennas that are representative of the kinds of equipment that's available?

Thanks.