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  1. Principio da LOS (Line of Sight)

    Os sinais RF são atenuados a medida que passam pelos objectos como paredes, edificios etc. O nivel de sinal atenuado é dificil de determinar até porque a natureza do edificio ou parede e complexo.
    Para ter boa comunicação com o minimo de atenuação possivel, o principio de LOS é preciso. Significa que não deve haver nenhum obstaculo entre as duas antenas, de uma antena ou estação deve ser visivel a outra.


    Perda de ondas pelo espaço

    A seguinte tabela apresenta os valores tipicos de perca nos 2.4Ghz:

    Metros -> Perca(dB)

    100 -> 80.23
    200 -> 86.25
    500 -> 94.21
    1,000 -> 100.23
    2,000 -> 106.25
    5,000 -> 114.21
    10,000 -> 120.23


    Calcular a distancia

    Formula para Calcular a distancia em 2.4Ghz:

    X= (TX Power + | RX sensitive | + Antena Gain - Cable Loss - 100(dB)) /6


    Exemplo:

    2 APs + 2 Antenas Direcionais (14dB) + 2 Cabos (com perca de 2,5dB)

    AP: Tx Power = 13dB, RX Sensitivity = -83dB
    Antena Gain: 14+14 = 28dB
    Cable Loss: ((2 * 0,6) + (2 * 2,5)) = 6.2dB

    X = (13+83+28-6.2-100) / 6

    X = 17.8 / 6 = 2.96

    A distancia maxima é: 2^2.96 = 7,7812395792982841481816167578363

    vamos resumir isto e arredondar... o que dá : 8 KM


    Espero que isto sirva para alguma coisa...[/b]

    Ja agora quem quiser melhor veja este URL:

    http://my.athenet.net/~multiplx/cgi-...eless.main.cgi

    outro:

    http://www.signull.com/fsc.php

    http://www.swisswireless.org/wlan_calc_es.html


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  3. #2
    Wireless_Brasil
    Oi Tiago,

    Bacana essa tabela, eu fazia de outra forma.
    Eu fiz uma que calcula a potencia (Effective Isotropic
    Radiated Power (EIRP) )

    http://www.wirelessbt.com.br/conversor.php

  4. Citação Postado originalmente por Wireless_Brasil
    Oi Tiago,

    Bacana essa tabela, eu fazia de outra forma.
    Eu fiz uma que calcula a potencia (Effective Isotropic
    Radiated Power (EIRP) )

    http://www.wirelessbt.com.br/conversor.php
    dBm to Watt Conversion Table


    --------------------------------------------------------------------------------

    dBm Watts dBm Watts dBm Watts
    0 1.0 mW 16 40 mW 32 1.6 W
    1 1.3 mW 17 50 mW 33 2.0 W
    2 1.6 mW 18 63 mW 34 2.5 W
    3 2.0 mW 19 79 mW 35 3.2 W
    4 2.5 mW 20 100 mW 36 4.0 W
    5 3.2 mW 21 126 mW 37 5.0 W
    6 4 mW 22 158 mW 38 6.3 W
    7 5 mW 23 200 mW 39 8.0 W
    8 6 mW 24 250 mW 40 10 W
    9 8 mW 25 316 mW 41 13 W
    10 10 mW 26 398 mW 42 16 W
    11 13 mW 27 500 mW 43 20 W
    12 16 mW 28 630 mW 44 25 W
    13 20 mW 29 800 mW 45 32 W
    14 25 mW 30 1.0 W 46 40 W
    15 32 mW 31 1.3 W 47 50 W



    --------------------------------------------------------------------------------

    Usage and Maximum Power Limit Guidelines

    Before we can go on, first we need to separate the two different classes of users for Spread Spectrum devices that exist and set some guidelines of some of the specs.

    Consumers and IT Professionals Operating Spread Spectrum (DSSS) gear:

    Users operate under FCC Part 15 rules and regulations.

    Frequencies include 902-928 MHz, 2400-2483.5 and 5725-5850 MHz.

    Maximum Transmitter Power Output (TPO) is 1.0 watt or 30dBm.

    The formula for converting antennas from dBi to dBd is dBi-2.2=dBd.

    There are two different classifications for operation. You'll commonly hear these modes referred to as Point to Point (PTP) and Point to Multipoint (PTMP). PTP is when two sites talk only to themselves. PTMP is when many sites talk to a single core site. Each of these modes have different EIRP (Effective Isotropic Radiated Power) limitations.

    Point to MultiPoint:

    The maximum EIRP power allowed is 36dBm (4 watts).

    Maximum transmitter power versus largest antenna table for PTMP:

    Transmitter RF power Antenna Gain EIRP in watts
    30dBm 1W 6dBi 3.98
    27dBm 500mW 9dBi 3.98
    24dBm 250mW 12dBi 3.98
    20dBm 100mW 15dBi 3.98
    17dBm 50mW 18dBi 3.98
    14dBm 25mW 21dBi 3.98
    10dBm 10mW 24dBi 3.98

    Losses from the transmitter via cabling, lightning suppression, filtration can be removed from the transmitted power dBm figure. An example here would be say a 30dBm 1 watt amplifier with 100ft of LMR400 (at 6.7dB of loss) brings transmitter power down to 23.3dBm, allowing a 12dBi antenna.

    Point to Point:

    Higher EIRP is allowed if the antennas are directional in nature.

    Systems operating in a point-to-point operation may employ transmitting antennas with directional gain greater than 6 dBi provided the maximum output power of the transmitter is reduced by 1 dB for every 3 dB that the directional gain of the antenna that exceeds 6 dBi. Maximum transmitter power versus largest antenna table for PTP:

    Transmitter RF power Antenna Gain EIRP in watts
    30dBm 1W 6dBi 3.98
    29dBm 800mW 9dBi 6.35
    28dBm 630mW 12dBi 10.14
    27dBm 500mW 15dBi 15.81
    26dBm 398mW 18dBi 25.23
    25dBm 316mW 21dBi 40.28
    24dBm 250mW 24dBi 62.79
    23dBm 200mW 27dBi 100.2

    This information is provided as a guideline. If you are not a professional installer we highly recommend that you read the FCC Part 15 rules and understand them before attempting installations.



    Amateur Radio Operators operating under licensed spectrum:

    Users operate under FCC Part 97 rules and regulations.

    Frequencies usable from over-the-counter consumer gear include the 33cm 902-928 MHz band and the 13cm 2390-2450 MHz band.

    In the 13cm band, 802.11 channels 1 thru 6 are the only channels in the 2390-2450 MHz bandplan.

    Maximum Transmitter Power Output (TPO) is 100 watt or 50dBm.

    If more than 1 W is used, automatic transmitter control shall limit output power to that which is required for the communication.

    You must enable broadcasting of your SSID, which has to include your callsign.

    WEP encryption is not permitted.

    Only authorized licensed operators should be able to access Part 97 installed hardware, so care should be taken to prevent unauthorized users from utilizing said hardware.

    It's highly suggested for Amateurs visit the ARRL website and participate in the HSMM (high speed multimedia) working group. The HSMM group only deals with working on high speed data via Amateur radio. This group is producing proposed rule making changes to be submitted to the FCC that would make operating simpler and allow more reasonable usage of for example encryption. The author of this document, Dave Anderson is a licensed amateur radio operator (KG4YZY) and is on the ARRL HSMM Working group.


    Mais um complemento para seu material amigo

    Tiago Matias

  5. Citação Postado originalmente por Wireless_Brasil
    Oi Tiago,

    Bacana essa tabela, eu fazia de outra forma.
    Eu fiz uma que calcula a potencia (Effective Isotropic
    Radiated Power (EIRP) )

    http://www.wirelessbt.com.br/conversor.php

    Como a malta sabe, o limite de potência para a aEuropa é de 100mW. Não de 100mW à saída do AP mas sim o EIRP (ou seja a potência equivalente isotrópica irradiada total). Isto significa que, por exemplo se tivermos um AP com 50mW (o que se vende por ai) e se colocarmos uma simples catena para emitir, estamos a violar a lei. neste caso o EIRP fica qq coisa como 20dBm (50mW) + 10 dBm (ganho da catena) = 30 dBm = 1 W, ou seja 10 x mais o que é permitido por lei !!!!!!!!!!



    dBm to Watt Conversion Table


    --------------------------------------------------------------------------------

    dBm Watts dBm Watts dBm Watts
    0 1.0 mW 16 40 mW 32 1.6 W
    1 1.3 mW 17 50 mW 33 2.0 W
    2 1.6 mW 18 63 mW 34 2.5 W
    3 2.0 mW 19 79 mW 35 3.2 W
    4 2.5 mW 20 100 mW 36 4.0 W
    5 3.2 mW 21 126 mW 37 5.0 W
    6 4 mW 22 158 mW 38 6.3 W
    7 5 mW 23 200 mW 39 8.0 W
    8 6 mW 24 250 mW 40 10 W
    9 8 mW 25 316 mW 41 13 W
    10 10 mW 26 398 mW 42 16 W
    11 13 mW 27 500 mW 43 20 W
    12 16 mW 28 630 mW 44 25 W
    13 20 mW 29 800 mW 45 32 W
    14 25 mW 30 1.0 W 46 40 W
    15 32 mW 31 1.3 W 47 50 W



    --------------------------------------------------------------------------------

    Usage and Maximum Power Limit Guidelines

    Before we can go on, first we need to separate the two different classes of users for Spread Spectrum devices that exist and set some guidelines of some of the specs.

    Consumers and IT Professionals Operating Spread Spectrum (DSSS) gear:

    Users operate under FCC Part 15 rules and regulations.

    Frequencies include 902-928 MHz, 2400-2483.5 and 5725-5850 MHz.

    Maximum Transmitter Power Output (TPO) is 1.0 watt or 30dBm.

    The formula for converting antennas from dBi to dBd is dBi-2.2=dBd.

    There are two different classifications for operation. You'll commonly hear these modes referred to as Point to Point (PTP) and Point to Multipoint (PTMP). PTP is when two sites talk only to themselves. PTMP is when many sites talk to a single core site. Each of these modes have different EIRP (Effective Isotropic Radiated Power) limitations.

    Point to MultiPoint:

    The maximum EIRP power allowed is 36dBm (4 watts).

    Maximum transmitter power versus largest antenna table for PTMP:

    Transmitter RF power Antenna Gain EIRP in watts
    30dBm 1W 6dBi 3.98
    27dBm 500mW 9dBi 3.98
    24dBm 250mW 12dBi 3.98
    20dBm 100mW 15dBi 3.98
    17dBm 50mW 18dBi 3.98
    14dBm 25mW 21dBi 3.98
    10dBm 10mW 24dBi 3.98

    Losses from the transmitter via cabling, lightning suppression, filtration can be removed from the transmitted power dBm figure. An example here would be say a 30dBm 1 watt amplifier with 100ft of LMR400 (at 6.7dB of loss) brings transmitter power down to 23.3dBm, allowing a 12dBi antenna.

    Point to Point:

    Higher EIRP is allowed if the antennas are directional in nature.

    Systems operating in a point-to-point operation may employ transmitting antennas with directional gain greater than 6 dBi provided the maximum output power of the transmitter is reduced by 1 dB for every 3 dB that the directional gain of the antenna that exceeds 6 dBi. Maximum transmitter power versus largest antenna table for PTP:

    Transmitter RF power Antenna Gain EIRP in watts
    30dBm 1W 6dBi 3.98
    29dBm 800mW 9dBi 6.35
    28dBm 630mW 12dBi 10.14
    27dBm 500mW 15dBi 15.81
    26dBm 398mW 18dBi 25.23
    25dBm 316mW 21dBi 40.28
    24dBm 250mW 24dBi 62.79
    23dBm 200mW 27dBi 100.2

    This information is provided as a guideline. If you are not a professional installer we highly recommend that you read the FCC Part 15 rules and understand them before attempting installations.



    Amateur Radio Operators operating under licensed spectrum:

    Users operate under FCC Part 97 rules and regulations.

    Frequencies usable from over-the-counter consumer gear include the 33cm 902-928 MHz band and the 13cm 2390-2450 MHz band.

    In the 13cm band, 802.11 channels 1 thru 6 are the only channels in the 2390-2450 MHz bandplan.

    Maximum Transmitter Power Output (TPO) is 100 watt or 50dBm.

    If more than 1 W is used, automatic transmitter control shall limit output power to that which is required for the communication.

    You must enable broadcasting of your SSID, which has to include your callsign.

    WEP encryption is not permitted.

    Only authorized licensed operators should be able to access Part 97 installed hardware, so care should be taken to prevent unauthorized users from utilizing said hardware.

    It's highly suggested for Amateurs visit the ARRL website and participate in the HSMM (high speed multimedia) working group. The HSMM group only deals with working on high speed data via Amateur radio. This group is producing proposed rule making changes to be submitted to the FCC that would make operating simpler and allow more reasonable usage of for example encryption. The author of this document, Dave Anderson is a licensed amateur radio operator (KG4YZY) and is on the ARRL HSMM Working group.


    Mais um complemento para seu material amigo

    Tiago Matias

  6. #5
    Wireless_Brasil
    Essa Tabelinha eu tenho tbem, mto útil. =)

    Valew vamos trocar fiugurinhas!!!

    Abracos


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