Anthena 3:1 or 1:1

Answered Question
Mar 25th, 2010
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Hello,


I am confused of reading different versions. Which is true:


A) FCC Anthena requirement for Point-To-Point. For every 1dBm of transmit power you decrease you can add 3dBm of anthena gain (1:3) or is it only a 1:1?


B) FCC anthena requirement for Point-To-Multipoint. For every 1 dBm of transmit power you decrease you can add 1dBm of anthena gain (1:1) or  is it only a 1:3?


Please help with this confusion!

Thanks.

Correct Answer by Kayle Miller about 7 years 1 month ago

Part of the confusion regarding your question comes from the obscurity of the terms Point-to-Point and Point-to-Multipoint. The FCC regulatory limit states that the maximum EIRP is 36dbm, although they make exceptions to that for dedicated point-to-point installations that are using direction yagi type antennas (also note the antenna must be over 6dbi.).


Typically in a Point-to-Multipoint installation you have the root side with an omni-directional antenna which in this case your maximum EIRP will be 36dbm or 4 watts.


So in terms of the Point-to-Point, if you are using an antenna with gain higher than 6dbi, you must lower the transmit power 1db for every three db that the antenna is over 6dbi. as shown in the example below:


Transmit power  +   Antenna Gain  =   EIRP


30db  +  6dbi  =  36dbm


28db  +  12dbi  =  40dbm



does that make sense??



Point-to-Multipoint is a 1db to 1db progression.



How this helps. Please rate the answer.


Thanks,


Kayle

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Correct Answer
Kayle Miller Thu, 03/25/2010 - 13:14
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Part of the confusion regarding your question comes from the obscurity of the terms Point-to-Point and Point-to-Multipoint. The FCC regulatory limit states that the maximum EIRP is 36dbm, although they make exceptions to that for dedicated point-to-point installations that are using direction yagi type antennas (also note the antenna must be over 6dbi.).


Typically in a Point-to-Multipoint installation you have the root side with an omni-directional antenna which in this case your maximum EIRP will be 36dbm or 4 watts.


So in terms of the Point-to-Point, if you are using an antenna with gain higher than 6dbi, you must lower the transmit power 1db for every three db that the antenna is over 6dbi. as shown in the example below:


Transmit power  +   Antenna Gain  =   EIRP


30db  +  6dbi  =  36dbm


28db  +  12dbi  =  40dbm



does that make sense??



Point-to-Multipoint is a 1db to 1db progression.



How this helps. Please rate the answer.


Thanks,


Kayle

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