Preparation | 65
Aprisa SRi User Manual 1.1.0
The Aprisa SRi has a maximum mean output power of +26 dBm into a 50 ohm antenna which equates to a
maximum peak power of +30 dBm PEP. To determine the maximum power to be set on the Aprisa SRi, the
following installation parameters must be known:
1.
Aprisa SRi equivalent average power for maximum permitted EIRP (specified in dBm)
R
dBm
2.
Antenna isotropic gain (specified in dBi)
G
dBi
3.
Feeder coax loss between Aprisa SRi and antenna (specified in dB/m)
L
dB/m
4.
Length of feeder coax between Aprisa SRi and antenna (specified in metres)
d
m
From these the above information, the power setting of the Aprisa SRi (
P
dBm
) can be calculated to ensure
operation within the regulatory requirements using the formula:
𝑃
𝑑𝐵𝑚
= 𝑅
𝑑𝐵𝑚
+ (𝑑
𝑚
× 𝐿
𝑑𝐵/𝑚
) − 𝐺
𝑑𝐵𝑖
Antenna gain information can be obtained from the Antenna manufacturer and is either expressed in terms
of dBi, referenced to an isotropic radiator, or dBd, referenced to a dipole.
If the gain is expressed in dBd, it can be converted to dBi by adding 2.15 dB to the gain value.
The following is an example of transmitter power calculations:
Antenna Type
and Gain
Feeder Coax Length and Loss
Regulatory
Limit
Maximum SRi
Power Setting
Yagi, 11 dBi
10
m of ½” Heliax @ 0.11
dB/m gives 1.1 dB loss
+36 dBm PEP
22 dBm
Panel, 12 dBi
33 m of RG214 @ 0.22 dB/m gives 7.3 dB loss
+30 dBm
25 dBm
Dipole, 3.5 dBi 3 m of RG214 @ 0.22 dB/m gives 0.66 dB loss
+30 dBm
26 dBm
Grid, 18 dBi
15
m of ½” Heliax @ 0.11
dB/m gives 1.65 dB loss
+30 dBm
13 dBm
Canada
This radio transmitter Aprisa SRi ISED: 6772A-SI902M160 has been approved by Industry Canada to operate
with the antenna types listed below with the maximum permissible gain indicated. Antenna types not
included in this list, having a gain greater than the maximum gain indicated for that type, are strictly
prohibited for use with this device.
Mexico
La operación de este equipo está sujeta a las siguientes dos condiciones:
(1) es posible que este equipo o dispositivo no cause interferencia perjudicial y
(2) este equipo o dispositivo debe aceptar cualquier interferencia, incluyendo la que pueda causar su
operación no deseada.
Este equipo ha sido diseñado para operar con las antenas que enseguida se enlistan y para una ganancia
máxima de antena de 6 dBi.
El uso con este equipo de antenas no incluidas en esta lista o que tengan una ganancia mayor que 6 dBi
quedan prohibidas. La impedancia requerida de la antena es de 50 ohms.