Redhawk II GSM Modem Users Guide
Draft: 10/30/00
52
Part Number: 07100020 version 00B
© 2000 Xircom, Inc. All rights reserved.
All trademarks and copyrights are the property of Xircom, Inc.
Formula Examples
Example 1 :
The installer has a nominal 7dB gain antenna, is using RG-223 cable, and is using
the modem in a fixed application.
G = 7 dB
p = 7 dB
a = 0.29 dB/ft
then Attenuation needed = 7 – 7 = 0 dB
and L = (7 – 7) / 0.29 = 0 ft
In this example, the length of cable the installer must use does not matter because
he does not need any loss in the line to meet the FCC requirements.
Example 2 :
The installer has a nominal 7 dB gain antenna, is using RG-223 cable, and is using
the modem in a mobile application.
G = 7 dB
p = 3 dB
a = 0.29 dB/ft
then Attenuation needed = 7 – 3 = 4 dB
and L = (7 – 3) / 0.29 = 13.8 ft
In this example, the installer must use at least 13.8 feet of cable or use a 4 dB “in
line attenuator”, or a combination of the two.
Example 3 :
The installer has a 10 dB nominal gain antenna, using RG-223 cable, and the modem
is in a fixed application.
G = 10 dB
P = 7 dB
a = 0.29 dB/ft
the Attenuation needed = 10 – 7 = 3 dB
and L = (10 – 7) / 0.29 = 10.3 ft