User's Manual

FT-512 Trailblazer Installation and User Manual version 1.08 33
5.1.5 Installation
The use of an external antenna with Model FT-512 Trailblazer Pro system
mandates professionally trained personnel to ensure compliance with FCC rules
and regulations. Specifically the installer must ensure that the EIRP of the
transmitting antenna does not exceed the requirements of the Code of Federal
Regulations, Title 47, paragraph 15.247.
Calculating the EIRP of an External antenna
The output of the FT-512 Trailblazer radio is calibrated at the factory to +16 dBm
+/- 2dB. It is not adjustable in the field. The 36 inch LMR 400 “N” to “N” short
cable allows the Trailblazer system to be located just behind the antenna with
losses totaling approximately 2 dB. The external antenna sold by CWT has a gain
throughout the 2.4 ISM band of 24dBi.
Using this as an example one can calculate the following:
Given a radio maximum output power of 18 dBm - interconnecting cable losses of
2 dB = total power arriving to antenna of 16 dBm. Now adding the 24 dB Antenna
gain of 24 dB = A total Effective Rated Power of 40 dBm.
The “3 for 1” FCC rule states that for every 3 dB above 6 dB of antenna gain you
must lower the maximum RF power available to the antenna from +30 dBm by 1
dB. In this example the antenna gain is (24 – 6) 18 dB above 6 or (18 / 3) or 6
times 3 dB above 6 dB. Checking to see if the transmit power meets the rule is
done by subtracting 6 from +30 dB equaling +24 dBm. The transmitter output RF
power is +18 dBm max.
Following this guideline ensures compliance with the maximum transmitter ERP
allowed with the antenna provided as a system.
Note that this manual is designed for Professional Installers Only.
Detached antennas, whether installed indoors or out, should be installed ONLY by
experienced antenna installation professionals who are familiar with local building
and safety codes and, wherever applicable, are licensed by the appropriate
government regulatory authorities. Failure to do so may void the CWT product
warranty and may expose the end user to legal and financial liabilities."
"Regulations regarding maximum antenna gains vary from country to country. It is
the responsibility of the end user to operate within the limits of these regulations
and to ensure that the professional installer is aware of these regulations, as well.
"
Installations of the Model I WLL Trailblazer System require topographic analysis,
site survey, and link budget calculation; therefore CWT trained professionals are
required to perform the installation.