User's Manual

Radio Activity S.r.l. 29 / 44
If an external branching is connected to the equipment, it must be designed to ensure minimum reflected
power at the TX port (VSWR referenced to 50 Ohm less than 1.3) and the needed isolations between
transmitter and receivers. See the branching paragraph in the engineering specification appendix.
4.4.1 Maximum permitted antenna gain for mobile usage
Please note that there is an ERP limit in both SRSP-500 specifications by IC and in FCC Part 90 I, equal to 30
Watts (that is 44.8dBm) ERP, for mobile equipment. As Kairos can generate a maximum RF power of 25W
(44dBm), the margin between maximum radiated ERP power and transmitted power is 0.8dB (corresponding
to 3dBi). The consequence is that for mobile usage of Kairos, the maximum permitted antenna gain (by IC
and FCC) is 3dBi.
4.4.2 Maximum permitted antenna gain for fixed usage
Please note that there is an ERP limit in both SRSP-500 specifications by IC and in FCC Part 90 I, equal to 125
Watts (that is 51dBm) ERP, for fixed equipment. As Kairos can generate a maximum RF power of 25W
(44dBm), the margin between maximum radiated ERP power and transmitted power is 7dB (corresponding
to 9dBi). The consequence is that for fixed usage of Kairos, the maximum permitted antenna gain (by IC and
FCC) is 9dBi.
4.5 AF interface
These IN/OUT ports are balanced and ground referred (NOT FLOAT! don’t apply to these pins more than
20Vdc). For long line use, it is recommended to insert an external 1:1 transformer in order to isolate the port
from static voltage difference that can be arise between the line ends.
A 2/4W telephone line can be connected to the equipment only using an external circuit with high isolation
and with discharges to prevent damages due to eventual atmospheric discharges on the line.
4.6 Manual settings
No manual settings are required for KAIROS repeaters.
4.7 Self-test process
During self-test process internal parameters of modulator and demodulators are tuned by generating a signal
through the synthesizer of the transmitter, by automatically connecting its output to the input of the receiver
and by analyzing the received signal. If a strong signal is received by the external antenna during self-
calibration, it is possible that the process ends with errors (a corresponding “warning” alarm will be displayed
on both frontal leds and monitor of PC for remote control). In this case the DSP will load from flash memory
the previously saved parameters without any problem for the transceiver.
To obtain better results from self-test process, it is recommended to set the calibration frequency as near as
possible to the transmitter frequency; if there is a range of allowed frequencies for transmission, it is
recommended to set the centre of this range as the calibration frequency.