User's Manual

KAIROS User Manual - version 1.3
Radio Activity S.r.l. 12/11/2014 28 / 41
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.
4.8 PPS signal
For applications in simulcast networks where the source of synchronization is the PPS signal by GPS, if this
signal is missing, the radio coverage of the areas which are reached by several repeaters with the same field
strength, is not ensured. Attention must be paid in choosing and placing the GPS antenna.
The GPS quality and the effective antenna efficiency can be checked connecting to the equipment through
the setup tool.
4.9 On site check list
Once the equipment is placed in the transmission site it is a good practice to measure some parameters to
be sure that the site is ready and for future reference.
The main measures should be:
∞ Power supply voltage; it should be 13,2Vdc measured at the KAIROS input. The internal monitor,
accessible via the setup tool, should indicate around 13,2V +/- 300mV in standby; this standby
value should not decrease for more than -600mV in TX @10W and -800mV in TX @25W (values
valid for VHF model). Be sure that, at the nominal RF power, the power supply be at least 12Vdc.
Remember that noisy power supply may produce unwanted disturbs both in TX and in RX.
∞ TX power to the antenna; keeping in account the branching loss, it should be within +/-1 dB (+/-2W
@10W) respect to the nominal power set.
∞ Antenna and branching system; verify the reflected power at the TX output and at the branching
output to the antenna. Unless the TX has got a built-in protection to a load mismatching, it is
strongly recommended to achieve at the TX output connector a VSWR (referenced to 50 Ohm)
between 1 to 1.3. In presence of higher value of VSWR, the system performance will be degraded.
In this case a variety of symptoms might appear, like:
1. The reflected power might change varying the length of cable between transmitter and the
branching system.