User's Manual

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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.
2. The transmitter might generate spurious radiations.
3. The transmitter might increase its floor noise; this can produce de-sensitivity on the receiver
path.
4. The transmitter output power might become erratic, either too high or too low as measured on
a wattmeter.
In case of a poor branching system, the use of a ferrite isolator at the output of the transmitter should
solve the reflected power problem.
∞ RX sensitivity; since KAIROS is a digital transceiver, the sensitivity should be measured in digital.
Anyway, considering that the digital demodulation is only a SW algorithm, it is enough to measure
the sensitivity in analog. The sensitivity should be measured on both channels, Main and Diversity,