Receiver voting - Diversity
In radio systems with multiple receivers on the same channel
you will often receive the same audio from several receivers at the same time,
but with different signal strengths.
Multiple base station receivers is an easy way of getting
better coverage for hand portable radios that have low output power.
Using a voting system (diversity) it will
select the best one of the audio signals and you will always hear the best
possible signal from all of your base station receivers.
In the drawing below three radio sites with the same
Marine-VHF radio channel are connected to one PC operator.
If a ship is between site A and site B both receivers will
pick up the signal. The voting system will then determine which of the two
signals are the strongest and present only that signal to the operator.
This gives the operator two advantages:
- He will only hear audio from one receiver (the best
one), meaning no distortion.
- He will get a visible indication on his screen
telling if it was site A, B or C that had best reception. He will then know
on which transmitter to respond to get best possible transmission back to
the ship. He will also know roughly where the ship is.
Three receiver system with one operator.
The diversity option (3103) uses the RSSI output (signal
strength) from the radio, for example a Motorola GM360, and needs an option board (3102)
inside the network interface to handle the signal.
Also radios like Motorola MotoTrbo has a signal strength
output that can be used for comparison in a voting system.
All radios in each voting group needs to be of the same
type to make the correct comparison.
When setting up the operators radio connections you also set which radios are
to be treated as being in the same diversity group.
You can have as many groups as you like and as many radios as you like in
each group, up to the maximum number of radios in your operator position,
normally 8 or 30 radios.
The comparison of the signal strengths are made in each operator software.
This means that each operator can be set up differently in the system. Not all
needs to have the Voting option.