Mimer Receiver Voting - Diversity
When you have problems to receive for example your portables or marine radios.
Multiple base station receivers is an easy way of getting better coverage for hand portable radios that have low output power. Multiple base stations is also practical in marine systems where you have a long coast line or for example a long river to cover.
Often you will find that the transmitting radio is in coverage of two or more base station receivers. In such cases you will receive the same audio from several receivers at the same time, with different signal strengths and therefor also different audio quality.
If you add Voting (a.k.a. Diversity) to the system it will select the receiver with the best signal strength from all receivers, and present only the audio from that receiver. A new voting will be done for each time the transmitting radio starts a new transmission. So even if the ship moves during the conversation the system will automatically shift the audio if there is a receiver with higher signal strength.
In the drawing below three radio sites with the same Marine-VHF radio channel (CH16) are connected to one PC operator. One radio site also have a second channel (CH23). The three CH16 receivers are connected in a Voting group in SoftRadio.
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 sites with CH16 connected with diversity to one operator
On for example the Marine VHF radio band many channels are simplex (same Tx frequency as Rx frequency). This means that when the dispatcher transmits on one base radio, the transmission will be picked up by the other base stations receivers and you will hear yourself as an echo.
With the Voting system comes a blocking function that stops reception from the receivers in the same voting group when transmitting. In this way effectively blocking all echo.
The blocking is done internally in the SoftRadio software.
The diversity option (3103) uses the RSSI output (signal strength) from the radio. (Not all radios have an RSSI output, please check)
All radios in each voting group needs to be of the same type to make the correct comparison.
The base radios shall be “fixed channel radios”. The system only makes sense if all receivers in each voting group works on the same channel.
When setting up the operators radio connections you also set which radios are to be treated as being in the same voting 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.