Roaming is possible when a radio is set to automatically move between Repeaters
depending on which Repeater receives the strongest signal. In a roaming system it is
necessary to set the RSS threshold which is the minimum signal strength that the
radio will consider strong enough before it starts searching for a stronger
signal. The RSSI needs to be programmed into the radio.
Consider a radio moving between three repeater coverage areas. As the radio moves from Repeater 1 the signal strength slowly reduces and reaches a point where the signal from Repeater 1 reduces below the pre-programmed RRSI threshold. At this point, the radio will search through a list of Repeaters programmed into a Roam List to see if they have a stronger signal at that location. The Roam List is simply a list of all Repeaters that the radio could use. If one Repeater in the Roam List does have a stronger signal the radio will switch to using that repeater automatically. So as the user moves closer to Repeater 2 the radio will switch to Repeater 2 and as the Radio moves closer to Repeater 2 the RSSI level will increase and the radio will stop searching for other repeaters. If the radio starts to move towards Repeater 3, the signal will fall below the RSSI level and the radio will start searching for a stronger signal. It should detect Repeater 3 and switch to that channel. Once the RSSI is strong enough the radio should stop searching for a stronger repeater and remain with Repeater 3 until the signal, once again, falls below the RSSI threshold.
Consider a radio moving between three repeater coverage areas. As the radio moves from Repeater 1 the signal strength slowly reduces and reaches a point where the signal from Repeater 1 reduces below the pre-programmed RRSI threshold. At this point, the radio will search through a list of Repeaters programmed into a Roam List to see if they have a stronger signal at that location. The Roam List is simply a list of all Repeaters that the radio could use. If one Repeater in the Roam List does have a stronger signal the radio will switch to using that repeater automatically. So as the user moves closer to Repeater 2 the radio will switch to Repeater 2 and as the Radio moves closer to Repeater 2 the RSSI level will increase and the radio will stop searching for other repeaters. If the radio starts to move towards Repeater 3, the signal will fall below the RSSI level and the radio will start searching for a stronger signal. It should detect Repeater 3 and switch to that channel. Once the RSSI is strong enough the radio should stop searching for a stronger repeater and remain with Repeater 3 until the signal, once again, falls below the RSSI threshold.
Roaming Through the Repeater Network
Requirements
Repeaters have to be able to connect to each other and relay
the same audio at the same time on at least one common Talk Group. On Hytera and
Motorola systems this is called IP Multi-Site Connect. This works well in
commercial systems dedicated to only a few users but in Amateur radio this can
be more difficult. I amateur radio many talk groups are used and are linked
differently. Some Talk Groups are linked to all other repeaters all over the
country, whilst others are linked to repeaters within a specific area and some
are user-activated. Area-specific Talk Groups can be programmed in such a way
that the radio will only roam on Repeaters that have that Talk Group.
Issues
The major problem is that somebody may be operating on
another talk group on a Repeater when you roam onto it. This is where roaming
would fail in amateur radio. The conversation would have to be terminated or
manually set the radio to use another Repeater. A second issue is with user-activated Talk Groups. User activated Talk Groups will only become activated on
a specific repeater when you have manually transmitted onto that Talk
Group. If you activate the talk group on one repeater and then roam into the
coverage of another repeater, the talk group will not be activated on the second
repeater.
Ensure that the desired Static Talk Groups are programmed
onto each repeater in the network and this will work. The only time there may be
problems is if another operator is occupying the Repeater and using a different
Talk Group.
