Setting the TX Preamble Duration to a value greater than zero causes the radio to insert a string of bits in front of a data or control message (e.g. Text Messaging, Location Messaging, Registration, Radio Check, Private Call, etc.). This preamble prolongs the message in order to reduce the chances of the message being missed by a receiving radio.
This duration may need to be increased if the radios on the system use scan and there are a number of channels in the scan list. This value can be increased in all the transmitting radios if scanning radios are often missing data messages. However, a larger preamble occupies the channel longer. Therefore, increasing the TX Preamble Duration will increase the success rate of data received while other radios are scanning, but will decrease the amount of data that can be transmitted on the channel (channel loading).
For nearly all applications, the default value of 960 ms is sufficient. Further details about TX Preamble Duration and scan can be found in the MOTOTRBO System Planner.