TX Preamble is a string of null bits added in front of a data or control message. This has the effect of prolonging the message hence reducing the chances of it being missed by a receiving radio while it is scanning. The CPS TX Preamble Duration defines the amount of time the radio should send preamble bits.
This duration would need to be increased in proportion to the number of channels in the scan list – if scan is used. This value should be increased in all transmitting radios if you find that scanning radios are often missing data messages.
The suggested guidelines for the preamble duration is provided in the following table. Preamble is not required for Single/Multisite Capacity Plus Single configurations since scan is not used in such cases.
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Remember that a large preamble value makes the radio occupy the channel for longer and consequently adds to the loading of the system.