Field Guide · term

Also known as: symbol rate, baud

Symbol rate (baud) is the number of modulation symbols transmitted per second.1 It differs from bit rate whenever each symbol carries more than one bit.

0111001001 5 symbols (baud) × 2 bits = 10 bits time → · bit rate = baud × bits-per-symbol
The symbol rate (baud) counts symbols per second; with 2 bits per symbol the bit rate is twice the baud.

How it works

The relationship is bit rate = symbol rate × bits-per-symbol. P25 and DMR run at 4800 baud with 4-level modulation (2 bits/symbol), giving 9600 bps. Higher symbol rates need more bandwidth.

Relevance to SDR

The symbol rate sets the rhythm that clock recovery must lock to, and the minimum capture bandwidth for a clean decode.

Sources

  1. Symbol rate — Wikipedia, for the baud definition and the bit-rate relationship. ↩

See also

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