This read-write object sets the transmit modulation type to one of BPSK(0), QPSK(1), OQPSK(2), 8-PSK(3), 16-QAM(4) (Turbo or Viterbi+RS only), or 8-QAM(5), noting not all selections are valid depending on FEC type. Modulation choice directly trades spectral efficiency against required signal margin -- moving from QPSK to 16-QAM roughly doubles the bits carried per symbol and thus potential throughput in the same bandwidth, but demands a substantially higher Eb/No to maintain the same error rate, so this choice must be balanced against the link's actual available power and antenna size. A remote site with a small antenna and limited transmit power would typically stay at QPSK rather than attempting 16-QAM, since the higher-order modulation's stricter signal-quality requirement would likely exceed what that station's smaller RF budget can reliably deliver.