> Graham G0NBD wrote: > > Follow on from last night , As the olivia system transmits > tones in parallel it requires a linear system, > however , MFSK is a single tone phase continuous system >
Hi Graham, Olivia mode does not transmit tones in parallel. It transmits each tone one at a time, in series. At any instant, there is only one tone being transmitted. Olivia is a modified form of FSK. It has amplitude wave shaping, and like any other amplitude-changing waveform, it is benefited by using a transmitter with linearity. The beginning and end part of the waveform of each Olivia tone is smaller amplitude than the middle of each tone. In between each tone, at instant of frequency shift, the amplitude of the waveform is near zero. This provides narrower bandwidth between the tone frequencies, and thus better inter-frequency tone recognition by the decoder. This also helps enable close-spaced tone frequency shifts to be realized, and thus, better throughput and better decoding sensitivity because of less intersymbol interference. The PSK31 mode has amplitude-changing parts of its waveform, and that is the reason it benefits by using a linear transmitter. Some common FSK modes do not have amplitude- changing waveforms, such as conventional RTTY, ALE, etc. These FSK modes do not need very linear transmitters. RTTY does not have a clearly defined tone-shift keying transition, but some other modes have their keying transition carefully defined at either the peak of the waveform or the zero-crossing of the waveform. Olivia information: http://hflink.com/olivia Image of ALE waveform (FSK) tone keying transition: http://hflink.com/technical/ Bonnie KQ6XA
