--- In digitalradio@yahoogroups.com, "expeditionradio" <expeditionra...@...> wrote: > > > 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 >
Ok I had observed a clipped 'am' type of modulation envalope when using the mode, which i assumed was caused by the deployment of more than one tone at any time , What 'we' did find was, the x8 mfsk and x8 olivia produced similar decodes at range on 500khz and from simple observaton the average power as observed on the 'bird was approx 30% lower for the olivia system, the tx peak levels being the same with mfsk showing 100% duty cycle. The reason for the field trial, a lot of stations on 500 have constructed class E pa systems (meat grinders) where as psk31 functions well on 500 in the uk there are only to date (6/1) 2 stations that can transmitt it, one with conventional system (me) and the other M0BMU who has designed a linear eer system, details (http://groups.google.com/group/uk500khz/web/eer-transmitting) Thus showing, that with a construction of a simple tx downconverter, good use can be made of the more rhobust data modes via there existing station's and hopefully may increase activity. G .
