100's of kHz wide. For FSK you need about the symbol rate spacing between tones, so for 2FSK at 115 kbit/s, the tones are spaced at 115kHz-ish, plus a bit more, think we use 400 kHz separation in practice.
Yes we only managed these fine results through very careful engineering, and deliberately avoiding the common trap or re-using legacy FM radio kit. Cheers, David On 12/03/17 17:42, Stuart Longland wrote: > On 28/02/17 11:24, David Rowe wrote: >> We have managed to send HD images over 100km paths using just 50mW: >> >> http://www.rowetel.com/?p=5344 > > Quoting the site: >> We were receiving 115 kbit/s data on just 50mW of tx power at ranges of over >> 100km. > > Okay, silly question, how wide, approximately, was the transmitted > signal? 115kbps is bloody good for 70cm FSK, giving D-Star 23cm digital > data (which runs at 128kbps) a run for its money! > > I suspect it is wider than the standard 25kHz FM channel, hence the need > for a "specialised" dongle (okay, bog standard digital TV receiver > dongle based around the infamous Realtek chipset). > > It might be that the discriminator output available via the 9600 baud > packet radio jacks isn't up to the task… but even ¼ of this data rate > would be a brilliant alternative to the Bell-203 modulation we're used to. > > Regards, > ------------------------------------------------------------------------------ Announcing the Oxford Dictionaries API! The API offers world-renowned dictionary content that is easy and intuitive to access. Sign up for an account today to start using our lexical data to power your apps and projects. Get started today and enter our developer competition. http://sdm.link/oxford _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
