The RF issue of range, carrier frequency, channel width is quite separate from the deliverable audio path.
The Opus audio codec has revolutionized audio coding. It's able to deliver full-bandwidth audio at bitrates not much more than what was once typical of a telephone call. This means that the RF band need not be large to deliver high quality audio over a digital link. There are a diverse range of wireless microphone and monitors. Some have multi-channel capability in support of unique pathways for the various artists in an ensemble. Their RF characteristics are made to match regulatory realities in different jurisdictions. Some are analog (ex. companded FM) others digital. To my knowledge, none are IP-based. There are folks in the HAM radio space using digital compression techniques to deliver wideband audio over extremely low-bitrate links. Think sub-3 kbps for voice. Michael Graves mgra...@mstvp.com http://www.mgraves.org o(713) 861-4005 c(713) 201-1262 sip:mgra...@mjg.onsip.com skype mjgraves -----Original Message----- From: Sursound <sursound-boun...@music.vt.edu> On Behalf Of Chris Woolf Sent: Thursday, May 30, 2019 11:08 AM To: sursound@music.vt.edu Subject: Re: [Sursound] wifi audio (was Re: Deconstructing soundbar marketing B.S.) Answering this specific question... On 30/05/2019 10:42, Augustine Leudar wrote: > ... I had some walkie talkies that had a range of one KM with > admitedly terrible audio (surely this could be > improved) . Whereas Senheiser in ear monitors have a really short > distance range of around 40 metres and use much higher electromagnetic > frequencies > ((863 mhz) . Why is it something cant be done with the same sort of > range as the walkie talkies but for.multichammel audio (according to wikipedia > 30 - 400 mhz) ? Walkie talkies run on a 12.5kHz narrow band, and need ~50kHz of channel space. Broadcast quality FM (as in radio mics) uses a channel space of ~250kHz. Given than channel "skirts" are quite a bit wider multiple local channels cannot sit close to each other, and are commonly spaced ~500kHz apart. They also have to avoid numerical frequencies which would cause intermodulation. Thus remarkably few analogue radio channels can fit into a single (8MHz) TV channel space. The usual answer is ~12 at best. Some claim more but range and mutual interference may suffer. With digital modulation this can improve to ~20 because the effects of interference are reduced. Range is directly related to bandwidth, transmission power, and RF signal-to-noise limitations of the receiver. Narrow band with limited audio bandwidth and restricted (audio) signal-to-noise is a much easier task with a couple of AA cells than 20kHz audio with 100dB (companded) dynamic range. Digital radio mics have been even harder to make that can modulate something that equates to full broadcast bandwidth and dynamic range into the the same 250kHz bandwidth as analogue, and with roughly the same range/battery power. I've no idea what the .multichannel audio is - can you elaborate? And I can't imaging that there is any spectrum clear in the 30-400MHz region. Chris Woolf --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on. _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.
