El 24/02/19 a las 23:15, Gregory Maxwell escribió: > Are there really many places where spectral efficiency is actually > important for VHF+ ham communications? It was my impression that ham > DV systems were pushing on spectral efficiency only because of being > receiving commercial system hand-me-downs. > > (and even on the commercial trunked radio systems, I wonder how much > of the pressure for increased spectral efficiency comes from an actual > need for additional capacity vs what differentiators someone could > stuff on an RFP-- certainly when I worked on a muni digital trunked > radio system RFP process twenty years ago we liked the additional > capacity but didn't actually have a really clear need for it, and > today the trunked radio system in the municipality I live in is pretty > lightly loaded) > > If anything, I think switching to modes that transmitted two > relatively narrow signals 100KHz apart coding the same data (perhaps > randomly permuted for better temporal gains) in order to get more > multipath diversity would make more sense than striving for the > narrowest signal.
Hi Gregory, If you look at the band plans (at least in region 1), you'll see that there is not a lot of room to spare, especially on 2m. Even 25kHz channelization is getting too crowded and now 12.5kHz channelization is recommended. That being said, there is still a lot of room for experimentation, but one has to be a bit careful with spectrum usage. Your idea of using a couple of well-spaced signals for diversity is interesting and could work. 73, Dani.
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