Hi Charles, The latest version of MultiPSK has AX25 using PSK 250 (or PSK 63) modulation. I would be interested to see whether PSK 250 is any better or worse than FSK 300.
73 Sholto K7TMG Charles Brabham wrote: > > > > > > ----- Original Message ----- > *From:* Tony <mailto:d...@optonline.net> > *To:* digitalradio@ yahoogroups. com > <mailto:digitalradio@yahoogroups.com> > *Sent:* Tuesday, June 09, 2009 6:56 PM > *Subject:* Re: [digitalradio] Re: another "can you ID this mode" request > > > Howdy, Tony! > > There are two advantages that HF Packet has over other modes, one > being that it operates under AX25, the other being the existence of > a wide-scale network already being in place that covers many locations. > > > > AX25 gives Packet a distinct edge for a large-scale network with > many served locations ( participants ) in that up to a dozen > stations can occupy and utilize a bit of spectrum wide enough for a > single station. In practice, there are rarely more than six to eight > stations utilizing the same slot at the same time, this being due to > scheduling or taking turns as the case may be. For example, I > schedule most of my transfers in the mornings, other stations on the > same frequency do so later on in the day. This gives Packet an edge > in spectral efficiency that allows many more served locations than > any other system, without spreading out all over the band, QRMming > other hams QSOs. For a wide-scale network, this capability is > indispensible. - This assumes of course that we are talking about an > independent, all-amateur radio digital network, not one that > utilizes non-ham resources as a crutch to make up for poor or > backward design, and that the primary goal is to serve as many > locations as possible. > > The other edge that Packet has on HF is the existence of a > wide-scale network already in place, with many participants. ( > locations ) > > It is true that many other digital modes offer greater throughput, > but none of them offer the same spectral efficiency, independence > from non-ham resources, and established community that Packet does. > For one-on-one QSO's, I use PSK modes but in order to participate in > an independent, wide-scale Ham Radio digital network, Packet has no > competition at all. - There simply isn't a second-place choice to > consider. SkipNet members have experimented with Q15x25 mode for > example, which also runs under AX25, but found that in the kind of > operating conditions we encounter every day, Packet was more > reliable and offered better throughput. Our search continues but to > this date, no other AX25 mode has emerged which actually works > better than Packet. When one does turn up, you be sure that the > SkipNets will be giving it a workout. > > If you know of another digital mode that operates under AX25 and > performs better than HF Packet, be sure and let us know about it > here on this reflector! If the "better" digital mode is unfriendly > to other amateurs, takes up more spectrum to do the same task, or > has to lean on non-ham resources in order to do the job, then it is > not a better digital mode for our purpose. ( Independent Wide-Scale > Amateur Radio Digital Network ) > > The greatest non-AX25 advance for wide-scale ham radio networks to > come down the road has been HF Multicast. - Read about it at > USPacket.Org, in the read-only 'library' section. HF Multicast > offers better spectral efficiency than anything else by one or > possibly more orders of magnitude. - It is truly amazing in its > potential. The folks at VOA ( Voice Of America) have contacted us > about our work with HF Multicast, planning on utilizing the mode for > wide-scale distribution of news and information to the many areas of > the globe that have no reasonably priced and available internet > access. We hope to incorporate HF Multicast capability in the > SkipNets soon, when software for a multiple stream version of it is > developed and ready to go. The single-stream version is now out of > beta test and ready to go, for those who would like to give it a > test run. > > 73 DE Charles, N5PVL > n5...@uspacket. org <mailto:n5...@uspacket.org> > > http://www.uspacket .org <http://www.uspacket.org> > > > Charles, > > I think HF packet is a useful mode, but I can tell you that it does > fall short in terms of sensitivity compared to many others. > > More importantly, path simulations and on-air testing show that it > doesn't take much in the way of HF channel distortion to cause > throughput issues with 300 baud Packet. > > The mode tends to fail with moderate path distortion regardless of > how high the signal-to-noise is so it's not something that can be > overcome by turning on the amp. > > This doesn't mean it won't work as you an attest to, it just means > that other modes are superior, especially if the goal is to get the > message through with less power under adverse conditions. > > Tony -K2MO > > . > >
