----- Original Message ----- From: Tony To: 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 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 Recent Activity a.. 8New Members b.. 1New Files Visit Your Group Drive Traffic Sponsored Search can help increase your site traffic. Yahoo! Groups Mental Health Zone Find support for Mental illnesses Group Charity Be the Change A citizen movement to change the world .
