Hi Mark, I am not sure why any legal issues are involved. To my knowledge there has been only one major mode that has been prohibited by the FCC. Even AM is still grandfathered, however it is also true that if AM was used extensively, there would be a groundswell to have to eliminated due to the extreme bandwidth requirements in a very limited environment. It is mostly used by a few who like using legacy equipment (which when I was first licensed was state of the art, HI), and I suspect a few other reasons, such as audio quality, ease of tuning, even if it does take a much larger amount of power to have equal range.
I completely agree with you about packet and signal strength vs quality of the ionosphere. As another ham mentioned, packet has severe limitations on HF. In an ideal world it would never have been used for HF, but consider that at the time we had no other choice available at that speed and I believe that some have pointed out that we were in a good sun spot condition in the early 1980's when first developed so it could work even on 10 meters for substantial distances and even at 1200 baud. For a technical reason, modes that require stable ionospheric conditions, can get that from the bands that are open and as close to (but not exceeding) the MUF (Maximum Usable Frequency). If you have followed the incredibly valuable information from Tony, K2MO, with many tests of various modes, you should be able to see the pattern of which modes fail or succeed and why. The technical issues are very important to understand and my perspective is that we have three main parameters affected by the path: 1) mode sensitivity, or SNR (Signal to Noise Ratio) required 2) ISI (Inter Symbol Interference) or how much multipath is present at any one time 3) Doppler or frequency spread of an individual symbol Some modes are more resistant than others and this has been one of the most interesting things for me to follow over several decades of improvements in our digital technology. We do know that without either training pulses (MIL-STD-188-110A, et al) or with baud rates above about 50, even modest ISI can make communications impossible with modes with no FEC. And conversely, modes with low baud rates, that can tolerate extreme ISI, can ironically fail because their slow baud rate leads to susceptibility to Doppler. This is why Pactor developers selected 100 baud and only 100 baud for P2 and P3. They make up for the higher baud rate which would normally be a problem, with FEC active at all times, and then change the modulation (and with P3, the number of tones and spacing of tones) to adjust for conditions. The modulation used for packet was developed by adapting existing FSK (RTTY) techniques for a simple mode that could be accomplished without any computer or DSP since this was not available back in the late 1970's. This worked fairly well for VHF and higher where you had a stable path. It was not as successful for effective use on HF similar to the situation with ASCII which turned out to be a disaster on HF after all the work to get FCC approval. Packet is really ASCII with an ARQ checksum but no FEC thus the predictable performance, or lack of it due to its requirement for a good signal to noise, almost no Doppler or ISI. Unfortunately, not always easy to come by with HF:( I can well understand why you continue to use it. What other choice is there? It has to dovetail with the existing infrastructure that is already in place. At one time we had a well developed packet system, even a world wide system with some assists from HF forwarding and yes, "wormholes" which were really the early internet running on mostly non RF paths. Some areas are impossible to bridge such as across the Great Plains of the U.S. without HF. But it became obsolete when the internet preempted it. Your characterization of nets, is very accurate. There is a mindset that there is nothing we can do about it. Of course there are things that can be done, but due to inertia, maybe some agendas, etc., they don't get done and things do not progress. Even something very basic like moving below the FoF2 frequency for NVIS use is rarely done. I have specifically asked our STM about this within the last two months and although they realized it could be done, there is little interest in making such a change. Same thing with using modes such as Olivia in place of CW, especially now that the speeds of traffic handling seem to be slowing down and few new hams are taking up the slack with CW, but maybe they would with digital? Some of us get into a lot of trouble because we ask the questions that make people uncomfortable. I am surely one of those. We have a number of dramatically better technologies and in some cases they are not being used to improve what we already have in place because like you point out thats "the way it is." It is fortuitous timing, but in recent days, Maiko,VE4KLM, joined this group. He is one of the few people in the world who has both the knowledge, ability, and perhaps most important, the interest to help with new melding of technologies. Several years ago, Maiko further developed JNOS into JNOS2 and got it to work with several hardware devices on HF. I think that includes the SCS Pactor modems and maybe even the HAL P-38 modem. But if he is able to get a networking system to provide BBS, e-mail, various alternative routing, and do it via a sound card solution, this could be an important breakthrough. Maybe it is a few years late, considering the other technologies almost here, but what do you think? (P.S. to Maiko ... it has to simple to set up and operate, right? HI). In order for networking to succeed though, it has to have a purpose. Just doing it for fun is OK for a few, but it won't interest most hams. I have seen no resurgence of packet and networks except for one reason and that is with the interest in public service/emergency use. Even if only at the local and/or regional level. But in general I surely agree with most all of your comments and are well spoken. 73, Rick, KV9U Mark Milburn wrote: > Well, one can have an opinion on whether or not there ought to be 300 baud > packet...but one might just as well have an opinion on whether there ought to > be PSK, or any other mode. The fact that it is legal and some hams want to > use it should be enough to justify its existence. Gracious, we still have > hams using AM, even through all the arguments of the 50s and 60s. > > Yes, there are a LOT of repeats when the bands are poor. Signal strength is > not the only criteria. I don't have a technical background to explain it or > even understand it, but there are plenty of days when a signal of S7 will be > solid copy..and other days when it will not. I just accept that as "the way > it is" and we do the best we can. It's the same on any regular net. If the > net is supposed to meet every day at noon, it does so whether conditions are > good or not. If that requires lots of repeats, then "that's the way it is". > > I use MixW for HF packet, but most of our stations use a TNC. I have > MultiPSK on the computer and have tried to use it a little bit, but have not > been able to get it to perform as well as MixW. That may be just that I need > to do some tweaking, but with MixW working so well here, there isn't much > incentive to spend the time at it. And you are right that the stations > should be on the same frequency, and we work at it, but most of the TNCs > don't have a "tuning eye" so we end up with what everyone thinks is his best > frequency. > > Our HF nets were an attempt to patch over the loss of the old hop hop hop > system on VHF. In the less populated sections of the country we kept losing > nodes to forward on VHF because of legal problems having to do with towers, > so many of the technical minded hams moving on to the next "newest thing", > etc. and we have huge gaps in the system. HF at least lets us move the > messages longer distances to skip over the missing nodes. We are still tied > to the old 300 baud system but as you note, there are some still working on > improved system, and I think it won't be too long until we come up with > something better. Pactor is obviously better, but requires a large > investment that most hams are not wanting to make for that kind of an > operation when it appears that it is a short term mode. Someone will come up > with a sound card based system that will be close enough to pactor in > usefulness and probably free or at least low cost. > > Yes, most of our stations also have VHF ports for users. The number of > users is down overall, I think, but in some areas there is an upsurge in the > number of hams wanting to use packet. It depends on the information that the > local hams get. If there is activity, they will be interested in it...if > there is not, they won't even think to try it. An educational effort on the > part of the present packeteers will bring in new users. > > Enjoy. > > 73 Mark > > > > > > > > --- On Wed, 2/4/09, Rick W <mrf...@frontiernet.net> wrote: > > >> From: Rick W <mrf...@frontiernet.net> >> Subject: Re: [digitalradio] HF packet >> To: digitalradio@yahoogroups.com >> Date: Wednesday, February 4, 2009, 2:58 PM >> Actually, I was getting the signals very well, but they were >> not >> decoding. I had an S1 noise level and some packets were S9. >> Now on 20 >> meters noise is S1 and packets are just above the noise and >> not decoding >> unless they get up to S5 or so from what it looks like. >> Even though I >> know that packet is usually not very effective on HF in >> terms of the >> protocol, I should have been able to decode the stronger >> ones. I was >> using Multipsk and maybe I have something set wrong. So I >> downloaded >> MixW, which is the only other sound card program that I am >> aware of and >> it is decoding at least some headers. >> >> I see a lot of repeats of things like: >> >> N6MAT-9>K7MCH>SABM>P >> >> also >> >> K7MCH>N9LYA>RR3>P >> >> But like most packet that I have copied, it seems that a >> lot of it is >> just headers retrying over and over until they time out:( >> The concept of >> packet is great, (time sharing, multiple connects, routing, >> etc.) but it >> requires signals that are not really possible for HF on a >> consistent >> basis. Even on VHF, packet requires pretty good signals, >> well above zero >> dB S/N and if only we had something that could provide the >> BBS and >> forwarding part with an improved HF practical mode. The >> only thing that >> is in the right direction is FAE400, but there does not >> seem to be much >> interest:( >> >> We have an 80 meter packet group in the state, I think >> mostly in the >> southern half. Not sure what they do but seems like it must >> be friends >> who keep in contact or have an interest in DX maybe, and >> share info. >> >> When I first started setting up with my rig, I was thinking >> 2125/2295, >> HI, but then when I saw the waterfall, immediately realized >> that it had >> to be around 1700 center frequency with 200 Hz shift. I >> have noticed a >> great deal of variation when attempting to monitor packet >> and it >> surprises me that everyone is not within a few Hz since it >> would make >> the situation even worse! I have rigs that are mostly TCXO >> controlled so >> can be quite close. Even our ICOM IC-7000's have it. >> >> Is the purpose of your network to do RF forwarding and then >> go into some >> local VHF network? We used to have a very extensive system >> here about a >> decade ago but all of that is completely gone. Some nodes >> are still >> used, but were converted to APRS as I understand it. >> >> What software do you recommend to decode? Is this something >> you use on >> the fly or after you collect some data? Maybe there is no >> sound card >> based technology available? >> >> 73, >> >> Rick, KV9U >> >> Mark Milburn wrote: >> >>> Hi Rick... >>> >>> The bands were pretty awrful this morning so I >>> >> wasn't hearing a whole lot myself. It will get better >> this afternoon and I'm thinking it will be much better >> tomorrow. Wisconsin is always a tough haul from Iowa, it >> seems, but you will be hearing everything better this >> afternoon. >> >>> The frequency I gave you is very approximate, since >>> >> radios seem to vary widely in their accuracy, and is based >> on the most usual TNC setting of 1600-1800 HZ. Some TNCs >> have different tones, but most are set at 1600-1800. >> >>> One other caveat...since we are doing forwarding of >>> >> bulletins, the bulk of the transmission are in FBB >> compatible compression, so unless you are using a BBS >> program such as FBB or MSYS, you will be seeing compressed >> characters with only some titles sent in clear English. >> That may serve to get you what you want, or if you want to >> dig in a little deeper, you may need to download and install >> a program that decodes compressed packets. >> >>> If I can be helpful, let me know how. >>> >>> 73 Mark KQ0I >>> Des Moines, IA >>> >>> >>> >> >> ------------------------------------ >> >> Announce your digital presence via our Interactive Sked >> Page at >> http://www.obriensweb.com/sked >> >> >> >> Yahoo! Groups Links >> >> >> >> > > > > > ------------------------------------ > > Announce your digital presence via our Interactive Sked Page at > http://www.obriensweb.com/sked > > > > Yahoo! Groups Links > > > > ------------------------------------------------------------------------ > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 8.0.233 / Virus Database: 270.10.17/1934 - Release Date: 02/03/09 > 17:48:00 > >
