On Tuesday 21 February 2006 18:45, KV9U wrote: > With the unfolding technologies we won't be needing subbands. For the > older technology such as PK-232 equipment the stop gap is to keep the > automatic operation areas in place for now. Ideally, they would > eventually not be needed. At this time I am not sure that the SCS modem > is a solution. It would require improved software to go with the modem. > But there is no reason that this could not be developed as a retrofix.
I think you missed my point. Even with the new technology, sub-bands will be needed. You are only fooling yourself if you think busy detection by itself will eliminate the QRM from the hidden transmitter problem. Let me emphasize, *THE COMMERCIAL INDUSTRY* could not solve this problem during FCC hearings on the smart radio concept. It doesn't matter what kind of busy detection the automatic station has. If it can't hear anyone on the frequency it will, sooner or later, respond to a query. If you force the protocol to use an extended leaky bucket type of timing to respond to queries when activity has been detected at a prior time then you only load the channel up further with connection requests thus causing even more congestion than occurred before. This hurts the channel efficiency tremendously. If you program the protocol so that a session is stopped whenever another station is detected, you tremendously lower the throughput. When you make the channel less efficient you force more channels to be used to carry the traffic load. This causes even more opportunities for interference to happen. It's a merry-go-round with no way off. The only answer is to establish sub-bands where this kind operation can exist in an efficient manner so as to maximize spectrum efficiency and minimize impacts on the rest of the spectrum. > > From everything I have been discovering, there is very little support > (or even knowledge of ) the NTS/D. The current direction seems to be to > move toward the internet as the solution for handling e-mail traffic > with minimal ham activity. This is partially due to the desire for > timely traffic handling (one hour maximum delivery time that can not be > done by NTS/D) and partially due to the desire to reduce the number of > automatic stations operating on HF. Have you listened to the latest testimony in front of Congress concerning the use of email for handling tactical traffic? It's not good. It's what so many have been saying for a long time but can't get anyone to hear - especially the ARRL. When Mike Brown said he sent emails to a number of people in Washington about the situation in New Orleans, the answer was "Email? Who can dig out information like this when I get 600 emails a day?" (I'm paraphrasing of course - but this was the bottom line meaning!) There was one witness, I belive a vice-admiral, who said that there should have been telephone or radio contact to pass this kind of message - i.e. human to human contact. If the ARRL doesn't rethink their priorties after this testimony, there isn't any hope for amateur radio to be a useful entity in the future, at least for important types of messages. It is important for a system with human intervention for delivery to be available for handling priority traffic - there just isn't anything else that works. You can't tell a computer to run down the hall and wake someone up to get them a message. That shouldn't be the only lesson learned either. In talking with a couple of people who were in the Superdome, a vast, vast majority of the people there could not have used email to notify anyone of their situation even if computers had been available. Even in this day and age there is a large majority of our population that do not use email let alone even have enough computer training to make use of it. Winlink and the ARRL would be useless to thses people. Only the NTS with its use of telephone numbers for delivery and with an established delivery network manned with actual personnel is set up to handle this -- assuming the ARRL ever gets off their behind and negotiates agreements that actually lets amateur radio help these victims. The automatic stations in the NTS-D aren't a problem. As far as I know, all operation by stations in the system occurs inside the automatic subbands. Those subbands just aren't big enough to cause a problem to most of the amateur radio community - as long as people are aware that they exist. > > This is the basic philosophy of the Winlink 2000 system: only use ham > radio for a short distance to bridge a gap in the internet, (unless > longer distances are needed for wide spread disasters or for isolated > stations such as boaters), keep HF stations off the air as much as > possible to avoid HF forwarding due to the lack of bandspace as it is, > and handle most of the short distance traffic via VHF/UHF packet to > further keep messages off of HF, and also because an increasing number > of new entrants do not have HF capability. As I said earlier, this only works for email. It doesn't work for messages delivered to telephone numbers or which need to be delivered by a human to a human. Winlink doesn't have a delivery network capable of providing these functions. The NTS does. > > For casual types of operation, I think this is a good thing. I do not > consider such systems true emergency communications systems because with > certain single point failures, the system becomes inoperative. The > decentralized NTS system can still get through, albeit with inaccuracies > in the information and not necessarily in a timely manner. Sometimes > that is still better than nothing getting through at all. Based on current testimony, it may in fact be the best thing of all. The inaccuracies can be addressed through other means. The ARRL started to do that several years ago and then dropped it. Moving to high intelligibility SSB systems would be a start for voice messages. Keeping messages on the NTS-D most of the way would help as well. > > As far as Winlink 2000's content or any other newer e-mail systems, > there is no broadcasting to my knowlege. All the connections are from > one station to the other station. In fact, it would be very difficult > (not impossible, but very difficult) for anyone to even monitor the > transmission content. Since the content is not transparent to the > amateur community, unlike almost any other amateur mode, this is a root > problem that we have not come to grips with. > If you don't like the broadcast analogy, then consider if an ARES group in St. Louis decided to send the entire current NWS weather forecast on 3963khz everytime someone requested it. They would staff the frequency 24/7 with operators and would just play the NWS radio through the mic whenever someone requested it. How long would it be until they got a letter from Riley outlining all the complaints that this is third party traffic being sent on a regular basis and is tying up amateur frequencies for a purpose that can be met by other radio services (i.e. the NWS broadcasts). tim ab0wr Need a Digital mode QSO? 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