lauren@vortex.UUCP (Lauren Weinstein) (05/19/83)
A number of areas already run informational services on FM (SCA) subcarriers, and the technology is well established. Unfortunately, there are a number of problems: 1) Many NPR-related stations will probably refuse to run SCA since it can degrade signal/noise ratio in fringe areas. Since many NPR stations are "fine arts" oriented, they are often very concerned about their overall signal quality. 2) SCA informational services are generally low speed. A speed of 2400 baud is most typical -- error rates get too high at 4800 and there's no way to request a repeat of a bad packet. You have to wait until it gets repeated on its own to fill in the missing data. This means that you must repeat data over and over to try make sure everyone receives it. 3) NPR will almost certainly be filling the entire bandwidth (low as it is) with their own information. It is very doubtful that they will have the ability or the interest to handle outside data sources. I was involved in an SCA data project a few years ago. Problems like the above made us finally give up. Problem #1 can be particularly serious: many stations simply refuse to run SCA -- and if they DO decide to support it they want to run (fairly lucrative) backround music services, not data! --Lauren-- P.S. On the subject of "high speed" data: I have sitting in the next room a 4800 baud FULL-duplex modem that purports to operate over dialup lines, even long distance. I will be testing this device with the vortex UUCP shortly, as soon as the matching unit is set up at a (fairly local) VAX. Needless to say, there aren't a hell of a lot of places to call with this thing yet. I will be reporting on how well this beastie performs in my tests, some of which will involve noisy circuits and long distance usage. If it really works, it might be a useful item for the "backbone" Usenet sites to consider in some cases. I believe it costs around $4100 quantity one. More after I get it fired up. --LW--