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Technology Stocks : LAST MILE TECHNOLOGIES - Let's Discuss Them Here -- Ignore unavailable to you. Want to Upgrade?

To: lml who wrote (2638)	12/23/1998 12:10:00 PM
From: DenverTechie	Read Replies (1) \| Respond to of 12823

I thought you might be looking for more explanation of the cable technology. I'll try to keep it brief. Suffice it to say that many people spend their careers working on this stuff. To answer your questions: 1. Higher frequencies in the RF spectrum equates directly to greater bandwidth available to the subscriber. There is much more bandwidth in a 750 MHz system than in a 450 MHz system. 2. Higher frequencies does not equate to less spacing between channels. Each analog channel always takes 6 MHz of spectrum whether it's a 750 MHz system or a 450 MHz system. And the guard bands (small slices of spectrum dedicates to make sure the channels don't interfere with each other) are always the same size in any cable system. 3. and 4. The size of spectrum available and the higher frequencies in larger capacity systems does not inherently affect the amount of distortions of the channels. What I was getting at is that higher frequencies (like 650 MHz) in the cable system lose energy faster than lower frequencies (250 MHz). Because of this, the signal degrades faster, in less distance on the cable (attenuation). The cable engineer must therefore place amplifiers and line extenders at shorter intervals on the cable to make up for this loss. Each amplifier boosts the signal back up to acceptable viewing standards, but each time they also introduce a little bit of noise to the signal. And each active device added can fail, reducing the overall reliability of the system. As an example, there are almost twice as many amplifiers in some experimental 1 GHz systems as in a 450 MHz system. So although the bandwidth is dramatically increased, the spacing of the amplifiers is much shorter, there are many more of them, and reliability of those devices becomes critical to the services offered on the system. Hope that makes sense and clears up your questions about why fiber is almost always introduced into the networks when you go to these high bandwidth cable systems. The deeper the fiber into the network, the less coax there is, the fewer amplifiers in the system when carrying high frequencies in the system. As to whether or not this spells trouble, that's hard to say, but I doubt it. I don't think subscribers are being shortchanged either. Here's why. You say you are already getting 80 channels in your present system. That tells me you are on a 750 MHz cable network (a 550 MHz system can only handle 77 or 78 channels at best and usually they are not filled up to capacity). But be careful on this issue. Cable companies can play games to make it look like you have more channels than you actually do. One common one is to place 2 channels in one area of spectrum and the first channel is on 7AM to 10 PM and the other 10PM to 7AM so it looks like 2 different channels when it reality there is only 1. So if you have a few of those, you could still be on a 550 MHz system, but I can't tell without seeing your exact channel lineup. If you are on a present 750 MHz system, then upgrade to 860 MHz to add some advanced services is no big deal, really a piece of cake in relative terms. The spacing of amplifiers at 860MHz is essentially the same as at 750 MHz so no respacing and no additional locations are required. This is what we call a "drop-in" upgrade where the modules are just swapped out to allow the greater bandwidth. But most, if not all, 750 MHz cable systems in existence today have at least SOME fiber in them. Even if it is just at the highest level of the network, known as a "fiber backbone" which alleviates many of the reliability and amplifier issues discussed above. The number of homes passed per fiber node in a fiber backbone system is still high -- upwards of 2000, sometimes as many as 4000 homes -- but it helps. This is not true HFC (hybrid fiber/coax) which seeks to limit the number of amplifiers and distortions allowed in any given node by not going over typically 1200 homes passed per node. I would venture to say your cable reps said no fiber optic upgrade needed because it's already there for the 750 system and that no fiber would be going into your neighborhood to support the increase to 860 MHz. So from a technical point of view, it all makes sense and you will be getting a state-of-the-art cable system with lots of bandwidth when it's done. Let me know if you have any questions on this or if my "assumptions" about your system are not right based on conversations with your cable reps.