N0JCG
join:2003-07-18
Minneapolis, MN | Observations Yes, this is a positive development. I have a few observations.
1. Progress Energy is admitting the obvious; that BPL will affect HF communications. I commend them for this.
2. Like all other BPL implementations, the HF noise is roughly 300 feet either side of an affected power line (about a football field; either side).
3. BPL must fill this space with harmful interference, but the frequency band is adjustable at the discretion of the BPL operator.
4. It's kind of like a water balloon; you squish it in one area and it pops out another. Where do we let it 'pop' out? SW broadcast? Aeronautical mobile? Marine? Maybe there is a range that the NTIA will give up. How do we manage that? Maybe BPL should have a "call sign". Then a licensed user can ask for 'space'; although how, and how often?
5. Local HF transmitters will affect the bit rate of BPL: BPL will have to live with it.
6. How many BPL operators will be as Forward thinking as Progress? |
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| If being forward-looking is really at stake here, I would argue that investors (&Progress) should look at stringing fibre on the access segment, now that Chairman Powell has finally agreed that BPL makes no sense in rural areas. What problem are we trying to solve BTW? Sounds a whole lot cheaper, less risky, and operable to have a fiber solution. If Chairman Powell still wishes to encourage entrepreneurship and deliver the internet to the AC outlets, he really does not need to encourage further messing on the access segment. Entrepreneurs can't change the law of physics in regards to emissions on unshielded wires no matter how creative they get or how much financing they can raise. |
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N0JCG
join:2003-07-18
Minneapolis, MN | I agree, fiber is the ultimate solution. BPL would be a spectrum management nightmare. Why bother? |
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N0JCG
join:2003-07-18
Minneapolis, MN | reply to CheeseWare
BTW, if the housing development in question was new, why didn't the developer put in fiber? |
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| This smells very fishy... Maybe the AC outlets will have the internet (but they still do not need to mess with the access segment). Perhaps somebody in sales did not explain the difference in between the home and the access segment. Or perhaps they are shielding and burrying all the wires. Or maybe they are actually using underground fiber but are saying that they are using BPL with the intent to demonstrate no harmful interference. I will bet on that last explaination.;) |
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| reply to N0JCG
said by N0JCG:
2. Like all other BPL implementations, the HF noise is roughly 300 feet either side of an affected power line (about a football field; either side).
Can't agree with that. Reception of the BPL signal at a moderate level at a distance of just under a mile away shows clearly that the interference potential would not be confined to the immediate vicinity of the line carrying BPL, at least in the case of overhead lines.
said by N0JCG:
4. It's kind of like a water balloon; you squish it in one area and it pops out another. Where do we let it 'pop' out? SW broadcast? Aeronautical mobile? Marine? Maybe there is a range that the NTIA will give up. How do we manage that?
For the 3.5 Mhz wide employed channel used by Amperion in this test, there are a total of two slots below 30 MHz where that channel may be placed that would avoid overlapping amateur allocations and zero places that simultaneously avoid the amateur and broadcast allocations.
There's one additional slot in the 30-50 MHz region in which Ameprion's hardware can operate that wouldn't overlap police/fire/public safety allocations; provided that is the NTIA agrees it's okay for BPL to share with the DoD.
Frequency management for the BPL architecture described would seem not to be a delicate jigsaw puzzle, but rather a game of musical chairs with someone always being left out. |
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| said by Ad astra:
For the 3.5 Mhz wide employed channel used by Amperion in this test, there are a total of two slots below 30 MHz where that channel may be placed that would avoid overlapping amateur allocations and zero places that simultaneously avoid the amateur and broadcast allocations.
There's one additional slot in the 30-50 MHz region in which Ameprion's hardware can operate that wouldn't overlap police/fire/public safety allocations; provided that is the NTIA agrees it's okay for BPL to share with the DoD.
Frequency management for the BPL architecture described would seem not to be a delicate jigsaw puzzle, but rather a game of musical chairs with someone always being left out.
Also consider that they have to use different frequencies between repeater segments. Frequencies can be reused further down the line, but it's my understanding that you need to have several repeater segments before a frequency can be reused. So it's very likely you'll see that 3.5 Mhz downstream and 2.5 Mhz upstream channel hit every chunk of 2-30 Mhz somewhere in a given neighborhood.
Something I wonder about is what kind of bit density they are getting. If it's something like 2 bits per hertz, it won't take long to saturate a 3.5 Mhz channel with traffic, especially when you're carrying traffic from other segments in the neighborhood back to the feedpoint and you take into account the "overhead tax". |
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