The power wiring in a building resembles a juniper bush which means that RF in the nest of wiring finds lots of antennae near a suitable wavelength that are “stubs” on the main trunks.
One can imagine that the various attempts to use that wire, as tempting as it seems to electricity, is not really a transmission line by RF but an opportunity as antennae. As the map expands to the external wiring grid, there is a self-same replication. Fractals come to mind. Home Plug power is promoted to use “power wiring” as the medium of propagation. It really does work well. It’s low power seems to avoid interference with other services. I’ve always been curious as to the real path the coupling takes…through the wire or crippled Wi-Fi-type via radiation coupling to near-by stubs…stub-to-stub. Ham Radio is not the problem. All the power-wire systems, like DSL, negotiate bands of frequencies that bypass strong interference. The large scale use of power lines, as tempting as it seems at 60Hz, forgets that RF doesn’t propagate through the copper/aluminum but on the surface…just looking for a suitable or partially suitable stub with a lower radational impedence with which to jump off. It’s been a mystery to me all these years as folks confuse in-conductor power with surface-conductor and short wavelength electromagnetic energy as being kissing cousins on a wire. . . . j o n a t h a n From: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org] On Behalf Of Clay Stewart Sent: Saturday, December 28, 2013 5:19 PM To: WISPA General List Subject: Re: [WISPA] Ethernet over power lines (not the failed power company BPL trials) Funny to see this today. I was upgrading a customers equipment today who works for the Electric company that provided service for BPL here, until it failed. He was telling me how they are still, after two years, finding and pulling the equipment off their poles and piling them up in a heap. I would like to make a correction on A above. It was not a trail and it did not fail due to ham radio interference. This one company walked away after failing due to the technology... after spending well over 130 million dollars of tax payer money. I would suggest twice that in order expenditures, such as the direct costs to our local Electric Cooperative company. The best speeds obtained were 4-5, but 90% or more was less then 400k!! Fact, I replaced many of these, including a manufacturer two blocks away from the BLP NOC, who had 300k D and 45k U! The technological issues were plenty, but the reason they failed, went bankrupt, was because the business model did not match the technology reality. When a lightning storm came through, it would take out several relays which were used to bypass pole transformers. Then, not the ISP, but a certified electrician and line man had to do the repairs... usually several down a route at great expense. Storms were draining the money... until tornadoes in Alabama threw in the last straw... so many outages on poles combined with loss revenue... killed the company. For that kind of money, a WISP could have built dozens of 110' towers across many counties and delivered many times the speed. What a loss... what a waste... this is a hidden story where the funding (granting) agency should have been hung. As for home automation... this stuff has been around for many years. Using Radio Shack control switches, I automated a home in the early 80s. I deautomated it in the early 90s before selling the house.... the reason... after a few short years, most control units had been fried from normal surges in the electric system (storms). On Sat, Dec 28, 2013 at 9:49 AM, ralph <ralphli...@bsrg.org> wrote: I am writing this because I just read an old thread from around 9/20/13 on AFMUG in which BPL was being discussed. I’m no longer on that list due to the amount of traffic, but I’d like to discuss it more here. A. The failed power company BPL trials were a unique technology. However the frequencies used were not compatible with both Amateur Radio and with International broadcasters. They were shut down due to much lobbying from both groups as well as several technical and economic challenges. It also still required WiFi of some type to get the signal from the pole/transformer to the end user. Good riddance to them and their noisy interference! B. But the technology that has proven to be useful is more localized: Home Power Line Networking. Check out https://www.homeplug.org/home/ There is a lot of potential for us in these devices. They originally began as “Home Plug” which carried data at up to at 14 Mbps back in 2001. They have a newer, more robust standard called Homeplug AV and supposedly is good for 200 Mbps. We have tested them for a year and have been (or plan to be) experimenting with several applications: 1. We do a lot of Marinas. We already have our WiFi APs plugged in to AC at each dock. We will use HPAV to deliver “hardwired” connectivity to those who don’t want to use WiFi. 2. We do Muni WiFi. Since we are already on the poles and have access to the power company secondary, we may plug in a unit along with our other devices in the box on the pole. This will allow us to deliver “hardwire” connectivity to at least half the houses on that transformer. So in a lot of cases it will be useful. 3. We do MDUs. Same rationale as #2, but equipment closets instead of poles. Yes we know all about the transformer issue. It will eliminate some potential users, but we are on a lot of poles and in a lot of closets. In some cases we can access both legs of the single phase line anyway. We can send the customer to many places both local and online to get their home unit. Here is the only rub: All the units I have tried require the two units to be “married” You can have many units on a “network” but their security requires the users to press a button to synch the with the master one. This is actually setting an AES security key And you have to press a button on the master each time you add a remote. I am calling them master and remote here, but the units are identical. I’m using the term to differentiate between the home unit and the one on the pole. Someone did tell me of a set they tried that “just worked” In most of my applications, the AES security does not matter- remember the core system is an open WiFi network anyway. I would rather users be able to use a simple, easy to obtain unit. With the newer paired units having that preset, it may knock out some flexibility. These may be what the person referenced above may have had. What I really want to see a manufacturer come out with is a manageable unit we can put as the “base”. Similar to a WiFi AP, we could do authorizing (similar to MAC authentication or like DOCSIS cable modems are remotely activated with the CMTS) of remote devices on the same line. Customer plugs in, calls up, gives address of his unit and we authorize it. If they don’t pay, they get shut off. Of course we could stock and ship units that were preset with our AES code, but it would be a nightmare keeping all that straight as well as an investment in equipment we wouldn’t want to make. As I said, there is lots of potential in Home Plug AV right now, and even more if the equipment becomes a little more flexible. I’m just putting the ideas out there. Anyone else using them or planning to use them in novel ways. _______________________________________________ Wireless mailing list Wireless@wispa.org http://lists.wispa.org/mailman/listinfo/wireless -- -- SCS Clay Stewart CEO, Tye River Farms, Inc., DBA Stewart Computer Services 434.263.6363 O 434.942.6510 C cstew...@stewartcomputerservices.com “We Keep You Up and Running” Wireless Broadband Programming Network Services
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