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w2co
join:2003-07-16
Longmont, CO | reply to JohnnyKnowal
Re: Obligatory FAQ Link Post :-) Yes I agree that it would be good if it does not cause interference to existing radio services through unintended radiation from the power line grid. I don't know about there, but over here the power lines are in sad shape and have been neglected over the years by the power companies. This is true for most of the country, some places worse than others though. The poor line conditions will cause non-linear components to be radiated as well through poor insulators, leaky connections/splices etc. The power companies here have a hard time responding to legitimate interference complaints now, which would be very easy to remedy, if they respond at all. What's to say they will take care of additional complaints after BPL is deployed? I don't think the give a damn - never will. All they want is money money money. Why deploy an archaic technology when there is broadband in most places already (cable modem, DSL, satellite, etc etc.)? Heck most internet users still are happy with just a "dial up" connection from their homes, and they use T1 lines at work to do any downloading.
But I also understand how people would want a cheap broadband solution too, so they can do online gaming and downloading that porn stuff that they can't do at work.
If they want to complete that "last mile" then just finish laying the fiber optic cable that was started 10 or more years ago. It should've been done by now but the networking companies got greedy and kept the termination ends in their server locations and then just farmed out connections to it. The data I am compiling is incomplete as of yet because BPL is not being tested in my location yet, so far I only have the normal "quiet" s-3 type noise floor here on most bands from 80meters up to 1.2GHz. This I can use against any new readings after deployment here. If you had looked at the videos at ARRL webpage taken in Manassas, Va. you would see why we are all upset. It shows s-9 +15db of hash noise across the entire 20 meter band. That happens to be my favorite band, and I do weak signal DXing there, have for years. It also is right smack in the middle of the BPL spectrum when under light user loads. QRP operation would be all but usable. Oh well they are removing CW requirements now, so what's stopping them from destroying any weak signal HF work? Nothing. It's who's got the money.
To hell with physics and any common sense. Physics will not change for any money hungry companies, an open wire will radiate when an RF signal is introduced to one end, regardless of frequency. Many studies on this BPL technology have already been done in other countries and have shown excessive interference to HF/VHF bands and either banned all together or put on the shelf until something is invented that will improve it. Those who ignor history are doomed to repeat it. Nothing has been done to show the effects to BPL when HF transmissions occur nearby. That is a whole other subject but will the companies responsible do any studies on this direction before deployment? I seriously doubt it, they have hardly shown the interference potentials to date why should they when the dollar sign is in their eyes. | |
w2co
join:2003-07-16
Longmont, CO | Interference to PLC systems Interference to PLC systems from Amateur Radio Operation
Interference is a two-way street, and PLC systems are at significant risk from amateur HF operation. In the US, amateurs are limited to 1500 watts PEP RF output, but there is no limit to the antenna gain. As a practical matter, few amateur antennas exceed 13 dBi on HF. This means, however, that the EIRP from amateur stations can exceed 20,000 watts. These stations can have antennas that are as close as about 10 meters or so the the electrical distribution systems.
Here is an estimate of the interference potential of a more modest HF station on 7.15 MHz:
Those unshielded overhead power lines are not great antennas, but they can and will pick up our signals. Here is a quick calculation:
Transmit power: +26 dBW (400 watts)
Transmit frequency: 7.15 MHz
Distance between antenna and power line: 20 meters
Path loss: -15.6 dB
Transmit antenna gain (with ground reflection): 6 dBi
Power-line antenna gain: -10 dBi (estimate)
Power picked up on power line:
+26 dBW
-15.6 dB
+6 dBi
-10 dBi
-------
+6.4 dBW (4.4 watts)
The total power of their signal inside the line is going to be about 10 milliwatts, and when we transmit, PLC wiring may pick up 4 watts of our power right inside the frequencies PLC is using. It is unlikely that PLC systems will continue to function in the presence of these signal levels. And this example is of a completely legal operation of an amateur radio station on 40 meters. Now on 20, 15, and 10 meters it will be possible to have much higher eirp because of the directional antennas in use there, many of which are on an even level with the power lines and many of which are using horizontal polarization. This will ad a few more db to the "gain" of the system into the power lines. | |
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