roamer1
sticking it out at you
join:2001-03-24
Atlanta, GA
clubs:
| reply to Qumahlin
Re: You've got to be kidding me
said by Qumahlin  :
Cable and Electricity are two completely separate entities. It is very easy to separate one cable frequency from another and filter the frequencies etc..whereas electricity it is much more difficult
Cable plants are specifically designed to avoid leakage of signal passing through the cables (there are even FCC signal leakage standards that all but the smallest cable systems must meet.) Telephony generally uses twisted pair cables, which help cancel out stray signals. How in the world can one stop signal leakage on open wire, short of lowering transmit power?
Also, given other statements here that BPL uses frequencies between 2 and 80 MHz, in addition to the concerns of hams, BPL systems could very well interfere with licensed users of frequencies in that spectrum (highway patrols, some rural fire/police departments, some utilities, etc. are in the 30-40 MHz range) and could face being shut down if a licensed user complains of interference. 
-SC
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TACSPEED
Premium
join:2001-04-14
Tacoma, WA
 ·Advanced Stream
| quote:
also cables are shileded to minimize interference..power lines are not and therefore will only increase the EMI and RFI they already geneerate
Phone lines aren't shielded, and most likely generate interference too. The key is to keep the intensity of the RFI low enough as to not cause RFI problems with the majority of the people or to interfere in a frequency spectrum that's not occupied.
Also shielding is not perfect, fittings leak and critters chew on the cable. In other words, shielded cables leak RFI too.
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N0JCG
join:2003-07-18
Minneapolis, MN
| said by TACSPEED :
quote:
The key is to keep the intensity of the RFI low enough as to not cause RFI problems with the majority of the people or to interfere in a frequency spectrum that's not occupied.
Exactly! Which is why the 5GHz UNII band is the place for this stuff! 5GHz permits interference management through geography. |
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