K McAleavey
Premium
join:2003-11-12
Voorheesville, NY
| Dirty signals
When DSL first came out, it was an anathema for 160 and 80 meter reception, as well as "dirt" all the way up to 6 meters. I can understand the concern. At least PHONE LINES are twisted pair, so there's some electromagnetic cancellation of the harmonics if the lines are properly balanced. The TRICK is for the power companies to get their RF carriers up to a high enough frequency that any potential interference won't hit the ham bands or other critical communication bands. The potential PROBLEM is that power lines are NOT twisted pair where cancellation of the offending radiated signals isn't possible.
But I remember what a mess early DSL was - folks near lines carrying DSL had NO hope of AM radio. Then came Rush Limbaugh and nobody really cared anymore. 
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Kevin McAleavey support@nsclean.comhttp://www.nsclean.com/ |
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contsole
Premium
join:2003-12-30
Bloomfield, CT
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"At least PHONE LINES are twisted pair, so there's some electromagnetic cancellation of the harmonics if the lines are properly balanced."
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Ironically, my phone line's 200' trip up my driveway is NON-twisted pair (looks like zip cord, heavy solid copper conductors) and the utility line IS twisted ...but I realize we're talking about the lines on the streets. |
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kfolsom
Where the fit hits the shan
Premium
join:2003-01-31
Yucaipa, CA
 ·Verizon west (ex G..
| reply to K McAleavey
said by K McAleavey  :
The TRICK is for the power companies to get their RF carriers up to a high enough frequency that any potential interference won't hit the ham bands or other critical communication bands.
I respectfully submit that the TRICK is more than that... Getting RF carriers to a "high enough frequency" is never going to work... The trick is to get power companies to not interfere with ANY licensed service, emergency or otherwise.
All RF communication channels between 2 and 80 MHz are at risk here, as well as whatever spectrum that will be affected by "sum and difference" products. These are unpredictable, and will be next to impossible to mitigate, IMHO.
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"Maybe" is twice as good as "No", but only half as good as "Yes"... »www.folsomtech.com |
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KB2PSM
join:2002-08-06
Long Beach, NY | reply to contsole
I suspect that the power line is probably not twisted, but probably twisted around a line used to support the AC wires from the pole to your house. |
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bonnyman
join:2003-04-16
Rome, GA
| Re: Dirty signals (drop cable trivia)
I suspect that the power line is probably not twisted, but probably twisted around a line used to support the AC wires from the pole to your house.
Utility drops from the transformer to the home often have insulated conductors stranded around a bare, grounded messenger/neutral. This affords a measure of safety -- should the insulation fail, the line shorts straight to the bare neutral and on to ground via the utility's grounding system. Such arrangments also get special treatment under the National Electrical safety Code.
This is not done for communications reasons.
As for the telephone drop cable that looks like zip cord, that may be a self-supporting drop cable. Underneath the jacketing, one side of the zip cord-looking cable may contain a steel messenger, the other a twisted pair.
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Al Bonnyman
Fiber Planners Inc.
See my weblog at:
Community Broadband Networks for FTTH, municipal broadband and powerline broadband news |
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Nighttime
join:2001-11-30 | reply to contsole
Re: Dirty signals
That and any harmonic generated by poor connectors. So your band all belong to us! Not just the 2 to 80 mhz! |
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xdeadhead
220, 221, Whatever It Takes.
Premium
join:2000-11-08
Mechanicsburg, PA | hahah someone set up us the bomb.
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I am not Herbert. |
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