[RFI] Power Line Noise
Hare, Ed W1RFI
w1rfi at arrl.org
Fri Apr 17 10:45:11 EDT 2020
There is also no certainty that the horizontal wires are equally balanced, so it is not necessariy going to cancel, imbalances on what else is connected to those wires on each side of the source, imbalances in the ways that each wire couples to other sources and to the grounds, both horizontal and vertical, will generally result in emissions that are vector of horizontal, vertical and other wiring. Many sources are at pole, many of which have ground wires and feeds going to houses, so, just Mke says, everything radiates.
From: RFI <rfi-bounces+w1rfi=arrl.org at contesting.com> on behalf of Michael Martin, RFI Services <mike at rfiservices.com>
Sent: Friday, April 17, 2020 6:43 AM
To: Jim Brown <jim at audiosystemsgroup.com>
Cc: AA5CT via RFI <rfi at contesting.com>
Subject: Re: [RFI] Power Line Noise
Actually the radiation comes from everything metallic in the area like the ground wire, the primary, the neutral, the cable TV, the telephone system, the street light brackets, that down guys and the secondary bus hold a pole and secondary Pole to house.
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On Apr 16, 2020, 11:30 PM, at 11:30 PM, Jim Brown <jim at audiosystemsgroup.com> wrote:
>On 4/16/2020 2:32 PM, K9MA wrote:
>> The current from an arcing device like a lightning arrestor flows in
>> BOTH directions away from the source on the horizontal lines, so the
>> horizontal component largely cancels out. It's like the top of a "T"
>I'd buy that if the wires were close together, but NOT at the wide
>spacing typical of HV lines. Think about it -- twisted pair is FAR
>better (20-30dB) than "zip cord" at rejecting all forms of crosstalk
>coupling, simply because interfering fields are close to one conductor
>than the other. That's a fairly small differential, but the two
>conductors in the AC distro system have far greater spacing. They're
>also typically 3-phase.
>> The radiation then mostly comes from the vertical ground wire.
>I'm good with this (and I've seen it), but for a different reason -- it
>can be carrying the arcing of both conductors, perhaps from GFCIs?
>> Generally, I've found the HF beam heading to be pretty accurate for
>> distant sources, perhaps because the vertical component is attenuated
>> more quickly.
>I agree with Mike that antenna arrays develop their directivity in the
>far field, and can be VERY different in the near field. Polarization of
>the RX antenna might be part of it.
> With the VHF tracker (135 MHz), I do find I have to
>> sometimes turn it vertically, but not consistently up close. I expect
>> the shorter wavelength has something to do with that.
>> In any case, the moral of the story is don't just look in the
>> your HF beam thinks it's coming from!
>I'm not suggesting that anyone in this thread might be making this
>mistake, BUT -- remember that antenna arrays are all based on spacing,
>phase relationships, and spatial relationships between elements as
>ELECTRICAL length. A tri-bander only exhibits it's design directivity
>those three bands. Its directivity on any other band, including 2M,
>should be thought of as "random," like the infinite number of monkeys
>and typewriters. :)
>73, Jim K9YC
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