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Re: [RFI] Power Line Noise

To: "Michael Martin, RFI Services" <mike@rfiservices.com>, Jim Brown <jim@audiosystemsgroup.com>
Subject: Re: [RFI] Power Line Noise
From: "Hare, Ed W1RFI" <w1rfi@arrl.org>
Date: Fri, 17 Apr 2020 14:45:11 +0000
List-post: <mailto:rfi@contesting.com>
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@contesting.com> on behalf of Michael 
Martin, RFI Services <mike@rfiservices.com>
Sent: Friday, April 17, 2020 6:43 AM
To: Jim Brown <jim@audiosystemsgroup.com>
Cc: AA5CT via RFI <rfi@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.

⁣RFI Services
Michael Martin
240-508-3760
rfiservices.com

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On Apr 16, 2020, 11:30 PM, at 11:30 PM, Jim Brown <jim@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"
>> antenna.
>
>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
>and
>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
>more
>> 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
>direction
>> 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
>on
>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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