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Re: [TowerTalk] [Bulk] How far does RFI travel?

To: towertalk@contesting.com
Subject: Re: [TowerTalk] [Bulk] How far does RFI travel?
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Mon, 9 May 2016 09:18:04 -0700
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Ray cross posted this topic on the RFI list and this list. Here's what I wrote on the RFI list, tagging it onto a post from an RFI investigator from a power company.

=   =   =   =   =   =

As always, great advice. I'll expand on it only to help understanding. RFI is like any other radio transmitter connected to an antenna -- make RF current flow on a piece of wire and it will radiate. The more power and the better the antenna, the greater the strength of the radiated RF. The antennas can be anything conductive connected to the source -- power supply conductors, audio cables, video cables, etc. Wires running down a wooden pole to "ground" power wiring are ANTENNAS, and will radiate any RF current that they carry, including arcing on the power system. Coax carrying video and/or internet signals are antennas, and will radiate RF trash generated by the equipment to which they are connected. Virtually everything connected to a power source (battery or AC power system) is a potential noise source, every piece of electronics, including microprocessors built into products like refrigerators, washing machines, dryers, etc.

73, Jim K9YC



On Mon,5/9/2016 8:50 AM, Frank N. Haas KB4T wrote:
There is no definitive answer to this question. In just a few replies, you
can see that RFI can travel great distances. There are an infinite number
of combinations all of which result in a widely varying range.

There is no way to predict if the new subdivision will raise your noise
floor. It's likely but impossible to predict. The suggestion made to begin
measuring and recording your current noise floor is a good one. As the
subdivision grows you may see your noise floor come up.

Check to see if the electrical utilities planned for the new subdivision
will be overhead or underground. If underground, less noise is likely.

Frank N. Haas KB4T
Utility RFI Investigator

On Mon,5/9/2016 7:32 AM, Grant Saviers wrote:
One thing I noticed when driving around with a PC+ USB spectrum analyzer to find a new QTH, was how much quieter neighborhoods with in ground utilities were from those with the old "poles and pigs" distribution systems. Another observation was that big HV transmission systems were quieter than expected when a few hundred yards from them. My conclusion is the buried systems shield and choke the rf, just as happens with buried coax. IMO, much of the rf trash we hear is generated by bad devices and then radiated from pole systems. 60 acres NW of me were recently developed, 20 homes on 2 acre lots plus open space and underground utilities and so far so good. A plasma TV SW from me is an S4 problem, but I haven't tracked it down. Hopefully, the new subdivison near you will be all buried.

Several local hams here are seriously affected S9+ all bands by large grow lights for recreational substances that are clearly not FCC compliant re radiated and conducted emissions. The distance can be significant - 1/4 mile or more. Most are probably illegal but of no interest to law enforcement given trends of the new laws. The FCC either "doesn't have the resources" or "won't investigate where illegal activity may be happening without law enforcement present". A perfect Catch22. In the past, when growing was clearly illegal, law enforcement used AM radios to find the grow sites.

Grant KZ1W
Redmond, WA

On 5/9/2016 0:21 AM, Ray Benny wrote:
body {height: 100%; color:#000000; font-size:12pt; font-family:arial, helvetica, sans-serif;}This may seem a strange question to ask and there maybe many answers, so I will try to be specific as to what I am looking for. A new subdivision is being built about 1/4 mile away, east and north east, towards EU. The homes are custom build on 1 acre parcels. What I am trying to find out: can I expect my noise level to go up as more homes are built? I spend a lot of time on 160m. I have a RX 4SQ and 2 wire beverage, and I do hear a number of small RFI noises in a number of directions from nearby homes in my rural area. Most of the time they do not cause any long term problems. My thought is that when new housing comes in, new and more electronic gadgets will be inside that can generate more RFI. I have done some RFI tracking, mostly electric fences and leaking/defective power line hardware, but these sources are usually very distinctive and usually easy to fine. Finding wall wart, LED, etc RFI is harder to find, especially on someone else's property. Another way to ask my questions: "Does this type of RFI noise typically radiate more than several hundred feet"?
Any thoughts or experiences are welcome.
Tnx & 73,
Ray, N6VR
Chino Valley, AZ


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