[RFI] Inverse Square Law and RFI

[Dave Cole (NK7Z)]

Sorry to have followed your answer Dave, I resorted my email and your 
email looked like something newer than the RFI question...

73s and thanks,
Dave
NK7Z
https://www.nk7z.net

On 06/11/2018 05:57 PM, Dave Cole (NK7Z) wrote:
> No question is silly...  All questions answer something someone does not 
> know, and hence are useful.  Thank you for asking!  Please feel free to 
> ask any question you want an answer for again.
> 
> Inverse Square Law:
> Yes, all RF follows this rule, RFI is something that RF can cause.  Here 
> are a few examples:
> 
> a.  You are on 7.050 CW.
> b.  I open up on 7.010 with RTTY, there is no RFI.
> c.  If I then move to 7.050 and transmit RTTY, and it interferes with 
> you, then I am causing RFI.
> d.  If I start a saw, and it blasts 7.050, and no one hears it, then 
> there is no RFI...
> 
> It's sort of like the "If a tree falls in the forest, and no one hears 
> it did it make a noise?", question.
> 
> This could be rewritten for RFI as follows:
> 
> "If RFI is generated and no one hears it, is it RFI?"  The answer in 
> this case is no, it is not RFI.  RF needs to interfere with something to 
> be RFI, otherwise it is just stray RF.
> 
> Power lines carrying RFI:
> Yes, it is common for this to happen.  The RFI is "conducted" via the 
> power lines from the source, to your antenna, sometimes across miles, 
> sometimes across yards...
> 
> Location:
> Get the ARRL RFI book, and "AC Power Line Interference by Loftness.  AC 
> Power can be gotten here:
> 
> https://www.amazon.com/Power-Interference-Handbook-Marv-Loftness/dp/0965376036 
> 
> 
> The ARRL book can be gotten here:
> 
> http://www.arrl.org/shop/The-ARRL-RFI-Book-3rd-Edition
> 
> Both are good reading for the RFI hunter...  They cover a bevy of 
> situations, and can help you understand what you are up against.  This 
> helps you better locate your RFI.
> 
> Conducted RFI, (carried by the wires), can be difficult to locate, but 
> for the most part it is not...  Conducted RFI, carried via underground 
> power wiring is more difficult, but not impossible...
> 
> I hope that helps...
> 
> 73s and thanks,
> Dave
> NK7Z
> https://www.nk7z.net
> 
> On 06/11/2018 02:36 PM, Tony wrote:
>> All:
>>
>> These might be a silly questions, but given how complex this subject 
>> is, I thought I'd ask anyway.
>>
>> 1. Does the inverse square-law apply to all devices that emit RFI 
>> where the RF energy emanating from the device falls off exponentially 
>> with distance?
>>
>> 2. Is it common for power and other utility cables to carry and 
>> radiate RFI from a device located in a neighbors home over long 
>> distances before being attenuated?
>>
>> In a case like that, I would imagine locating the source of 
>> interference would be nearly impossible with all that RFI being 
>> radiated by utility lines.
>>
>> 73, Tony -K2MO
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