[RFI] Power Line Noise

K9MA k9ma at sdellington.us
Fri Apr 17 12:45:00 EDT 2020

The 1/6 wavelength is just a rough rule of thumb. For a yagi with a 24 
foot boom, the calculator below says the far field starts at 15 feet. 
1/6 wavelength is 11 feet. Both are much smaller than the distance to my 
nearest power line, about 130 feet.

Scott K9MA

On 4/17/2020 10:24, Eddie Edwards wrote:
> Scott,
> I think this calculator will be a bit more accurate than your 1/6th calculation.
> https://www.everythingrf.com/rf-calculators/antenna-near-field-distance-calculator
> Also don't forget to use the full size (either dimeter or length) of the entire yagi array as Jim Brown pointed out.  When I do this for typical 20 meter yagi, please correct me if I'm wrong, but I get a far field distance of 9.5 meters or about 31 ft for a typical 20 meter yagi.  It still might be this far away if across the street.
> 73, de ed -K0iL
> -----Original Message-----
> From: RFI On Behalf Of K9MA
> I believe near field for antennas is generally considered to be about
> 1/6 of a wavelength. That's only 11 feet on 20 meters.

Scott  K9MA

k9ma at sdellington.us

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