Wind Farm

FM does it with frequency!
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grich
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Wind Farm

Post by grich » Wed Dec 04, 2019 10:57 am

One of my clients just called me...they received documents from a big wind energy provider that's been putting up wind farms in the area...it seems they want to place some windmills very close to their FM tower. They're still trying to decipher the legal descriptions of where the sites are going to be.

There has to be SOME interaction between the transmitted signal and a windmill in close proximity...will it be enough to worry about?

TPT
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Re: Wind Farm

Post by TPT » Wed Dec 04, 2019 6:29 pm

WWPN in Westernport, Maryland, had to abandon their studio because of a wind farm built in line with their STL path. The blades and disturbed air did quite a number on the 950 signal.

Commercial religious, they were able to relocate into some extra rooms at a local church.

I would suspect some interesting effects on the actual FM signal if the wind mills were built close enough to the FM tower. There may be some recourse available through the filing of an environmental objection to the construction of the towers based on potential interference to the FM signal.

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Deep Thought
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Re: Wind Farm

Post by Deep Thought » Thu Dec 05, 2019 12:08 am

Define "very close". If they are more than several dozen wavelengths from the antenna I doubt you'll notice anything.

At STL frequencies they become a fairly effective reflector so the 950 MHz anecdote doesn't surprise me.
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

grich
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Re: Wind Farm

Post by grich » Thu Dec 05, 2019 11:09 pm

Deep Thought wrote:
Thu Dec 05, 2019 12:08 am
Define "very close". If they are more than several dozen wavelengths from the antenna I doubt you'll notice anything.

At STL frequencies they become a fairly effective reflector so the 950 MHz anecdote doesn't surprise me.
Still haven't heard from the owners, so I don't know how close very close is.

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jthorusen
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Re: Wind Farm

Post by jthorusen » Fri Dec 06, 2019 1:41 am

As far as wind turbines go, the support structure is steel and represents a permanent reflector, but as Deep Thought suggests, that is probably a minimal problem if many wavelengths away. Of course, FM is not analog TV, but I know of one instance where a tower caused a permanent reflection (ghost) in a TV picture in a major market.... cured only by the affected station putting up a taller tower.

I also remember, back in the good ol' days, that one could sometimes detect aircraft on a TV set due to the varying multi-path induced by reflections from the airframe. The TV picture would show the usual changing multi-path artifacts (shimmering ghosts). I wonder how reflective the wind turbine blades are? Again, analog (AM) TV days... FM is different... but how different?

Please let us know the results.

Regards,
James K. (Jim) Thorusen
KB6GM
Central Coast Electronics
www.centcoast.com
NW Oregon Consulting Bdcst Eng.

DaveSt
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Re: Wind Farm

Post by DaveSt » Fri Dec 06, 2019 12:05 pm

jthorusen wrote:
Fri Dec 06, 2019 1:41 am
As far as wind turbines go, the support structure is steel and represents a permanent reflector, but as Deep Thought suggests, that is probably a minimal problem if many wavelengths away. Of course, FM is not analog TV, but I know of one instance where a tower caused a permanent reflection (ghost) in a TV picture in a major market.... cured only by the affected station putting up a taller tower.

I also remember, back in the good ol' days, that one could sometimes detect aircraft on a TV set due to the varying multi-path induced by reflections from the airframe. The TV picture would show the usual changing multi-path artifacts (shimmering ghosts). I wonder how reflective the wind turbine blades are? Again, analog (AM) TV days... FM is different... but how different?

Please let us know the results.

Regards,
I think the blades are usually carbon fibre/fibreglass so they may not be too reflective at VHF.

kcbooboo
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Re: Wind Farm

Post by kcbooboo » Sat Dec 07, 2019 5:52 am

Airplanes flying overhead definitely affect the 50-54 MHz amateur FM band, just like they do with analog TV signals. It manifests itself as a rapid-to-slow-to-rapid fluttering of the signal strength as the signal bounces off the plane. Even stations 45 miles apart using vertical polarization have this problem.

Bob M.

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