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[TowerTalk] Commercial FM Station Interference

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Subject: [TowerTalk] Commercial FM Station Interference
From: W8IK@IBM.NET (Joe Subich, W8IK)
Date: Tue, 10 Jun 1997 19:50:14 -0400
At 04:32 PM 6/9/97 -0700, you wrote:
>Is there a station engineer or otherwise knowledgeable person
>on FCC standards for location of Commercial FM stations.

As a Director of Engineering at a channel 13 TV station, I suspect 
I have a bit fo experience in this area. 

>The station in question is a Class A at 107.5 MHz (second harmonic is
>in Ch13 the local CBS affiliate!) running 6KW to an Omni antenna at 
>60 feet above local terrain.  Is this a normal situation for such stations?

6 KW at 60 feet above average terrain is a bit out of the ordinary. 
The FCC rules for Class A stations permit 6 KW at 100 meters above 
average terrain ... frankly, I don't know why the station isn't 
operating at the maximum height unless the 60 feet was just for 
testing.  If 60 feet is for testing, 100 meters will eliminate all 
the TVI (what you're seeing is major front end overload of the TV 

We have a local 107.9 (class B1, I think ... about 25 KW at 300 feet)
and no interference at all.   

>I've searched the FCC web sites and can't find any guidelines on 
>locating such antennas/stations within residential areas.

There is nothing in the FCC rules regarding antenna siting.  The 
closest thing to limits are the FAA rules on height vs. distance 
to airports and the EPA limits on exposure to radio frequency 



    ... Joe Subich, W8IK  ex-AD8I

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