Translator Clearance...

FM does it with frequency!
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knoxbob
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Location: East Tennessee

Translator Clearance...

Post by knoxbob » Tue Jun 06, 2017 3:46 am

I was looking @ radio-locator tonight and noticed WOPI-AM has a translator @ 97.9 with a CP to change to 98.1...there is a Class C station WBRF @ 98.1 that can't be anymore than 75 miles away. The translator signal looks to be inside some of WBRF's coverage area. How can they get this approved?

TPT
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Re: Translator Clearance...

Post by TPT » Tue Jun 06, 2017 5:14 am

Look at 74.1204---The translator must protect WBRF's 60 dbu contour against any overlap of the translator's (50/10) 40 dbu contour.
Two tools to play with:

https://www.fcc.gov/media/radio/haat-calculator
https://www.fcc.gov/media/radio/fm-and- ... ion-curves

Of course, you can always pull up the translator application to see how they dealt with this

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KPJL FM
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Re: Translator Clearance...

Post by KPJL FM » Tue Jun 06, 2017 7:47 am

At first, I thought the title of this post referred to a sale on new translators... :roll:
Trim to fit, paint to match, tune for minimum smoke.

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Deep Thought
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Re: Translator Clearance...

Post by Deep Thought » Wed Jun 07, 2017 1:38 pm

Radio-locator's contours are wildly inaccurate, plus only the inside circle (60 dBu) is relevant in most circumstances unless you're dealing with a class-B or B1 protected station. Radio-locator doesn't even show the 54 or 57 dBu protected contour for those.

The bigger issue in this case is whether you can hear the class-C station in that area and whether any one listens to it there.
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

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Shane
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Re: Translator Clearance...

Post by Shane » Wed Jun 07, 2017 11:43 pm

Radio-locator's inaccuracies aside, if you zoom way in on the area of overlap of the two signals under discussion, the translator's 40 dBu just misses the FM station's 60 dBu.

Something else to keep in mind when looking at radio-locator's maps, their AM contours are somewhat unusual. They use 2.5 mV/m for the local coverage (not 2.0 or 5) and 0.15 mV/m for the fringe (not 0.1). Only the middle contour is what we might consider a standard commonly used: 0.5 mV/m.

In any event, they should not be taken as gospel truth and there is a disclaimer to the effect that the maps are "for entertainment only." That's about right.
Mike Shane, CBRE
---Omaha---

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Deep Thought
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Re: Translator Clearance...

Post by Deep Thought » Thu Jun 08, 2017 2:21 pm

Radio-locator's FM contours are 60, 50 and 40 dBu, f(50,50). They are not f(50,10) interference contours. This is not an allocation tool by any stretch of the imagination.
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

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