[BC] FM TX spacing question (cross-post)

[Phil Alexander]

On 8 Feb 2006 at 12:33, Mark Humphrey wrote:

> The requirement that a 73.215 applicant must assume short-spaced non-215
> stations are operating with maximum facilities for their class sometimes
> produces illogical results.
> 
> An application was filed recently by an upstate PA licensee to short-space
> his facility to an adjacent-channel Class A station with a ridge-top site.
> This station's actual HAAT is nearly 400 meters, but the 73.215 contour
> analysis required an assumption of "maximum Class A facilities" of 6 kW at
> 100 meters, effectively pushing the antenna 250 meters (820 feet)
> underground!  In this unrealistic terrain situation, the predicted contours
> resembled a figure-8 (pinched in along the ridge) when, in reality, they are
> much more circular.
> 
> If the applicant had been required to evaluate this station according to its
> licensed mountaintop facilities (maximum Class A power for that height),
> there would have been some prohibited overlap, but by "burying" the antenna
> as required by the rule, his proposal was deemed acceptable and a CP was
> granted.

Mark,

Dale Bickel maintains an HAAT/ERP calculation facility on the FCC site 
that will do these calculations. 

<http://www.fcc.gov/mb/audio/bickel/haat_calculator.html>

In essence, if the HAAT is not 100 M, the ERP is adjusted for essentially 
the same coverage on the coverage calculator. Play with the calculator.
I think you will find it both useful and interesting.

Note: An increase in HAAT and reduction in ERP according to the 
calculator has the same effect as in the real world. Although the
70 and 60 dBu contours are essentially the same, the distance to
the 34 dBu is extended by increasing HAAT and reducing ERP.


Phil Alexander, CSRE, AMD
Broadcast Engineering Services and Technology 
(a Div. of Advanced Parts Corporation) 
Ph. (317) 335-2065   FAX (317) 335-9037





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