Question on contours

[duckfan98]

Greetings all -

I picked up a demo (30 day) version of Comstudy 2.2 - I am practicing around with it, trying to learn how to find open frequencies, etc. Doing and upgrade type scenario.

I was curious what type of contours to plot. I know that stations have to be treated at there full power / haat, not their actual power haat; but what contour would I use to display that? Is it the 60dbu f(50/50)? There are also options to plot the 'FM Allocation' and also a check box for 'Force Station HAAT'.

In other words, how do I see if Station A would not overlap Station B, etc.

Any advice would be much appreciate. Regards

 

[oldiesstation]

You might get more input if you post this on the engineering thread..

 

[TomT]

1. Commercial stations are protected by distance separations, not contours. In some instances the contours may overlap (especially where one station is grandfathered with higher power/coverage than now allowed) but this is permitted under the rules. See Section 73.207

2. Educational stations (88.1 to 91.9) are protected by the contour overlap rules. The relevant contours to be used depend on the relationship of the stations. See section 73.509.

For example, a co-channel station may not overlap its 50/10 40 dbu contour to another stations 60 dbu 50/50, nor can it accept interference greater than 40 dbu from that station on to it's 60 dbu contour. The same relationship for adjacent channel stations is 54 dbu to 60. There are two sets of curves used to determine interfering and protected contours--50/10 (50% of the locations 10% of the time) is used to determine interfering contours. There is probably a check box to set to determine which set of curves the program uses to draw the contours.

Contour overlap is also used under Section 73.215 to determine the amount of power a short-spaced station can run in the commercial band; and under Section 74.1204 to determine the amount of power a translator can run without interfering with existing stations.

The rules are available from the FCC website FCC.Gov--go to the transition (old web page) portion, and look for "rules" in the listing on the left hand side of the screen.