FCC Broadcast Contours
- Elizabeth Carlton (Deactivated)
Signal Pro has the ability generate FCC contours according to the FCC rules. These are used particularly for simple coverage for services such as FM radio, Broadcast TV, and Land Mobile Radio. These contours were conceived in the 1960’s and is the method used to approximate coverage and interference when computing power was nonexistent. There are more comprehensive methods to determine coverage and interference that are more accurate.
What are Contours
Contours are created using Carey Curves created in the 1960. See https://transition.fcc.gov/oet/info/documents/reports/R-6602.pdf. There are 3 different reliability values used in these curves. The contours are a contiguous polygon without any “donuts” or areas of no coverage inside these regions.
F(50,50) Contours
This contour is used to predict coverage to receivers using analog modulation. The calculation based on whether the probability of a given field strength is exceeded for 50% of locations and 50% of time. NTSC TV and analog LMR radio typical describe their coverage using contours with these reliabilities.
F(50,90) Contours
This contour is used to predict coverage to receivers using digital modulation. The calculation based on whether the probability of a given field strength is exceeded for 50% of locations and 90% of time. DTV and digital LMR radio typical describe their coverage using contours with these reliabilities.
F(50,10) Contours
This contour is used to predict interference to receivers using both analog and digital modulation. The calculation based on whether the probability of a given field strength is exceeded for 50% of locations and 10% of time.
How to Generate FCC Contours in Signal Pro
There are several way to generate FCC contours in Signal Pro.
Studies Menu- Go to Studies->Interference Contour Studies
The follow dialog will display. This will allow the user to plot contours and set styles for coverage (service) and interference contours. Notice the user can vary the Percent Time parameter and the signal level contour for a given transmitter group and CPE type.
The user can also plot contour on a per site basis by going RF systems->Transmitter/Base/Hub Router and edit a site
Pressing the Quick contours will display the following dialog. Note the user can adjust % time and % location variability as well as the contour signal level.
When the user presses calculate a report will be created detailing model input to the contour model. The user may also chose from different contour propagation models. See https://help.edx.com/help/propagation-model-overview for more information.
The user can also plot contour on a transmitter group basis by running a field strength at remote study using FCC-type area study display style in the area studies dialog.
Coverage and interference contour requirements for different services
FM Radio-F(50,50) protected contours are defined as follows:
54 dBu contour for commercial Class B stations
57 dBu contour for commercial Class B1 stations
60 dBu (1 mV/m) contour for commercial Class A, C3, C2, C1, and C stations
60 dBu for all classes of noncommercial educational stations in the reserved band (88.1 to 91.9 MHz)
For more information see Part 73 of the FCC rules
Digital Television (DTV)
28 dBu for Channels 2-6
36 dBu for Channels 7-13
41 dBu for Channels 16-69
For more information see Part 73 of the FCC rules
Public Safety
Band | Frequencies | Service | Interference | Adjacent Channel Deratings, if applicable |
|---|---|---|---|---|
VHF Low Band | 30-50 MHz | 31 dBµ F(50,50) | 13 dBµ F(50,10) |
|
VHF High Band | 150-174 MHz | 37 dBµ F(50,50) | 19 dBµ F(50,10) | 44 dBµ F(50,10) 7.5 kHz adjacent channel* |
UHF | 450-512 MHz | 39 dBµ F(50,50) | 21 dBµ F(50,10) |
|
| 700 and 800 | 40 dBµ F(50,50) | 22 dBµ F(50,10) |
|
| 800 NPSPAC | 40 dBµ F(50,50) | 5 dBµ F(50,10) co-channel | 25 dBµ F(50,10) 12.5 kHz adjacent channel |
For more information see: https://transition.fcc.gov/oet/info/documents/reports/R-6406.pdf
For more information on displaying coverage and interference please see:https://edxwireless.atlassian.net/wiki/spaces/KD/pages/599654637
FCC-EDX Propagation Model-
The FCC0EDX propagation model is the most flexible of the contour type models. It not only allows the user to configure the percent time and location variability but also it allow for the user to input a correction value and change the curve used independent of the transmitters center frequencies. Also the user may enter a decibel value as a correction factor. This is typical in public safety as the curves generated assume fixed 30 FT receiver and the public safety mobile is typically closer to ground level. These may be accessed using the supplemental parameters.
Interference Studies
Using the tables above an interference study can be produced by using different transmitter groups for the desired and undesired. The Lyme station below is consider the interferer and thus a 19 dBu contour is used to represent the offending site contour level. KRP879 is considered the desired site and its coverage is areas with its 37 dBu contour. As can be seen below the two contours do not intersect thus the two station do not interfere with each other.
After increasing the power of the Lyme site by 10 dB, it interferes with KRP879 as the contours intersect.
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