Nuts and Bolts of FCC FM Allocations Doug Vernier – V-Soft Communications Telecommunication Consultants Prepared for the SBE Webinar

FM Allocations Service Assumptions Operate within power and antenna height maximum and minimums required for class Serve the licensed Principal City Cause no interference Meet 73.207 minimum separations Short space if necessary using 73.215 rules

FM Station Classes Zone I and Zone 1A East U.S. , Southern California & P.R. • A (6 kW at 100 m HAAT) • B1 (25 kW at 100 m HAAT) • B (50 kW at 100 m HAAT Zone II – Most of the rest of the U.S. • A (6 kW at 100 m HAAT) • C3 (25 kW at 100 m HAAT) • C2 (50 kW at 150 m HAAT) • C1 (100 kW at 299 m HAAT) • C0 (100 kW at 450 m HAAT) • C (100 kW at 600 m HAAT)

73.207 Minimum separations FM band: Channels 200 – 300 87.9 – 107.9 MHz Channel Band Width = 200 kHz

Minimum Separations Study

Area to Locate Transmitter – 73.207 Plot

Service to Principal City Commercial FM 70 dBu With 80 percent of the principal city area or population covered. Non-commercial FM 60 dBu with at least 50% of the principal city covered The FCC has allowed waivers where the applicant uses TechNote 101 calculations (Longley-Rice)

Protected F(50-50) Contour Distances Class A, 3 kW = 24.2 km, old class A Class A, 6 kw = 28.49 km, 60 dBu (1 mV/m) Class B1 = 44.7km, 57 dBu Class B = 65.1 km, 54 dBu Class C3 = 39.1 km, 60 dBu Class C2 = 52.2 km, 60 dBu Class C1 = 72.3 km, 60 dBu Class C0 = 83.4 km, 60 dBu Class C = 91.8 km, 60 dBu Class L1 = 5.2 km

FCC Coverage CURVES F(50-50)

73.215 and 73.509 Contour Protection Ratios – D to U Co-channel: - 20 dB - *if 60 dBu is protected F(50-10) interference contour = 40 dBu First-Adjacent: - 6 dB 2nd and 3rd adjacent +40 dB * if the 60 dBu is the protected contour, interference contour = 100 dBu 

Interference Curves F(50-10)

Where did the D/U ratios come from? Project #22231. In 1947, the FCC "Laboratory Division" conducted tests on FM Radios and published reports on "Characteristics of Commercial FM Broadcast Receivers". Data was included in the results concerning the interference rejection ratios on both co-channel and adjacent channels. These measurements are the basis for the interference ratios still used in the FM rules (first adopted in 1951.)

Converting Curves to Machine readable tables

F(50-10) FORTRAN TABLE * F(50,10) FIELD STRENGTH DATA FOR THE LOW VHF PROPAGATION CURVE * * ( FM AND TV CHANNELS 2 THRU 6 ) * DATA ( ( F51LV(I,J), J = 1, IH10 ), I = 1, ID10 ) / & 52.2, 58.4, 64.3, 68., 70.5, 72.3, 74.2, 75.9, 77., 78.2, & 80.8, 81.8, 82.2, C & 41.4, 47., 53., 56.5, 59., 60.9, 63., 64.8, 66.2, 67.6, & 71.2, 73.8, 75.5, & 36.4, 40.9, 45.9, 49., 51.7, 53.7, 56., 57.9, 59.6, 60.9, & 64.5, 67., 69., & 33., 36., 39.9, 43., 45.4, 47.5, 50., 52., 54., 55.2, & 58.9, 61.4, 63.3, & 30., 31.9, 35., 37.7, 40., 41.9, 44.4, 46.7, 48.5, 50., & 53.9, 56.3, 58.4,

HAAT FM - radial 3 to 16 km Minimum of 51 elevation points along a radial

Radials for Determining Average HAAT

Digital Terrain Elevation Databases

Popular Terrain ElEvation Databases 3 arc-second and 30 arc-second U.S.G.S. databases in use today by the FCC have the least accuracy of available databases. The 30 arc-second database was derived from the original 3 arc-second U.S.G.S. data base which was digitized from 1:250,000 scale maps. Since each second of latitude approximates 100 feet, the 30 arc-second terrain elevation database will have an elevation point every 3,000 feet. The 3 arc- second database will have a point every 300 feet. Both databases are said to have a number of errors in them such as mountain peaks being off as much as 15 seconds. In 2004 the USGS released the National Elevation Datum (NED) data set. This dataset was developed by merging the highest-resolution, best quality elevation data available across the United States into a seamless raster format. NED is the result of the maturation of the USGS effort to provide 1:24,000-scale Digital Elevation Model (DEM) data for the conterminous US and 1:63,360-scale DEM data for Alaska. The newest database to be released is from the Shuttle Radar Topography Mission (SRTM). In this mission NASA obtained elevation data on a near global scale to generate the most complete high-resolution digital topographic database of the Earth.

ReturnING to Minimum Separations Study Where they came from

Spacings Table It’s based on “flat earth” and uniform terrain.

FM Short-Spacing Under 73.215 73.207 separations cannot be met Short-space distance must be less than what is shown in 73.215(e) If the protected station is not already a 73.215 short-space facility, you must change its power and HAAT to the standard class maximum If protected station is directional assume its an omnidirectional facility Use contour to contour protection to short-spaced station.

The underground antenna

KWVE-FM with Antenna at Licensed Height and Power – Using Omni antenna

KWVE-FM with OMNI Antenna

KUZZ-FM Antenna Goes Underground Real Antenna at 6 kW HAAT: 416M 73.215 Antenna at 50 kW HAAT: 150M

Grand Fathered Shortspace Assignments 73.213 These assignments are numerous in Zone 1 Created before 1964 and adoption of separations tables Pre 1989 short-space caused by allowing all class A stations to increase from 3 kW to 6 kW 2nd and 3rd adjacent spacing requirements are not followed allowing a stations transmitter to be within the protected contour of the shortspaced station.