Many 3000 watt Class As are basically stuck. If to go 6 kW they have to be directional, they're often better off with 3000 watts nondirectional with favorable tower mounting.
If you look at many FM DAs, the real measured patterns on license applications are much less than the FCC Pattern Envelope (with all the 1.000 ratios where the measured pattern is much less, even in the major lobe). Many also have unneccessarily deep measured nulls. Don't get me started on the short spaced Class Bs which have had to relocate their tower under newer 73.213 rules.
Keep in mind that short spacing is usually caused by new FCC rues. The original pre 1964 FM station rules, which are available in the 1960 NAB Engineering Handbook, available on worldradiohistory.com, explain how this began. There were just two classes. Class A was 1 kW/250 feet/76 meters HAAT, and Class B was 20 kW/500 feet/152 meters HAAT. There were exceptions in the original Zone II, which resulted in all the grandfathered Class B superpower stations. All stations were protected to the 1 mV/m (60 dBu F(50,50) contour. Interference was protected contour and interference ratio based. NCE-FM station protection rules continue, using interference ratios. That would be a good start for new rules for the non reserved 92-108 MHz band, along with revised second and third adjacent interference ratios. Cochannel and first adjacent interference ratios should stay the same.
Some of those "agreements" to upgrade a Class As short spaced as a 6 kW nondirectional to a Class B are like de facto bribes to the big group owners of the Class Bs. Some of these were "suburban" stations allowed under the old rules, and those are the most problematic to move or upgrade under present rules.
If you look at many FM DAs, the real measured patterns on license applications are much less than the FCC Pattern Envelope (with all the 1.000 ratios where the measured pattern is much less, even in the major lobe). Many also have unneccessarily deep measured nulls. Don't get me started on the short spaced Class Bs which have had to relocate their tower under newer 73.213 rules.
Keep in mind that short spacing is usually caused by new FCC rues. The original pre 1964 FM station rules, which are available in the 1960 NAB Engineering Handbook, available on worldradiohistory.com, explain how this began. There were just two classes. Class A was 1 kW/250 feet/76 meters HAAT, and Class B was 20 kW/500 feet/152 meters HAAT. There were exceptions in the original Zone II, which resulted in all the grandfathered Class B superpower stations. All stations were protected to the 1 mV/m (60 dBu F(50,50) contour. Interference was protected contour and interference ratio based. NCE-FM station protection rules continue, using interference ratios. That would be a good start for new rules for the non reserved 92-108 MHz band, along with revised second and third adjacent interference ratios. Cochannel and first adjacent interference ratios should stay the same.
Some of those "agreements" to upgrade a Class As short spaced as a 6 kW nondirectional to a Class B are like de facto bribes to the big group owners of the Class Bs. Some of these were "suburban" stations allowed under the old rules, and those are the most problematic to move or upgrade under present rules.
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