LPFM to double power from change to globe data from ngc

[semoochie]

In my area, an LPFM has applied and quickly been granted an increase from five to ten watts, by using Globe data. This is an established station, on the air for at least two years. I'm wondering if this situation is limited to LPFM or if say, a Class C1, that had to reduce to 50KW under NGC, could increase power to 100KW. If so, this could be a very big deal!

 

[joebtsflk1]

Yes, this is a situation that mostly affects the LPFM class, and to a lesser extent the 250 watt translator class if HAAT is limited, i.e. not a "fill-in" translator.

Is this a mountainous area? In flatland areas, eight radial HAAT comps are usually within 1 or 2 meters of 360 radial computations, but wildly varying terrain really messes with HAAT. Before I cancelled the LPFM here in Cañon City CO I was studying a hillside site with a big discrepancy between HAAT figured with the standard FCC eight radial method versus the 360 radial method that is commonly used in most full power engineering showings. In this case, eight radials produced a lower and more conservative ERP than the 360 radial method. As eight radials is the standard used by the FCC for automatically computing LPFM HAAT (remember that LPFM apps don't require a formal engineering showing and the FCC tells you what your HAAT is on the CP) what may have happened was that the LPFM in your case filed an app to modify its license that used 360 radials.

With LPFM limited to 30 meters HAAT before having to cutback power, a small change in HAAT can make a big difference. Per FCC's FMpower page, an LPFM at 135 meters = 5 wats, while it would be 10 watts at 100 meters. For a C1 to be required to cutback to 50 kW, its HAAT would be about 399 meters. Since the power cutbacks below 100kW for C1 stations starts at over the 299 meter level, that would have to be one really BIG mountain hiding between the eight radial method and the 360 radial method.

 

[semoochie]

Yes, this is a situation that mostly affects the LPFM class, and to a lesser extent the 250 watt translator class if HAAT is limited, i.e. not a "fill-in" translator.

Is this a mountainous area? In flatland areas, eight radial HAAT comps are usually within 1 or 2 meters of 360 radial computations, but wildly varying terrain really messes with HAAT. Before I cancelled the LPFM here in Cañon City CO I was studying a hillside site with a big discrepancy between HAAT figured with the standard FCC eight radial method versus the 360 radial method that is commonly used in most full power engineering showings. In this case, eight radials produced a lower and more conservative ERP than the 360 radial method. As eight radials is the standard used by the FCC for automatically computing LPFM HAAT (remember that LPFM apps don't require a formal engineering showing and the FCC tells you what your HAAT is on the CP) what may have happened was that the LPFM in your case filed an app to modify its license that used 360 radials.

With LPFM limited to 30 meters HAAT before having to cutback power, a small change in HAAT can make a big difference. Per FCC's FMpower page, an LPFM at 135 meters = 5 wats, while it would be 10 watts at 100 meters. For a C1 to be required to cutback to 50 kW, its HAAT would be about 399 meters. Since the power cutbacks below 100kW for C1 stations starts at over the 299 meter level, that would have to be one really BIG mountain hiding between the eight radial method and the 360 radial method.

Thank you for your explanation. It's a fairly small hill at the bottom of a bigger one in the middle of the Tualatin Valley, west of Portland OR. They made no other changes, just the power level. I was mainly interested as to if it would apply to a full power station. That could really shake things up! Thank you again.