I saw this posted over at the NYRMB by Scott Fybush in response to a question about signal range. He offers a good summary that answers one of the frequently asked questions about HD Radio, so I thought it deserved to be posted here for future reference:
There are four basic classifications of licensed FM stations : A, B, C and D. On average, the range of their analog (non-HD) signals are as follows:
Class A goes about 25-30 Miles
Full Class B goes about 50 Miles
Full Class C goes about 70 Miles
Class Ds usually go 5 miles or less.
Class B1s go about 30-40 miles
C1s go about 60 miles.
C2s go about 40-50 miles
C3s go about 30-40 miles
[Scott]:
Those are decent rule-of-thumb figures for usable reception on a good radio, albeit perhaps a little on the generous end for a class A (especially the older 3 kW class As, of which there are still many in the northeast).
But those numbers also assume that the station in question is operating with full spacing to other stations in its area, which is almost never a viable assumption in the crowded northeast. Nearly all the FMs in the NY metro area are short-spaced, some to a small degree, others massively so. (Think WCBS vs. WBEB on 101.1, where WCBS-FM becomes unusable as little as 30-35 miles from Empire in the direction of Philadelphia.)
Those numbers also assume analog-only operation. IBOC sidebands on short-spaced stations further exacerbate the problem. WCAA on 105.9 already has IBOC. I don't think WBLI on 106.1 does, but when that happens, it will create even more unusable area between the two signals over Nassau County.
In practice, for good digital (HD) reception, the magic signal threshold appears to be somewhere in the 65-68 dBu range, just shy of the 70 dBu that the FCC considers "city-grade."
A rough rule-of-thumb on those distances, again assuming full spacing and maximum antenna height for the class, goes like this:
3 kW A - 8-10 miles
6 kW A - 10-12 miles
25 kW B1/C3 - 18-20 miles
50 kW B/C2 - 25-30 miles
100 kW C1/C0 - 30-35 miles
100 kW C - 35-40 miles
For a class D station, you probably want to be able to see the antenna...
There are four basic classifications of licensed FM stations : A, B, C and D. On average, the range of their analog (non-HD) signals are as follows:
Class A goes about 25-30 Miles
Full Class B goes about 50 Miles
Full Class C goes about 70 Miles
Class Ds usually go 5 miles or less.
Class B1s go about 30-40 miles
C1s go about 60 miles.
C2s go about 40-50 miles
C3s go about 30-40 miles
[Scott]:
Those are decent rule-of-thumb figures for usable reception on a good radio, albeit perhaps a little on the generous end for a class A (especially the older 3 kW class As, of which there are still many in the northeast).
But those numbers also assume that the station in question is operating with full spacing to other stations in its area, which is almost never a viable assumption in the crowded northeast. Nearly all the FMs in the NY metro area are short-spaced, some to a small degree, others massively so. (Think WCBS vs. WBEB on 101.1, where WCBS-FM becomes unusable as little as 30-35 miles from Empire in the direction of Philadelphia.)
Those numbers also assume analog-only operation. IBOC sidebands on short-spaced stations further exacerbate the problem. WCAA on 105.9 already has IBOC. I don't think WBLI on 106.1 does, but when that happens, it will create even more unusable area between the two signals over Nassau County.
In practice, for good digital (HD) reception, the magic signal threshold appears to be somewhere in the 65-68 dBu range, just shy of the 70 dBu that the FCC considers "city-grade."
A rough rule-of-thumb on those distances, again assuming full spacing and maximum antenna height for the class, goes like this:
3 kW A - 8-10 miles
6 kW A - 10-12 miles
25 kW B1/C3 - 18-20 miles
50 kW B/C2 - 25-30 miles
100 kW C1/C0 - 30-35 miles
100 kW C - 35-40 miles
For a class D station, you probably want to be able to see the antenna...
