Just out of curiosity, what would the coverage be in Gallatin if a low power signal were transmitted off the old 104.5 tower up on the ridge north of Gallatin? roughly 1000 feet above town..i know from the back part of that property at night you could see the lights in nashville at one time..and..what constitutes low power wattage wise ?
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LOW POWER FM
- Thread starter deltas69
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scottwmro
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deltas69 said:Just out of curiosity, what would the coverage be in Gallatin if a low power signal were transmitted off the old 104.5 tower up on the ridge north of Gallatin? roughly 1000 feet above town..i know from the back part of that property at night you could see the lights in nashville at one time..and..what constitutes low power wattage wise ?
Delta,
Do you recall back in the 80's when Kicks 104 had major transmitter problems and all they had to stay on the air was a 10 watt exiter used by the main transmitter? I think the problem lasted longer than 5 or 6 days.
I picked up that 10 watts all the into Downtown Nashville in the car. Protable Walkmans had just come out and I could hear Kicks in Madison on that 10 watt exciter. I guess the bays, which I think are still up there on that tower the last time I looked are still there. Wasn't it 7 or 8 bays? Those bays can amplify your signal.
Recall WVCP had 1000 watts with on bay up there and in the 80's before WAYM (WAY-FM) went on? You could hear WVCP 88.5 almost to Spring Hill, TN
i don't recall kixx 104 problems..i do know when we owned it, there was a backup tower just outside the control room window that we had to use a couple of times when tinker was working on the main transmitter. that smaller tower was only 40 feet high or so..it's still there although bent in half from storm damage..i'm sure we didn't go 50K on that small stick..i've done a little research on low power fm and the info i found was pretty much what you said..the higher the better...and a ten watt station theoreticaly reach 30 miles under ideal conditions..i don't have a clue about the bays..he!!..i don't even know what they are..
deltas69 said:Just out of curiosity, what would the coverage be in Gallatin if a low power signal were transmitted off the old 104.5 tower up on the ridge north of Gallatin? roughly 1000 feet above town..i know from the back part of that property at night you could see the lights in nashville at one time..and..what constitutes low power wattage wise ?
The max for LPFM is 100W/100ft......... or the equivalent thereof.
You'd probably have to drop to signle digits.. and the coverage would be good, but the building penetration would be horrible.
100 feet ? a 100 foot tower ? based on what elevation ? a 100 foot tower in my backyard would not be the same as 100 foot tower on top of a 1000 foot hill..a 100 watt signal on top of the ridge(1000 foot elevation)..should cover a lot of area..as opposed to sitting at the bottom of the ridge ..forget nashville for the time being..100 watts/100 foot tower on top of the 1000 foot hill..wouldn't that penetrate buildings in gallatin, portland ?
deltas69 said:Just out of curiosity, what would the coverage be in Gallatin if a low power signal were transmitted off the old 104.5 tower up on the ridge north of Gallatin? roughly 1000 feet above town..i know from the back part of that property at night you could see the lights in nashville at one time..and..what constitutes low power wattage wise ?
There is a FM signal up there, being transmitted from one of the adjacent ham radio towers. It's W230AD on 93.9, relaying WNAZ 89.1 last I was there.
A LPFM station is 100 watts/30m. For higher antennas power must be reduced to limit the 60dBu service contour to 5.6km. (the same as for a 100w/30m station) If the old WVCP-88.5 antenna at 119m were to be used for a LPFM, it would be limited to 6 watts ERP - and by definition would have a service contour of 5.6km, about 3-1/2 miles.
(W230AD is a translator, not a LPFM, and is not limited by the same rules. Its predicted service contour is 11km, about 7 miles. W230AD is about 15' lower than WVCP used to be.)
I would not be surprised if the coverage in practice was considerably better than 3-1/2 miles in the direction of Gallatin. Because the height above terrain in the direction of the city is considerably greater than the height above terrain to the north.
10 watts at 1000 feet the 1.0 mv goes 6.3 miles.
100 watts at 1000 feet the 1.0 mv goes 11.6 miles.
1000 watts at 1000 feet the 1.0 mv goes 20 miles.
All of this depends on terrain but 1 milli-volt signal contour provides some degree of building penetration. If your car radio can go down to 50 uV, then you could hear the 10 watt rig out about 27 miles with line of sight.
100 watts at 1000 feet the 1.0 mv goes 11.6 miles.
1000 watts at 1000 feet the 1.0 mv goes 20 miles.
All of this depends on terrain but 1 milli-volt signal contour provides some degree of building penetration. If your car radio can go down to 50 uV, then you could hear the 10 watt rig out about 27 miles with line of sight.
deltas69 said:100 feet ? a 100 foot tower ? based on what elevation ? a 100 foot tower in my backyard would not be the same as 100 foot tower on top of a 1000 foot hill..a 100 watt signal on top of the ridge(1000 foot elevation)..should cover a lot of area..as opposed to sitting at the bottom of the ridge ..forget nashville for the time being..100 watts/100 foot tower on top of the 1000 foot hill..wouldn't that penetrate buildings in gallatin, portland ?
See FCC Regulation 73.313(d) http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=32e5f4706746e7504a52b0a8baa5bc04&rgn=div8&view=text&node=47:4.0.1.1.2.2.1.26&idno=47. This defines "Height Above Average Terrain", or "HAAT", something you'll see a lot of if you read engineering documents!
Basically, you draw 8 radial lines on a topographic map, starting at your tower and going out 16km. (10 miles) You average the elevations of all points on each radial between 3 and 16km (2 and 10 miles) from the tower. That's "average terrain".
Let's say those elevations average to 150m (490') above sea level. Let's say that the center of your transmitting antenna is 250m above sea level. That's 100m higher than average terrain - your station's HAAT is 100m.
For each class of FM station there is a maximum HAAT and a maximum power. For example, for a Class A station like Lightning 100, the maximum HAAT is 100m and the maximum power 6,000 watts. You can have your antenna higher than the maximum, but you have to reduce power to compensate. Lightning 100's antenna is 360m high - and they're required to reduce power to only 200 watts to compensate.
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