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fl-lpfm
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I will like to know how to measure the power that I need to use if I raise my antenna? Right now i'm at 100watt at 95 feet.
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I would like to find an "official" table or chart on this topic also.
I went through Radio Locator and selected a number of LPFMs that I assumed were in mountainous areas and harvested their antenna height and power. This is probably close enough for rough planning. A consulting engineer could nail it down to a number the FCC will live with.
Height
Above
Average
Terrain..............Radiated
(HAAT)..............Power
100 100
116 72
126 61
128 59
161 36
178 29
179 29
183 27
192 25
199 23
311 9
340 8
387 6
413 5
608 3
653 2
Hope this helps. Maybe someone has a table with more points listed.
I went through Radio Locator and selected a number of LPFMs that I assumed were in mountainous areas and harvested their antenna height and power. This is probably close enough for rough planning. A consulting engineer could nail it down to a number the FCC will live with.
Height
Above
Average
Terrain..............Radiated
(HAAT)..............Power
100 100
116 72
126 61
128 59
161 36
178 29
179 29
183 27
192 25
199 23
311 9
340 8
387 6
413 5
608 3
653 2
Hope this helps. Maybe someone has a table with more points listed.
fl-lpfm said:I will like to know how to measure the power that I need to use if I raise my antenna? Right now i'm at 100watt at 95 feet.
The FCC links below will enable anyone to do this for stations in the contiguous US.
Use the first link to determine the HAAT of the radiation center of the antenna; then the second link to determine what ERP reduction may be needed for that elevation.
http://www.fcc.gov/mb/audio/bickel/haat_calculator.html
http://www.fcc.gov/mb/audio/bickel/fmpower.html
//
These are amateur calculations so there may be a bit of error.
The highest altitude above average terrain you could put an LPFM antenna with 2 watts would be 942 feet.
The highest altitude above average terrain you could put an LPFM antenna with 1 watt would be 1476.
(The rules and regs state that 450 meters is THE MAX! (1476 feet)
The FCC will not license LESS than 1 watt.
When you say 2 watt translator is covering Chicago, you may have to define Chicago (City limits? Suburbs?)
And then, what is coverage? I can listen with my Walkman portable? I can listen at the far reaches if I use my car radio? Or: I can pick up the 2 watts if I have an external antenna up above my roof-top connected to a very sensitive receiver.
I think we are totally talking theory here. I ran a search using the RecNet frequency finder and you are not going to get an LPFM frequency in Chicago. I asked the search to assume they do away with the 3rd adjacent channel problem, and that they assume all the translator invasion frequencies just go away, etc. etc and the computer still said: No, there is NOTHING available in Chicago.
An if you could get a frequency, could an LPFM afford the rent for an antenna on a building at 1450 feet?
The FCC's intention is that the primary coverage area for an LPFM would reach out a MAXIMUM of 5.6km which translates to 3.48 miles.
I was in a town this week that has an LPFM. I wanted to see it but IT IS NOT where the FCC records show it to be. (tsk, tsk, shame, shame) As I drove through and across town, I was able to pick it up on my car radio for about 7 to 8 miles... which means it had an effective range of about 3-1/2 miles.
The highest altitude above average terrain you could put an LPFM antenna with 2 watts would be 942 feet.
The highest altitude above average terrain you could put an LPFM antenna with 1 watt would be 1476.
(The rules and regs state that 450 meters is THE MAX! (1476 feet)
The FCC will not license LESS than 1 watt.
When you say 2 watt translator is covering Chicago, you may have to define Chicago (City limits? Suburbs?)
And then, what is coverage? I can listen with my Walkman portable? I can listen at the far reaches if I use my car radio? Or: I can pick up the 2 watts if I have an external antenna up above my roof-top connected to a very sensitive receiver.
I think we are totally talking theory here. I ran a search using the RecNet frequency finder and you are not going to get an LPFM frequency in Chicago. I asked the search to assume they do away with the 3rd adjacent channel problem, and that they assume all the translator invasion frequencies just go away, etc. etc and the computer still said: No, there is NOTHING available in Chicago.
An if you could get a frequency, could an LPFM afford the rent for an antenna on a building at 1450 feet?
The FCC's intention is that the primary coverage area for an LPFM would reach out a MAXIMUM of 5.6km which translates to 3.48 miles.
I was in a town this week that has an LPFM. I wanted to see it but IT IS NOT where the FCC records show it to be. (tsk, tsk, shame, shame) As I drove through and across town, I was able to pick it up on my car radio for about 7 to 8 miles... which means it had an effective range of about 3-1/2 miles.
I have a related question.
If a little village is nestled right up next to a 400 foot high "starter mountain", it could be served by a seven watt ERP if space could be acquired atop the little mountain.
Someone has suggested to me that even though the seven watts at 466 fee will go out as far at the 100 watts will and 100 feet, that seven watts may not penetrate buildings well at the base of the mountain at a distance of half to three-quarters of a mile.
Who has some real world experience with a scenario like this?
Mr. Fry, I would value YOUR input on this topic.
If a little village is nestled right up next to a 400 foot high "starter mountain", it could be served by a seven watt ERP if space could be acquired atop the little mountain.
Someone has suggested to me that even though the seven watts at 466 fee will go out as far at the 100 watts will and 100 feet, that seven watts may not penetrate buildings well at the base of the mountain at a distance of half to three-quarters of a mile.
Who has some real world experience with a scenario like this?
Mr. Fry, I would value YOUR input on this topic.
Goat Rodeo Cowboy said:.... Mr. Fry, I would value YOUR input on this topic.
If the great majority of the populated coverage area consists of the little village you mentioned, then it might be best to install an LPFM system in about the center of that village, using as much ERP as allowed.
If the goal is to place a 1millivolt/meter signal or better over the largest land area, then the hilltop location might be preferable.
If you post the coordinates of the village center and of the summit of the 400' hill nearby, I could do a quick, terrain-based approximation of the resulting field strengths in the village from these two sites.
The greater the field in that village, the better the "building penetration," other things equal.
The choice of antenna will be important no matter where the transmit site is located. Some of them offered/used by LPFM stations may not achieve the power gain and radiation patterns advertised or assumed for them, which means that ERP can be less toward the populated areas than was licensed by the FCC.
//
I hope you can understand that I am hesitant to post the co-ordinates here and announce to the whole world something I might be doing if we have a LPFM Application Window. I am sending you an e-mail with the village name and the co-ordinates of the critical points and elevations.
If you choose to run the calculations post the advice on low antenna/higher power vs. tall antenna/low power and the ability to penetrate buildings here for all to share.
This is a mountain village, tourist magnet town, retirement town, university town. Mountain top to village center: 5/8th of a mile. Elevation difference from village center to mountain top 300 feet.
Have fun.
If you choose to run the calculations post the advice on low antenna/higher power vs. tall antenna/low power and the ability to penetrate buildings here for all to share.
This is a mountain village, tourist magnet town, retirement town, university town. Mountain top to village center: 5/8th of a mile. Elevation difference from village center to mountain top 300 feet.
Have fun.
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