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How far can a antenna see?Highthwise?
I seem to recall reading about a 'standard', it went something
like this,,,, a two meter antenna at 100 feet can "see" or be useable for 17 miles. I don't recall where I read this,,, but would really appreciate any and all input on the question,,,,,,,,,,,, How far can a base two meter radio antenna transmit and recieve so as to be 'useable' when the antenn is 100 feet tall above the earth, and the surronding area is fairly level. (no hills or mountains). I am talking about a 50 watt base and 50watt mobil. If there is a formula somewhere, would appreciate the input. The reason I ask, is on the way by some very tall tv antennas 1000 and 1200feet, I got to wondering,,, they don't work well with ""my formula"" (17miles=100feet) they (the tv channels #2,#4 #5) are out of 'gas' at about 70 miles.....?????????? Hope you can 'blumb up my brain'. thanks in advance. cl.73 |
I seem to recall reading about a 'standard', it went something like this,,,, a two meter antenna at 100 feet can "see" or be useable for 17 miles. I don't recall where I read this,,, but would really appreciate any and all input on the question,,,,,,,,,,,, How far can a base two meter radio antenna transmit and recieve so as to be 'useable' when the antenn is 100 feet tall above the earth, and the surronding area is fairly level. (no hills or mountains). I am talking about a 50 watt base and 50watt mobil. If there is a formula somewhere, would appreciate the input. The reason I ask, is on the way by some very tall tv antennas 1000 and 1200feet, I got to wondering,,, they don't work well with ""my formula"" (17miles=100feet) they (the tv channels #2,#4 #5) are out of 'gas' at about 70 miles.....?????????? Hope you can 'blumb up my brain'. thanks in advance. cl.73 A rough rule of thumb is to take the square root of the height in feet and that will give you the miles from the antenna to the ground. YOu do this again for the other antenna and add the number of miles. This can be multiplied by about 1.2 to 1.3 for radio waves. For example if the transmitter antenna is 625 feet high and the receiving antenna is 16 feet high. YOu get sqrt 625 = 25 miles, then sqrt 16 = 4 miles. YOu add 25+4 = 29 miles for the visual distance. Then multiply this by 1.3 to get 37.7 miles of radio range. |
Ralph Mowery wrote:
I seem to recall reading about a 'standard', it went something like this,,,, a two meter antenna at 100 feet can "see" or be useable for 17 miles. I don't recall where I read this,,, but would really appreciate any and all input on the question,,,,,,,,,,,, How far can a base two meter radio antenna transmit and recieve so as to be 'useable' when the antenn is 100 feet tall above the earth, and the surronding area is fairly level. (no hills or mountains). I am talking about a 50 watt base and 50watt mobil. If there is a formula somewhere, would appreciate the input. The reason I ask, is on the way by some very tall tv antennas 1000 and 1200feet, I got to wondering,,, they don't work well with ""my formula"" (17miles=100feet) they (the tv channels #2,#4 #5) are out of 'gas' at about 70 miles.....?????????? Hope you can 'blumb up my brain'. thanks in advance. cl.73 A rough rule of thumb is to take the square root of the height in feet and that will give you the miles from the antenna to the ground. YOu do this again for the other antenna and add the number of miles. This can be multiplied by about 1.2 to 1.3 for radio waves. For example if the transmitter antenna is 625 feet high and the receiving antenna is 16 feet high. YOu get sqrt 625 = 25 miles, then sqrt 16 = 4 miles. YOu add 25+4 = 29 miles for the visual distance. Then multiply this by 1.3 to get 37.7 miles of radio range. Yep!! That's the way to do it!! |
Ht of ant over gd Optical range limit Ht ant above sealevel limit
optical rg 5 ft 3.2 miles 1000 ft 45 miles 20 6.4 2000 63.5 50 10.0 3000 78 100 14.2 4000 90 500 32 5000 100 Horisontal dist calculated from S = 1.42root H S = miles H = ht of observers eyes in feet above sea level Above table gives horizon distance for various heights of antenna above sea level RADIO DATA REFERANCE BOOK RSGB aRT "Ralph Mowery" wrote in message ... I seem to recall reading about a 'standard', it went something like this,,,, a two meter antenna at 100 feet can "see" or be useable for 17 miles. I don't recall where I read this,,, but would really appreciate any and all input on the question,,,,,,,,,,,, How far can a base two meter radio antenna transmit and recieve so as to be 'useable' when the antenn is 100 feet tall above the earth, and the surronding area is fairly level. (no hills or mountains). I am talking about a 50 watt base and 50watt mobil. If there is a formula somewhere, would appreciate the input. The reason I ask, is on the way by some very tall tv antennas 1000 and 1200feet, I got to wondering,,, they don't work well with ""my formula"" (17miles=100feet) they (the tv channels #2,#4 #5) are out of 'gas' at about 70 miles.....?????????? Hope you can 'blumb up my brain'. thanks in advance. cl.73 A rough rule of thumb is to take the square root of the height in feet and that will give you the miles from the antenna to the ground. YOu do this again for the other antenna and add the number of miles. This can be multiplied by about 1.2 to 1.3 for radio waves. For example if the transmitter antenna is 625 feet high and the receiving antenna is 16 feet high. YOu get sqrt 625 = 25 miles, then sqrt 16 = 4 miles. YOu add 25+4 = 29 miles for the visual distance. Then multiply this by 1.3 to get 37.7 miles of radio range. |
Art, KB9MZ wrote:
"Horizontal distance calculated from S = 1.42 root H----." The 1.42 is rounded from 1.414 which is the square root of 2. The formula previously given is: Miles to the horizon = sq rt 2H H is in feet. You can remove 2 from under the radical by expressing it as 1.414. That is all the RSGB did. I think it is easer to leave the 2 under the radical, that is just to take the square root of 2x the antenna height in feet when you are estimating the distance to the horizon in miles. Usually you can do this in an instant in your head. The results are most often good enough. Best regards, Richard Harrison, KB5WZI |
See Guide to Transmitter Range From Artsci --- URL:
http://www.artscipub.com/simpleton/simp.range.html Also see VHF/UHF Line of Sight Calculator http://www.vwlowen.demon.co.uk/java/horizon.htm And Calculating the Distance to the Horizon URL: http://www.wolfram.demon.co.uk/rp_horizon_distance.html -- 73 From The Wilderness Keyboard ----------------------------------------------------------------- wrote in message ... I seem to recall reading about a 'standard', it went something like this,,,, a two meter antenna at 100 feet can "see" or be useable for 17 miles. I don't recall where I read this,,, but would really appreciate any and all input on the question,,,,,,,,,,,, How far can a base two meter radio antenna transmit and recieve so as to be 'useable' when the antenn is 100 feet tall above the earth, and the surronding area is fairly level. (no hills or mountains). I am talking about a 50 watt base and 50watt mobil. If there is a formula somewhere, would appreciate the input. The reason I ask, is on the way by some very tall tv antennas 1000 and 1200feet, I got to wondering,,, they don't work well with ""my formula"" (17miles=100feet) they (the tv channels #2,#4 #5) are out of 'gas' at about 70 miles.....?????????? Hope you can 'blumb up my brain'. thanks in advance. cl.73 |
Wilderness Keyboard wrote:
"See Guide to Transmitter Range from Artsci---." See the 19th edition of the "ARRL Antenna Book" pages 23.5 and 23.6. Eqn. 3: Dmiles = 1.415 sq rt Hfeet This can be rewritten: D = sq rt 2H Wasn`t it Albert Einstein who wrote something like: "Don`t make things any more complicated than necessary?" Solutions to Eqn 3 are plotted in Fig 6. Example: 20 ft gives 6 miles. The approximate sq rt of 40 is 6 miles. Example: 50 ft gives 10 miles. The approximate sq rt of 100 is 10 miles. Example: 200 Ft gives 20 miles. The approximate sq rt of 400 is 20 miles. Etc., etc., etc.. Best regards, Richard Harrison, KB5WZI |
Richard Harrison, KB5WZI, wrote:
See the 19th edition of the "ARRL Antenna Book" pages 23.5 and 23.6. Eqn. 3: Dmiles = 1.415 sq rt Hfeet This can be rewritten: D = sq rt 2H Wasn`t it Albert Einstein who wrote something like: "Don`t make things any more complicated than necessary?" I think it was: "Everything should be made as simple as possible, but not simpler". -- Albert Einstein But... whatever. I think Herr Doktor Einstein would appove of the derivation from first principles found on: http://www.wolfram.demon.co.uk/rp_horizon_distance.html K7JEB Glendale, AZ |
Artsci takes into account
To properly estimate a signals range, you must have a few important figures: -- Frequency / Band -- Transmitter power (in watts) -- Antenna height (from sea level) -- Antenna gain (net after coax loss) And that is what the original poster asked for (I thought) -- 73 From The Wilderness Keyboard "Richard Harrison" wrote in message ... Wilderness Keyboard wrote: "See Guide to Transmitter Range from Artsci---." See the 19th edition of the "ARRL Antenna Book" pages 23.5 and 23.6. Eqn. 3: Dmiles = 1.415 sq rt Hfeet This can be rewritten: D = sq rt 2H Wasn`t it Albert Einstein who wrote something like: "Don`t make things any more complicated than necessary?" Solutions to Eqn 3 are plotted in Fig 6. Example: 20 ft gives 6 miles. The approximate sq rt of 40 is 6 miles. Example: 50 ft gives 10 miles. The approximate sq rt of 100 is 10 miles. Example: 200 Ft gives 20 miles. The approximate sq rt of 400 is 20 miles. Etc., etc., etc.. Best regards, Richard Harrison, KB5WZI |
K7JEB wrote:
"But....whatever, I think Herr Doktor Einstein would approve of the derivation from first principles found on---." No doubt, as that illustrates it is a problem involving geometry. But in all cases the distance to the horizon is inexact due to constant variations in refraction of the atmosphere. Most often the earth appears to have a radius of about 4/3 the actual which means the earth appears flatter than it is so that radio waves range farther than many predictions. When propagation for line-of-sight signals gets tough in the early am under still air conditions, the earth can apper to have 2/3 its actual radius or even less. Bad news out on the fringes! Terman says: "Theoretical analysis indicates that the earth curvature reduces the received signal below the value calculated by Eq. (219) by the factor given by Fig. 362. This factor takes into account that refraction in the atmosphere and also the diffraction of the energy around the curved surface. Under practical conditions the reduction factor of Fig. 362 is negligible as long as a straight line path exists, but at greater distances it decreases rapidly and the signals soon become unusable because of fading, as mentioned below." Terman also has a height versus distance chart similar to that in the ARRL Antenna Book. Fact is that the experimentally determined formula is related to the geometric calculations and is plenty close enough for practice. I`ve used it commercially many times and for more than half a century and never been embarrassed by inaccuracy causing excess expense nor excess outage time. It is a good indicator of the radio distance to the horizon under "usual" propogation conditions. It is easy to remember and simple to apply. Best regards, Richard Harrison, KB5WZI |
K1YW wrote:
"Artsci takes into account: To properly estimate a signal`s range, you must have a few important figures---- Frequency / Band Transmitter power (in watts) Antenna height (from sea level) Antenna gain (net after coax loss) As a practical matter, first you must have a line-of-sight path. Then you can worry about path attenuation, gains, losses, transmitter power and receiver sensitivity. Attenuation between stations with an obstructed path (including earth bulge) rises so rapidly with the obstruction that non of the other factors matters except in the case of brute force communication, such as atmospheric scatter. Best regards, Richard Harrison, KB5WZI |
Terman also says the radio horizon as seen from a ground-mounted vertical
antenna is at distance of - 50 / Cuberoot(FreqMhz) miles. This does not mean the ground wave suddenly weakens at this distance but that Earth curvature and atmospheric refraction begin to have a significant effect on ground-wave propagation. At MF and LF, useful ground-wave propagation can occur at distances considerably greater than the radio horizon. At HF the skywave can provide stronger signals. ---- Reg, G4FGQ |
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K1YW wrote:
"So Artsci should help him (KC5CQA)." 50-watt radios will talk with plenty of exess fade margin over any line-of-sight path from a 100-foot tower to any land mobile in the two-meter band. Beyond line-of-sight, VHF propagation is kaput because the signal does not follow earth curvature as Reg`s low and medium frequencies do. Over smooth earth or sea, the horizon is sq rt of 200 from a 100-foot high antenna. That is about 14 miles. Add 4 or 5 miles of range due to the mobile antenna height and that is near the maximum range. 5 watts, 100 watts, or 500 watts make very little difference in range. Range is extended with increased power very slightly. There is some noise reduction. In my experience, I found it advantageous to use 50-watt mobiles and 500-watt base stations. This is because the mobile is often in a noisier environment than the base station. Obviously the path length is the same in both directions in this VHF application. The dominant requirement in VHF communication is a line-of-sight path. Once that is obtained, all else is secondary. Most of the microwave stations I`ve put in have 100-milliwatt transmitters and these produced 30 dB fade margins on paths of more than 20 miles. For land mobile VHF service, you usually have no significant antenna gains, but you also have significantly lower path and transmission line losses, higher receiver sensitivities, and higher transmitter powers. Received carrier power to produce full quieting in a good receiver is very small indeed. This makes line-of-sight the only significant requirement for single-channel, single-hop VHF communications. Noise is cumulative, so for a multi-hop system, big signal surplus is required on each hop to supress noise to make the cumulative total acceptable. Best regards, Richard Harrison, KB5WZI |
There is almost always some kind of enhanced propagation. With 50W SSB to a
10 element 2 meter beam at 40 feet, 90% of the time my range is 75 - 100 miles when talking to another base station. I don't think they all have 1000 foot towers. Tam/WB2TT "Richard Harrison" wrote in message ... K1YW wrote: "So Artsci should help him (KC5CQA)." 50-watt radios will talk with plenty of exess fade margin over any line-of-sight path from a 100-foot tower to any land mobile in the two-meter band. Beyond line-of-sight, VHF propagation is kaput because the signal does not follow earth curvature as Reg`s low and medium frequencies do. Over smooth earth or sea, the horizon is sq rt of 200 from a 100-foot high antenna. That is about 14 miles. Add 4 or 5 miles of range due to the mobile antenna height and that is near the maximum range. 5 watts, 100 watts, or 500 watts make very little difference in range. Range is extended with increased power very slightly. There is some noise reduction. In my experience, I found it advantageous to use 50-watt mobiles and 500-watt base stations. This is because the mobile is often in a noisier environment than the base station. Obviously the path length is the same in both directions in this VHF application. The dominant requirement in VHF communication is a line-of-sight path. Once that is obtained, all else is secondary. Most of the microwave stations I`ve put in have 100-milliwatt transmitters and these produced 30 dB fade margins on paths of more than 20 miles. For land mobile VHF service, you usually have no significant antenna gains, but you also have significantly lower path and transmission line losses, higher receiver sensitivities, and higher transmitter powers. Received carrier power to produce full quieting in a good receiver is very small indeed. This makes line-of-sight the only significant requirement for single-channel, single-hop VHF communications. Noise is cumulative, so for a multi-hop system, big signal surplus is required on each hop to supress noise to make the cumulative total acceptable. Best regards, Richard Harrison, KB5WZI |
Tam, WB2TT wrote:
"There is almost always some kind of enhanced propagation." True. It is also true that a 10-element beam and high power extend transmission range. Terman has eqn. (22-7b) on page 820 of his 1955 edition: "Radio horizon distance in miles = sq rt 2h Again, h is in feet." Terman also says: "In the special case of the standard atmosphere, k = 1.33 and the horizon distance becomes, miles = sq rt 2h." 1.33 means the earth`s radius appears as 4/3 the actual value.due to atmosphere causing the radio horizon to be more distant than the optical horizon. On page 825, Terman says: "Fading is most pronounced when the received signal is much weaker than the free-space value for the distance involved. Thus fading is usually greatest near the radio horizon and in the shadow zone, and tends to be small when a "good" optical path is present." My experience agrees with Terman. We all know that VHF propagation does not always follow the simple rules. My contention is that path clearance outshines other considerations in determining "How far can an antenna see?". Terman`s eqn. (22-7b) is the usual answer. Best regards, Richard Harrison, KB5WZI |
O.K. CAN YOU HEAR ME NOW ?
"Tarmo Tammaru" wrote in message ... There is almost always some kind of enhanced propagation. With 50W SSB to a 10 element 2 meter beam at 40 feet, 90% of the time my range is 75 - 100 miles when talking to another base station. I don't think they all have 1000 foot towers. Tam/WB2TT "Richard Harrison" wrote in message ... K1YW wrote: "So Artsci should help him (KC5CQA)." 50-watt radios will talk with plenty of exess fade margin over any line-of-sight path from a 100-foot tower to any land mobile in the two-meter band. Beyond line-of-sight, VHF propagation is kaput because the signal does not follow earth curvature as Reg`s low and medium frequencies do. Over smooth earth or sea, the horizon is sq rt of 200 from a 100-foot high antenna. That is about 14 miles. Add 4 or 5 miles of range due to the mobile antenna height and that is near the maximum range. 5 watts, 100 watts, or 500 watts make very little difference in range. Range is extended with increased power very slightly. There is some noise reduction. In my experience, I found it advantageous to use 50-watt mobiles and 500-watt base stations. This is because the mobile is often in a noisier environment than the base station. Obviously the path length is the same in both directions in this VHF application. The dominant requirement in VHF communication is a line-of-sight path. Once that is obtained, all else is secondary. Most of the microwave stations I`ve put in have 100-milliwatt transmitters and these produced 30 dB fade margins on paths of more than 20 miles. For land mobile VHF service, you usually have no significant antenna gains, but you also have significantly lower path and transmission line losses, higher receiver sensitivities, and higher transmitter powers. Received carrier power to produce full quieting in a good receiver is very small indeed. This makes line-of-sight the only significant requirement for single-channel, single-hop VHF communications. Noise is cumulative, so for a multi-hop system, big signal surplus is required on each hop to supress noise to make the cumulative total acceptable. Best regards, Richard Harrison, KB5WZI |
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