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VHF Marine Radio Communication
Readers may find this article of interest:
VHF Marine Radio Communication http://continuouswave.com/whaler/reference/VHF.html |
In article ,
James Hebert wrote: http://continuouswave.com/whaler/reference/VHF.html I find your math to be very good, but your conclusions don't track very well with REAL World experience. Bruce in alaska -- add a 2 before @ |
Would you care to be more specific?
"Bruce in Alaska" wrote in message ... In article , James Hebert wrote: http://continuouswave.com/whaler/reference/VHF.html I find your math to be very good, but your conclusions don't track very well with REAL World experience. Bruce in alaska -- add a 2 before @ |
On Sun, 9 Jan 2005 07:47:25 -0800, "Chuck Tribolet"
wrote: Would you care to be more specific? "Bruce in Alaska" wrote in message ... In article , James Hebert wrote: http://continuouswave.com/whaler/reference/VHF.html I find your math to be very good, but your conclusions don't track very well with REAL World experience. off the top of my head, looking at the article, i think there's an error. he says EACH antenna needs to be 12.4 feet above the surface, but i think the SUM of the antenna heights needs to be this...IOW each antenna needs to be 6.2 feet high. --------------------------- to see who "wf3h" is, go to "qrz.com" and enter 'wf3h' in the field |
On Sun, 09 Jan 2005 23:52:46 -0500, James Hebert
wrote: In article , (Bob) wrote: off the top of my head, looking at the article, i think there's an error. he says EACH antenna needs to be 12.4 feet above the surface, but i think the SUM of the antenna heights needs to be this...IOW each antenna needs to be 6.2 feet high. --------------------------- to see who "wf3h" is, go to "qrz.com" and enter 'wf3h' in the field If two vessels are ten miles apart, they will each need antennas 12.4 feet high in order for their radio horizons to be in view (line-of-sight) of each other. why is that? the equation sez 12.4 feet for antenna height. does that mean 1 antenna could be on the ground and the other at 12.4 feet? --------------------------- to see who "wf3h" is, go to "qrz.com" and enter 'wf3h' in the field |
In article ,
James Hebert wrote: If two vessels are ten miles apart, they will each need antennas 12.4 feet high in order for their radio horizons to be in view (line-of-sight) of each other. The case presented shows how much margin there is in a typical circuit. There are many poor radio installations aboard recreational vessels which can barely talk to the marina office from its dock own gas dock, but this does not constitute a negation of laws of physics. this is where the Practical and empirical evidence shows that the math isn't showing what really is hapopeneing. I have two 1 watt Vhf handhelds, with rubber antennas. I can talk 16 miles over water with these two radios. Both myself and my wife are less than 6.5 ft tall. We are both standing at sealevel. (water lapping at our feet) Now how does you MATH explain this empirical DATA? Do my handhelds have receive sensitivity lower than atmospheric noise? Maybe the Laws of Physics cease to apply north of 58 degrees? Since this is a perfectly viable Path 24/7 and we have used it daily for the last 15 years, what is your explanation? Me who actually does know the answer......... |
"Me" wrote in message
... this is where the Practical and empirical evidence shows that the math isn't showing what really is hapopeneing. I have two 1 watt Vhf handhelds, with rubber antennas. I can talk 16 miles over water with these two radios. Both myself and my wife are less than 6.5 ft tall. We are both standing at sealevel. (water lapping at our feet) Now how does you MATH explain this empirical DATA? VHF waves tend to follow the curvature of the earth slightly (just like light diffracts around sharp corners), which indeed gives you more range than the maths tells you. Meindert |
Sealevel is not a word. If you mean sea level, that does not equate to
"water lapping at our feet". If you are claiming a 16 mile range, direct, when you are both at 6.5 feet above sea level, I say your full of crap. If this is a riddle, then I say your both at a seperate body of water with a valley between, or your communicating via a repeater. Eric "Me" wrote in message ... In article , James Hebert wrote: If two vessels are ten miles apart, they will each need antennas 12.4 feet high in order for their radio horizons to be in view (line-of-sight) of each other. The case presented shows how much margin there is in a typical circuit. There are many poor radio installations aboard recreational vessels which can barely talk to the marina office from its dock own gas dock, but this does not constitute a negation of laws of physics. this is where the Practical and empirical evidence shows that the math isn't showing what really is hapopeneing. I have two 1 watt Vhf handhelds, with rubber antennas. I can talk 16 miles over water with these two radios. Both myself and my wife are less than 6.5 ft tall. We are both standing at sealevel. (water lapping at our feet) Now how does you MATH explain this empirical DATA? Do my handhelds have receive sensitivity lower than atmospheric noise? Maybe the Laws of Physics cease to apply north of 58 degrees? Since this is a perfectly viable Path 24/7 and we have used it daily for the last 15 years, what is your explanation? Me who actually does know the answer......... |
On Mon, 10 Jan 2005 17:38:06 GMT, (Bob) wrote:
On Sun, 09 Jan 2005 23:52:46 -0500, James Hebert wrote: In article , (Bob) wrote: off the top of my head, looking at the article, i think there's an error. he says EACH antenna needs to be 12.4 feet above the surface, but i think the SUM of the antenna heights needs to be this...IOW each antenna needs to be 6.2 feet high. --------------------------- to see who "wf3h" is, go to "qrz.com" and enter 'wf3h' in the field If two vessels are ten miles apart, they will each need antennas 12.4 feet high in order for their radio horizons to be in view (line-of-sight) of each other. why is that? the equation sez 12.4 feet for antenna height. does that mean 1 antenna could be on the ground and the other at 12.4 feet? --------------------------- to see who "wf3h" is, go to "qrz.com" and enter 'wf3h' in the field It means that the horizon is halfway between. If one antenna was at sea level and the other at 12.4 feet you would only talk half the distance. Regards Gary |
In article ,
"Meindert Sprang" wrote: "Me" wrote in message ... this is where the Practical and empirical evidence shows that the math isn't showing what really is hapopeneing. I have two 1 watt Vhf handhelds, with rubber antennas. I can talk 16 miles over water with these two radios. Both myself and my wife are less than 6.5 ft tall. We are both standing at sealevel. (water lapping at our feet) Now how does you MATH explain this empirical DATA? VHF waves tend to follow the curvature of the earth slightly (just like light diffracts around sharp corners), which indeed gives you more range than the maths tells you. Meindert Yes, Meindert (the engineer) come up with the answer. Vhf does indeed extend beyond Line of Sight, in all cases, and your math does not take this into account. The straight that I live on, is 16 Statute Miles wide, and my wife stands on one side, at the end of a road, at a boat ramp, and I stand on the other side, in front of my cabin, on the beach. Both our feet, are being lapped at by the water, at exactly Sea Level, at that moment, and YES, we do communicate with one watt, Motorola handheld radios with rubber antennas, and have for the last 15 years. You made a BAD Assumption, when you stated that VHF (156Mhz) RF Propigation was only Line of Sight. This is the downfall of your whole construction. When you have as many years as I have in RF Communications, you should, by then, have a better understanding of the basic Laws of Physics, that underpin the technology that your espousing. Me who knows the difference between Theory and Practice.... |
On Tue, 11 Jan 2005 20:12:43 GMT, Me wrote:
In article , "Meindert Sprang" wrote: "Me" wrote in message ... this is where the Practical and empirical evidence shows that the math isn't showing what really is hapopeneing. I have two 1 watt Vhf handhelds, with rubber antennas. I can talk 16 miles over water with these two radios. Both myself and my wife are less than 6.5 ft tall. We are both standing at sealevel. (water lapping at our feet) Now how does you MATH explain this empirical DATA? VHF waves tend to follow the curvature of the earth slightly (just like light diffracts around sharp corners), which indeed gives you more range than the maths tells you. Meindert Yes, Meindert (the engineer) come up with the answer. Vhf does indeed extend beyond Line of Sight, in all cases, and your math does not take this into account. The straight that I live on, is 16 Statute Miles wide, and my wife stands on one side, at the end of a road, at a boat ramp, and I stand on the other side, in front of my cabin, on the beach. Both our feet, are being lapped at by the water, at exactly Sea Level, at that moment, and YES, we do communicate with one watt, Motorola handheld radios with rubber antennas, and have for the last 15 years. You made a BAD Assumption, when you stated that VHF (156Mhz) RF Propigation was only Line of Sight. This is the downfall of your whole construction. When you have as many years as I have in RF Communications, you should, by then, have a better understanding of the basic Laws of Physics, that underpin the technology that your espousing. Me who knows the difference between Theory and Practice.... The old saying by the Motorola salesman selling low band radios to the farmers was "100 watts goes 100 miles". It would do that on many days but you dare not design a system around those figures. Regards Gary |
Salesman's name was P.T. Barnum as I recall :)
"Gary Schafer" wrote in message ... On Tue, 11 Jan 2005 20:12:43 GMT, Me wrote: In article , "Meindert Sprang" wrote: "Me" wrote in message ... this is where the Practical and empirical evidence shows that the math isn't showing what really is hapopeneing. I have two 1 watt Vhf handhelds, with rubber antennas. I can talk 16 miles over water with these two radios. Both myself and my wife are less than 6.5 ft tall. We are both standing at sealevel. (water lapping at our feet) Now how does you MATH explain this empirical DATA? VHF waves tend to follow the curvature of the earth slightly (just like light diffracts around sharp corners), which indeed gives you more range than the maths tells you. Meindert Yes, Meindert (the engineer) come up with the answer. Vhf does indeed extend beyond Line of Sight, in all cases, and your math does not take this into account. The straight that I live on, is 16 Statute Miles wide, and my wife stands on one side, at the end of a road, at a boat ramp, and I stand on the other side, in front of my cabin, on the beach. Both our feet, are being lapped at by the water, at exactly Sea Level, at that moment, and YES, we do communicate with one watt, Motorola handheld radios with rubber antennas, and have for the last 15 years. You made a BAD Assumption, when you stated that VHF (156Mhz) RF Propigation was only Line of Sight. This is the downfall of your whole construction. When you have as many years as I have in RF Communications, you should, by then, have a better understanding of the basic Laws of Physics, that underpin the technology that your espousing. Me who knows the difference between Theory and Practice.... The old saying by the Motorola salesman selling low band radios to the farmers was "100 watts goes 100 miles". It would do that on many days but you dare not design a system around those figures. Regards Gary |
On Tue, 11 Jan 2005 20:12:43 GMT, Me wrote:
In article , "Meindert Sprang" wrote: "Me" wrote in message ... this is where the Practical and empirical evidence shows that the math isn't showing what really is hapopeneing. I have two 1 watt Vhf handhelds, with rubber antennas. I can talk 16 miles over water with these two radios. Both myself and my wife are less than 6.5 ft tall. We are both standing at sealevel. (water lapping at our feet) Now how does you MATH explain this empirical DATA? VHF waves tend to follow the curvature of the earth slightly (just like light diffracts around sharp corners), which indeed gives you more range than the maths tells you. Meindert Yes, Meindert (the engineer) come up with the answer. Vhf does indeed extend beyond Line of Sight, in all cases, and your math does not take this into account. The straight that I live on, is 16 Statute Miles wide, and my wife stands on one side, at the end of a road, at a boat ramp, and I stand on the other side, in front of my cabin, on the beach. Both our feet, are being lapped at by the water, at exactly Sea Level, at that moment, and YES, we do communicate with one watt, Motorola handheld radios with rubber antennas, and have for the last 15 years. You made a BAD Assumption, when you stated that VHF (156Mhz) RF Propigation was only Line of Sight. This is the downfall of your whole construction. When you have as many years as I have in RF Communications, you should, by then, have a better understanding of the basic Laws of Physics, that underpin the technology that your espousing. Me who knows the difference between Theory and Practice.... By the way, the difference between radio line of sight and optical line of sight at 5 miles is only about .7 miles at that distance. The factor to multiply the height of the antenna by is about 1.33 for radio over optical. The difference is not great. There are phenomenon's such as ducting that take place on a regular basis over some radio paths. Usually not over 24 hours though. I can assure you that I can show you many places where hand held to hand held will not produce anywhere near 16 miles of range even over water but on rare occasions. Regards Gary |
In article ,
James Hebert wrote: Readers may find this article of interest: VHF Marine Radio Communication http://continuouswave.com/whaler/reference/VHF.html There seems to be some confusion regarding the calculation for radio horizon. I am afraid I did not collect anecdotal reports from anonymous USENET contributors, but instead relied on other sources. Cf.: definition of radio horizon: http://amsglossary.allenpress.com/gl...radio-horizon1 |
"James Hebert" wrote VHF Marine Radio Communication http://continuouswave.com/whaler/reference/VHF.html There seems to be some confusion regarding the calculation for radio horizon. I am afraid I did not collect anecdotal reports from anonymous USENET contributors, but instead relied on other sources. Cf.: definition of radio horizon: http://amsglossary.allenpress.com/gl...radio-horizon1 James, don't confuse 1w-rubber-duck man (anonymous "me" contributor) with logic. Heck, after reading his story, I may pull down my antenna and replace it with a rubber-duck. After all, I only get 20-25 miles reliable range to surface craft from a 60' amsl antenna w/25w! This might have something to do with small craft's antenna rocking through an arc of 60 degrees at the entrance to the Chesapeake Bay! Tropospheric Ducting is a real problem with VHF-Marine. While Bruce has some interesting stories to tell about making use of that up North, we normally find it a real hindrance to good communications in the mid-Atlantic. Having five or more CG Groups trying to answer the same mayday, and hearing traffic from a hundred or more miles up and down the coast is not a good thing for vhf-marine radio. see http://home.cogeco.ca/~dxinfo/tropo.html for ducting forecasts Jack Painter Virginia Beach, Virginia |
On Wed, 12 Jan 2005 01:43:12 -0500, "Jack Painter"
wrote: Tropospheric Ducting is a real problem with VHF-Marine. yes, as a ham i once talked from allentown, PA to n. carolina on VHF FM in the ham bands. While Bruce has some interesting stories to tell about making use of that up North, we normally find it a real hindrance to good communications in the mid-Atlantic. Having five or more CG Groups trying to answer the same mayday, yes, we CG radio operators try to avoid that situation but it's sometimes inevitable. what's even worse is that we sometimes don't respond to a mayday, assuming it's in some other CG AOR. --------------------------- to see who "wf3h" is, go to "qrz.com" and enter 'wf3h' in the field |
My turn for a radio sea story.
I was on Barter Island...north slope of Alaska near the Canada border (Kaktovik), when we had a three day RF 'event'. Whereas we generally could communicate with over-the-pole aircraft at ranges of 200 miles, we suddnely couldn't talk to them until they were just about overhead. Our radar also suddenly started painting the fuel tanks of the next DEW site west...but we couldn't see aircraft 50 miles away. Talk about refraction! Just for the record, I'm an RF guy too...I worked for a few years doing path studies, with all the measuring gear to confirm theory. The end results? On average, the math worked...but there were days it didn't. The more marginal the predictions (in terms of range), the more it varied from day-to-day. The folks paricipating in this thread suggesting that the physical/optical model of the earth is not the same as the RF model are right on. 4/3K ring a bell? Cranky tonight Norm B On Wed, 12 Jan 2005 22:51:00 GMT, (Bob) wrote: On Wed, 12 Jan 2005 01:43:12 -0500, "Jack Painter" wrote: Tropospheric Ducting is a real problem with VHF-Marine. yes, as a ham i once talked from allentown, PA to n. carolina on VHF FM in the ham bands. While Bruce has some interesting stories to tell about making use of that up North, we normally find it a real hindrance to good communications in the mid-Atlantic. Having five or more CG Groups trying to answer the same mayday, yes, we CG radio operators try to avoid that situation but it's sometimes inevitable. what's even worse is that we sometimes don't respond to a mayday, assuming it's in some other CG AOR. --------------------------- to see who "wf3h" is, go to "qrz.com" and enter 'wf3h' in the field |
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