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| howto:hambasics:sections:hfops [2020/10/07 08:07] – va7fi | howto:hambasics:sections:hfops [2021/12/27 21:49] (current) – ↷ Links adapted because of a move operation va7fi |
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| On HF, if other operators are using the designated net frequency just before the start of the net, the net controller can ask them to relinquish the frequency for the net operations. Although they should move to a different frequency as a courtesy, they are not obliged to. In this case the net controller should conduct the net on a frequency 3 to 5 kHz away from the regular frequency so that regular net participant can easily find the net without causing interference to the others using the regular net frequency. | On HF, if other operators are using the designated net frequency just before the start of the net, the net controller can ask them to relinquish the frequency for the net operations. Although they should move to a different frequency as a courtesy, they are not obliged to. In this case the net controller should conduct the net on a frequency 3 to 5 kHz away from the regular frequency so that regular net participant can easily find the net without causing interference to the others using the regular net frequency. |
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| See our [[/nets#other_nets |Nets page]] for more details. | See our [[nets:home#other_nets|Nets page]] for more details. |
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| ====== Morse ====== | ====== Morse ====== |
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| Looking at a map, it looks like the answer would be to fly roughly due East along the 49th parallel, over Canada, across the Atlantic Ocean, and over Europe: | Looking at a map, it looks like the answer would be to fly roughly due East along the 49th parallel, over Canada, across the Atlantic Ocean, and over Europe: |
| {{ ..:vantoiran1.png }} | {{ vantoiran1.png }} |
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| Or would it be to go West instead, across the Pacific Ocean and over China? | Or would it be to go West instead, across the Pacific Ocean and over China? |
| {{ ..:vantoiran2.png?750 }} | {{ vantoiran2.png?750 }} |
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| Well, it turns out that neither is right. The shortest path is over the north pole: | Well, it turns out that neither is right. The shortest path is over the north pole: |
| {{ ..:vantoiran3.jpg }} | {{ vantoiran3.jpg }} |
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| Drawing a straight line on a "conventional" map usually results in an actual path that curves and is longer than it could be. For example, if you flew due East along the 49th parallel, you'd need to be turning left a little bit all the time to stay at the same latitude. This may seem like a weird idea, but supposed that you were right at the North Pole. If you moved off a bit and walked circles around the North Pole flag, you'd be walking on one latitude line (probably like 89.99999º or something). But the point is that unless you're at the equator, following one latitude line due East or West means that you have to be turning (left if going East and right if going west). So you're not going in a straight line((On a sphere, a "straight line" is called a //geodesic// and it's always along a [[wp>Great_circle |great circle]])). The converse is also true: a real straight line will have to be drawn like a curve on a "conventional" map unless it's right on the equator or going in the north-south direction. | Drawing a straight line on a "conventional" map usually results in an actual path that curves and is longer than it could be. For example, if you flew due East along the 49th parallel, you'd need to be turning left a little bit all the time to stay at the same latitude. This may seem like a weird idea, but supposed that you were right at the North Pole. If you moved off a bit and walked circles around the North Pole flag, you'd be walking on one latitude line (probably like 89.99999º or something). But the point is that unless you're at the equator, following one latitude line due East or West means that you have to be turning (left if going East and right if going west). So you're not going in a straight line((On a sphere, a "straight line" is called a //geodesic// and it's always along a [[wp>Great_circle |great circle]])). The converse is also true: a real straight line will have to be drawn like a curve on a "conventional" map unless it's right on the equator or going in the north-south direction. |
| * Once the geodesic is drawn, you can move either end to see how the path changes. | * Once the geodesic is drawn, you can move either end to see how the path changes. |
| Notice how North-South paths appear straight, but not East-West paths)): | Notice how North-South paths appear straight, but not East-West paths)): |
| {{ ..:vantoiran4.png }} | {{ vantoiran4.png }} |
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| For ham operators, being able to find the shortest straight line between two points on Earth is important because radio waves travel in straight lines. Sure, they bounce, reflect and refract, but they don't just turn left to follow a latitude line. So if you want to know where to point your antenna to reach a specific region, a conventional map won't be much help. Instead, we use what's called an Azimuthal map. | For ham operators, being able to find the shortest straight line between two points on Earth is important because radio waves travel in straight lines. Sure, they bounce, reflect and refract, but they don't just turn left to follow a latitude line. So if you want to know where to point your antenna to reach a specific region, a conventional map won't be much help. Instead, we use what's called an Azimuthal map. |
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| For example, here's one centred on Vancouver showing that the shortest straight line to the Caspian Sea has a bearing of 5° East of North. That's where you'd need to point your antenna if you wanted to talk to someone there: | For example, here's one centred on Vancouver showing that the shortest straight line to the Caspian Sea has a bearing of 5° East of North. That's where you'd need to point your antenna if you wanted to talk to someone there: |
| {{ ..:vantoiran5.png?750 }} | {{ vantoiran5.png?750 }} |
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| Here are a few important things to know about Azimuthal maps: | Here are a few important things to know about Azimuthal maps: |
| * But more importantly: there is NO //one// Azimuthal map. Instead, everyone needs their own with their location at the centre. These maps only work from the centre outward. You can't use these maps to find the distance and direction between two off-centre points. This is one case where putting yourself at the centre of the world is necessary. | * But more importantly: there is NO //one// Azimuthal map. Instead, everyone needs their own with their location at the centre. These maps only work from the centre outward. You can't use these maps to find the distance and direction between two off-centre points. This is one case where putting yourself at the centre of the world is necessary. |
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| <WRAP round tip box center 80%> Here's a really convenient [[https://ns6t.net/azimuth/azimuth.html |online tool]] to create your own map.</WRAP> | <WRAP round tip box center 80%> |
| | * Here's a really convenient [[https://ns6t.net/azimuth/azimuth.html |online tool]] to create your own map. |
| | * And here's a [[howto/hambasics/azimuthal |few tricks]] on how to use the tool. |
| | </WRAP> |
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| <wrap info>Fun fact</wrap>: the United Nations flag is an Azimuthal map centred on the North Pole. | <wrap info>Fun fact</wrap>: the United Nations flag is an Azimuthal map centred on the North Pole. |
| {{ ..:un.png }} | {{ un.png }} |
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| ====== Short / Long Path ====== | ====== Short / Long Path ====== |
