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Teaser Answer: It's a dipole antenna, 22-feet long

The other day I ran a teaser (actually a trainer, too) for many of the new hams who recently obtained their licenses and it had to do with antennas.

The point is not whether you can actually do the math or make the antenna (we'll show you how later), but the point was simple to note the importance of antennas in the Ham Radio hobby.

Learned from Elmers

As I learned about a billion years ago when I got my ticket (a lesson taught me by my Elmers – hams who help others and I guess I'm an online Elmer – WA1UEH (SK) and WA1IGL (SK) – antennas are, next to radios, of course, the most important part of any station and it is best to run your station into a resonant antenna.

A resonant antenna is one that is made for a specific frequency and where all parts are in balance. Think of it like the tinkling of a fine bell. If you want a specific note, it has to be made for that note so the bell is resonant at a frequency. The same is true of an antenna.

A resonant antenna means:

  • You do not have to purchase or build an expensive transmatch right away

  • You can attach your radio directly to the antenna with no fear of damage

  • You are on he air quickly.

And it is also the answer to the teaser.

So what are the answers to the teaser (It's actually a multi-part)?is the answer:

  1. How much wire do you need for a 15-meter antenna. Let's see, a meter is about 39.37 inches long so you would multiply 39.37 inches (3.308 feet) times 15 which comes out to 49.625 feet for a full wavelength, but that antenna won't be resonant and you will need a transmatch. However, if you were to slice the antenna in half, it would be a resonant half-wavelength (antennas are funny about that unless you being to change their configuration. If you made this full-wave antenna into a loop, it would be resonant, but this isn't germane right now, so let's just leave the wire straight and it will hear very well in the direction it is stretched, but won't do too well off that particular line, although some would say it hears best off the end and well off to each side.

  2. Leaving the resonant full-wave loop aside, let's see how you make a resonant dipole antenna. A resonant dipole antenna would, if the wire were stretched from the left side of this page to the right hear well coming out of the screen and going out the back of your computer screen. To make a resonant dipole or a one-half wave antenna which is also called self-resonating, you need a simple formula: ant length=468/frequency of operation.:

Or, to put it another way, let's say you want to operate at 21.250. If you did, your antenna would be 468/21.250 or 22.02 feet. To make this antenna work work correctly, you would need one more math move, you would have to split the 22.02 into 2 11-foot lengths of wire to which you can directly attach your antenna feedline and put it right into the back of your transceiver. It might need a bit of trimming and the purists would tell you need a balun, but you really can just attach your coaxial feedline and start working.

This is the basic self-resonant antenna we have been working with thanks to the folks at www.radio-electronics.com from whom we borrowed the image. Note three key items:

  1. The feedline (coaxial cable) is directly attached to each half of the antenna

  2. The voltage minima is at the center point of the antenna

  3. The current maxima is at the center point of the antenna

In other words it is in resonance. Next time, we'll show you how to make an antenna with a slideshow.

The other day I ran a teaser (actually a trainer, too) for many of the new hams who recently obtained their licenses and it had to do with antennas.

The point is not whether you can actually do the math or make the antenna (we'll show you how later), but the point was simple to note the importance of antennas in the Ham Radio hobby.

Learned from Elmers

As I learned about a billion years ago when I got my ticket (a lesson taught me by my Elmers – hams who help others and I guess I'm an online Elmer – WA1UEH (SK) and WA1IGL (SK) – antennas are, next to radios, of course, the most important part of any station and it is best to run your station into a resonant antenna.

A resonant antenna is one that is made for a specific frequency and where all parts are in balance. Think of it like the tinkling of a fine bell. If you want a specific note, it has to be made for that note so the bell is resonant at a frequency. The same is true of an antenna.

A resonant antenna means:

  • You do not have to purchase or build an expensive transmatch right away

  • You can attach your radio directly to the antenna with no fear of damage

  • You are on he air quickly.

And it is also the answer to the teaser.

So what are the answers to the teaser (It's actually a multi-part)?is the answer:

  1. How much wire do you need for a 15-meter antenna. Let's see, a meter is about 39.37 inches long so you would multiply 39.37 inches (3.308 feet) times 15 which comes out to 49.625 feet for a full wavelength, but that antenna won't be resonant and you will need a transmatch. However, if you were to slice the antenna in half, it would be a resonant half-wavelength (antennas are funny about that unless you being to change their configuration. If you made this full-wave antenna into a loop, it would be resonant, but this isn't germane right now, so let's just leave the wire straight and it will hear very well in the direction it is stretched, but won't do too well off that particular line, although some would say it hears best off the end and well off to each side.

  2. Leaving the resonant full-wave loop aside, let's see how you make a resonant dipole antenna. A resonant dipole antenna would, if the wire were stretched from the left side of this page to the right hear well coming out of the screen and going out the back of your computer screen. To make a resonant dipole or a one-half wave antenna which is also called self-resonating, you need a simple formula: ant length=468/frequency of operation.:

Or, to put it another way, let's say you want to operate at 21.250. If you did, your antenna would be 468/21.250 or 22.02 feet. To make this antenna work work correctly, you would need one more math move, you would have to split the 22.02 into 2 11-foot lengths of wire to which you can directly attach your antenna feedline and put it right into the back of your transceiver. It might need a bit of trimming and the purists would tell you need a balun, but you really can just attach your coaxial feedline and start working.

This is the basic self-resonant antenna we have been working with thanks to the folks at www.radio-electronics.com from whom we borrowed the image. Note three key items:

  1. The feedline (coaxial cable) is directly attached to each half of the antenna

  2. The voltage minima is at the center point of the antenna

  3. The current maxima is at the center point of the antenna

In other words it is in resonance. Next time, we'll show you how to make an antenna with a slideshow.

The other day I ran a teaser (actually a trainer, too) for many of the new hams who recently obtained their licenses and it had to do with antennas.

The point is not whether you can actually do the math or make the antenna (we'll show you how later), but the point was simple to note the importance of antennas in the Ham Radio hobby.

Learned from Elmers

As I learned about a billion years ago when I got my ticket (a lesson taught me by my Elmers – hams who help others and I guess I'm an online Elmer – WA1UEH (SK) and WA1IGL (SK) – antennas are, next to radios, of course, the most important part of any station and it is best to run your station into a resonant antenna.

A resonant antenna is one that is made for a specific frequency and where all parts are in balance. Think of it like the tinkling of a fine bell. If you want a specific note, it has to be made for that note so the bell is resonant at a frequency. The same is true of an antenna.

A resonant antenna means:

  • You do not have to purchase or build an expensive transmatch right away

  • You can attach your radio directly to the antenna with no fear of damage

  • You are on he air quickly.

And it is also the answer to the teaser.

So what are the answers to the teaser (It's actually a multi-part)?is the answer:

  1. How much wire do you need for a 15-meter antenna. Let's see, a meter is about 39.37 inches long so you would multiply 39.37 inches (3.308 feet) times 15 which comes out to 49.625 feet for a full wavelength, but that antenna won't be resonant and you will need a transmatch. However, if you were to slice the antenna in half, it would be a resonant half-wavelength (antennas are funny about that unless you being to change their configuration. If you made this full-wave antenna into a loop, it would be resonant, but this isn't germane right now, so let's just leave the wire straight and it will hear very well in the direction it is stretched, but won't do too well off that particular line, although some would say it hears best off the end and well off to each side.

  2. Leaving the resonant full-wave loop aside, let's see how you make a resonant dipole antenna. A resonant dipole antenna would, if the wire were stretched from the left side of this page to the right hear well coming out of the screen and going out the back of your computer screen. To make a resonant dipole or a one-half wave antenna which is also called self-resonating, you need a simple formula: ant length=468/frequency of operation.:

Or, to put it another way, let's say you want to operate at 21.250. If you did, your antenna would be 468/21.250 or 22.02 feet. To make this antenna work work correctly, you would need one more math move, you would have to split the 22.02 into 2 11-foot lengths of wire to which you can directly attach your antenna feedline and put it right into the back of your transceiver. It might need a bit of trimming and the purists would tell you need a balun, but you really can just attach your coaxial feedline and start working.

This is the basic self-resonant antenna we have been working with thanks to the folks at www.radio-electronics.com from whom we borrowed the image. Note three key items:

  1. The feedline (coaxial cable) is directly attached to each half of the antenna

  2. The voltage minima is at the center point of the antenna

  3. The current maxima is at the center point of the antenna

In other words it is in resonance. Next time, we'll show you how to make an antenna with a slideshow.

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