http://www.worldwidedx.com/cb-antennas/39765-antenna-basics-part-1-a.html
Antenna Basics: Part 2
Chances are - that if you are new to this hobby or are considering it - you will probably just buy your first antenna - than build one. Which is quite understandable. Although antennas can be simple, there are also some of 'bewares' involved to get it right when "rolling your own". I'm not saying that you can't. In fact; if you are the kind of person that likes to learn and spend very little money in brewing your own - here are a couple of YouTube videos you can watch.
This first video is using scrap wire and scrap material:
YouTube - Make An 11 meter dipole (Short)
I wouldn't use multi-core wire; just any 14 ga wire will do. Of course you will need a coax connector; but that can be found at an electronics surplus store or out of a radio that is no longer usable. I would also use thicker plastic than he used as well...
This next video used old aluminum tent poles. It uses the SAME principles as the wire dipole in the first video; but the use of the aluminum makes it easier to mount permanently when at home. I would warn NOT to use a metal stand as he did; better to use cheap PVC pipe and put it up about 10-13 ft off of the ground too. But I still I like this one best:
YouTube - home made portable 10-11meter antenna
Dipole antennas are generally used horizontally. There is an important difference between verticals and horizontal antennas. This video will help demonstrate. Watch as the dipole that is being held changes as it is turned from horizontal to vertical. The light will dim, because the transmitting antenna is set horizontally - while the receiving dipole is being moved. Dipoles will work for the most part with other dipole antennas. Vertical antennas don't receive them as well - and vice-versa. That is the point of this video produced by MIT:
YouTube - MIT Physics Demo -- Dipole Antenna
In addition to ANY antenna setup; one must acquire a cheap SWR meter and learn how to use it. This following link is an excellent explination and will show you what must be done. Be patient; you will need to learn this point well if you are considering this hobby!
Here is how:
SWR
What a SWR meter will be able to tell you if the antenna has the right resistance/'impedance' when transmitting. To make sure that the radio doesn't burn up due an improper match; one needs to use the SWR meter and adjust the antenna so that a 1.1 to 1.5 SWR is attained. Better to adjust for 1.1 SWR - if it will adjust that close. This will ensure that you are matching the radio's need to see 50 ohms impedance. So, the antenna will need to be as close as 50 ohms as possible to ensure this 1.1 to 1 match. Impedance is not the same as resistance. Resistance is measured in DC current; while impedance is measured by AC current. Radio transmissions are AC; so any antenna will show either no resistance or infinity resistance when using an ohm meter. If you are going to buy an antenna - you will only need to have an SWR meter to set it up properly.
Antenna resonance and resistance aren't necessarily related to each other. Resonance is the frequency on which the antenna will have the most power output flow from the radio due to its selected length. This is accomplished already if you have purchased an antenna. But if you build your own, it will take a field strength meter to determine at what frequencies the home built antenna is most resonant. Not something for a beginner to do; but not so hard to do if you understand what you are trying to accomplish either.
http://www.cbtricks.com/members/toban/swrset.htm
This article is meant for the beginner...
Any questions?
Please feel free to join - and ask away!
Antenna Basics; Part 3 - tomorrow "Choosing an Antenna"
http://www.worldwidedx.com/cb-anten...io-radio-antenna-basics-choosing-antenna.html
Antenna Basics: Part 2
Chances are - that if you are new to this hobby or are considering it - you will probably just buy your first antenna - than build one. Which is quite understandable. Although antennas can be simple, there are also some of 'bewares' involved to get it right when "rolling your own". I'm not saying that you can't. In fact; if you are the kind of person that likes to learn and spend very little money in brewing your own - here are a couple of YouTube videos you can watch.
This first video is using scrap wire and scrap material:
YouTube - Make An 11 meter dipole (Short)
I wouldn't use multi-core wire; just any 14 ga wire will do. Of course you will need a coax connector; but that can be found at an electronics surplus store or out of a radio that is no longer usable. I would also use thicker plastic than he used as well...
This next video used old aluminum tent poles. It uses the SAME principles as the wire dipole in the first video; but the use of the aluminum makes it easier to mount permanently when at home. I would warn NOT to use a metal stand as he did; better to use cheap PVC pipe and put it up about 10-13 ft off of the ground too. But I still I like this one best:
YouTube - home made portable 10-11meter antenna
Dipole antennas are generally used horizontally. There is an important difference between verticals and horizontal antennas. This video will help demonstrate. Watch as the dipole that is being held changes as it is turned from horizontal to vertical. The light will dim, because the transmitting antenna is set horizontally - while the receiving dipole is being moved. Dipoles will work for the most part with other dipole antennas. Vertical antennas don't receive them as well - and vice-versa. That is the point of this video produced by MIT:
YouTube - MIT Physics Demo -- Dipole Antenna
In addition to ANY antenna setup; one must acquire a cheap SWR meter and learn how to use it. This following link is an excellent explination and will show you what must be done. Be patient; you will need to learn this point well if you are considering this hobby!
Here is how:
SWR
What a SWR meter will be able to tell you if the antenna has the right resistance/'impedance' when transmitting. To make sure that the radio doesn't burn up due an improper match; one needs to use the SWR meter and adjust the antenna so that a 1.1 to 1.5 SWR is attained. Better to adjust for 1.1 SWR - if it will adjust that close. This will ensure that you are matching the radio's need to see 50 ohms impedance. So, the antenna will need to be as close as 50 ohms as possible to ensure this 1.1 to 1 match. Impedance is not the same as resistance. Resistance is measured in DC current; while impedance is measured by AC current. Radio transmissions are AC; so any antenna will show either no resistance or infinity resistance when using an ohm meter. If you are going to buy an antenna - you will only need to have an SWR meter to set it up properly.
Antenna resonance and resistance aren't necessarily related to each other. Resonance is the frequency on which the antenna will have the most power output flow from the radio due to its selected length. This is accomplished already if you have purchased an antenna. But if you build your own, it will take a field strength meter to determine at what frequencies the home built antenna is most resonant. Not something for a beginner to do; but not so hard to do if you understand what you are trying to accomplish either.
http://www.cbtricks.com/members/toban/swrset.htm
This article is meant for the beginner...
Any questions?
Please feel free to join - and ask away!
Antenna Basics; Part 3 - tomorrow "Choosing an Antenna"
http://www.worldwidedx.com/cb-anten...io-radio-antenna-basics-choosing-antenna.html
