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Balun Ratios?
- Thread starter Se7en
- Start date
1:1 50 ohm in 50 ohm out, 1:2 100 ohm in 50 ohm out, 1:4 200 ohm in 50 ohm out, 1:6 300 ohm in 50 ohm out.
The 1 side is coax. The other side is twin lead. You multiply the other number by the impedance of the feed line on the coax side to get the twin lead side impedance.
If you have 50 ohm coax with a 4:1 balun you will have 200 ohm of impedance on the twin lead side.
If you are running a 75 ohm coax into the same balun you will have 300 ohms on the twin lead side.
The DB
If you have 50 ohm coax with a 4:1 balun you will have 200 ohm of impedance on the twin lead side.
If you are running a 75 ohm coax into the same balun you will have 300 ohms on the twin lead side.
The DB
Don't feel stupid. Most of this stuff flies over my head the first few times. My cousin reads a few paragraphs and it sinks right in, I need read and read and ask questions and read some more.
Assuming a 50 ohm coax.
1:1 is 50 ohms in and 50 ohms out.
1:2 is 50 ohms in and 100 ohms out.
1:3 is 50 ohms in and 150 ohms out.
1:4 is 50 ohms in and 200 ohms out.
1:5 is 50 ohms in and 250 ohms out.
1:6 is 50 ohms in and 300 ohms out.
...
I've seen them go up to 1:12.
...
1:12 is 50 ohms in and 600 ohms out.
X:Y is nothing more than a ratio from one side to the other. For instance a 1:2 could be 50 ohms on one side and 100 ohms on the other. 100 ohms is twice as high as 50 ohms hence 1:2. With 1:12 one side has 12 times the impedance as the other, such as 50 ohms in and 600 ohms out. Again 600 is 12 times 50.
In and out really doesn't matter to a balun. A balun works equally well either way. That being said, many people see the coax (unbalanced) side as the input as most radios have a coax output and that needs to be converted to a balanced feed line for some antennas.
The DB
1:1 is 50 ohms in and 50 ohms out.
1:2 is 50 ohms in and 100 ohms out.
1:3 is 50 ohms in and 150 ohms out.
1:4 is 50 ohms in and 200 ohms out.
1:5 is 50 ohms in and 250 ohms out.
1:6 is 50 ohms in and 300 ohms out.
...
I've seen them go up to 1:12.
...
1:12 is 50 ohms in and 600 ohms out.
X:Y is nothing more than a ratio from one side to the other. For instance a 1:2 could be 50 ohms on one side and 100 ohms on the other. 100 ohms is twice as high as 50 ohms hence 1:2. With 1:12 one side has 12 times the impedance as the other, such as 50 ohms in and 600 ohms out. Again 600 is 12 times 50.
In and out really doesn't matter to a balun. A balun works equally well either way. That being said, many people see the coax (unbalanced) side as the input as most radios have a coax output and that needs to be converted to a balanced feed line for some antennas.
The DB
It's not just about the feedline impedance - it's also about the antenna's impedance. An example is if you are using an antenna with an especially low impedance, a balun can greatly improve matching. For example, if you're using a Buddipole on 40 meters, the antenna's impedance could be pretty low, like 12 ohms or so (I'm just guessing here). Using a 4:1 balun brings the impedance seen by the transmitter much closer to the 50 ohm range.
Using my example, a 1:1 current balun would only help limit feed line radiation.
balun
The main purpose of a balun is to assist in the matching of an unbalanced (coax) system to a balanced antenna (dipole, quad) or feedline. It allows the power to flow equally into both halves of the system which it may not do if the unbalanced coax (source) is connected to the balanced output.
As well as this it can also change the impedance between the source and output as noted above.
Coaxial cable is essentially an unbalanced system as we want all the power flowing through the center conductor.
Lots of reading available on the net and lots of baluns available to buy and make.
Sometimes they make matters worse! But usually the right balun in the right place does help the antenna to radiate
The main purpose of a balun is to assist in the matching of an unbalanced (coax) system to a balanced antenna (dipole, quad) or feedline. It allows the power to flow equally into both halves of the system which it may not do if the unbalanced coax (source) is connected to the balanced output.
As well as this it can also change the impedance between the source and output as noted above.
Coaxial cable is essentially an unbalanced system as we want all the power flowing through the center conductor.
Lots of reading available on the net and lots of baluns available to buy and make.
Sometimes they make matters worse! But usually the right balun in the right place does help the antenna to radiate
In the illustration you provided, the "balun" is a matching transformer to match the 37 ohm dipole to the 52 ohm coax.
When dipoles are used as driven elements in yagis, their impedance may not 50 ohms. There are many designs that are 12.5 ohm and 28 ohm. Mostly determined by the spacing of the first director to the driven element. Purpose being to increase gain slightly. This comes at a cost in bandwidth, and often rain and ice will detune a low impedance yagi.
I have an inverted V up for 40/15 meters. I have a 1:1 current balun, on it as the center insulator. It prevents common mode currents on the feedline and helps ensure that the dipole elements do the radiating and not the feedline going into the shack. Also helps prevent picking up noise on receive from all the electronic devices in and around the house.
What I use: http://www.dxengineering.com/search...vick-w2fmi-series-current-baluns?autoview=SKU
When dipoles are used as driven elements in yagis, their impedance may not 50 ohms. There are many designs that are 12.5 ohm and 28 ohm. Mostly determined by the spacing of the first director to the driven element. Purpose being to increase gain slightly. This comes at a cost in bandwidth, and often rain and ice will detune a low impedance yagi.
I have an inverted V up for 40/15 meters. I have a 1:1 current balun, on it as the center insulator. It prevents common mode currents on the feedline and helps ensure that the dipole elements do the radiating and not the feedline going into the shack. Also helps prevent picking up noise on receive from all the electronic devices in and around the house.
What I use: http://www.dxengineering.com/search...vick-w2fmi-series-current-baluns?autoview=SKU