Questions tagged [balun]
Devices for connecting balanced and unbalanced feed lines/antennas. Also covers questions about ununs, unbalanced-to-unbalanced connection.
25
questions
42
votes
7
answers
48k
views
Using a balun with a resonant dipole
I am preparing to construct a resonant, center-fed, horizontal dipole. I have seen people use baluns at the feedpoint of the antenna, and some people swear by them, but I have never gotten a ...
- 1,901
6
votes
2
answers
7k
views
How does a folded balun work?
A folded balun is made from two quarter-wavelength, parallel conductors. A picture is worth a thousand words:
Here are some pictures of an actual construction from Gisela & Joe Noci on diydrones....
- 51.7k
9
votes
2
answers
6k
views
Does a balun need to be made with coax?
The short version
My understanding is that one of the main reasons to use a balun with coax is to prevent the outside of the shield from becoming part of your antenna system. If that's the case, won'...
- 555
17
votes
4
answers
18k
views
Where are the baluns for VHF and higher? How can one be made?
In another question, commenters recommended that I look into adding a 1:1 balun to a dual-band dipole to eliminate the feedline as a radiator. As I understand it, a 1:1 balun also functions as a choke,...
- 803
8
votes
2
answers
4k
views
Understanding coax radiation and "current on the shield"
I'm having trouble understanding what seems to be the fundamental principle behind baluns (and probably other related topics).
Perhaps some of my confusion comes from an audio background, where one ...
- 7,411
25
votes
3
answers
44k
views
Why are some 1:1 current baluns twice as complicated as others?
I would like to add a balun/choke to my dipole for the reasons outlined in Using a balun with a resonant dipole. In the spirit of continued kit and/or DIY building for my ham shack, I set out to ...
- 7,411
19
votes
3
answers
3k
views
Why do amateur radio operators call an RF choke a balun?
When using a balanced antenna such as a half wave dipole, with an unbalanced feed line such as coax, an RF choke can be used to block RF current emitted by the transmitter from splitting up at the ...
- 3,685
7
votes
1
answer
5k
views
How to determine number of turns for a 1:1 balun?
I would like to make a 1:1 balun with М1000НМ ferrite core (magnetic permeability - 1000) and 1 mm thick copper wire using triple bifilar winding. Unfortunately I didn't manage to find a clear ...
6
votes
2
answers
4k
views
How to measure a balun for effectiveness?
It seems there are almost as many "balun" designs as there are web pages about "baluns". There's lots of accusations pointed in all directions ("design Z isn't a balun OR a choke", "design Y is ...
- 7,411
3
votes
1
answer
1k
views
How does a 1:4 current balun work?
I'm having little difficulties understanding the following schematic:
I understand the part regarding current distribution. I understand why this schematic suppresses common mode current. Also I ...
2
votes
5
answers
5k
views
Balun and tuner configuration for multiband dipole
I'm putting up a multiband dipole in some tall trees. (Perhaps it's more correct to call it a "dipole-doublet"). The situation I'm imagining looks like this:
The legs of the antenna are each 100 ...
- 255
2
votes
1
answer
2k
views
Do I need a Balun for a single band QRP antenna?
I have a little MFJ QRP CW 20m rig that I plan to turn into a portable kit for SOTA peaks. I have everything figured out except for the antenna. I am wanting to make a dipole. However, I was wondering,...
- 37
11
votes
2
answers
4k
views
Why isn't twisted pair used for feedlines?
My son was asking about some Ethernet cable (Cat 5 unshielded twisted pair), and since he recently passed his Technician exam and we both have "radio stuff" on our minds, I tried to make the analogy ...
- 7,411
7
votes
2
answers
5k
views
Do end-fed dipole antennas need choke baluns?
I have a couple of end-fed wire antennas I bought that came with matching baluns. One has a 9:1 unun, and I'm not sure about the other one. In addition to those, should I also put a choke balun on the ...
- 1,381
7
votes
2
answers
648
views
Why aren't there baluns that do BOTH balanced/unbalanced transformation and common mode current attenuation?
I have read myself blue, about baluns. Especially 1:1 ones.
Some claim they're only there to balance the unbalanced signal, and that's what's in the name also, but I find several that claims that the ...
- 227
6
votes
3
answers
5k
views
Why do we distinguish between balanced and unbalanced?
I hear all the time, "you need a balun between your balanced dipole and unbalanced coax to stop the common-mode current" when it seems the proper advice is "you need something to stop common-mode ...
- 555
6
votes
3
answers
3k
views
Impedance Matching Different Feedlines
(I promise there will be a question in this wall of text. I'm just giving context.)
I've been wanting to try my hand at building my own antenna system for the last few weeks and in doing research, a ...
- 183
5
votes
1
answer
1k
views
Connect Printed Yagi-Uda Dipole Array with Balun to coaxial cable correctly
I am making the Printed Yagi-Uda Dipole Array with Balun (that is the full name). I used Antenna Magus to calculate dimensions. I am not sure how to properly connect it to coaxial cable. Here is what ...
- 153
4
votes
3
answers
4k
views
Do I need an 9:1 UNUN for a half-wave end fed?
I was using a 10-ish meter wire as my HF rx antenna. That's all I can install in my QTH. However I realised that my ~10 m wire can be turned into an end fed dipole for 20 meter band.
But there is a ...
- 195
3
votes
1
answer
129
views
RFID extension cable
I am trying to build an extension cable to relay an RFID signal (125kHz) to various distances (2,5,10m). I am using 2 identical antennas at the two ends of a 75Ohm coax cable, and I also put 2 ...
- 41
3
votes
1
answer
364
views
UHF cubical quad VNA analysis interpretation
I've designed a two element UHF cubical quad. It was designed to resonate at 385 Mhz. I used 0.1mm thick and 1cm wide copper tape instead of wire to lower the antenna Q. I used PVC electrical conduit ...
- 173
3
votes
2
answers
241
views
VHF Balancing, necessary? Methods?
This is a question about power dissipated due to radiation and ohmic heating caused by common mode current in the coaxial shielding, specifically at VHF frequencies.
When a balanced antenna (such as a ...
- 160
2
votes
4
answers
1k
views
Is an off-center fed dipole (and/or doublet) inherently unbalanced?
Does a balun/choke have to "work harder" in an off-center fed dipole than when the feedpoint is at the center? Or do the standing waves that develop keep the antenna balanced electrically ...
- 7,411
2
votes
4
answers
7k
views
Voltage vs. Current Balun for Dipole
I'm a new radio amateur setting up a half-wave 10-meter inverted vee antenna fed by 50 ohm coax. I understand that the inverted vee lowers the normal 72 ohm dipole closer to 50 ohms, so I only need to ...
- 385
1
vote
2
answers
214
views
Serial matching stub combined with RF choke
If I use RG6 coaxial cable in odd multiples of 1/4 wavelength as a serial matching stub, can I also use it, without modifying the length, as a coiled RF choke balun at the antenna feed point?
- 31