Devices for connecting balanced and unbalanced feed lines/antennas. Also covers questions about ununs, unbalanced-to-unbalanced connection.
Questions tagged [balun]
104 questions
42
votes
7 answers
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 satisfactory answer on why you would use/need a balun. All…
W5VO
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24
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3 answers
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 investigate how I might best proceed "from…
natevw - AF7TB
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19
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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 antenna feed point and traveling along the antenna…
Andrew
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17
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4 answers
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, but is more efficient because... reasons?
When…
William
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15
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What is the purpose of a balun and a unun in a feed line?
I have never understood how a balun or a unun works and under which situation I need to use either of them in an antenna feed line.
Dinesh Cyanam
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9
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2 answers
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't a design like the one pictured below be…
Dominick Pastore
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2 answers
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 between coax transmission lines and the balanced…
natevw - AF7TB
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9
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How is a 1:1 current balun different from a choke?
I have a 10m dipole and am going to feed it with 50 ohm unbalanced feed line (coax). My understanding is the feed point of this style antenna is about 50-75 ohms, and since it is a balanced antenna I'm thinking I need some type of balun. I'm…
Java42
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When would we ever want to use a voltage balun in ham radio?
In a world where common mode current is the enemy, and we're constantly doing what we can to avoid RF in the shack, why would we ever choose a voltage type balun over a current balun?
I understand that, in general, one uses a voltage balun to keep…
user3191449
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Importance of Ferrite Size in Coax Choke Balun
The question is quite simple: When making a coax choke balun, does the size of the ferrite matter, and if so, why?
I have seen design notes that say to use a single FT240-43 toroid for powers up to 400W, and then to use two stacked FT240-43 toroids…
M1GEO
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8
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6 answers
Use a TV coax and balun for a poor-man's OCFD?
Can I use TV coax and a cheap TV balun to build a poor-man's OCFD? Marginal performance is acceptable if it saves money. If I could listen to 10% of transmitters within a 100 mile radius that would be acceptable. And as for the coax length, probably…
SlowBro
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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 coax before the matching one?
Pablo Fernandez
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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 main thing at the point of a balun is common mode…
Hans Neve
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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 has "balanced" and "unbalanced" cabling in a way…
natevw - AF7TB
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7
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1 answer
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 instruction on how to determine the required number of…
Aleksander Alekseev - R2AUK
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