Questions tagged [balun]

Devices for connecting balanced and unbalanced feed lines/antennas. Also covers questions about ununs, unbalanced-to-unbalanced connection.

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2answers
38 views

What is the delay through a 1:4 Guanella balun?

I need to estimate the signal delay through the 1:4 Guanella balun shown here: Is the delay simply the delay through the winding on CORE1 or CORE2? For example, assume each winding comprises 0.1-m ...
14
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1answer
2k 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 ...
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3answers
61 views

Can I build a guanella balun using single strand wire instead of coax?

I am trying to homebrew a cobweb antenna and need some help understanding the guanella balun used as described here: http://www.karinya.net/g3txq/cobweb/ This author used RG316 coax around the ...
4
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2answers
127 views

Actual Impedance of a folded dipole at resonance

I am using a Folded Dipole which I bought when I first got my General License. It was advertised as an all band antenna. My results with it were less than the claims made by the makers to say the ...
3
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1answer
88 views

Trying to understand the work of 4:1 coax balun

Let's consider the following picture (source): When current passes the half-wavelength matching section it changes the phase to the opposite, this is why we get +V and -V in the feed point, 2V ...
4
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2answers
81 views

Does a dipole require a 1.5:1 balun?

Dipoles ideally have 72 ohms impedance. I know most of the time this isn't what one gets and it can vary a lot. But let's assume we can build this perfect dipole that exhibits this impedance. Why do ...
2
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1answer
79 views

300 ohm to 50 Balun at antenna feedpoint, or near receiver?

If I build a folded dipole, it will have an impedance close to 300 ohms. I have to match this impedance to the 50 ohms of my transceiver. I know many people match that impedance with varying lengths ...
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0answers
25 views

UHF cubical quad VNA analysis interpretation (part2)

This is the follow up to: UHF cubical quad VNA analysis interpretation This is a S21 and S31 analysis of an oversized 385 Mhz 50 Ohm to 90 Ohm balun between 100 Mhz and 600 Mhz I tested phase ...
1
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1answer
58 views

Rotatable Dipole & RF Choke

I have a Diamond HFV-5 (rotatable dipole) in the attic fed by ~30ft of coax. The antenna system comes with a Balun at the feedpoint. Would it be worthwhile to add an inline RF Choke (Unun) in addition ...
5
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5answers
144 views

How to match low impedance of NVIS Dipole?

I want to match a 50-ohm coax feed wire to a 40-meter NVIS half-wave dipole. NVIS antenna examples I've found are usually based on a regular dipole (72 ohms in free air). However the impedance drops ...
2
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2answers
114 views

Will using a 1:1 balun at the feedpoint of a center feed dipole result in no common mode current on the outside of the coax?

Will using a 1:1 balun at the feedpoint of a center-fed dipole when using coax result in no common mode current on the outside of the coax ?
3
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1answer
55 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 ...
4
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2answers
94 views

Dipole increased CM current using choke balun

My 20 meter inverted vee dipole is fed with 56 feet of 50-ohm coax. The SWR measures 1.2 at the center of the band. According to http://arrl.org/grounding a balanced antenna doesn't need a ground, so ...
3
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1answer
95 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 ...
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3answers
174 views

How to calculate impedance in antenna design's practice?

I would like to make a match half wave length (λ) dipole antenna (or probably a short dipole antenna). So I would like to make it by measure using LCR meter. What I am still confuse is about what is ...
2
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2answers
257 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 ...
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0answers
48 views

advice needed for balanced line terminals

I am designing a portable antenna with a radiating element and a balun that are not close to each other. The impedance has been designed to be close to 50 ohms. ...
3
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2answers
253 views

Can I use a 1:1 current balun to feed a 1/4λ vertical?

I have an LDG RBA-1:1 current balun, and I was wondering if it behaves as a common-mode choke that I can use for a ground-mounted quarter wave vertical w/ 16 radials. The other choice I have is a 4:...
3
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2answers
86 views

Tips for HF Antenna with house near AM transmitter

My back garden is very small - about 500sqft. I also live near an AM transmitter and requires an AM filter. I would appreciate some general tips on the best approach to receiving HF signals (Ham and ...
5
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3answers
380 views

Determining Impedance With An Antenna Analyzer

I need some help interpreting some information from my antenna analyzer (RigExpert AA-35). I want to use the information to impedance match my AM receiving antenna system to AM radios. No ...
5
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3answers
458 views

Coax or bifilar windings for a choke?

Making a common mode choke out of bifilar windings has proven rather difficult. For me the difficulty lies in getting the impedance to remain a constant 50 ohms from on the HF bands. I've tried 14 ...
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2answers
120 views

Why some hams test their baluns with an SWR meter?

There are videos on YouTube that show how to make a 1:1 current balun. When the balun is done some people connect a 100W 50 Ohms resistor to the balun and measure SWR say in 7.000-7.200 MHz range. If ...
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2answers
436 views

Simple Longwire/Dipole Antenna design

In a couple of days I am going to a mountain cabin and I were thinking about making myself a semi broadband antenna for LF/HF (300KHz - 20MHz or so) for receiving only. I was thinking about creating ...
6
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1answer
920 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 ...
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2answers
631 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 ...
2
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1answer
144 views

Power Amplifier Balun Question

Second (and last hopefully) question on the classic Solid State Design for the Radio Amateurs (SSDRA) book by Hayward et al. Again it's a power amplifier circuit (Chapter 4, pg. 66), and again it's ...
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2answers
143 views

Using a common-mode choke on symmetrical antenna system

I am curious as to what happens to a symmetrical dipole center-fed with balanced feeder-line. Let's assume the dipole is arranged as a sloper - that means it's not parallel to ground (horizontal). ...
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3answers
258 views

RF ground and balanced antennas

Suppose that a ham radio setup uses several antennas with a 50 ohm coaxial switch to operate some natively unbalanced antennas and some balanced ones through baluns at the feedpoint. An RF ground for ...
1
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1answer
245 views

Folded balun, impedance matching

I am planning on building a half-wave dipole that is fed by a coaxial cable. I found a way to do this on antenna-theory (http://www.antenna-theory.com/definitions/foldedbalun.php). The article talks ...
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1answer
507 views

Connecting a coaxial cable as feed to a halfwave dipole

I have as assignment to make a half wave dipole antenna, that radiates at 433 MHz. I am trying to figure out how to use a coaxial cable as transmission line. I know that the coaxial cable is ...
6
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4answers
2k 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 ...
2
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2answers
438 views

What core material do I need to construct a 1:1 unun for 6M?

I want to build a 1:1 unun for a 6M dipole. Power level 100W. What core material should I use?
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4answers
2k views

Turn 75 Ω TV “Rabbit Ears” with a balun into a 50 Ω dipole antenna

I got myself a TV "Rabbit Ears" module originally for a TV. It came with a small length of coax, permanently attached to the antenna foot, and a Belling-Lee connector on the other end. My idea was to ...
4
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3answers
318 views

Is RF current always confined to the inner diameter of a braided outer conductor of coaxial cable?

Prompted by a previous question found at Using a balun with a resonant dipole -- an answer there included the following text: "For transmission lines (twin-lead or coax) to not radiate, each ...
2
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1answer
796 views

Feedline and balun for 80m horizontal delta loop

I am new to HF. I'd like to put up an 80m delta loop. Due to aesthetic considerations I need to use coax to the shack. If tuned for 3.55MHz, I anticipate having a good SWR on 80m, 40m, and 20m. The ...
5
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2answers
2k 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 ...
5
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1answer
470 views

How to build a balun transformer for 2m RX with low insertion loss

I'm looking into ways to match a 137MHz RX dipole antenna to an unbalanced coax + amplifier. I know there are several types of baluns which can be categorized under magnetic baluns (where there are ...
7
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6answers
878 views

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 ...
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1answer
49 views

Can I use two voltage baluns to make a common mode choke?

I have two 1:4 voltage baluns. If I connect them together so that I have 1:4-4:1, is that the equivalent of putting a 1:1 common mode choke on my feed line?
2
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3answers
4k views

How do you construct a 1:1 balun?

I have been researching how to construct a 1:1 current balun. I have a few questions and am looking for feedback on what I plan to do. First, I want to use the balun from 10m to 160m at 100w. I plan ...
12
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3answers
6k 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,...
2
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2answers
2k 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 ...
1
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2answers
132 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?
2
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1answer
119 views

What effect does a balun have on s-parameter, beam patterns?

I have a dual-dipole antenna with a subreflector slightly above it and a ground plane below it, and attached to the ground plane is a balun. While simulating in CST microwave studios, I didn't include ...
3
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2answers
242 views

Why don't baluns require precise conductor spacing as in twin-lead?

This is a follow up to another recent question of mine: Does a balun need to be made with coax? In that question, we establish that a choke balun doesn't actually work by protecting the "third ...
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2answers
3k 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'...
3
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1answer
425 views

Balun identification from picture

I thought maybe this was a 4:1 balun, but a number of 4:1 single core balun diagrams that I found online had different connections. N1HFX's balun page and the bottom of G4WPW's page show a connection ...
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2answers
134 views

what is choking reactance in TLT?

I was studying about the Guanella 1:1 balun and came across the term "choking reactance". What does this mean? Why does its value need to be large?
2
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1answer
523 views

Will adding a balun to a full-wave dipole help?

I have made a dipole for 40 m, no swr to speak of on 7040 kHz, but I've been told that it should also work on 20 m as it is 20 meters long (2× 9,92 m) but there I get SWR in the 7-9 range. Will this ...
5
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2answers
472 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 ...