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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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Resonant 80m End Fed Halfwave Antenna With Counterpoise - Questions

Originally, I built an 80m EFHW, 130.5 feet long cut for approximately 3.58Mhz. I attached a 49:1 UnUn at the feed point 13 feet above the ground with coax back to the shack. I did not use a ...
Ron K5TDF's user avatar
6 votes
1 answer
421 views

Why do 9:1 ununs use type 2 material for the core?

I do not understand how a 9:1 unun wound on a T200-2 works. I understand the transformer voltage and current ratios. I have wound several toroid chokes and 49:1 ununs and know how they work. What is ...
Dereck's user avatar
  • 656
2 votes
2 answers
125 views

Long Distance antenna feedline for UHF/2.5GHz signal

I'm building a boat towed underwater platform. This underwater platform has a single board computer with a remote wifi antenna connection via a u.fl connector. I'm experimenting around with a way to ...
leeprevost's user avatar
1 vote
1 answer
82 views

I would like to know more about designing broad bandwidth transformers and current baluns using binocular cores

Internet pickings seem mighty slim, would appreciate links to books, articles or websites. If there are good "how to" items that explain the design, that too. Thanks and 73s
Jimbo47's user avatar
  • 86
2 votes
1 answer
197 views

UnUn for VHF and UHF

Is it possible to build an UnUn for VHF or UHF like in HF? Goal is to use a simple endfed wire or piece of metal as an antenna. EDIT: I meant "endfed halfwave".
microfox's user avatar
0 votes
1 answer
69 views

How to assemble a DB8 antenna balun

I have an old (2009) Antenna Direct DB8 antenna that has never worked great. I would get good reception then poor reception and not due to atmospherics. I finally decided to take it down and inspect. ...
LAD's user avatar
  • 1
2 votes
2 answers
1k views

Hi SWR with End Fed HF Wire 9:1 UNUN

Good Day I understand every antenna set up is different, so I'm looking for advice on what I could change to alter my findings. The set up is new including the EFHFW - 20 which was bought off the ...
Simon Hefford's user avatar
1 vote
0 answers
112 views

Testing a balun in isolation

Consider a microwave RF source going to an unbalanced coaxial cable, then using a 1:1 balun to feed a dipole/Yagi style antenna. How can I test this 1:1 balun in isolation, independent of the type of ...
butterflypea's user avatar
3 votes
1 answer
137 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 ...
gcaglion's user avatar
3 votes
1 answer
389 views

Using PVC coated solid-core wire for a small number of turns on toroid

I'm researching making my own 49:1 unun using an appropriate mix ferrite toroid and some reasonable gauge solid-core wire. (This is for an experimental HF end-fed antenna, though this detail probably ...
user avatar
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 ...
natevw - AF7TB's user avatar
2 votes
1 answer
632 views

RG-174 vs RG58 for winding toroid

I'm building a balun for a fan dipole, and this chart suggests 9 turns of RG-58 on two FT240-31 cores will give good performance over the frequency range of interest. However, I don't feel confident ...
RoadieRich AE8RL's user avatar
3 votes
1 answer
149 views

Ferrite choice for fan dipole

I am intending to build a two element fan dipole for 80 and 20m. How should I go about choosing a ferrite toroid and number of windings for the balun, to operate effectively over such a range of ...
RoadieRich AE8RL's user avatar
2 votes
2 answers
2k views

End fed long wire antenna causing issues

I use a hex beam to operate from 20 meters to 6 meters with amazing results. I wish to operate 40 meters and 80 meters also, and can only really install an end fed long wire due to my installation ...
Engineer999's user avatar
0 votes
1 answer
606 views

How to Feed 2 x Co-Phased 4 Element Yagi Antennas?

I am wanting to build 2 x 4 element vertical yagi antennas for 28 MHz and co-phase them and feed with one 50 ohm coaxial transmission line. If i were to use a gamma match for each yagi and tune them ...
Andrew's user avatar
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0 votes
1 answer
3k views

End fed long wire antenna for 40 meters length

I have a hex beam antenna that gets me onto bands from 20 meters to 6 meters very well. I wish to have an antenna that gets me onto 40 meters at night very well also. Recently I purchased an end fed ...
Engineer999's user avatar
3 votes
4 answers
2k views

Issues with high SWR on HF Kits EFHW 49:1 UnUn kit

I recently tried assembling a EFHW kit, and some problems came up in testing. I believe this is the kit; I bought it through ARRL: HF Kits website. This is my first time making an UnUn and EFHW kit. ...
nerdenator's user avatar
1 vote
2 answers
709 views

How do I configure a NanoVNA v2Plus4 to check a 1:1 Balun?

Note that the menus are different than those I'm seeing on YouTube which aren't for the V2plus4. What's missing is "Isolation" and of course, there is an additional standard for that which ...
NonYaBidnezz's user avatar
3 votes
2 answers
262 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 ...
elplatt's user avatar
  • 160
2 votes
3 answers
350 views

Ferrite unun transformer to match antenna resistance loads of <50Ω?

For LF/MF (2200m/630m), I am interested in the situation of a vertical antenna with capacitance hat top-loading, where the vertical antenna is VERY short compared to wavelength, and the antenna is ...
photosynthesis's user avatar
6 votes
2 answers
329 views

How much attenuation (dB) from a balun is expected?

I'm building a dipole antenna for 433 MHz, first one ever. I will have to use a ferrite bead to balance the feed. How many decibels of attenuation should I expect from the ferrite bead?
AllYourBaseAreBelongToUs's user avatar
6 votes
3 answers
3k views

When is a balun a Guanella?

I've searched this site, wikipedia, other sites, and haven't found a clear answer: What features or parameters of a balun or choke put it into the category/definition of a "Guanella"? Where ...
Jay Rabe - KJ7TTT's user avatar
-2 votes
2 answers
666 views

Can an end-fed be fed with an Isolation transformer? [closed]

Typical half-wave end-fed antenna kits include either a 9:1 or 49:1 toroidal balun or unun, which is a transformer for impedance matching, but with one primary winding endpoint (for the coax shield) ...
hotpaw2's user avatar
  • 13.5k
2 votes
2 answers
781 views

Can I wind my 9:1 unun with two wires instead of three?

All the 9:1 unun tutorials out there are using three wires to wind, but I was wondering if it is possible to wind it using two wires similar to how this 49:1 is built (https://elginradio.files....
Richard Hum's user avatar
0 votes
2 answers
327 views

At near-QRP levels should I include a balun/unun in the antenna system? [duplicate]

To my comprehension a BALUN/UNUN is an RF Transformer. If this is correct and since a BALUN/UNUN is part of the antenna system ... how much power does one expect to lose there? Specifically, how much ...
VU2NHW's user avatar
  • 2,834
3 votes
2 answers
425 views

1:4 Guanella unun current balun

I am having trouble understanding the 1:4 Guanella current balun here. So at DC, or low frequencies, I think the current path would be a short to ground. At higher frequencies, I am getting confused ...
Erik McKee's user avatar
1 vote
1 answer
441 views

There are good guides for building 1:1 current baluns. What about 4:1?

Some dedicated hams have spent a lot of effort gathering empirical data on various constructions for common-mode chokes. For example, G3TXQ's work is commonly referenced, and K9YC's is pretty well-...
Dominick Pastore's user avatar
4 votes
1 answer
875 views

Debugging SM0VPO's spiral loop antenna build

I had built SM0VPO's spiral loop antenna. And here it is. Recently I got myself a NanoVNA to see how finnicky it is to be tuned with that poor man's tuning cap. I brought it from 12 MHz into the 14 ...
Gunther Schadow's user avatar
3 votes
1 answer
155 views

Is this "floating" output single-ended or differential and against GND or VCC?

I'm looking at a simple FM transmitter output (see picture). It is from the collector of a transistor and it goes through a DC blocking capacitor before the antenna would be connected. The entire ...
pgibbons's user avatar
  • 444
0 votes
4 answers
476 views

Weatherproofing coax connection to balun

How should a coax-to-housing connection like this be weatherproofed? It doesn't seem like taping is going to do much good here
Brad Mace's user avatar
  • 421
4 votes
3 answers
2k views

What is the capacitors purpose on a balun?

Per the subject, what is the capacitors purpose on a balun? Used a lot on wire wound ferrite toroidal baluns.
t252's user avatar
  • 697
4 votes
2 answers
489 views

Heat-shrink as dielectric for bazooka balun?

I'm intending to make a sleeve balun (aka bazooka) for 2m, but rather than keep the lossy coax jacket as a dielectric (I have some RG58), was considering to remove it and replace it with heat shrink ...
webmarc's user avatar
  • 4,353
0 votes
1 answer
920 views

Pondering variations on the vertical bazooka antenna

I've seen these antennas built out of coax that are called a bazooka vertical. It's a kind of 1/4 wave vertical, or perhaps a 1/2 wave dipole. Constructing such an antenna is to roll back the outer ...
MacGuffin's user avatar
  • 359
5 votes
2 answers
2k views

How does this quarter-wave stub balun work?

I was searching for 1:1 balun designs that would be efficient at VHF yet could easily be made from commonly available materials when I came across these two: While the design on the right seems ...
Ivan R2AZR's user avatar
9 votes
2 answers
5k views

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 ...
Paul's user avatar
  • 791
9 votes
2 answers
3k views

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 ...
M1GEO's user avatar
  • 223
2 votes
2 answers
2k views

Is a balun really necessary for a small loop antenna?

I am in the process of designing a small receiving loop antenna for the lower HF bands. By small I mean a circumference of less than $0.2\lambda$. Thus, a uniform current distribution can rightly be ...
Troels Folke's user avatar
0 votes
2 answers
905 views

2 meter coax cable balun dimensions for use with a ground plane?

I have a commercially manufactured ground plane antenna for 2 meters. It will be fed with about 150 feet of RG 8/U . I've seen pictures of a coil of the feed line going to a 2 meter ground plane; this ...
timbo20's user avatar
3 votes
0 answers
1k views

9:1 unun material and power loss

I need to build another 9:1 unun and I start searching for my toroids... (I have build 2-3 something like 4 years ago)... In parallel I checked on Google about the correct toroid etc so I found 2-3 ...
OHTO's user avatar
  • 149
5 votes
2 answers
292 views

4:1 Balun question

With an OCF dipole, does it matter which leg, short or long, is connected to which side of the 4:1 balun, hot(coax center) or shield? How can you tell which is which, the balun is not marked. Thank ...
John's user avatar
  • 51
5 votes
0 answers
143 views

What causes differences in properties of ferrite cores from same material?

Why are the shapes of the impedance curves different for cores made of the same ferrite material? The impedance (Z) of an inductor wound on a ferrimagnetic core is: $$Z=j\omega L_s + R_s = j\omega ...
Brian K1LI's user avatar
  • 7,878
2 votes
1 answer
236 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 ...
Brian K1LI's user avatar
  • 7,878
19 votes
3 answers
4k 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 ...
Andrew's user avatar
  • 3,723
1 vote
3 answers
498 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 ...
SandPiper's user avatar
  • 777
4 votes
2 answers
614 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 ...
Tom Horne W3TDH's user avatar
3 votes
1 answer
2k 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 ...
Aleksander Alekseev - R2AUK's user avatar
4 votes
2 answers
2k 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 ...
hjf's user avatar
  • 1,219
2 votes
1 answer
2k 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 ...
hjf's user avatar
  • 1,219
0 votes
0 answers
37 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 ...
rodv92's user avatar
  • 173
1 vote
1 answer
123 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 ...
Inisheer's user avatar
  • 135