Questions tagged [dipole]

Use this tag for questions relating to dipole antennas.

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votes
1answer
123 views

How much leeway does an antenna tuner give me?

As far as I can tell, currently a 20m dipole has to be within a few inches to have a reasonable SWR without a tuner. How does this change with one? Does it depend on what tuner I have?
3
votes
1answer
670 views

How to feed an array of dipoles for an end-fire pattern

An array of dipoles can be fed to achieve an end-fire pattern. If the phase of the current on each element is equal, the array will have maximum radiation broadside to the array. If the phase of the ...
2
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6answers
650 views

For a half wave dipole antenna, what's the value of the reactances that cancel out when the antenna is resonant?

According to a few books and articles on antenna fundamentals I've read recently, including Wikipedia and the ARRL Handbook, when a half wave dipole is resonant, the inductive and capacitive ...
2
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2answers
234 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 ?
2
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2answers
275 views

How does a 40/15m dipole with capacitance hats work?

I followed an article Antenna Here is a Dipole [PDF] by James Hearly, NJ2L to build a dual band 40/15m dipole: The antenna works more or less as expected. My 40m dipole was resonant at 7.030 MHz and ...
2
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2answers
3k views

Effective area of a dipole

Effective area of a dipole is $\lambda^{2}/4*\pi$. Consider 1 GHz em waves. Consider two antenna of length 15cm ie half wave length and 1 cm. Both have same effective area. This is very non-intuitive ...
2
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5answers
1k views

What happens if an HF dipole is made longer?

Does a longer dipole (than half wavelength), for example twice as long, tuned to 50 Ω using an antenna tuner perform better than a half wavelength dipole for the same frequency?
2
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1answer
1k 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,...
2
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2answers
80 views

Destructive interference between two close antennas

let's consider this two planar biconical dipoles of total length and width each one 10mm, at a distance D = 25.6mm. They are excited with the discrete ports in the picture, which corresponds in this ...
2
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3answers
152 views

Which antenna would you use?

I'm starting to study RF propagation at college, and I'm thinking about what antenna I should choose for this scenario: The distance between the transmitter and receiver is just 700 meters, and the ...
2
votes
5answers
3k 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 ...
2
votes
2answers
91 views

Does propagation affect magnetic and electric fields equally?

In the HF bands loop antennas are common, which, if I understand correctly, emit most of their radio energy into the magnetic field, whereas most dipoles emit largely into the electric field. To take ...
2
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3answers
899 views

Doublet with ladder line vs coax w.r.t. noise

I live in the city, with 50’x 100’ lots. I use an 80 meter doublet at 30 feet, fed with ladder line to a tuner. My noise floor ranges from S5 to S9 depending on the time. Would a coax feed reduce ...
2
votes
2answers
261 views

Can anyone tell me how to make a 35 m long wire antenna work on 80, 40, 20, 15 and 10 metres?

I have one straight horizontal wire antenna 35 meters (114.83 feet) long. I want to make it work the best on average for the 80, 40, 20 ,15 and 10 meter amateur bands. Can anyone tell me the best ...
2
votes
1answer
139 views

How to find transmitting (voice and CW) Amateur stations in UK?

Background info: I own an SDR (model "SDRPlay RSP1") and I have a fully working HDSDR software system installed on my PC. I can successfully use this to tune-in to my local airport's radio traffic ...
2
votes
1answer
214 views

When I am told that a dipole must have a determined length, does that include the space between both elements?

I am trying to build an antenna for receiving NOAA satellites and I need to build two 137,5MHz dipoles. When I enter the frequency and width of the wires in a calculator, I obtain that $λ/2=1.09\,\...
2
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1answer
63 views

Wire dipole antenna proving ground / test bench

i am considering building two movable (concrete base with wheels) non metallic poles with hooks every ten centimeters or so, in order to test wire dipoles of various sizes at various heights with an ...
2
votes
1answer
1k 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 ...
2
votes
1answer
60 views

Identical HF Horizonal Dipoles Operating in Close Proximity

I'm planning to use a multiwave horizontal dipole oriented to work comms toward Alaska from Colorado. That ends up being awkwardly oriented to work east coast and Europe. If I placed a second ...
2
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2answers
380 views

How to estimate a dipole feedpoint impedance?

An ideal dipole, at resonance, will have an impedance around 73 ohms. A folded dipole, around 280 ohms. How can I calculate the impedances when not at resonance? Let's assume I have a span of 15M in ...
2
votes
1answer
209 views

Yagi-Uda antenna - energy flow density calculation

This task is our milestone, even the lecturer doesn't know how to do it, I will be grateful for even the smallest clue, thank you in advance. There are given two, identical, parallel, short dipoles ...
2
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1answer
805 views

What material is best to design a dipole antenna working at VHF frequency? [duplicate]

I need to design an antenna using the tool FEKO. The antenna is supposed to work in VHF frequency and has a gain of around 2.2 dB. What is the best material to use and what are the specifications of ...
2
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1answer
619 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 ...
2
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1answer
271 views

How Does the Performance of an Inverted V Dipole Compare to a Linear Dipole?

The NEC4.2 comparison in the answer below shows one example, for a practical set of installation conditions.
2
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2answers
135 views

How Does the Low-Angle Radiation of a Horizontal Dipole Compare to That of a Vertical Monopole?

Conventional wisdom based on the far-field (only) patterns calculated by M-o-M software such as NEC show that low-angle radiation from a horizontal dipole is very low, and zero in the horizontal plane....
2
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1answer
143 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 ...
2
votes
1answer
325 views

Relay specifications for linked dipole

I currently have a linked dipole up and running at 40,20,15 and 10M. While I have looked at trapped dipoles the losses discourage me as I wish to use as little power as possible. So I now I'm ...
2
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1answer
58 views

Phase shifts in antenna arrays

Let's consider a simple antenna array. For instance, this three-elements equispaced dipole array: Each dipole is connected to a signal voltage source. It's well known that it's possible to choose the ...
2
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1answer
102 views

Half wave dipole with parasitic element, (Gain calculation)

good morning all, I have difficulties to find the correct formula that allows me to calculate the gain of half wave dipole in parallel with another parasitic half wave dipole. I'm trying to calculate ...
2
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1answer
2k views

Balun and impedance matching suggestions for dipole antenna

I'm a newbie who is attempting to build a half-wave dipole antenna that will be located in the rudder of a sailplane. 123.3 MHz is the most important frequency to me, although it's reasonable to ...
2
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1answer
798 views

Horizontal dipole radiation gaps

Consider the radiation pattern of a horizontal dipole mounted at a height of 1.75λ. Is it possible for a receiving station's antenna to be mounted at a certain height such that the radiation of the ...
2
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1answer
70 views

How does the material of a fishing-pole mast affect antenna performance?

I'm a newly-licenced ham and currently starting out with HF. My home doesn't allow for a permanent setup. I can therefore only operate portable from parks and such, with limited TX power (my rig goes ...
2
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0answers
46 views

Printed Dipole Transmission Line Equivalent Model

let's consider a printed dipole on a substrate with a GND plane: I've seen many times an equivalent model which uses transmission lines like this (reference): This model is useful to understand the ...
1
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4answers
1k views

How to increase the bandwidth of half-wave dipole antenna?

I have designed a half-wave dipole antenna for frequency range of 150 to 200 MHz. Due to resonant frequency of 175 MHz, Its dimensions are: L=817.44 mm, R=1.71 mm. Impedance is also equal to 73 ohms. ...
1
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4answers
3k 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 ...
1
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2answers
4k views

What is Electrical length in RF and how to electrically cut and measure the RF cable in degree?

What is electrical length in detail? Why is it so that 1/4 wave , 1/2 wave dipole antenna works properly and not a full wave antenna? What is the role of electrical lengths in degree?
1
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1answer
725 views

How the performance of the half wave dipole antenna changes as the length changes?

I have been doing some research online and I found that some sources say if you have a full wave dipole antenna, there would be no transmission on the other hand some sources say that this is not true....
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3answers
146 views

Why half-wave dipole is the most efficient one in comparison to other electrical lengths of that antenna?

I have a problem on the understanding of a half-wavelength antenna. Namely, why is the half-wave antenna has a highest power emission. Considering Far Field factor F($\theta$), which is known from the ...
1
vote
1answer
444 views

What is the equation for the arm lengths of a half wavelength dipole antenna?

I was operating under the impression that the arm length of a half dipole antenna is λ/4 while making one that operated at the 145Mhz frequency using a piece of 9.525 mm (3/8 inch) copper tubing, at a ...
1
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1answer
270 views

Transition Point Between Fan and Cage Dipoles

A fan dipole is a dipole with multiple active elements, either for different frequencies or different directions (see turnstile antenna) while a cage dipole emulates a larger conductive by having ...
1
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2answers
265 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). ...
1
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1answer
94 views

Is a MagLoop antenna better than my 50ft end fed di-pole for 20-80 meters?

I'm restricted to putting antennas in my attic which is 50 feet long and peaks at about 8 feet. I'm currently using the Nelson UJM-150-50 end-fed dipole 80-10 meter antenna. The attic is about 25 feet ...
1
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1answer
408 views

440MHz collinear dipole array - suitable coax?

friends! Finally found my next antenna project..a collinear dipole array for the 70cm US ham band. The general idea: (image courtesy https://link.springer.com/referenceworkentry/10.1007%2F978-981-...
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1answer
108 views

Resistance of antenna dipoles

A quick question: Is it a disaster if the two legs of a v-dipole antenna are different resistances? Thanks.
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2answers
684 views

Linear-Loaded Cage Dipole?

I've recently learned about linear loaded dipoles as one way of building a physically shortened antenna. As I understand it, any shortened antenna will have reduced bandwidth and linear-loaded dipoles ...
1
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1answer
72 views

What kind of wire would be good for a 160m - 40m fan dipole?

I want to know the best copper wire or tinned copper wire for a fan dipole for 160, 75, 40 meters. It would be coax fed and I would like it to handle 1500 watts or more. I would like 65/30 strands of ...
1
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1answer
144 views

Yagi performing far worse than a dipole

A few months ago, I built a 6 element yagi: 3 driven elements, and 3 reflectors. For 10-15-20m. I was able to tune it to SWR 1:1 for the FT8 frequencies in each band. This antenna is only 6m above ...
1
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1answer
105 views

How Does the Propagation of H-pol E-M Fields Compare to That of V-pol E-M Fields (other things equal)?

A rather popular belief on this topic is that h-pol is superior to v-pol. Probably that is traceable to published "far-field" patterns over a lossy ground plane generated by Method of ...
1
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1answer
170 views

Double Cross Dipole antenna for 437 MHz don't tune

I'm building a Double Cross Dipole antenna for 437 MHz to be used with a SDR receiver for CW cubesat. The idea is to follow this "classic" paper from Gerald Martes, KD6JDJ. I tuned every single dipole ...
1
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1answer
80 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 ...