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Questions tagged [dipole]

Use this tag for questions relating to dipole antennas.

0
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1answer
46 views

Antenna Type of a Chinese Antenna

Recently, I have received an antenna from one of the Chinese manufacturer and they haven't disclosed the detailed specification with us. Below is the picture of my antenna (please ignore the ...
1
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2answers
67 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?
8
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3answers
171 views

How can the voltage at the center of a resonant half wave dipole be zero if the input impedance is 75 ohms?

If the input impedance of a resonant half wave dipole at the feed point is 75 + j0 ohms, then if an AC sine wave voltage V is applied to the feed point, how can the voltage at the center be zero ? ...
4
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1answer
164 views

Dipole antenna radiation field equation

Can anybody provide me with an idealised formula that describes the radiation pattern of an omnidirectional dipole antenna? In particular I am interested in the formula that creates a plot similar to ...
2
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2answers
64 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....
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2answers
76 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). ...
2
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1answer
37 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
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2answers
57 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 ...
3
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3answers
357 views

The right antenna size

I'm preparing for the USA Technician exam and I was reading in the manual that the ideal size for a dipole is following this strange formula: 1/2-lambda. But based on what I read after, it seems it ...
4
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3answers
177 views

Efficiency of short dipole receiving antenna

For a transmitting dipole antenna, its length is important. If it is close to half the wavelength, it will be efficient and most of the input power will be radiated. How important is the length of ...
1
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1answer
99 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 ...
1
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1answer
111 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 ...
1
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1answer
83 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....
2
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3answers
125 views

One dipole for multiple bands?

I've just get my license, and I'm reviewing some equipend my father in law had when he passed away. I have found a dipole antenna with 15m aprox in each side, so, 60m band antenna. It feels weird to ...
1
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4answers
497 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 ...
3
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2answers
204 views

How low can a vertical dipole be mounted?

An answer to this question suggests that raising a vertical dipole sufficiently can create the effect of a phased array. How about the opposite. How low can a vertical dipole be mounted? Can a ...
4
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2answers
356 views

Using two short mobile HF antennas to make a vertical dipole

Instead of using a metal vehicle roof or multiple radials as the counterpose to a shortened vertical antenna, can one use two of them, one pointed downward to construct a balanced vertical dipole, and ...
2
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1answer
107 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
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3answers
124 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 ...
3
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2answers
323 views

proximity of rain gutter to dipole antenna

I am a new ham and wish to mount a center-fed G5RV dipole antenna under the eaves of my house, where I have a 78' clear run available two stories above ground. The problem is a metal rain gutter which ...
1
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1answer
68 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.
3
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1answer
92 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?
2
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5answers
189 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?
5
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1answer
597 views

What frequency to set trap on?

I plan to build trapped multiband dipole so I read lots of documentation I found. There is one thing that confuses me: various authors recommend setting resonant trap frequency differently: some say ...
2
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1answer
471 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 ...
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2answers
296 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
102 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 ...
5
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4answers
1k views

Grounding a dipole

How do you properly ground a dipole (RX only for VHF scanning) to protect it against ESD/lightning? In my set up i'm putting a dipole on my roof. I've connected the two dipole elements together with ...
6
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2answers
514 views

Dipole Antenna Current Distribution at any Time Instant

Above is a connection of half-wave dipole antenna. The book states that the current profile is same at any given time instant on both the radiators, each of quarter wavelength length. Now my ...
3
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1answer
79 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 ...
4
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1answer
243 views

Dipole Center Spacing

I have a question about dipole construction. I am working with a turnstile, but building dipoles to validate my system with linearly polarized transmission before moving on to circular. My design has ...
3
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1answer
116 views

Polarisation loss Dipole antennas

For a school assignment I need to calculate a link budget between two half wave dipole antennas, but I am stuck at calculating the polarisation losses in the antennas. the antennas are ideal and ...
2
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1answer
145 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
388 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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3answers
3k views

Calculating bandwidth of antenna?

Is there a way to calculate bandwidth of an classical dipole antenna having this information: center frequency wire velocity wire diameter I would disregard antenna height, to simplify. I am not ...
3
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1answer
369 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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1answer
906 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 ...
0
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1answer
519 views

Which matters most in a fan dipole: Overall linear length or actual wire length?

I'm in the midst of constructing a fan dipole for 80, 40, 30, 20 and 10 meters. I have everything laid out and am about to start cutting wire. I have an ugly balun (RF choke) wound at the feed point ...
5
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3answers
1k views

Running ladder line through window from inside shack to outside dipole antenna - what to watch out for?

For HF operating, I am considering running a ladder line from the ATU just inside a window, through the window (squeezing it between the window and the window frame; not actually through the glass), ...
5
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1answer
406 views

What happens to the “Yo-Yo Tenna” when you coil up its ends for use on higher frequencies?

I have gathered what is basically a Yo-Yo Tenna using some Camco laundry reels and a spool of cheap speaker wire split in half (pretty much exact duplicate of this build as it turns out). I've got a ...
2
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1answer
260 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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2answers
3k views

2 Meter horizontal or vertical dipole polarization?

When should I use one polarization over the other on 2 meters? I've looked at the radiation patterns for horizontal dipole and seen how it changes based on mounting height. I haven't been able to ...
4
votes
1answer
497 views

Correct number of elements in 4nec2 antenna simulation

I am designing a 1.25-wavelength dipole antenna with the 4nec2 software. What I noticed is that the input impedance of antenna is changing greatly when I change the number of segments. How many ...
2
votes
1answer
766 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,...
4
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2answers
3k views

What is the impedance of a 1.25 λ dipole antenna?

I would like to make a dipole antenna. This particular antenna is used for reception only; no transmission is involved. I would like to receive as much power as possible by this antenna as it is used ...
3
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1answer
420 views

How to center-feed a single wire dipole?

I have heard that it is possible to feed single wire like a dipole from the center-point without actually making two separate wires. How would I do this, what impedance would I expect to see, and ...
8
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6answers
21k views

What is a Gamma match in the context of the driven element of a Yagi antenna?

How (and why) does a Gamma match work, when used on the driven element of a Yagi antenna? As shown here: http://www.iw5edi.com/ham-radio/files/2elyagi10m_4.jpg (source: http://www.iw5edi.com/ham-...
10
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4answers
2k views

Why does ice on a wire dipole affect the SWR?

We just had snow and ice overnight and my wire dipole was coated in ice. Why does the ice covering negatively affect the SWR of the antenna?
2
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2answers
73 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 ...
13
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4answers
11k views

Why do folded dipoles have greater bandwidth than ordinary resonant dipoles?

This is something I've read in passing, but never encountered an explanation of why. For example, Wikipedia says: Another common place one can see dipoles is as antennas for the FM band; these are ...