Questions tagged [dipole]

Use this tag for questions relating to dipole antennas.

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4
votes
3answers
78 views

Why does no one use a Buddipole as an Inverted V?

I have been looking at the Buddipole, and I've seen the most popular configuration is as a standard dipole with the arms parallel to the ground. I've also seen it configured as an upright V, as well ...
3
votes
1answer
92 views

What are the effects of a ground plane under a horizontal dipole?

What are the effects on signal propagation if this ground plane is just a metal object and what are the effects if the ground plane is actually grounded? I am asking this question because someone ...
1
vote
1answer
40 views

Passive receiver power needs & data rate

I'm working on a project to design a space-based low frequency array. It will only be receiving signals, and it will operate between 10MHz - 100MHz. It is made of short wave crossed dipole antennas. I ...
3
votes
1answer
133 views

3 Band (80-40-20 Meter) Fan Dipole Tuning Question

I built a fan dipole according to the basic instructions in the SRI publication describing the theory and basic design. My questions is about next steps in tuning for the various bands. I am ...
5
votes
2answers
62 views

Effective Area of Dipole Array

I'm trying to design a low frequency dipole interferometer antenna array. I am realizing how little I know about radio antennae. I'm confused by the concept of effective area $A_e$ and how it applies ...
5
votes
2answers
83 views

Does a loop antenna have less susceptibility to atmospheric noise than an open ended antenna?

I always get the feeling that an antenna which has a loop for the driven element such as a folded dipole or quad will pick up less static or 'high impedance' noise than an antenna that has free ends ...
1
vote
1answer
264 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 ...
2
votes
3answers
147 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 ...
6
votes
3answers
225 views

Estimating the efficiency of a shortened (loaded) antenna

Recently I've build a trap dipole for 20/40/80m bands. I followed an article by John DeGood, NU3E and got following measurements: From balun to 20m trap: 485 cm From 20m trap to 40m trap: 362 cm From ...
5
votes
2answers
113 views

How can I calculate current distribution on an end-fed dipole antenna in theory?

I understand that in a half-wave center-fed antenna current distribution has a sinusoidal wave approximately, so the current in the center has max value and it has to become zero at the ends of dipole ...
0
votes
2answers
187 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 ...
4
votes
4answers
163 views

Partially Collapse Telescoping Antenna to Change Effective Length

I recently purchased a cheap RTL-SDR kit to experiment with SDRs and different frequency bands. This kit came with 23cm and 100cm telescoping antennas. I now wish to use the 100cm antenna to pick up ...
6
votes
1answer
567 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 ...
2
votes
2answers
178 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
151 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 ...
0
votes
1answer
30 views

Indoor RX VHF dipole and preamplifier box

I am currently looking for a good solution to create a simple VHF dipole connected to a RF preamplifier / band pass filter. The intended use is 88-108 FM RX. I see basically two solutions for a rigid ...
0
votes
1answer
74 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
vote
2answers
351 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?
7
votes
3answers
274 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
votes
1answer
237 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
votes
2answers
83 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....
1
vote
2answers
121 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
votes
1answer
51 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
2answers
266 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
votes
3answers
407 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
votes
3answers
401 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
vote
1answer
186 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
vote
1answer
361 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
vote
1answer
321 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....
3
votes
4answers
460 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
vote
4answers
1k 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
votes
2answers
504 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 ...
3
votes
2answers
640 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
votes
1answer
112 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
3answers
134 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
votes
2answers
558 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
vote
1answer
80 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
votes
1answer
105 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
votes
5answers
309 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?
4
votes
1answer
961 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
votes
1answer
576 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 ...
1
vote
2answers
420 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
vote
1answer
149 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 ...
4
votes
4answers
2k 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
votes
2answers
685 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 ...
2
votes
1answer
107 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
votes
1answer
319 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
votes
1answer
154 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
votes
1answer
178 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
votes
1answer
493 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 ...