# Questions tagged [dipole]

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### Are swivel/rod antennas always dipole antennas?

I'm confused, Digikey has a huge range of antennas, that look like the one above, which they characterize as "whip antennas". Wikipedia says here that a "whip antenna is a form of ...
47 views

### Does an aggregation of two lambda/2 dipole antennas z-axis oriented radiate towards the mentioned axis?

I'm asked whether by grouping two dipole antennas pointing towards the z-axis, they'll radiate in that direction. I'm aware each dipole alone doesn't do that thus refraction lobes in the z-axis ...
• 31
1 vote
158 views

### Does the directivity of a λ/2 dipole antenna depend on its length?

They tell me to choose the correct answer (one and only one) regarding a half-wave antenna from the following options: a) Its directivity depends on its length. b) They all have the same radiation ...
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309 views

### How to calculate frequency band of a dipole antennae

I'm a bit puzzled on why dipole antennas can be used in FM receivers. Given that dipole antennae is just tuned to one particular frequency which can be derived from it's length using $\frac{c}{2L}$ ...
67 views

### Plotting the radiation pattern of a half-wave dipole antenna with a frequency of 144 MHz in MATLAB

I need to plot the radiation pattern of a half-wave dipole antenna with a frequency of 144 Mhz in MATLAB but I don't know the code, can someone please help me?
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150 views

### Antenna tuner for 1MHz to 150MHz

I am trying to build an antenna tuner for my 2m (1m + 1m) dipole antenna. It has a 1:1 balun and is connected to a coaxial cable which is connected to my radio with an impedance of 50 ohm. I can't ...
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1 vote
593 views

### Why are patch antennas used instead of planar dipole antennas?

As far as I know, the major advantage of patch antenna over dipole antenna is its directivity. If the planar dipole antenna can achieve the same directivity then why do we use patch antennas? Are ...
382 views

### Why is the charge distribution of printed dipole antenna different from patch antennas?

Why in planar dipole antenna current is perpendicular to the feed while in patch antenna the current is parallel to the feed line? Is the direction of current dependent on the input supply terminals? ...
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143 views

### Interaction between half wave dipole and power supply lines in 433 MHz RF module

For a second iteration of the 433 MHz transmission between Espressif ESP8266 modules, I switched to RF modules based on the SYN115 and SYN480R devices. Largely because these work much better with the ...
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920 views

### Finding the electric field due to a "point" dipole in different locations

I'm currently taking a course in Electrical fields and circuits and came across this example problem from the course book. I am having trouble figuring out how to solve it. Below you will find my ...
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548 views

### Is half wave the best distance between dipoles in an antenna array?

In the 4NEC2 program, I observed the radiation patterns for the antenna array composed of two half-wave dipoles. I researched for different distances between the dipoles: λ/4, λ/2, λ and 2λ.Both ...
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393 views

### Near Field from a Dipole Antenna

What are the equations defining the near field of a half-wave dipole antenna? What is the rate of decay of E-field and H-field in the near field (both reactive and radiative zones)? How are the ...
• 179
1 vote
601 views

### Design of feed gap of a dipole antenna

I am unsure of the formula used to calculate the feeding gap of a dipole antenna. When I go through some research papers, the formula given to calculate the feed gap of a dipole antenna is L/200. I ...
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1 vote
837 views

### Can we use any electromagnetic wave (eg: radio wave, light waves etc) for cooking food?

A microwave oven cooks food using microwaves. The oscillating electric field in microwaves rotates the water molecules in our food. As all waves have oscillating electric fields, my question is why we ...
• 21
76 views

### Printed dipole vs ordinary (3D) dipole

In order to make a comparison between an ordinary (3D) half - wavelength dipole and its printed (planar version), I've done a simulation in both cases. Both were designed to work at 3GHz (100mm ...
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244 views

### More on standing waves in a dipole antenna

I have a background in physics and I'm trying to get into antenna theory for a personal project. I had some questioning about standing waves, and reading Standing waves in Dipole antennas and the ...
2k views

### Dipole antenna resonance frequencies

let's consider a simple dipole antenna of length L. The following picture refers to a half-wave dipole: In general, at different frequencies, it's known that different modes are possible. Precisely, ...
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277 views

### Why exactly is a Hertzian dipole inefficient?

http://farside.ph.utexas.edu/teaching/em/lectures/node94.html states: Note that the formula (1100) is only valid for $l\ll \lambda$. This suggests that $R_{\rm rad} \ll R$ for most Hertzian ...
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1 vote
814 views

### Dipole array antenna radiation pattern

I have the radiation pattern for a dipole antenna with working frequency of 11 GHz, it looks like figure 1. I wanted to create an array antenna consisting of 2 elements with that same individual ...
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591 views

### How can adding a reflector to a half-wave dipole (in a Yagi Uda antenna) increase the gain by more than 3dB?

I have been designing a Yagi Uda antenna using CST Microwave Studio. For a half-wave dipole the directivity (at 1.3GHz) was 2.116dBi. After I added a Reflector, the directivity improved to 6.074dBi. ...
120 views

### Measure antenna S11 next to another source

I have a dipole antenna designed to work on ~800MHz and 2.44GHz frequency, and a miniVNA Tiny USB device that I can use to measure return loss of the antenna. I connect the antenna directly to the DUT ...
241 views

### Why is a transmitter dipole's ends the max/min voltage instead of the middle?

If the AC voltage source is connected to the middle of the dipole, I'm confused on why the edges have the max/min voltage instead of the middle. In my mind, the middle of the dipole is closer to the ...
2k views

### Standing waves in Dipole antennas

I'm relatively new to antennas. In most of the textbooks, it is said that we want to minimize standing waves in the transmission lines by matching the characteristic impedance of the line with the ...
191 views

### How can I tell if an antenna is a dipole antenna

Background I'm trying to select an antenna for an FCC/IC-approved cellular module, SIM7000A. Apparently, to meet IC modular certification, you need to select an antenna which has a) equal or less ...
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118 views

### Dipole Antenna impedance and feed point, what is the effect of long distance to coax connector?

I have a folded dipole being made with a pair of twisted wires where each wire is 1/4 λ long and the dipole is constructed by twisting the centers of the wires so that the twisted pair is ...
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740 views

### Unexplained differences in behaviour between U.FL-terminated antenna and SMA-terminated antenna

I would like your opinions/advice regarding an unexplained observation between a U.FL-terminated antenna and an SMA-terminated antenna. Both antennas are from the same manufacturer and normally tuned ...
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1 vote
564 views

### Standing waves feedline length and dipole antenna feedline

so I have a question regarding reflections/characteristic impedance and there relation with a quarter wave transformer and its feed line. Now I have found this video very useful for visualising what ...
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67 views

### Calculating inner resistance of a linear dipole

I've been stuck on a question for a while now, so I'd really appreciate if you could take a look at this: I'm supposed to calculate the dipole's inner resistance. I've got that E= 15V, R1= 1200 Ohm ...
99 views

### Linear antenna: with electromagnetic coil, trap circuit

I am trying to understand the concept of the linear antennas. I have read that the linear antennas are the simplest form of the antenna in the case of asymmetrical (coaxial) feed. what happens if I ...
1 vote
447 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 ...
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1 vote
6k views

### Shortening a long antenna with a capacitance

In many circumstances it is not possible to make a dipole antenna that has the optimum length of $\lambda/2$ (or monopole with ground plane of length $\lambda/4$). Car antennas are for example ...
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1k views

### Length of the dipole antenna

I know it is really stupid question, but I can’t understand. I have a picture with dipole antenna (different length). If I have the current distribution along the length, that it is easy to determine ...
212 views

### Dipole antenna director

Say a free metal rod is placed at a distance λ/2 from a dipole antenna (fig), both being of same length. I understand it will reflect and dampen the signal going to the left. But how will it impact ...
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### Which of the impedance values below represent an pasive dipole that absorbs both active power P and reactive power Q, and why?

I stumbled upon this exercise and I can't find anything in my notes regarding to this notion where it absorbs both kind of powers. You guys might have any ideas? These are the impedance values: Z1 = ...
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4k views

### Why is the bunny-ears TV antenna normally connected to 300 ohm twin lead?

The bunny-ears antenna is similar to a dipole, which has an impedance of ~75 ohm. Why are the elements of such antennas connected directly to 300 ohm ladder line? Wouldn't that cause mismatch losses (...
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173 views

### Ground under PCB pads for wire dipole?

I have a wire dipole antenna that I am connecting to a PCB. I know that ground should be cleared under most antennas. However, in my case the wire will be mounted away from the PCB. Do I need to ...
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454 views

### Why are this monopole and dipole antenna so similar?

I opened two different GSM antenna housings as shown on the images. The first image shows the RF SOLUTIONS ANT-GHEL2R-SMA antenna, which is an helical 1/4 wave monopole antenna. The second image is ...
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399 views

### Dipole Sleeve Antenna design in fresh water - Transmission frequency and emitted power?

Hello dear antenna enthusiast, I would like to receive and emit EM signals with a dipole antenna in the range of **433.9 to 434.5 MHz in fresh water. So I chose a half-wavelength dipole sleeve-...
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602 views

### Dipole antenna electric field generation

An antenna that is of half wavelength of a signal is a dipole antenna. When a signal is fed to this antenna, it should induce an electron flow. However, it is also said that this electron flow ...
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2k views

### Dipole Antenna Current Distribution

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 ...
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615 views

### Why for a dipole antenna half wave length is optimum size?

For a dipole antenna, half wave length is optimum size. Why is this so? What I understand is that radiation resistance of antenna is around 50 ohms at this size, which matches with the characteristic ...
2k views

### near field power density formula for a dipole antenna

I am looking for a formula for near field power density from a dipole antenna antenna. Is cylindrical model is sufficient? Do I have to consider ground reflection too? Please share your ideas?
80 views

### How do you account for receiver sensitivity in tranceiver half wave dipoles?

if you are to design 2 halfwave dipoles, both can transmit to each other using 3 watts and have receiver sensitivity of -80dbm (a picowatt). Suppose they are 800m and have same height from ground. How ...
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271 views

### Dipoles lengths underwater vs on land

A submarine (for example) uses a VLF communications system to remain in contact with its headquarters while submerged. The submarine drags a resonant dipole wire antenna behind it in the water. The ...
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