Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [dipole]

41 questions
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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 attempt. From the textbook about point-dipoles An…
NoName123
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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 (even with the other end going into a balun)?
Mark
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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 antenna's impedance. My confusion is regarding the…
TheDorkSide
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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 dipole antennas: i.e., the radiated power is swamped…
divB
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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-antenna design that I made by myself out of coax cable…
AndRe
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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 the SIRETTA DELTA2C/X/SMAM/S/RA/25, which is,…
Jager
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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 there any other advantages of patch antennas over…
Mrunal Shinde
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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 know that the minimum gap is zero and the maximum…
Bobby
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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 don't use other waves (radio, visible, gamma…
Prerna
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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 radiation pattern and a spacing of 0.75*wavelength, it…
DaDSPGuy
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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 port of the VNA and run the measurement. I am…
Anonymous
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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 solder for about 1/2 inch. The two pieces of wire are then…
Mel Pama
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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 is happening with standing waves…
Hart22
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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 NOAA APT signals at 137 MHz. Many sites with…
Alex Wulff
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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 shorter than they should be, which would result in…
DK2AX
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