Questions tagged [dipole]

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38 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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2answers
31 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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0answers
45 views

Reactance of a dipole antenna

I am interested in calculating the input impedance \$Z_{in}=R_{in}+jX_{in}\$ of a dipole antenna numerically. However, I am unsure how I would compute the imaginary part of the impedance (\$X_{in}\$). ...
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1answer
51 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 ...
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0answers
52 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 ...
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2answers
52 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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1answer
546 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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1answer
128 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 ...
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0answers
94 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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0answers
24 views

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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2answers
1k 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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0answers
87 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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1answer
226 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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1answer
242 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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1answer
266 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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2answers
742 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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1answer
132 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 ...
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1answer
1k 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?
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1answer
56 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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3answers
223 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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1answer
65 views

isoPower Input-to-output dipole emissions

In ADI's Application Note: Recommendations for Control of Radiated Emissions with isopower Devices. Section "Input-to-output dipole emissions", it says: Input-to-output dipole radiation is ...