Questions tagged [dipole]
The dipole tag has no usage guidance.
22
questions
1
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0answers
93 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 ...
0
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0answers
42 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 ...
1
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2answers
44 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 ...
0
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0answers
52 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}\$).
...
-2
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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
54 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 ...
0
votes
2answers
58 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 ...
0
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1answer
732 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 ...
1
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1answer
156 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 ...
0
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0answers
103 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 ...
0
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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 = ...
6
votes
2answers
2k 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 (...
1
vote
0answers
98 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 ...
2
votes
1answer
235 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 ...
3
votes
1answer
249 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-...
0
votes
1answer
278 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 ...
1
vote
2answers
775 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 ...
0
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1answer
134 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 ...
0
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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?
0
votes
1answer
57 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 ...
1
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3answers
225 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 ...
0
votes
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 ...
