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Questions tagged [dipole]

Use this tag for questions relating to dipole antennas.

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Two different dipoles attached to three trees

I wish to erect two separate antennas, one 20 meter dipole and one 40 meter dipole. My property has 3 trees that are the correct distance apart from each other. They are oriented such that when the ...
Tony565's user avatar
  • 21
0 votes
1 answer
50 views

Natural dipole / monopole filtering

Word has it these antennas are broadband, however my calculations show one may not need FM / AM BCB wave traps if not operating around those frequencies. I have run the script here for: ...
kellogs's user avatar
  • 205
0 votes
1 answer
97 views

Converting a 470-694Mhz TV antenna for 433Mhz reception

I'm working on a project which requires me to pick up LoRa signals that will be transmitted from a relatively low gain antenna. I've figured out that a large dipole would be idea for the receiver ...
Hristos's user avatar
0 votes
2 answers
100 views

How is the length of an inverted V affected by being too close to the ground?

In the near future, I'm planning to build an indoor inverted V dipole. However, I won't be able to raise the ends significantly above the floor. I understand that this will adversely affect ...
Someone's user avatar
  • 604
0 votes
1 answer
134 views

Input impedance of a shortened dipole antenna

I want to make myself a antenna for 40m and 20m wavelength band, but i don't have enough space for a full scale dipole, and even for more compact configurations like delta-loop or inverted v, so i ...
ZecosMAX's user avatar
  • 109
0 votes
2 answers
137 views

How to determine the best length for a short dipole antenna

If I were to design a dipole antenna that's significantly shorter than usual for the frequency, how can I determine the best length to use? In other words, given a frequency and a maximum length (...
mrog's user avatar
  • 1,023
2 votes
1 answer
113 views

Insulated mounting pole section for vertical dipole?

I am considering improving my 2m vertical dipole by replacing the top section of mounting pole with non-conducting tube. Will this have a positive effect on gain? I am theorising that the downward ...
Alex Mac's user avatar
2 votes
4 answers
178 views

Wave bounce inside a resonant antenna

Let's assume we have a transmitter, a feed line, and a standing wave antenna (dipole, etc.). The transmitter is matched with the feed line, and the feed line is matched with the antenna, which is why ...
elgroovy's user avatar
3 votes
3 answers
357 views

Advice on constructing half wave dipole with reduced velocity factor for site that is not quite big enough?

I want to construct an antenna competent on the 160m band, but I haven't got quite enough space, here's my thinking, please let me know if/what you agree/disagree with. I have a plot of land with ...
spl's user avatar
  • 255
1 vote
3 answers
2k views

Why does SWR of a dipole decrease the closer it is to the ground?

I experimented with a 20m dipole made of a 1:1 balun connected to 2x ~5-meter lengths of copper wire, running parallel to the ground (by "ground" I mean "pavement", not quite the ...
JayPulsar's user avatar
1 vote
3 answers
127 views

Tips for getting a 2m dipole higher while out in the field

I want to start operating the 2m band while camping, but with my current setup, my antenna would be very close to the ground and ineffective. So I'm wondering, does anyone have tips for constructing ...
I_like_python's user avatar
1 vote
1 answer
227 views

How to splice a 12 gauge, stranded wire to a ladder-line stranded wire?

I am building a zs6bkw dipole using a ladder-lock. For mechanical strength, I am looping the 12 gauge wire, as in the image below, and swaging it. The next step is to join the thick antenna wire to ...
A Bit of Help's user avatar
3 votes
2 answers
232 views

What kind of crimp part is used for stress relief on dipole?

I like the way that the person provides stress relief for the dipole antenna wire in the following image. However, I cannot figure out what kind of crimp "device" they are using for making ...
A Bit of Help's user avatar
2 votes
0 answers
156 views

How to convert device with Monopole antenna to Directional/Dipole antenna?

I'm trying to increase the transmission range of a stationary wireless microphone toward its receiver by connecting a yagi antenna. Aside from the antenna sticking out of the top, I don't know where ...
user20377's user avatar
4 votes
1 answer
203 views

Chimney Flashing Affect on Dipole Antenna Resonance

I put up a 40m dipole off a metal mast attached to a chimney mount on a 25' roofline. The chimney has metal flashing on the top with a metal spark arrest dome on top. I have 125' of RG8X feeding an ...
K5KUE - Conrad's user avatar
0 votes
2 answers
287 views

1/2 wave dipole instead of 1/4 wave + ground plane

I have a transceiver operating at 150MHz using a 1/4 wave vertical whip and horizontal ground plane at 90 degrees. My end user doesn't like the antenna sticking up in the air (trip hazard) so I'm ...
P_J's user avatar
  • 43
5 votes
2 answers
337 views

What happens if I “open” a folded dipole so that the two wires are not connected anymore?

A folded half wave dipole consists of two wires in parallel with only one of the wires driven, but the ends of the two wires electrically connected. As I understand it (and I may well be wrong there) ...
anyfoo's user avatar
  • 153
1 vote
2 answers
189 views

How is it possible for a halfwave dipole antenna to be resonant?

I've been learning about antennas recently and I have some questions about the halfwave dipole antenna. My first question is about its resonance; as I understand it everything that oscillates has a ...
user avatar
2 votes
2 answers
149 views

Can I convert an inline 1:1 CMC into a balun feed for a dipole?

I built my first 1:1 CMC transformer recently using 100 ohm CAT5e pairs in parallel. I used an FT-114-43 with 9 turns on each side and squeezed it into a small box with female coax connectors. I plan ...
wbg's user avatar
  • 301
13 votes
1 answer
2k views

Hanging a dipole from a tree not code compliant?

I just got off the phone with my town's electrical inspector (in Massachusetts), and he informed me that you are not allowed to hang anything electrical from "vegetation". He said if I did ...
kr4sh's user avatar
  • 367
3 votes
3 answers
867 views

Antenna options for a small urban garden

I've narrowed down my antenna options to fit a small urban garden. It's tough, space is tight and a neighbour three doors down reports everything I do to the council so I'm routinely inspected for ...
rcx935's user avatar
  • 411
2 votes
2 answers
523 views

How bad is it to make dipole elements slightly helical?

I'm looking to make a dipole for 10 M. TX power won't be more than 10 W, likely less than 1 initially, but I would prefer that it be reasonably good performance for reception. EDIT: After a ...
Toby Eggitt's user avatar
2 votes
1 answer
735 views

What kind of wire would be good for a 160m - 40m fan dipole?

I want to know the best copper wire or tinned copper wire for a fan dipole for 160, 75, 40 meters. It would be coax fed and I would like it to handle 1500 watts or more. I would like 65/30 strands of ...
Paul's user avatar
  • 21
2 votes
3 answers
1k views

Why half-wave dipole is the most efficient one in comparison to other electrical lengths of that antenna?

I have a problem on the understanding of a half-wavelength antenna. Namely, why is the half-wave antenna has a highest power emission. Considering Far Field factor F($\theta$), which is known from the ...
Pierre Polovodov's user avatar
3 votes
1 answer
273 views

Calculating SWR for a dipole

I have a dipole wire antenna that is tuned to 14.0 MHz so that it has an SWR there of nearly 1:1. Is there a mathematical formula by which I can compute the expected SWR for other frequencies? I would,...
Bill KG5RMJ's user avatar
4 votes
1 answer
978 views

How does the material of a fishing-pole mast affect antenna performance?

I'm a newly-licenced ham and currently starting out with HF. My home doesn't allow for a permanent setup. I can therefore only operate portable from parks and such, with limited TX power (my rig goes ...
Ivan R2AZR's user avatar
0 votes
2 answers
148 views

Is the phase difference between the voltage and current of the standing wave on a dipole antenna constant along the dipole's length?

Everyone knows that a 1/2 λ dipole antenna has on it a standing wave of RF energy the voltage and current of which are about 90° out of phase with each other. The standing wave is circulating reactive ...
Andrew's user avatar
  • 3,693
1 vote
2 answers
228 views

Does the self inductance and velocity factor of the elements of a dipole antenna change its resonant frequency?

Below are well known equations from Wikipedia for the resistance and reactance in the impedance of a dipole antenna. where $a$ is the radius of the conductors, $k$ is the wave number 2πf/c, $η_0$ ...
Andrew's user avatar
  • 3,693
5 votes
2 answers
527 views

Can coax be run through the center of a radiating element without currents being induced on the coax shield?

I run a λ/2 vertical dipole for 20M that's fed to a 1.5:1 balun at its center with coax that is perpendicular to the dipole (parallel to the ground), for about 30 feet before it comes down to the ...
Louis Seaman's user avatar
  • 1,127
1 vote
2 answers
615 views

For a resonant half wave dipole, is the phase of the applied RF voltage at the feedpoint in phase with the current reflected from the ends?

For a resonant half wave dipole, the voltage and current of the standing waves on the antenna are 90 degrees out of phase with each other. At resonance, is the phase of the current reflected back from ...
Andrew's user avatar
  • 3,693
5 votes
3 answers
1k views

When a dipole antenna is fed via coax, what powers the ground-side of the dipole?

I've been trying to understand how dipole antennas work, and I believe I understand the basics when they're fed via a balanced feed line. In fact, every dipole physics YouTube video and web page I can ...
Asker2093022's user avatar
1 vote
1 answer
310 views

Is a MagLoop antenna better than my 50ft end fed di-pole for 20-80 meters?

I'm restricted to putting antennas in my attic which is 50 feet long and peaks at about 8 feet. I'm currently using the Nelson UJM-150-50 end-fed dipole 80-10 meter antenna. The attic is about 25 feet ...
Irv's user avatar
  • 11
2 votes
1 answer
225 views

Identical HF Horizonal Dipoles Operating in Close Proximity

I'm planning to use a multiwave horizontal dipole oriented to work comms toward Alaska from Colorado. That ends up being awkwardly oriented to work east coast and Europe. If I placed a second ...
Ceer - KL5DV's user avatar
2 votes
2 answers
272 views

Destructive interference between two close antennas

let's consider this two planar biconical dipoles of total length and width each one 10mm, at a distance D = 25.6mm. They are excited with the discrete ports in the picture, which corresponds in this ...
Kinka-Byo's user avatar
  • 279
5 votes
2 answers
2k views

Receiving the ISS SSTV: dipole antenna configuration and orientation

In short I am trying to receive SSTV Images from the ISS (145.8Mhz) and I all have is a simple "bunny ears" dipole antenna. In what configuration (straight, vee shaped, upside down vee, ...) ...
Steven's user avatar
  • 205
2 votes
0 answers
98 views

Printed Dipole Transmission Line Equivalent Model

let's consider a printed dipole on a substrate with a GND plane: I've seen many times an equivalent model which uses transmission lines like this (reference): This model is useful to understand the ...
Kinka-Byo's user avatar
  • 279
2 votes
1 answer
98 views

Phase shifts in antenna arrays

Let's consider a simple antenna array. For instance, this three-elements equispaced dipole array: Each dipole is connected to a signal voltage source. It's well known that it's possible to choose the ...
Kinka-Byo's user avatar
  • 279
-5 votes
4 answers
693 views

Exactly what is the cause for the zero reactance seen in the impedance at the center feed point of a resonant half wave dipole?

Lots of explanations i've read on the internet written by ham radio operators and in some text books state that a half wave dipole is resonant when the inductive and capacitive reactances cancel out. ...
Andrew's user avatar
  • 3,693
0 votes
0 answers
48 views

How to decide between Dipole and Monopole antenna for Cubesat Uplink (433 MHz)? [duplicate]

We are currently deciding between a dipole and a monopole for uplink (435MHz) , while the monopole is easier to feed, we are unsure of how effectively we'll be able to implement the ground plane, ...
Rishabh Hulsurkar's user avatar
2 votes
1 answer
207 views

Half wave dipole with parasitic element, (Gain calculation)

good morning all, I have difficulties to find the correct formula that allows me to calculate the gain of half wave dipole in parallel with another parasitic half wave dipole. I'm trying to calculate ...
Tarik L's user avatar
  • 45
2 votes
2 answers
1k views

How does a 40/15m dipole with capacitance hats work?

I followed an article Antenna Here is a Dipole [PDF] by James Hearly, NJ2L to build a dual band 40/15m dipole: The antenna works more or less as expected. My 40m dipole was resonant at 7.030 MHz and ...
Aleksander Alekseev - R2AUK's user avatar
1 vote
5 answers
4k views

How to increase the bandwidth of half-wave dipole antenna?

I have designed a half-wave dipole antenna for frequency range of 150 to 200 MHz. Due to resonant frequency of 175 MHz, Its dimensions are: L=817.44 mm, R=1.71 mm. Impedance is also equal to 73 ohms. ...
Mohammadsadeq Borjiyan's user avatar
1 vote
1 answer
553 views

Yagi performing far worse than a dipole

A few months ago, I built a 6 element yagi: 3 driven elements, and 3 reflectors. For 10-15-20m. I was able to tune it to SWR 1:1 for the FT8 frequencies in each band. This antenna is only 6m above ...
hjf's user avatar
  • 1,219
0 votes
0 answers
206 views

Built a 2 meter 5 element Yagi

Straight dipoles. I can't get the Yagi to tune. I have tried the 4:1 Balun method with coax but not able to tune. With the straight unbalanced input to the dipole I get a 1:1 swr on about 129 MHz ...
David J. Montgomery Sr.'s user avatar
0 votes
1 answer
893 views

Pondering variations on the vertical bazooka antenna

I've seen these antennas built out of coax that are called a bazooka vertical. It's a kind of 1/4 wave vertical, or perhaps a 1/2 wave dipole. Constructing such an antenna is to roll back the outer ...
MacGuffin's user avatar
  • 359
1 vote
2 answers
224 views

How Does the Propagation of H-pol E-M Fields Compare to That of V-pol E-M Fields (other things equal)?

A rather popular belief on this topic is that h-pol is superior to v-pol. Probably that is traceable to published "far-field" patterns over a lossy ground plane generated by Method of ...
Richard Fry's user avatar
  • 2,922
1 vote
1 answer
2k views

440MHz collinear dipole array - suitable coax?

friends! Finally found my next antenna project..a collinear dipole array for the 70cm US ham band. The general idea: (image courtesy https://link.springer.com/referenceworkentry/10.1007%2F978-981-...
user avatar
3 votes
3 answers
632 views

What is an expected SWR plot for a trap dipole?

I've build a trap dipole for 20/40m bands. Traps are made of a coil wound on an insulator of RG213 coax and 3 kV NP0 capacitors. The impedance measured with EU1KY antenna analyzer is following: This ...
Aleksander Alekseev - R2AUK's user avatar
2 votes
1 answer
2k views

How Does the Performance of an Inverted V Dipole Compare to a Linear Dipole?

The NEC4.2 comparison in the answer below shows one example, for a practical set of installation conditions.
Richard Fry's user avatar
  • 2,922
1 vote
1 answer
408 views

Double Cross Dipole antenna for 437 MHz don't tune

I'm building a Double Cross Dipole antenna for 437 MHz to be used with a SDR receiver for CW cubesat. The idea is to follow this "classic" paper from Gerald Martes, KD6JDJ. I tuned every single dipole ...
Carlo IU2KQB's user avatar