Questions tagged [antenna]

Questions about the design, selection, building, testing, mounting, or properties of antennas. See also specific tags: [antenna-theory], [antenna-construction], [dipole], etc.

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3
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0answers
11 views

Dipole loading coil winding directions?

A single inductive loading coil in a vertical or a pair of loading coils in a dipole are commonly used to match a given total antenna length parameter to a given frequency wavelength (where the ratio ...
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1answer
38 views

How do I design a dual band LPDA antenna?

Im not sure if this is the best place to ask a question like this but its the best place i could find. My goal is to build a dual band antenna similar to this one. https://www.telcoantennas.com.au/...
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1answer
35 views

Can I connect a 75 ohm antenna to a 50 ohm radio?

I have been looking for an affordable yagi antenna to use with a dual band handheld radio and I came across some very inexpensive VHF/UHF (HDTV) antennas. They are all 75 ohm though. Is it ok to use a ...
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1answer
68 views

What type of antenna is this?

I have very little knowledge about antennas (I just read about simple dipoles and monopoles recently) and I need to buy a directional antenna for my wireless device. I have found a cheap antenna (I ...
4
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3answers
80 views

Why does no one use a Buddipole as an Inverted V?

I have been looking at the Buddipole, and I've seen the most popular configuration is as a standard dipole with the arms parallel to the ground. I've also seen it configured as an upright V, as well ...
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0answers
23 views

Unsure how to assemble Shakespeare SSB antenna; not working [closed]

Have 23 foot Shakespeare SSB antenna. Can not connect through the side feed termination band? Antenna not working? What is the band supposed to look like? Is the termination band supposed to be ...
3
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1answer
64 views

fan dipole with loading coil(s)?

There seem to be plenty of construction articles on center-fed wire fan dipoles with pairs of arms of different lengths, each pair dimensioned for a different band (e.g. half-wave 80M+40M+20M,etc.). ...
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1answer
61 views

Radio antenna for my FM receiver / Android FM

I want to make a radio antenna at home which will be able to receive all FM frequencies for my FM radio or Android FM. How do I make it? Frequency it can catch : 88 - 108 MHz Thanks.
4
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1answer
80 views

Dipole symmetry?

In ideal free space, both arms of a tuned wire dipole will be of identical length. However, the real world is not perfectly symmetric free space. The support heights, ground levels, ground ...
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1answer
70 views

Simple antenna for LoRa 433 MHz module

I have some LoRa SX1278 433 MHz modules: However, I don't have an antenna. My question is: what would be a good antenna option for longest range? I don't really care that much about transfer speed, ...
3
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3answers
118 views

Applications for 100 GHz band?

I was reading this paper and I found it very interesting and the following question came up, What are the main applications (what is used for) 100 GHz band? I couldn't find any reference on what is ...
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1answer
77 views

Colinear Vhf antenna

Textbook colinear vertical antenna designs show coax cable with alternating braid to centre configuration. Commercial whips seem to utilise a single wire as the radiating element with .66 velocity ...
2
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1answer
45 views

Dielectric Constant of Insulation/RF Permeability

I recently purchased a 500-foot roll of military surplus 14 AWG stranded copper wire at a hamfest for next to nothing . It is Prestolite M13486/1-6 (spec sheet). It has very thick chlorinated ...
4
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3answers
130 views

Feeding a folded dipole

Can I feed a folded dipole constructed of hollow tubing by threading coax through the element to create both an impedance transformation and balun? I have fed coax through the tubing of the dipole ...
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2answers
133 views

Restricted line-of-sight communication

Why do line of sight communication links have a restricted range for a given tower height? Is it only because of the Earth's Curvature?
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2answers
380 views

Multiband vertical antenna not working as expected

I built a vertical out of a 5M aluminium pipe. It tunes fine (and wide!) on 20M. I decided to add a loading coil to operate it on 40M, and it also worked fine, albeit not so wide. While I was at it, I ...
3
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1answer
93 views

What are the effects of a ground plane under a horizontal dipole?

What are the effects on signal propagation if this ground plane is just a metal object and what are the effects if the ground plane is actually grounded? I am asking this question because someone ...
4
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2answers
91 views

Is there any practical advantage to a parabolic reflector over a high-gain beam antenna?

I've been looking at options for a high-gain directional antenna recently, and I've noted that there are commercially available parabolic antennae for the shorter bands -- specifically 70 cm, with an ...
2
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1answer
618 views

Difference between antennas for Wi-Fi vs. ham repeaters

I understand that Wi-Fi transmits on 2.4 GHz or 5 GHz whereas local ham repeaters transmit around 147 MHz or 450 MHz. What differences would be needed in antennas tuning into either of these ...
2
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1answer
70 views

Should I run RG8x / mini8 zip tied to a cat 5e ethernet cable?

I'm running a feed line from the end of my amplifier to the antenna for HF transmissions. I'm using RG8x / mini 8. There's an existing pathway through my house I'd like to use that has a cat 5e ...
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1answer
56 views

SWR characteristic changes when lifting coax off the ground?

I was at Anaheim HRO and few guys there were talking about an MFJ all band vertical antenna that does not need radials. I forget what model number it is but it is one of those "wife pleasing antennae" ...
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6answers
251 views

Are transmit antennas the same as receive ones?

Are transmit antennas the same as receive ones? I am making a extended Wi-Fi comms CCTV camera.
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3answers
150 views

Do I have to disconnect antennas during thunderstorms?

lightning damage can be extensive and costly, its even life-threatening. If I have properly grounded the equipment and have a Surge protection device, do I have to disconnect the antennas during the ...
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2answers
65 views

Will close-loop metal hangers affect antenna radiation?

I'm working on a kite-supported antenna for an 80m QRP rig -- to be flown at beaches, on mountaintops, and possibly other places where I want to work HF but don't want to lug poles or give up ...
3
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2answers
70 views

Determining whether signal meets the 12 dB SINAD voltage

The specification for a certain radio receiver says: Typically 12dB SINAD NBFM for 0.15uV at 145MHz. If I understand correctly, this means that the received radio wave should have a voltage level of ...
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3answers
90 views

Weakly directive VHF/UHF antenna

Most resources around the internel discuss common antena types, classifying them between directive (like Yagi) and nondirective (like a simple dipole). Directive antennas are good when you know from ...
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2answers
81 views

What is the best type of feedline for a base UHF VHF ground plane antenna with a distance of around 50-75 feet of coax?

I'm going to be putting up a Comet GP6 UHF/VHF Ground Plane Antenna. It will be chimney mounted to a mast, and the total height is around 40 ft. The upper half of the chimney starts at the first ...
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2answers
126 views

Beamwidth of omni-directional antenna with gain

I am looking to buy a wifi antenna for a boat to connect to shore based wireless hotspots that may be "far" away. Due to the waves, I am assuming that the antenna mast sways +-15° from vertical. The ...
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1answer
40 views

Passive receiver power needs & data rate

I'm working on a project to design a space-based low frequency array. It will only be receiving signals, and it will operate between 10MHz - 100MHz. It is made of short wave crossed dipole antennas. I ...
2
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2answers
86 views

Low mass, low frequency transmission line

I'm interested in a low frequency (10 MHz - 100 MHz) radio receiver array, made up of crossed dipole antennas. I'm working on a design project mainly focused on the mechanical engineering side of ...
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1answer
63 views

why is 3rd order intermodulation for 2110-2155 = 1710-1755?

Trying to calculate 3rd order intermodulation for a frequency range (2110 to 2155). I know the answer is 1710 to 1755, but I don't know how to get there. attempts: ...
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3answers
143 views

NMO bicycle mount antenna has unexpected SWR

I built a bicycle antenna mount featuring an NMO connector to allow quick changes. With a 2m 1/4 wave monopole it gives reasonable SWR results (1.4 or so in the band of interest), with a particular ...
5
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2answers
62 views

Effective Area of Dipole Array

I'm trying to design a low frequency dipole interferometer antenna array. I am realizing how little I know about radio antennae. I'm confused by the concept of effective area $A_e$ and how it applies ...
5
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2answers
73 views

distance between shack and antenna

I am putting a 40m antenna in my attic and I was wondering would it be safe to have a shack in the room right below the attic (10ft of coax or less) or should I have my shack in the basement/ground ...
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4answers
141 views

Real world performance of magnetic loop antennas?

I was investigating about magnetic loop antennas. In a paper about them I found some bold claims: and This almost sounds too good to be true, considering a lot of us hams are surronded by city noise ...
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4answers
134 views

Antenna options for a 10x20m property with a large metal roof?

I live in a house that sits in the middle of the city, in a lot 10x20m in size. The first 6x10m are covered by a metal roof with a rather low angle (IIRC only 50cm difference between the highest and ...
5
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1answer
86 views

How do I identify a genuine Nagoya antenna?

I recently purchased a Nagoya NA-771 that I believe is counterfeit given the overall feel of the antenna. How do I identify a genuine Nagoya antenna vs. a counterfeit?
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1answer
76 views

Hobby Wire for Ground Radials

I'm putting in a radial system for my inverted-L and am wondering if the hobby wire like the kind sold at Hobby Lobby or Home Depot for hanging pictures, which is 22-24 gauge copper or aluminum, would ...
2
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1answer
147 views

Bow Tie antennas impedance

I see on the internet that a radio amateur made bowtie antennas for transmitting and receiving on the 2 meter and 10 meter bands. They produced very good SWR bandwidth when fed with 50-$\Omega$ coax. ...
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2answers
109 views

RTL-SDR dongle - what antenna should I use for APRS receive only?

I was following this guide to setup an iGate using an RTL-SDR dongle and a Raspberry Pi. It worked, and I have been able to test it by seeing some APRS packets from a separate transmitter (Arduino+...
2
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1answer
104 views

What is the radiation pattern of an EH antenna?

I haven't been able to find NEC cards or pictures of radiations patterns. I'm used to seeing them as polar diagrams, however, the only description I've gotten is "[t]he modification of the loop ...
6
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1answer
110 views

Why does adding 50-ohm BNC Ethernet terminator(s) in parallel to my 4-element yagi improve my radio's reception? (70cm)

I have this radio, with a rubber duck antenna, and a repeater twenty miles away to my north-northwest. If I set my radio on the top of a cabinet in my bathroom, I receive the repeater fine. I can't ...
2
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1answer
94 views

How can the gain of an antenna be negative?

Aaronia released this ultra-wide-range antenna, that can measure up to 35GHz. This was really impressive for only 3000 Euros, so I was considering purchasing it, when I figured I would look at the ...
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1answer
56 views

How do I use multiple antennas with two or more radios?

I'm building multiple antennas tuned to different amateur bands and would like them connected to my SDR for remote listening and analysis, and a handheld radio for transmission, which I may upgrade or ...
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1answer
264 views

What is the equation for the arm lengths of a half wavelength dipole antenna?

I was operating under the impression that the arm length of a half dipole antenna is λ/4 while making one that operated at the 145Mhz frequency using a piece of 9.525 mm (3/8 inch) copper tubing, at a ...
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2answers
108 views

What are these antennas used for?

I noticed this antenna park in Heidmoosstrasse, Switzerland. What is it used for?
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2answers
99 views

How does an E-Z-O Antenna work and why does it appear in Wikipedia's article on quad antennas?

How are the conductors/radiators in the E-Z-O Antenna configured, and why is it described in Wikipedia's article Quad antenna? I see three circles and a spider web of wires inside each, but from an ...
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3answers
111 views

How to Measure Signal Strength

I am building several types of radio antennas, and I would like to test which is the most effective. I am wondering: What is the best way to measure the strength of the received signal? It is at ~151 ...
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1answer
53 views

Can radio waves be made to travel as or along a particle beam? [closed]

Can a laser be used as an antenna? Can a beam of any type extend transmission distance of an electromagnetic field? https://medium.com/starts-with-a-bang/this-is-why-the-2018-nobel-prize-in-...
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2answers
113 views

How can I calculate current distribution on an end-fed dipole antenna in theory?

I understand that in a half-wave center-fed antenna current distribution has a sinusoidal wave approximately, so the current in the center has max value and it has to become zero at the ends of dipole ...