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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Does an antenna pick up signals of all frequencies or only its resonant frequency?
I heard that an antenna picks up signals of all frequencies, and then these signals are filtered by a circuit using an inductor and capacitor, and that this is how a radio is tuned.
However, I also ...
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Portable indoor VHF antenna for SDR
I want to make / buy VHF antenna that can meet the requirements below:
Portable (easy to install and transport).
Indoor (I want to install the antenna at a windowsill).
Low noise level, no (or not ...
CommunityBot
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How does a Large Loop Antenna work physically?
I am learning about loop antennas at the moment. I read that the response of a small loop Antenna is proportional to the rate of change of magnetic flux through the loop which causes a uniform current ...
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Creating a single feed wearable wire antenna
When I was deployed, our commo guys gave us wire antennas we could thread through our body armor (through the MOLLE loops).
These antennas were just lengths of 50Ω coax that had the insulation ...
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60kHz WWVB receiver help
I have built a large ferrite loopstick antenna based off this video. I live in Washington state and am trying to receive and decode WWVB. I can get my antenna to resonate at 60kHz with ~700 pF of ...
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Converting an FM Antenna to a 2m/70cm Transmitting Antenna
I have a 2006 Honda Goldwing 1800 with an extra FM antenna that I would like to convert to a 2m (or 2m/70cm) transmitting antenna. Changing the connector to a PL-259 seems to be the easy part and I ...
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How does a mag mount antenna achieve a ground plane?
I've been thinking for some time about magnet mount mobile antennas and wondering how they establish their ground plane. Consider that many mag mount antennas have some kind of protective coating on ...
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Can I connect my station ground to my house's ground rod?
I'm setting up my first HF rig and I'm reading a lot of conflicting information regarding station grounding. Can I connect my HF rig/station's ground to my house's ground rod or do I need a stand-...
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Can an antenna be affected if mounted to a bull bar?
When I say 'mounted to a bull bar' I mean the antenna being metal on metal contact to the bull bar without any rubber or fiber glass keeping the materials from touching.
Could this affect the ...
CommunityBot
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Slot antenna for 2 meter mobile
My primary vehicle is a Smart car, with a roof that's a piece of plastic(100% moon roof). Not the most awesome of cars to use for grounds. I'm building a bumper mounted antenna tower, EMT with some ...
CommunityBot
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What antenna is in this cylindrical vertical omni
Recently, I have received an antenna from one of the Chinese manufacturers and they haven't disclosed the detailed specification.
Below is the picture of my antenna (please ignore the specification in ...
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Antenna Aperature for out-of-band frequencies
I am doing some calculations where I determine power at the input of Rx given some field strength at the antenna. I have a question about the antenna aperture:
$A_e = D\frac{\lambda^2}{4\pi}$
$D$ is ...
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2
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Why don't J-Poles need to be grounded?
I'm building my first J-Pole and the different projects and articles I read about differ slightly but one commonility is a J-Pole does not need to be grounded. Why is that?
I read that it is optional ...
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Antenna for use in a rotating environment
I'm trying to use a low power wifi connection to move about 20MB/sec of data between a instrument mounted on a rotating steel barrel about 20 inches in diameter and a stationary wifi unit. A low power ...
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Hi SWR with End Fed HF Wire 9:1 UNUN
Good Day
I understand every antenna set up is different, so I'm looking for advice on what I could change to alter my findings.
The set up is new including the EFHFW - 20 which was bought off the ...
CommunityBot
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Will spray painting a J-pole impede functionality? [duplicate]
I'm building a J-pole antenna like the one specified here: https://www.sysjolt.com/2022/building-a-j-pole
As you can see it's made of copper pipe and I'd like to camouflage the antennae a little bit.
...
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Antenna from the roof / coax cable to Ham and Weather radios
Just want to make sure I don't need anything else (to prevent damage to the radios)
I have an antenna on my roof. It used to be used for TV but I switched back to cable.
Can I literally just use a ...
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Utilising old CB Base Antena to 5g Antena
Is it possible to utilize an old CB Base Antenna (10 meters tall) as 5g Antenna to plug into the back of a 5g router that is currently only registering 4G? I have one on top of a single story unit ...
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How do these ceiling mount dome antennas work? Are these discone antennas or horn antennas?
The small cone is connected to the larger one. The coax center cable is terminated into the small cone and the coax shield into the larger outer cone.
The screenshots are from this video https://www....
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Noise power with and without antenna
I have designed a receiver at 440 MHz with a 10 MHz signal bandwidth. I have measured the sensitivity of the receiver in a cabled setup (coax cable between transmit and receive) and that is about -93 ...
CommunityBot
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How far does an antenna need to be from metal to avoid problems?
Living in an apartment, I'm struggling to get good antennas set up, especially for HF. Worse yet, I'm not allowed external antennas (but am willing to try something low profile on the balcony), my ...
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Connection for Moxon antenna (blank space)
I just printed a Moxon Antenna and want to wire it. The Antenna wiring has a blank space and I'm not sure how to wire this place. From picture bellow I got that I need to connect a coax shield to top'...
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Exposure to AN/FRD
Why are Wullenweber CDAAs obsolete?
My dad worked inside the FRD sites on various Navy duty stations and is suffering now from Parkinson's and dementia. Has anyone else heard or read of similar side ...
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Magnetic loop antenna : loops vs selectivity
I've built 2-turn magnetic loop RX antenna using 5 meters of 6.5mm copper tube. I was able to tune it with a variable air-spaced capacitor in the range of 1.8-10Mhz, but I noticed that as tuning ...
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ZS6BKW deaf on all bands except 40
I have purchased a high quality ZS6BKW from the U.K. I have it suspended up about 40' between 2 trees. There is 30' of coax from the ladder line to the radio (Kenwood TS-870).SWR on the MFJ269 shows ...
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How can an HT antenna be half wave?
There's a model of HT antenna for the GMRS band by Nagoya (NA-771G) that's specified as a half wave. How can that be? An end fed half wave antenna needs a 49:1 impedance transformer to match with ...
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How can I safely transmit without an antenna tuner or SWR meter?
Just what the title says.
An Antenna Tuner, henceforth AT, is almost a de facto piece of equipment in a shack; working the bands without one is tantamount to leaping off the diving board into a ...
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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 ...
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Off-center fed long wire antenna
I want to feed a horizontal wire antenna (approximately 150' long at 50' or more above the ground) for multi-band HF operation with an off-center (25-33%) feedline. The element wire will have no ...
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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 ...
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What is this vertical antenna with radials pointing up
I work next to "Koninklijk Marine Kadettenkorps Afdeling Oostende" (Royal Marine Cadet Corps Ostend). They have an antenna that I've been wondering about for years now:
It is a vertical ...
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Is 100m too long for hf feed wire?
I have room to erect a DX Commander, multi-band vertical, and to give it a good number of radials on a good clear site.
Problem is I would need to run about 80 - 100m of coax feed from operating ...
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Why does my received power rise so much when I connect an antenna?
I am in early stages of making a narrow-band radio receiver (block diagram below). To give you an idea, I am using a simple CP-FSK based modulation scheme, and have achieved 5dB SNR with a Tx signal ...
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HF vertical 1/4w antenna on a tin roof?
I would like to build a 1/4 ~ vertical antenna on my tin roof for a ground plane.
Does the angle of the roof matter?
Should the antenna be vertical, or perpendicular to the roof?
Would it be better ...
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Would a 3D-printed antenna case interfere with the antenna itself?
I primarily use a Baofeng for most of my contacts. I've got a pretty good antenna (14.5 inch whip), but when I have to pack it into any sort of bag, I'm always worried that it'll get bent. This has ...
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Is the noisy spectrum from 20MHz to 330 MHz normal?
I have recently been testing some VHF/UHF antennas for reception in my Lab, and have noted something I could not explain. Following are the spectrum plots captured on our R&S FSV spectrum analyzer,...
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How to Construct a Dual Polarization Cubical Quad Antenna for 10 m?
I want to make a four element diamond quad for 28 MHz which can be switched between horizontal and vertical polarization. The spreaders would be made of fiberglass.
The coax for the driven element has ...
CommunityBot
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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 ...
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TV Coax cable for QFH antenna
I'm new to this hobby and I'm trying to make me a QFH antenna for NOAA satelites myself. I would like to know if I can use AC15-380WH 4/8K TV coax cable with double ...
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How can cross-polarization loss be determined given the angle between two antennas?
This question addresses the case where two antennas are exactly 90° cross-polarized, but not other angles.
How can I determine the theoretical, and estimate the actual, attenuation from cross-...
CommunityBot
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Would two perpendicular dipoles work to avoid polarization mismatch?
What would happen if you made an antenna consisting of two perpendicular dipoles tuned for the same frequency and connected to the same feed line? Would this work to avoid polarization mismatch loss?
CommunityBot
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How to assemble a DB8 antenna balun
I have an old (2009) Antenna Direct DB8 antenna that has never worked great. I would get good reception then poor reception and not due to atmospherics. I finally decided to take it down and inspect. ...
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LTE (4G) - Is two (or multiple) antennas better than one?
I have two antennas. A "multiband" (1710~2170 Mhz, 22 dBi)...
...and a "fullband" (700~2600 MHz, 15dBi)...
Taking into account that my modem (router) is "fullband" and ...
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How does nitinol shape memory wire work as an Antenna in 60 MHZ whip antenna?
I'm trying to make a body whip antenna for some friends of mine running at 60 Mhz at 10 W power. We are in the military, and we are trying to make an antenna that can be routed through our gear to ...
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AX.25 protocol packet size
I am new to the world of amateur radio and I am carrying out a university project concerning the communication between satellites and ground stations.
My question is:
What is the packet size of the AX....
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Serial Inductors in Tuned Circuit - Elenco AM780K AM Radio Kit
I'm trying to understand a component of an AM radio kit that I have. (There is a document available here: https://www.elenco.com/wp-content/uploads/2017/10/AM-780K_REV-K-2.pdf describing the build ...
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How to create FM Radio Mesh
What (devices transmitters, receivers and transceiver) do i need to create a fm radio mesh, instead of using a single transmitter with big antenna, i want to build fm transceiver mesh radio to cover ...
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HF Vertical antenna with no radial and loading coil but only ATU for 80m to 10m in a boat
I am new to HF antenna designs. I want to build an antenna for my fishing boat. My question is - if I use an ATU (like the ATU-100) and a 10m aluminium pipe as an antenna and fix it with a mast, will ...
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How to produce a NEC antenna file (and what software to use it with)?
So I'm really trying to get to grips with antenna radiation patterns, and more importantly things that are to close to the antenna that might interfere.
I've downloaded Qantenna and 4NEC2 to try and ...
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Why did the International Telecommunications Union denote CY for Canada?
CGP Grey recently released a video on the history of airport acronyms, e.g., LAX. He briefly said that you may wonder why codes for Canada started with Y and formerly CY, and that it traced its ...
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