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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Antenna reciprocity how does an antenna increase receiving range?
According to Wikipedia antennas are reciprocal unless they're constructed of nonreciprocal materials.
There are a multitude of mathematical formulas which unfortunately I'm unable to understand due to ...
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Do I need an antenna tuner for new mobile antenna
I am looking to buy my first mobile antenna, for use with a 2m/70cm HT in the car. The HT needs 50 Ω impedence.
I was looking at this antenna, but another ham told me that I need 1/4 wave or 5/8 wave ...
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Using old vehicle through glass cell antenna
My old (2001) Seville had a cell phone with antenna mounted on the rear glass. The coax connects inside the glass, with signal passing through the glass to the whip mounting plate.
I'm wondering if I ...
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How can I inject an oscillator output into the RF input to my radio?
I have a Bodnar GPS disciplined oscillator, and I would like to inject its output into the antenna input to my HF rig. This will allow me to compare the frequency of received unknown signals to the ...
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does the shape of an antenna ground plane matter?
I would like to test a tranceiver setup I created before I mount it in my car. In my backyard, there's a length strip of metal; 10m in length, 10cm wide. Now I wonder if I can use that as a ground ...
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NooElec for Startup HF Communication
I am working on setting up a Ham Radio shack for long distance communication on the HF frequency. The goal is to transmit 1,200km from Alberta to Manitoba using skywave propagation. I would need to be ...
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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 ...
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Type of Ground Wire for an AM Crystal Radio - I'm using a longwire antenna
I have way too many choices for ground wire. I am using a crystal radio so I need the BEST not just what will 'get by'. I've seen solid copper 10gauge, aluminum wire etc. I've also seen wide ...
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cut or lengthen to reduce swr on vertical wire antenna
Have tried measuring antenna wire using formula 234/frequency for 1/4 wave vertical but this gives high swr. How do I lower swr on a wire vertical antenna. Do I Cut or Add? wire'
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Route cables on the inside of the tower?
I was visiting a customer site who had their equipment fried by lightning and granted they forgot to install surge protection, so that's most likely what did it, however I also noticed they had the ...
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How do antennas over 1/2 wavelength work?
I've been told countless times that an antenna should be 1/4, or 1/2 wavelength. That increasing this size to a higher multiple of 1/4 will work, but it will distort the radiation pattern to include ...
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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) ...
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Will two nearby yagis on different bands interfere when transmitting at the same time?
I'm working on a digital ham radio project that will require two 2m and/or 70cm yagi antennas to be transmitting and receiving in somewhat close proximity to each other. Each will have it's own ...
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Extend transmit range of my HT
Based on comments and new information I have rewritten this question entirely:
I need advice on a simple, inexpensive, and non invasive (no holes being drilled in walls) way to talk to repeaters in my ...
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Can an 'ugly balun' be too long?
Will an ugly balun exhibit adverse effects if more coax is wound onto it than the recommended 18 - 21 feet?
The antenna in this instance is a 40 Meter Delta Mono Loop that suggests using 22'-6" ...
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Understanding Impedance (R+jx)
In a typical antenna (lets say dipole for this discussion), the pattern below is observed in the impedance (R+jx) graph:
I'm trying to wrap my head around this graph.
Why does the resistance spike, ...
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Is this amount of loss normal with LMR400?
I have a run of about 150 feet of LMR400 (specifically, it's this DX Engineering "400MAX" product). It connects to an Ed Fong antenna (2m, 1.25m, 70cm tri-band J-Pole) about 75 feet up a ...
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Why do ham radio operators refer to current flow on the outside of coax as common mode current?
My understanding is that the desired mode of operation for a two wire transmission line is differential, where at any point along the line the addition of the voltage or current is zero, such that the ...
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ELF antenna receiver build instructions?
I built a vlf receiver in the nineties but good grief, that's a long time ago and have looked very little at receivers since.
I'm interested in frequencies from 12 - 18 Hz.
Looking at the following
...
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How do I rewire a simple a.m. loop antenna that became unwound?
This antenna has been around for decades and the design is as basic as can be.
Somehow the antenna I'd been using, became unwound. The total length of the wire is 4.9ft.
I need to know the proper ...
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YouLoop antenna for amateur satellite reception
I recently learned about the commercial YouLoop antenna and it seems to be quite simple to set up. They said it was possible to receive satellite signals on amateur VHF (e.g. NOAA and other CubeSats ...
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Radio without antenna?
Is it possible that there will ever be a radio system that does not require antennas? (Not small embedded antennas for microwave radios, but radios that actually do not have antennas)
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Transmission power of Apple Wi-Fi antennas (EMF and health)
(I hope this is the right place for this kind of question)
Background
I was looking a little bit into how Wi-Fi affects our health topic. While many people seem to be concerned about their Wi-Fi ...
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Why are longer antennas not suitable to pick higher frequencies?
I know that the length of an antenna depends on the wavelength of the frequency it's trying to receive.
A higher frequency needs a shorter antenna and vice versa.
I can see that with a high frequency ...
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VNA basics, antenna coax cable
Recently purchased my first VNA (Nano VNA) and I'm trying to learn the basics.
I have a 150MHz 1/4 wave whip antenna that I need to install on a large metal object so I was hoping to use a VNA to help ...
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Small shortwave (20MHz) directional antenna design
I'm trying to do some basic radio astronomy experiments, and I'm currently working on picking up radio bursts from Jupiter. These are emitted at around 20MHz; for all intents and purposes, Jupiter is ...
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Phase-tuning Yagi-Uda antennas
Related to my earlier question around the TET-Emtron HB35C antenna. It is advertised as a:
The HB35C is a full size tri-bander, efficiently utilising the DUAL
DRIVE HB9CV system with the ...
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259
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Cleaning an oxidized NMO Mount
Before going through a car wash, I took my mobile antenna off its NMO mount and it looks like water seeped in through the threads. It's not corroded (i.e., there's no metal flaking off) but it's not ...
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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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How should coax be physically wired to a "stud" mag mount?
I picked up a variety of antennas at a swap meet a while back, and am having trouble characterizing an unlabelled HF (or low VHF?) vertical element that screws into a stud in a magmount I also brought ...
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What's the effect of directly connecting ladder line to coax?
I was watching a video where ladder line (450-ohm) was directly connected to coax (50-ohm) without a matching transformer.
Mating your Coax to Ladder Line
Wouldn't this mismatch make it impossible to ...
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Are "end-fed" antennas really more multi-band than dipoles?
Several "end fed" antenna kits (including the ARRL's for example) include wording suggesting that they are useful as multi-band antennas.
But does feeding a wire antenna highly off-center ...
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Calculate antenna the length of an antenna for 477Mhz uhf radio [duplicate]
I'm very new to Ham radio and would like to know in simple terms how to calculate antenna the length of an antenna required for a 477 MHz uhf radio and or half wave or 1/4 wave whatever is better. I ...
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Issues with high SWR on HF Kits EFHW 49:1 UnUn kit
I recently tried assembling a EFHW kit, and some problems came up in testing. I believe this is the kit; I bought it through ARRL: HF Kits website. This is my first time making an UnUn and EFHW kit.
...
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G5RV ZS6BKW SWR problem
I bought this dipole wire antenna brand new. It came with the 1-1 Balum and 41’ of ladder line. I can only hang the wire 30’ off the ground. 11 feet of the ladder line hangs close to the ground with ...
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What is this BNC-type radio connector about 13mm diameter?
What is this radio connector? LIKE BNC, but it is about 13mm in diameter, odd.
Follow up:
It turns out putting a sma BNC adapter in the center of it does work.
In place of a "C" or "N&...
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How would I calculate the diameter of an dish from antenna gain, or effective aperture?
So far I've calculated the effective aperture using an equation. However I was wondering how to calculate dish diameter using the gain calculated earlier and if there's an equation for this?
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What is the best way to allow for SWR adjustment for a cubical quad?
The driven element of a multi-element cubical quad is usually made of wire, and there is no adjust for SWR. How can adjustable SWR be provided for such an antenna ? Can a gamma match be used ?
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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 ...
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36ft pole from the ground then adding 7.80 meters antenna on top is this legal
If I use a 36ft pole and a 7.80 meters antenna on top of the pole, is this going to break the law in Scotland?
My antenna that I'm planning to install is a siro 827.
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Building Antenna Trap: Highest impedance/lowest capacitance/greatest # of turns?
I made my first multi band antenna this weekend for 20 and 15 meters for an EFHW wire with a 49:1 unun, to be used with 5 W rig. I used a toroid I had on hand, T80-2.
I hang this antenna in my living ...
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Lightning Antennas 4 Element Quad Feed System Validity
I recently purchased a 4 element quad for 10 m from Lightning Antennas in USA. The antenna is designed to be mounted so the elements are diamond shaped. Notice in the picture how nice and straight the ...
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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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How do phased array antennas work when they produce spot beams?
Background
In a lot of literature regarding satellite communications with phased arrays, you'd see this kind of image:
Conceptually, I get the basic concept of how this works - a bunch of small ...
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Where can I find information regarding RESONANT long wire antennas?
So multiples (by 3x-5x) of full wave lengths long? It's my understanding that you can build an antenna that is 802.28 feet long and it's naturally resonant WITH GAIN on all the usual Field Day ...
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The Terrestar Genus was able to talk to a GEO satellite in a smartphone-sized package, where's the antenna on this thing?
Background
I'm doing some research on a company called ASTS who claims to be able to connect to regular smartphones from a satellite. Initially I wrote off their claims, but after looking into it a ...
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What's the methodology of MDF magnetic field antenna?
I get a MDF 9400 magnetic field antenna from school.
I am not able to disassemble this flat antenna to take a picture.
I am not sure if this antenna detect only magnetic field.
I am not sure if ...
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UHF/VHF Satellite ground station with a discone antenna
I'm in the process of building an SDR-based satellite ground station using a discone. The discone is chosen due to its wider frequency range. Additionally, a dual-band LNA with around 20 dBi in both ...
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Resonant RF transformer using a piece of wire (no capacitors)
I previously posted this in electronics StackExchange here, but I believe Ham is more proper place for it as it closely relates to antennas.
I'm curious if it is possible to build a spark-gap Tesla ...
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Why do mag mounts not achieve proper grounding seeing as the coax outer connects to ground?
Diamond instructions for my CR8900 antenna state that proper grounding is required for the antenna to work. The battery negative is already grounded and has continuity to the coax outer so isn't the ...
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