Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

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.

3
votes
2answers
86 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
votes
2answers
54 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 ...
4
votes
2answers
63 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 ...
3
votes
3answers
70 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 ...
7
votes
3answers
97 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
votes
1answer
72 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?
0
votes
1answer
72 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
votes
1answer
87 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. ...
1
vote
2answers
62 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+...
1
vote
1answer
64 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
votes
1answer
99 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
votes
1answer
85 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 ...
1
vote
1answer
44 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 ...
1
vote
1answer
234 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 ...
3
votes
2answers
103 views

What are these antennas used for?

I noticed this antenna park in Heidmoosstrasse, Switzerland. What is it used for?
3
votes
2answers
81 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 ...
3
votes
3answers
73 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 ...
0
votes
1answer
52 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-...
4
votes
2answers
96 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 ...
5
votes
1answer
92 views

Are there reasons why a receive-only wire antenna should not be λ/2 in length?

The answers to this question explain why it's difficult to transfer power from a transmitter to an antenna that is λ/2 in length (or a multiple for long wires, or as half a dipole's length). Are ...
3
votes
3answers
147 views

Why long wire antenna length shouldn't be a multiple of λ/2?

Numerous sources say that LW length shouldn't be a multiple of λ/2 for any frequency in interest. This will cause the antenna to have a high impedance at this frequency. Since the coax cable impedance ...
2
votes
1answer
72 views

What happens to the transmitted power cancelled out by a yagi antenna's reflector?

For a yagi antenna, for transmit, does the waveform traveling away from the driven element towards the reflector get cancelled out by the reflector and then simply disappear ? Or is that cancelled ...
0
votes
1answer
96 views

Antenna relay switch design

I want to build a generic multi-antenna switch using relays. Many projects on the web have done this but the relays have silver contacts. This would be fine if I were to transmit to all antennas so ...
2
votes
1answer
56 views

Can an indoor antenna damage unshielded electronics?

I have a 25w radio running through a ~4.5db gain antenna. If I use a 4W HT indoors, I can hear a loud buzzing noise emmanating from my computer speakers. If I used the 25w mobile with the 4.5db gain ...
6
votes
4answers
168 views

Why are there differences in antennas that depend on electrical component and magnetic component of a radio wave?

I understand the idea that when we are targeting the electrical component of the radio waves we need to have some form of a linear conductor that receives the electrical component, this creates a ...
4
votes
2answers
235 views

Share wide band antenna with multiple transceivers

I'm trying to incorporate several transceivers on my board design; I need WiFi (2.4 GHz) SatCom (~1.6 GHz) RF (~900 MHz) and GNSS (~1.5 GHz). I need to combine them into one antenna. I found a wide ...
2
votes
1answer
99 views

Magnetic Loop Antenna with RFI Choke

Because of space limitations, am purchasing a magnetic loop antenna. Because of needing to move the antenna around, do i need a RFI choke in the feed line?
8
votes
3answers
615 views

Why does “Ethics and Operating Procedures” suggest tuning on a dummy load?

The seminal work "Ethics and Operating Procedures for the Radio Amateur" suggests in subsection II.8.1 to perform tuning only on a dummy load. Sometimes before transmitting it is necessary to tune (...
0
votes
2answers
123 views

Simple Longwire/Dipole Antenna design

In a couple of days I am going to a mountain cabin and I were thinking about making myself a semi broadband antenna for LF/HF (300KHz - 20MHz or so) for receiving only. I was thinking about creating ...
2
votes
2answers
95 views

What's the earth in this antenna exactly?

This antenna: comes with an balun (or unun) that has three connectors. One for the coaxial cable to the radio, one for the antenna and one for the earth. My understanding is that the earth is an RF ...
4
votes
4answers
149 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
votes
1answer
61 views

6 meter mobile antenna grounding

So I've been looking at my different options for 6 meter mobile antennas. My question mainly pertains to grounding. I've heard hams talk about needing a ground to the frame of the vehicle when using ...
1
vote
1answer
62 views

Mobile VHF/UHF antenna coupling to surrounding objects?

Will a mobile antenna --either mag mount or NMO mount-- couple to surrounding objects such as tall trees, taller trucks, buses, or even people walking by? If that is the case, would you get slightly ...
3
votes
2answers
525 views

Antenna polarization when dealing with satellite communications

It's easy to understand, conceptually anyway, the difference between a horizontally polarized antenna and a vertically polarized one, when referenced to ground. However, when they are pointed nearly ...
7
votes
3answers
112 views

Can I use a helical ground plane radial in the same way that a loading coil works?

I'm working out the science behind mounting an antenna on a vehicle, and I came across the concept of ground planes. This answer says that longer is better but don't worry about it too much, but this ...
2
votes
1answer
34 views

Triband vertical antenna 6/2/70

I wish to fit this on the house gable end, however the location has a metal phone line bracket that will be just bellow the antenna radials. Will this cause any detrimental effects?
3
votes
1answer
106 views

Antenna for receiving 868MHz rocket telemetry: QFH(QHA), Helical, or?

I'm building a radio communication system for an amateur rocket project. We've decided to use LoRa 868MHz system. My question is, which antenna for the ground station will be the best choice? We're ...
2
votes
1answer
142 views

Yagi-Uda antenna - energy flow density calculation

This task is our milestone, even the lecturer doesn't know how to do it, I will be grateful for even the smallest clue, thank you in advance. There are given two, identical, parallel, short dipoles ...
0
votes
1answer
61 views

How to characterize and select UHF linearly loaded antennas?

Q1.1: Why can a helix calculator not be used for linearly loaded antennas? Those online calculators suggested that the turn pitch/wavelength should be around 0.25. However, a typical linearly loaded ...
3
votes
3answers
176 views

How thick should counterpoise wires be?

I would like to use a shortened whip antenna with a coil in it's base, e.g. OPEK HVT-400B. My transceiver maximum power is 100 W (and antenna's - 120 W). To make the antenna work I need counterpoise ...
3
votes
2answers
211 views

What are these large antenna structures (used for)?

Flying around the area, I noticed this from the air - I have tried doing some searching but have been unable to find the name of the design or its specific use; What is this massive antenna, and what ...
7
votes
2answers
123 views

How to derive antenna gain from radiation pattern

I need to calculate the antenna gain in both dimensions: azimuth and elevation. The datasheet of the antennas I am using has two different radiation patterns, one for the elevation and one for the ...
5
votes
2answers
584 views

RF Antenna - V pole - Should one leg go to ground and the other to signal?

I'm attempting to follow this white paper in order to build an antenna. This is my first antenna and as such I have a rather simple question. DIY 137 MHz APT Weather satellite antenna by Adam-9A4QV ...
3
votes
2answers
134 views

Will wrapping an antenna around my house next to metal affect it?

My unit is 25' by 25' each side and the front is 22' across. The overhang is about one foot with aluminum and vinyl underneath. If I wrap an OCF dipole (fed with 4:1 balun) around this overhang in ...
0
votes
1answer
66 views

ADS Simulation: How to model an antenna in a simple rectifier circuit?

As titled, I'd like to explore the output power of a simple diode-based rectifier circuit, excited by an antenna (assumed to be 50 ohm impedance). Please give me some advice as to how to do this. It ...
17
votes
5answers
4k views

How does the signal know where the cable ends and the antenna starts?

I know very little about antennas. I know, that for a certain frequency the antenna needs a certain lengths for good sending/receiving conditions. Often the antenna is at the end of a cable. Why doesn'...
1
vote
1answer
115 views

Raising height of inverted V by 2 meters

Now that I have a working G5RV Jr. and have had some good luck with DX (Croatia and Venezuela on 20m, Morocco on 40m from Michigan at 100w output), of course I want to mess with the configuration. It'...
6
votes
1answer
156 views

How to make a ferrite bar antenna for RTL-SDR?

I bought a RTL-SDR (blue one with little MCX antenna). I modified its Q branch, and can receive short wave radio with Degen 31MS antenna now. For MW, Degen 31MS antenna has a ferrite bar antenna ...
0
votes
1answer
68 views

Antenna Type of a Chinese Antenna

Recently, I have received an antenna from one of the Chinese manufacturer and they haven't disclosed the detailed specification with us. Below is the picture of my antenna (please ignore the ...
0
votes
1answer
100 views

Antenna height for LoRaWAN Gateway

I have designed a LoRaWAN gateway and it is under testing. I have been using omnidirectional ...