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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5answers
61 views

Optimal length of HT antenna for VHF UHF and diminishing return

I see folding antennas of various lengths that people are using for for their HT. My question is about the optimal length. I know it may "depend" on many factors so let me know if I need to provide ...
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1answer
56 views

How to model my rooftop vertical on 4NEC2?

A few months ago I built a coil loaded vertical, and put it on my rooftop. My roof is made of corrugated metal, so I connected GND to it, to act as a ground plane (or is it a counterpoise?). With some ...
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4answers
93 views

Building an AM Radio receiver

I am making an AM radio with the specifications of: Part 1. Design a circuit with an antenna for tuning your receiver to a signal of a specific carrier radio frequency so that you can select a certain ...
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1answer
60 views

How do I use a signal generator + oscilloscope to measure feeder length?

I could relatively easily take the feeder down and use a tape measure but it’s more of a challenge to learn how to measure the length using my oscilloscope -Red Pitaya - but I have to admit I have no ...
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3answers
2k views

How to receive a signal from multiple sources simultaneously (helical antenna)

I'm working on a system (theoretical at the moment) whereby I wish to receive data from multiple sources all transmitting at the same time. I've read that a helical antenna is capable of this. I'm ...
22
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3answers
4k views

How do Handheld antennas work without ground?

Dipoles have the 2 wires going to each leg of the antenna completing the circuit. Big AM towers use the second wire as a ground plane But how to handheld rigs transmit and recieve with just one wire ...
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0answers
65 views

What is happening in a gutter “antenna”?

can you explain me what is happening with RF in a iron gutter? I've tried to simulate with nec2, but I'm just a beginner and doesn't really know all the parameters to come close to reality. This is ...
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3answers
347 views

Bandwidth, Q-factor, Radiation Eff calculations

Is it possible to give approximate answers about what an antenna is capable of? There are a lot of formulas out there, but every single one I found is based on actual measurement; input, output, SWR ...
2
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1answer
58 views

144/430 MHz antenna on 155 MHz?

We have a local radio shop that started selling us Relm P150s with a high gain 9 inch antenna, and those are ok. He also has thrown in longer 15 to 14 inch dual band antennas saying use those in ...
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3answers
5k views

Conductive boom vs non conductive boom: what's the difference on a Yagi?

I designed a Yagi antenna using 4nec2, assuming that I would use a non conductive boom. If I use an aluminum boom but I insulate the elements from the boom, can I keep the same design? How does it ...
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4answers
100 views

Coax fed dipole: shield goes to one side, yet is grounded via chassis line to Earth

Suppose I have a coax-fed half-wave dipole antenna. The coax shield goes to one side of the antenna, the center conductor to the other side. The transceiver's chassis is connected (via the coax ...
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2answers
115 views

Working satellite on 2 meters, at what arc distance to sun (center) will noise floor be problematic to a disruption of a communication path?

Is there some simple utility, or published set of charts, or suite of formulae, where one can approach the situation by inputting a space weather summary, (sunspots, various indexes, etc), the receive ...
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2answers
102 views

Short low dipole, better if horizontal or vertical?

Say I have a shortened HF dipole (with significant inductive loading and/or capacitive hats), and can only mount it very close to ground level (but not touching), over lossy ground, and with no ...
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2answers
71 views

4:1 Balun question

With an OCF dipole, does it matter which leg, short or long, is connected to which side of the 4:1 balun, hot(coax center) or shield? How can you tell which is which, the balun is not marked. Thank ...
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5answers
3k views

Does mounting a ground plane antenna upside down change the takeoff angle?

A typical gain pattern for a quarter wave ground plane antenna is: Image from a similar question and see watermark. For a situation where the signals of interest are below the antenna in elevation (...
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2answers
67 views

Vertical antenna

I'm installing a vertical antenna in back yard. About 20 feet in height and using 1 counterpoise wire 16 feet for 20 meters. Does installing two or more counterpoise wires help?
2
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2answers
246 views

Strange Noise Floor observed in UHF Band

I have a tracking station for UHF band satellites which comprises of a cross yagi of 12 dBi and a wideband LNA of 40 dB Power Gain and 1.3 dB Noise Figure. I observe a Noise floor of about 300 kHz ...
4
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1answer
2k views

How to measure gain of an antenna?

I have dual stacked crossed yagi antenna. How can I practically measure the gain of the antenna combination? I know that this can be done in an anechoic chamber. But this is not feasible for me (...
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2answers
393 views

2,4GHz Spectrum Analyzer with wireless card

I am new in the world of Radio Technology and I would build an idea with Bluetooth 4.0 and want to see the frequency for debugging. So I will need a Spectrum Analyzer, but won't buy one of these. ...
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2answers
89 views

Small size vertical 10 m antenna with high gain

I need a directional antenna for 10 m that is less than half the size of a yagi or quad with more than about 7 dBi of gain, does anyone know if such a thing exists ?
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1answer
70 views

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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1answer
48 views

Squelch won't stay open on FM 2 meter band

I am currently using a Baofeng BF-F9V2+ radio. I have found the when listening, my squelch won't stay open, despite getting a good clean signal. I am using a homemade verticle dipole antenna for 2-...
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1answer
75 views

What gain and power are required for successful DX contacts on 2m/70cm bands in CW?

I would like to practice in CW on 2m/70cm bands when and if there will be a tropospheric or sporadic-E propagation. However I don't have mush space for the antenna. There is a possibility to install 3+...
4
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1answer
197 views

Is a ground plane antenna a poor choice to use in a forest?

Some time ago, when I just started with amateur radio, a few more experienced hams told me that an inverted-V works better in the forest than a ground plane, and that it has something to do with the ...
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2answers
83 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
561 views

Satelite dish modified for Wi-Fi (Signal Elevation Question)

I am doing a project where I will be re-purposing an old TV satellite dish as a directional Wi-Fi antenna. The dish is circular in shape, not oval. The dish has an arm coming from the bottom that ...
4
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0answers
63 views

Commercial Loopstick Antenna Manufacturers

Not sure this is the right forum for this but I thought I'd give it a shot. I am an electrical engineer working on a product that needs a loopstick antenna. I had thought that AM radios were so ...
5
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1answer
52 views

Do External Signals Affect Antenna S11/SWR Measurement?

Do external signals affect the S11/SWR measurement of an antenna? For example, if I try measuring the S11/SWR of an HF antenna with a SWR meter or a Vector Network Analyzer in the middle of a field ...
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1answer
69 views

Solid angle for different E/H plane beamwidths

The solid angle formula calculates the surface area on a unit sphere, from projecting a rectangular patch onto the surface of a sphere. Image source This is calculated using the azimuth angle $\phi$ ...
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3answers
159 views

Do I always need a tuner at both ends of the transmission line or is that only for certain types of antennas/circumstances?

Last night was my first night on the air as a General licensee and at HF. I've got an IC-7300 with the built-in antenna tuner. I'm pretty sure I understand how to operate the radio, for the most part. ...
3
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5answers
94 views

2.45GHz: constructing a horn of *thin* steel, what are good ways to join the edges (at least one joint along corner?)

TL/DR: How does someone make a good horn antenna system without using expensively made parts? Welding thin steel for this is not something even pro welders can do (it's a specialty app.) What are DIY ...
4
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1answer
71 views

no contacts with Rockmite

I finished building my Rockmite ][. It's running off of 3x 18650s, or 12v. I connected it to a MFJ-1840T and held the antenna horizontally in the air (also tried vertically) with my hand. I tried ...
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1answer
1k views

How does power received by a dipole relate to electric field intensity?

Let's say there's a transmitter far away, and I'm going to receive the transmitted signal. To keep things simple let's further say the transmitted signal is a pure, unmodulated sine wave. Further, let'...
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2answers
541 views

EFHW works only on one band - what am I missing?

I tried to build a multiband EFHW antenna as described in articles by PA3HHO, PD7MMA, G0KYA and many others. I decided to start with a short 40/20/(15?)/10 meters version without any loading coils. ...
7
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1answer
283 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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2answers
119 views

Can I use a “bunny ears” TV antenna for RTL-SDR?

I'm trying to get into SDR and was planning on buying an RTL-SDR. For an antenna, I was thinking of using an old set of bunny ears I have lying around. However, I first want to make sure that they'll ...
2
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3answers
459 views

Can I build a Yagi antenna for my Baofeng UV-5R?

I would like to build a Yagi antenna for my Baofeng UV-5R, but I'm a total newbie when it comes to amateur radios. The antenna will be for UHF and shouldn't be too long (like 1.5 meters max). So my ...
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1answer
74 views

Can any one explain E,H plane definitions?

I read in some text books that E-plane is formed by taking constant azimuth angle and scanning elevation angle from -90:90. H-plane is formed by taking a plane perpendicular to E-plane. What is ...
3
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1answer
107 views

Do Far-Field Radiation Patterns/Gains of NEC Software Accurately and Always Show the E-M Fields “Launched” by Vertical Monopoles?

Judging from posts on the Internet, this belief commonly is considered to be valid. But what is the correct answer?
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2answers
3k views

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 ...
2
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3answers
172 views

High Altitude Balloon Antenna Design

I'm designing a weather balloon with a club at college. We want to build the antenna from scratch to learn more about antennas but are at a loss as to which antenna design would actually work for high ...
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0answers
33 views

Center-loaded vertical, high SWR at lower frequencies

I built a center-ish loaded coil-shortened vertical. The lower radiator is 3 meters, then the coil, then 5M more radiator, like this (Early prototype with shorter radiators and no covers for the coil ...
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4answers
46k views

Effect of different metals for antenna elements

Other than rust, corrosion, and other reactions with air that would make the use of a metal unfavorable, how do different metals affect the performance? Let's give Yagi an example: Let's say I use 4 ...
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3answers
306 views

Why a capacitor is needed in Fuchs antenna?

I tried to understand the physics of Fuchs antenna and there is one thing that I don't quite understand. This is probably a very silly question, but I spent a lot of time looking for an answer (books, ...
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5answers
38k views

Good wire for wire antenna?

What properties should I look for in a good wire for building a wire antenna? Could anyone recommend something specific for me?
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2answers
135 views

What kind of loop antenna is this, and what is the relationship between its diameter and wavelength?

At the bottom of webpages in the advertisement swamps I keep seeing this image of an antenna, accompanied by an offer that I won't be clicking on. But the antenna itself looks quite intriguing. It's ...
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3answers
769 views

Efficiency of short dipole receiving antenna

For a transmitting dipole antenna, its length is important. If it is close to half the wavelength, it will be efficient and most of the input power will be radiated. How important is the length of ...
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3answers
1k views

How do I determine which HT antenna is better based on their very similar catalogue descriptions?

I'm considering getting an after-market antenna for my new 2 m/70 cm HT and am trying to decide which of the two antennas I should get. My primary reason for considering an alternative antenna is ...
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3answers
631 views

Would a 2.4ghz yagi antenna work for Ham Radio?

I am building a miniature yagi antenna that is made for 2.4ghz. Would a 2.4ghz yagi antenna work for Ham Radio?
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1answer
205 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 ...

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