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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1answer
324 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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2answers
135 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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2answers
205 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
213 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 ...
4
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1answer
127 views

Commercial Loopstick Antenna Manufacturers?

I am an electrical engineer working on a product that needs a loopstick antenna. I had thought that AM radios were so commoditized that I'd be able to find an off-the-shelf vendor. However the closest ...
5
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1answer
72 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 ...
4
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2answers
143 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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1answer
106 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
209 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. ...
4
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1answer
86 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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2answers
108 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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5answers
173 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 ...
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2answers
357 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 ...
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1answer
86 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 ...
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2answers
149 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 ...
3
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1answer
134 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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1answer
97 views

Convert NEC antenna file to .out-file for Wattwächter

I've just wrote a NEC Antenna file of my longwire with xnec2c on Ubuntu. To calculate protection distance with Wattwächter, I need an .out-file. Protection distance means the safety distance for human ...
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3answers
597 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 ...
2
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1answer
781 views

300 ohm to 50 Balun at antenna feedpoint, or near receiver?

If I build a folded dipole, it will have an impedance close to 300 ohms. I have to match this impedance to the 50 ohms of my transceiver. I know many people match that impedance with varying lengths ...
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3answers
327 views

To folded dipole, or not to folded dipole?

I currently operate a 20M half-wave dipole with a balun. It's a little lower than ideal, but it gets me on the air. I've read about folded dipoles. But I've found contradicting information about them....
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1answer
94 views

Use for Verizon 4G tower antenna

Our church had a Verizon Cellular site until about 6 months ago when Verizon cancelled the lease. After they left we negotiated for them to leave the cabling between the cell site and the antenna ...
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2answers
159 views

ISOTRON 80m 75m Antenna Position

I know, a dipole is the way to go, but cannot fit one, only a 'birdhouse' antenna like the 75m 80m Isotron antenna. Is it better to put at 15 feet Above Ground Level outside, or 20 feet AGL ...
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3answers
458 views

Tweak antenna resonant frequency higher

This is a very simple question and I'm sure if I had a bit more background knowledge, I could figure it out myself. Let's say I have a 1/4 wave vertical antenna that is slightly too long, but it is ...
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1answer
223 views

How would I calculate aperture efficiency for an antenna?

How to calculate aperture efficiency for an antenna with the following parameters: Big reflector diameter= 24 mm Gain= 9.265 dbi Frequency= 11.60 GHz
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1answer
214 views

When I am told that a dipole must have a determined length, does that include the space between both elements?

I am trying to build an antenna for receiving NOAA satellites and I need to build two 137,5MHz dipoles. When I enter the frequency and width of the wires in a calculator, I obtain that $λ/2=1.09\,\...
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2answers
145 views

Basic antenna matching theory?

I'm fairly new to antenna matching, other than having built a base loaded vertical. I'm also new to EZNEC and I tried to simulate an horizontal loop. I arbitrarily chose a 10x10M loop, so I added 4 ...
2
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2answers
280 views

How to estimate a dipole feedpoint impedance?

An ideal dipole, at resonance, will have an impedance around 73 ohms. A folded dipole, around 280 ohms. How can I calculate the impedances when not at resonance? Let's assume I have a span of 15M in ...
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1answer
68 views

Lead in wire size [closed]

I have a copper wire antenna about 100 feet long that I have relocated and now need about 75 feet of lead in wire. What type & size of wire should I use?
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3answers
2k 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 ...
4
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1answer
80 views

Voltages in a beam antenna's passive elements?

This question has good answers for the voltages reached in portions of a dipole antenna during transmit. In a beam (Yagi or Yagi-Uda) antenna, do points along passive or parasitic elements (...
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2answers
2k views

Base vs center loading a vertical antenna

I currently use a homebrew 40/60/80m vertical consisting of a 5M aluminium tube with a multi tapped coil at the base. The ground plane is the metal roof at my house, and the antenna is not centered in ...
5
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3answers
862 views

Cheap antenna for new HF HAM

I just got a 100W HF radio and I am new at this. What is the cheapest antenna I can hook up without burning up my radio or shocking myself?
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2answers
82 views

Beam antenna changed directivity

My Hy-Gain TH6DXX antenna has been up on a tower about 20 years, with excellent results. Suddenly, the gain of the antenna is off the side; in other words, when the boom is broadside to the ...
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2answers
143 views

Strong but unreadable signal received on 2m FM voice, transmitter less than 2km away. What could be the cause of the readability problem?

I conducted an experiment today using a prototype copper wire 2m dipole at a ground level base station (noted on images) and a FT2D HT with an SRH77CA antenna. I recorded my transmissions using a ...
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3answers
173 views

Do resonant antennas actually resonate?

Do resonant antennas actually resonate (in the lumped circuit sense, exchanging stored energy between inductive and capacitive elements at a natural oscillation frequency)? If so, can this resonance ...
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2answers
219 views

resonance vs resonator in antenna

Resonance in electronic means: reactance of zero. (maybe wrongly/correctly someone's calling the minimum VSWR, the resonance of antenna! and this cause confusion) I've heard in Antenna Design for ...
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1answer
138 views

Vertical Antennas

I have just changed from a ground mounted Vertical antenna , to a MFJ-1796 Vertical antenna, due to not having big enough ground to bury as many verticals as recommended. So far what I have found is ...
2
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1answer
114 views

Do these magnetic field measurements of end-fed and center-fed half-wave dipoles corroborate measurements made by antenna experimenters?

Using a sensor and procedure discussed in my article, I made the following plot comparing the magnetic field strength along a 30m-band half-wave dipole fed at center and one end. Key points include: ...
3
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3answers
138 views

Antenna testing, minimizing feed-line radiation?

Assume that one does not have access to a multi-million-dollar RF anechoic chamber. When testing an amateur radio HF or VHF antenna, how would one absolutely minimize the amount of any RF radiation ...
4
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1answer
237 views

How does a higher antenna reduce rain static on a lower antenna?

I have operated at several stations - including my own - where a 40m beam is stacked above a tribander. During a rain storm, there is so much QRN on the 40m beam that the band is unusable, but the ...
3
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1answer
112 views

How to simulate two antennas in 4nec2

I need to simulate 2 helix antennae placed side by side, and see the resultant radiation pattern. But after adding the second antenna with a separate and when I try to simulate 4nec2, only simulated ...
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3answers
519 views

Improve AM reception on an old Walkman that has no external antenna

I have an old Philips walkman that has AM/FM radio. I tried AM radio. Really I can get clearly 2 country radios. I catched very poorly 4 foreign radios or different countries, but they do lots of ...
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4answers
841 views

How does the thickness of the radiator affect an antenna

Another question (Metal for antenna construction?) covered some aspected of this question, but the answers didn't exactly answer it, so I'll make it specific. Given 2 dipole antennas, resonant at the ...
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1answer
322 views

Can I use a QFH antenna for transmission?

I've seen a lot of videos and tutorials on using the Quadrifilar Helix Antenna for receiving signals, but I haven't seen any material for transmitters. I'm just starting right now, but can a QFH ...
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1answer
96 views

Is this antenna “system” really work? [closed]

I posted yesterday asking how can I have signal inside my house which my house is obstructed by a hill from direct signal from the cellular's operator' Base Transceiver System (BTS). The schema of the ...
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0answers
81 views

Can I make a simple Tx/Rx antenna (Radio System) which will receive signal from BTS and broadcast/transmit it, and vice versa? [duplicate]

Consider a situation as below. I am stay in a farm field, which my house is 9.4km distance from the nearest and the only one BTS (Base Transceiver System), a cellular antenna for transmit and receive ...
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0answers
88 views

How do I Construct a Simple FM Antenna?

I recently bought a cheap stereo amplifier with built in FM receiver from Amazon at the first link below. Testing it out today I found the FM reception to be sub-par. All of my local stations that I ...
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2answers
1k views

Understanding RG6-75 ohm Cable Impedance

Here is my measurement to a piece of RG6 cable. It is around 30cm cable. On the shield is written COAXIAL CABLE 5C-2V 75 ohm. From my measurement I got data as below: From that table, we can see that ...
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0answers
39 views

Problem to paralel tv digital reciever [closed]

Here is my C-Band parabolic tv digital receiver. As shown by the pictures, the incoming coax cable (INPUT) connected both the outer and the core. One goes to digital receiver 1 (receiver 1), and ...
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3answers
3k views

How to calculate impedance in antenna design's practice?

I would like to make a match half wave length (λ) dipole antenna (or probably a short dipole antenna). So I would like to make it by measure using LCR meter. What I am still confuse is about what is ...

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