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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What is the wavelength of 144.52 0MHz frequency?

Problem What is the wavelength of 144.520 MHz frequency?
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0 answers
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Wanted ARC 5 for museum [closed]

How to calculate length of dipole ror 10 MHz? Can I post a wanted add - not for personal use ? PS Sorry I had to add characters to the title....and chaage text
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3 answers
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SMA Connector Impedance

I am new to antennas, and am trying to create a monopole that connects to an SMA female to transmit a 2.4ghz wifi signal. I know that the antenna needs to be a multiple of 3.1cm in order to have the ...
3 votes
2 answers
81 views

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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2 votes
1 answer
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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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4 votes
1 answer
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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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5 votes
4 answers
436 views

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 ...
4 votes
2 answers
103 views

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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2 answers
64 views

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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1 vote
1 answer
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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 ...
2 votes
2 answers
61 views

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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2 votes
1 answer
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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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3 votes
1 answer
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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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5 votes
2 answers
117 views

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 ...
5 votes
2 answers
138 views

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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3 votes
3 answers
174 views

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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3 answers
94 views

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 ...
4 votes
2 answers
233 views

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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5 votes
2 answers
127 views

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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1 vote
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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 ...
0 votes
2 answers
231 views

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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3 answers
131 views

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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2 votes
2 answers
143 views

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 ...
0 votes
1 answer
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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 ...
-2 votes
3 answers
126 views

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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-1 votes
1 answer
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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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9 votes
2 answers
2k views

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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4 votes
2 answers
354 views

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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1 vote
2 answers
117 views

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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2 votes
1 answer
112 views

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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2 votes
1 answer
108 views

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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1 vote
1 answer
107 views

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....
1 vote
2 answers
65 views

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 ...
5 votes
1 answer
327 views

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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7 votes
2 answers
691 views

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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0 votes
2 answers
187 views

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 ...
3 votes
4 answers
453 views

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. ...
0 votes
1 answer
250 views

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 ...
3 votes
1 answer
114 views

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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1 answer
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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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1 vote
1 answer
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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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1 vote
0 answers
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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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0 votes
0 answers
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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.
3 votes
0 answers
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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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1 vote
1 answer
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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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2 votes
2 answers
366 views

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-...
2 votes
1 answer
189 views

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 ...
2 votes
2 answers
181 views

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 ...
2 votes
1 answer
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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 ...
2 votes
4 answers
113 views

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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