10
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Can a 1:1 transformer be used as a protection from static electricity?
A transformer can help and could also make things worse. I have some bad experience with this.
The way that a radio is damaged by static is simple:
Something charges up to a high voltage, and then ...
- 10.5k
7
votes
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What is the attraction of vertical antennas for HF?
Cribbing a few quotes from answers to related questions, here's a start.
From https://ham.stackexchange.com/a/195/1362:
The primary advantages of vertical antennas are that they are ...
- 7,269
7
votes
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When and why does the size of a ground plane or radials matter?
Perhaps consider that the objective of the ground plane is to present a low impedance. At the feedpoint, the hope is to have all the current go into the antenna, and none of it on the coax common-mode....
- 51.6k
7
votes
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Radials on a vertical, spread out evenly or not?
The purpose of the radials is to increase the effective ground conductivity, thus reducing losses. As you propose to have 16 radials but in four groups, I'd expect the efficiency to be somewhere ...
- 51.6k
7
votes
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calculating all specifics for a 5/8 antenna
I congratulate you on your interest in working out the design issues from the ground up. Understanding the theoretical and comparing this to the field results is the beginning of a life long enjoyment ...
- 18.5k
7
votes
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HF Vertical antenna with no radial and loading coil but only ATU for 80m to 10m in a boat
On boats the traditional solution is to use the backstay as the radiator, with an insulator near the top, another near the bottom, and an insulated wire running to the tuner. The water serves as the ...
- 10.5k
6
votes
Accepted
How to calculate/estimate the effect of having conductive material nearby an antenna
In your particular case, I'd note 2 things:
The aluminium is directly above the whip, where the antenna's fields are the weakest.
Aluminium is a good conductor, so unless there is something about it ...
- 51.6k
6
votes
Marine VHF whip antennae - what are they?
Without having one of these antennas to disassemble (perhaps destructively), I can't tell you exactly how they are constructed. But maybe I can address some of your underlying concerns.
Firstly, ...
- 51.6k
6
votes
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Can a vertical antenna be used for NVIS?
Knowing that 1/4λ verticals are known in VHF/UHF applications to have nearly isotropic patterns
This is not a valid assertion. A UHF/VHF vertical antenna has > 0 dBi gain (more succinctly a ...
- 18.5k
6
votes
How Does the Performance of Elevated Radials Differ from That of Buried Radials?
The number of horizontal radial wires used in an elevated "counterpoise" can be far fewer than the 120 buried wires used by most AM broadcasters, and the even fewer numbers of buried wires often used ...
- 2,922
6
votes
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Stabilization of an antenna pole with anchoring cables
What you have is a basic civil engineering problem. You might calculate a sheer and moment diagram, look up all the material properties, and calculate the failure points of all the components. In the ...
- 51.6k
6
votes
Radial length for vertical antennas?
Rule of thumb: if the radials are elevated, at least two resonant radials for each band.
If the radials are buried or lying on the surface, at least 16 radials, each at least a 1/4 wavelength at the ...
- 51.6k
6
votes
Accepted
Vertical Antennas
First: do you know about pskreporter? You're definitely getting heard, including one spot on 40m from New Zealand. Sometimes FT8 takes some patience, and it seems like no one wants to come back to you ...
- 11.7k
6
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Why are many ground radials preferable to a single ground stake buried 1m deep?
The purpose of the ground radials isn’t to ground the counterpoise.
The purpose of a dense field of radials is to emulate as much as possible a perfect mirror surface, so that, to the far field, the ...
- 13.2k
6
votes
cut or lengthen to reduce swr on vertical wire antenna
If you're only measuring SWR at one frequency, or in a narrow range like the ham bands, you won't know until you cut it.
Mount the antenna in its final location as the SWR and resonant frequency will ...
- 10.5k
5
votes
Accepted
2 Meter horizontal or vertical dipole polarization?
For VHF, choice of polarization is not up to your desired radiation pattern, but who you want to be able to communicate with. In HF, the ionosphere causes random rotation of your signal's polarization,...
- 24.4k
5
votes
Using two short mobile HF antennas to make a vertical dipole
To begin the discussion, it is helpful to understand the effects of shortening any antenna to a length below resonance. In all cases, the directivity of the antenna is reduced but this tends to be a ...
- 18.5k
5
votes
How Does Earth Conductivity Affect the "Takeoff Angle" of a Vertical Monopole?
A common belief is that Earth conductivity mostly affects the "takeoff angle" of a vertical monopole.
However the NEC4.2 study below shows that the shape of the radiation patterns is quite similar ...
- 2,922
5
votes
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How low can a vertical dipole be mounted?
Here is an analysis of a vertical, 1/2 wavelength, 2 meter dipole suspended at various heights above ground:
As you can see, as you raise the bottom end of the antenna from near ground level up to ...
- 18.5k
5
votes
Antenna suggestions for 160m band in smallish yard?
Almost any 160 meter antenna is a compromise. With limited space or budget, the compromise tends to be larger.
At first glance, a dipole that is shortened by loading coils might appear quite ...
- 18.5k
5
votes
Are Elevated Radials Necessary for Elevated, 5/8-wave "Ground-Plane" Antennas?
Elevated radials are required in order to increase/optimise the radiation possible from any such elevated "GP" monopole or whip antenna.
If the elevated radials are symmetrically arranged and lie in ...
- 2,922
5
votes
Give vertical antenna directional gain?
Sure, that can work.
Here's a monopole yagi I designed:
Photo: Alaris Antennas MONO-A0005.
It's a half-yagi for remote control of a mine locomotive, improving the control range by firing one way ...
- 10.5k
5
votes
Multiband vertical antenna not working as expected
It may very well be that the open contacts are arcing, and I'm betting that's what is happening.
Here are some possible solutions. How about using different relays that have less tendency to arc:
...
- 7,864
5
votes
Colinear Vhf antenna
The ideal dipole antenna is roughly a half wave long.
A monopole is half of that, with the other half in the conductive surface below the monopole. The colinear antenna is a series of stacked and ...
- 5,651
5
votes
Accepted
Can a 1:1 transformer be used as a protection from static electricity?
Assuming that power losses in the transformer are acceptable, and that it's placed after 1:1 current balun (which eliminates common-mode current), is there any reason why it might be a poor solution?
...
- 51.6k
5
votes
Accepted
Why are many ground radials preferable to a single ground stake buried 1m deep?
A dipole antenna does not require a connection to an "r-f ground" reference, either in the form of a ground rod or a set of buried radials. Its radiation efficiency typically is ~95% or ...
- 2,922
5
votes
Is the Boom Strictly Necessary in a Vertical Dipole?
If you don't route the feed line away from a center-fed dipole antenna at 90 degrees, it will be in an unbalanced RF field, and thus will couple to the unbalanced RF field, to some degree, even with a ...
- 13.2k
5
votes
Can coax be run through the center of a radiating element without currents being induced on the coax shield?
That is a great idea. In fact antennas of this design are quite common, and you probably have a much smaller antenna of similar construction on your Wi-Fi router:
Effectively, the lower dipole ...
- 51.6k
5
votes
Grounding a vertical antenna from a balcony
Engineer999.
While it might seem like a good idea to connect your antenna to the building ground wire, my experience has been that for those vertical antennas which are designed to operate without ...
- 3,665
4
votes
Does mounting a ground plane antenna upside down change the takeoff angle?
To answer this very graphically:
Flipping the diagram geometrically can't work:
What you've actually build is kind of a waveguide, consisting of two grounded planes below (earth) and above (virtual ...
- 15.5k
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