7

If you look up "link dipole" or "linked dipole" you will find several designs that do just that. It works well for QRP or even for 100W. The ones I've seen have used several different connectors: alligator clips, quick disconnect spade terminals, Anderson PowerPoles, and banana plugs, to name a few. Of those, alligator clips are probably ...


7

A random longwire is just that, a random length. There is no optimum length, by definition. Usually people use random longwires for multi-band operation. Since the design frequency is "a lot of them", the strategy of a random longwire is more or less to give up on making the wire suit any particular frequency, and just deal with the mismatch with a ...


6

Don't worry, there have been many researchers before you, and you can borrow some of their work. Your English is fine. If you do a web search for "lightning spectrum", you will find a graph showing lightning intensity vs. frequency. The range of frequencies emitted by lightning discharges is very broad. From amateur radio experience I can tell ...


5

A choked end-fed antenna is (or acts just like) a highly off-center fed dipole, where the length of any stub between the common mode choke and the unun/transformer/feedpoint sets the off center ratio and thus the impedance at the antenna feed point. Your current 1 foot stub is less than 1% of the antenna, whereas a few percent is usually recommended, that ...


4

Unless I butt right up to the tree and the roof, I probably won't have room for a 40m band half-wavelength dipole. Then butt up to the tree and the roof. Of course it would be better if you had an enormous pair of towers in the middle of nowhere. It will still work. The neighbours.... The top floors is 20m away horizontally and 5m above vertically. ...


4

A bolt of lightning has an average center frequency of about 16 kHz, which varies with the height of the bolt. This is a distant stroke that I captured on one of my SDR lightning receivers, using three 4-turn 1-meter dia. vertical loop antennas, spaced 120° apart: (Ignore the apparent 50 mV offset) Note how the energy on this particular stroke is ...


3

I have seen wire antennas for the FM band before. Such an antenna usually has two wires that are connected to twin-lead feed line, which then connects to a device called a matching transformer or a balun that looks like this: So you could connect two wires to a device like that, and plug that into your receiver. The best way to arrange the wires is in a ...


3

First check your local regulations. Some specify the minimum gauge for wire antennas. For example NEC Article 810 specifies a minimum of 14 AWG for wire receive antennas. For temporary antennas such a POTA activation using a smaller gauge would be acceptable. I've also know hams to ignore the local regulations. If transmitting check that is can handle the ...


3

Here's the SWR curve for a half-sized "Slightly Off-Center Fed Dipole" described in the September 2019 issue of QST magazine: The antenna provides an SWR on your bands of interest that any rig's built-in matching network should handle with ease and mismatch losses in a modest run of coax should be minimal. Notice that the SWR is calculated for 200-...


3

A random long wire is just that, random. While large loops at the end or bending the wire might change the resonant frequency, a random wire isn't (unless by chance) resonant anyway. So loops and bends just make a different random wire antenna which is neither better nor worse. The shape of the antenna isn't going to affect efficiency directly. Think about ...


2

My gutter antenna experiments revealed that the gutter (metal of course!) itself can be used as end-fed half-wave antenna on the self resonance frequency. The efficiency is poor: the losses to conducting environment are very high, even with dry weather. For reception such antenna can be used, but all the interference generated in the house is coupled to the ...


2

That is WD-1 or WD-1A military telephone line. Lots of hams use it for switchable-direction Beverage receiving antennas, and with good results. The steel strands provide extra tensile strength.


2

In the May 2011 and October 2011 issues of ARRL's QST magazine, Joel Hallas, W1ZR, described a "Folded Skeleton Sleeve Antenna" as well as its "unfolded" companion: The antenna is constructed from "window line" - a two-wire transmission line created by polyethylene dielectric - with shorted ends and wires cut at appropriate ...


2

I've never heard the term "linear loading", and searching for it I can only find amateur definitions, many of them contradictory. Many reference J-poles and some reference (although they don't use the words) folded monopoles. What these have in common are transmission line stubs with the objective of modifying the feedpoint impedance. Calling ...


2

If you feed a wire antenna at its center with open wire or balanced line, where the length of the antenna may or may not be designed to be resonant on any operating frequency, then the result is usually called a doublet antenna. A doublet’s length is usually chosen so that it isn’t anti-resonant (a full wavelength, etc.) on any of the desired operating ...


1

If you are using copper wire, 14 gauge is about as small as you want to get. Be aware, however, that if you hang a long copper wire that thin, it will stretch. This is not a big deal as long as you don't care about its length for antenna purposes. If you use something like copper clad steel, you can go as low as 16 or 18 gauge and it will still support its ...


1

I think this is the wrong question. You ask does antenna X exist, but what you really should be asking is Given this configuration, can it be made resonant with a good SWR. Random wire antennas exist. All you need to make anything work is a good antenna tuner. Of course, this doesn't guarantee efficiency, radiation pattern, or that it radiates at all. ...


1

First, what bands are you listening to? You should hear activity on roughly 20m – 40m during the day (and 15m sometimes), and 40m – 160m at night. This is close to the bottom of the sunspot cycle, so signals are often fairly weak, but there should be a few loud stations on 20m and 40m. Your antenna would do better to be higher, but it's high enough for ...


1

It's not clear to me from your question, so I'll mention here that best practice is to end your antenna with an insulator and attach the insulator via rope or whatever to your tree or building. And yes, the length of the antenna includes that loop of wire around the insulator. [image credit: DX Engineering] HOWEVER, it's not unusual for a testing setup (or ...


1

Assumed the frequency range of interest is up to and including shortwave then the description below is the approach. A loop antenne can be used as passive antenna with or without tuning, or as active antenna with an amplifier. Most probably your question relates to passive wideband reception antennas. Then you can read further. Active antenna can be deduced ...


1

As an extension to the above answer, which mentioned the commercially available option, there is this calculator to make your own. This covers the necessary inductance of the loading coils. https://marmes100.dreamhosters.com/Ant_Short_Multi_Band_Dipole.html


1

If you do put your antennas in or between trees, make sure no uninsulated part of the antenna touches the tree, especially when wet. Because if it does, the tree becomes part of the antenna and will detune it. (Catching on fire or worrying your tree might get radiation burns is a separate issue.) But even if the tree doesn't detune it, it may absorb some ...


1

One important aspect of antennas in close proximity of trees or even touching branches is problem with correct and persistent tuning of such antennas. Needles to say totally unknown characteristic of radiation. Correctly calculated and tuned length of wires are often no longer correct in trees. SWR is something magically changing or flat across whole band ...


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