If you look back on chapter 2 of this series, some of the loop schematics indicates that they are not fed by the feedline directly. The calculators give you theoretical values, your actual construction will also affect the antenna greatly. Some plumbing skills are required here as you will need to use a blow torch with plumbers solder paste and solder so do not attempt this part if you do not. The little box at the bottom of the small one contains an air variable capacitor for tuning. The antenna consist from two loops 1 meter in diameter. There are many designs and information available on the net concerning magnetic loop antennas. This calculator enables you to test the design of an octagonal loop antenna and to answer what if questions until you arrive at a design that meets. Fractal reduced size magnetic loop antenna reduced size 3 times than conventional magnetic loop size 1. About magnetic loop calculator the resource is currently listed in in a single category. The objective of this article is to disseminate some practical. A magnetic loop antenna for 15 watts can be made fairly inexpensive.
The circumference of a true magnetic loop should be less than 110th wavelength and the coupling loop at 15 ratio to the main loop. In relation to a given frequency and current distribution, if loop length were greater than lambda4, youd theoretically need less capacitance to obtain resonance but your loop would stop performing as a magnetic antenna. Aug 17, 2016 i built a prototype today of a high voltage variable capacitor for the 40m magnetic loop antenna i am building. Im hoping that the coupling loop will suffice in one place where it ends up for both 40 and 80 but that remains to be seen. Steve has an excellent ms excelbased loop calculator. Using the software at the bottom of this page, i worked out that a 36cm length of wire, will need a capacitance of around 3.
The coaxial cable is connected to both sides of the capacitor box which is located at the bottom of the mast. A cheap magnetic loop antenna, part i on the edge of. This is usually accomplished by adding a parallel capacitance to cancel the inductive reactance of the loop at the desired frequency. So if you can help me out i would appreciate it and if u could tell me where to find the variable capacitor for the loop the rest i can get here if u can tell me low big the loop must be and what parts i need to build it and maybe draw a picture or. About magnetic loop antenna calculator the resource is currently listed in in 3 categories. Due to its highq nature, the bandwidth of the tune is necessarily narrow typically 10khz. Ldf550 based magnetic loop antenna having had great success with a loop made using ldf450 heliax and the much smaller 24. Excel on your pc, you can download a freeware viewer from microsoft here. The 8 shape magnetic loop is the best performing and most convenient small space antenna available to amateurs today. The basic configuration of an inductivefed small magnetic loop consists of the main loop, coupling loop, and capacitor fixed or variable. Calculator results for a loop with a diameter of 1 m 3. A simple magnetic loop modification with a big improvement. I want to make a magnetic loop for hf say 728mhz but i get confused. There are programs loop calculator that produce this information simply and quickly, but actually.
Now i do have the 19th edition of the antenna book but for an hf small transmitting loop covering 2010mtrs it reads that the circumference of the antenna is 8. Magnetic loop antenna calculator small transmitting loop antennas, commonly called magnetic loops or mag loops, can give surprisingly good performance when they are carefully designed and constructed. Magnetic loop antenna is dangerous because of magnetic component it radiates in near field. Design considerationsloop capacitor zlow loss capacitor means higher loop efficiency zbutterfly capacitors good. Homebrew, high voltage variable capacitor for magnetic. I built a prototype today of a high voltage variable capacitor for the 40m magnetic loop antenna i am building.
Download magnetic loop antenna magnetic loop antenna calculator that helps you compute details about the bandwidth, capacitor value and. Small loop antennas are often referred to as magnetic antennas. This transmit qrp magnetic loop antenna can create dangerous high voltages in excess of 1 kv across the capacitor plates, as well as the coax loop pl259 connectors. This forms a parallel resonant circuit which, if the component values are correctly chosen, can be tuned across the band of frequencies we are interested in. Like getting on the air for the first time or taking your license exam there is a certain amount of uncertainty when you first approach magnetic loop antennas, there are a few new ideas to grasp. Here is a great calculator for sorting out lengths, values, etc. Many configurations exist when constructing the main loop and secondary loop. In addition, specific models mentioned in the magnetic loop antennas forum like mfj and more are here for future reference. It can be analyzed as coupling directly to the magnetic field opposite to the principle of a hertzian dipole which couples directly to the electric field. Works either in standard and metric units, and let you choose on material, and loop. Loop area radiation resistance total loss resistance loop circumference loop inductance distributed capacitance q quality factor tuning capacitor capacitor voltage minimum plate spacing by steve yates aa5tb notes. Arrl antenna book source for the formulas used by aa5tbs design spreadsheet. Variable capacitor for magnetic loop antenna youtube.
An overview of the underestimated magnetic loop hf antenna by leigh turner, vk5klt aa5tb small loop site includes an excellent excel calculator for sizing loop components. Sep 04, 2011 i want to make a magnetic loop for hf say 728mhz but i get confused. Introduction loop antennas form another antenna type, which features. To automatically tune a magnetic loop antenna loftur e. Small transmitting loop antennas, commonly called magnetic loops or mag. Entering the dimensions of my new loop and the intended operating frequency and power levels i soon had some very. The first simple change ive seen to really make a difference in magnetic loop performance. High voltage capacitor need 10150pf for most applications. Here is a photo of w2bri with his 12 foot square magnetic loop antenna. The capacitor is the most difficult part of constructing this type of antenna. Compare it to the 5 foot in diameter loop on the right.
A cheap magnetic loop antenna, part i posted by matt under amateur radio, antennas, uncategorized. This link is listed in our web site directory since monday dec 9 20, and till today magnetic loop antenna calculator has been followed for a total of 5241 times. Magnetic loop ideal for restricted space locations,you can remotely tune to the ham bands in seconds reduces harmonic interference. Amateur radio antenna sold here,we update our stocks to keep in touch with modern improvements in magnetic loop antenna design. Magnetic loop antennas for the radio operator with limited space pt. The first requirement for a magnetic loop antenna is that the antenna must be resonant. Many kilovolts can be present across the capacitor, and produce concentrated electro magnetic radiation even at low power levels.
Ham radio a simple magnetic loop modification with a big. May 08, 2017 a remotely tuned magnetic loop antenna. The coupling loop i use on my 1020m loop only needs to be moved down closer to the loop from the higher 20m position on the mast when im on 17 and all the other bandsin other words, two positions between five bands. This indoor small magnetic loop antenna was an interesting antenna to build and use. This calculator enables you to test the design of an octagonal loop antenna and to answer what if questions until you arrive at a design that meets your needs without a lot of experience in electronics. Magnetic loops have very low radiation resistance, so.
Its a light magnetic loop antenna calculator that run on ms windows, and allow to calculate capacitor values and voltage based on loop circumference, conductor diameter, desired. Magnetic loop river city amateur radio communications. Metal strips and even the braid of a large size coaxial cable rg8 or rg2 can be used. The most common material for home building small ham radio loop antennas is common copper plumbing pipe. Magloop8, double magnetic loop, 8 shape magnetic loop. It acts like an lc resonator, and with a tuning capacitor, it can be tuned to any frequency in most environment.
Magnetic loop antenna calculator resource detail the. Magloop8, double magnetic loop, 8 shape magnetic loop antenna. A magnetic loop antenna is basically just a resonant circuit using an oversized inductor and an adjustable capacitor if the inductor has a circumference of much less than, say, 110 th of a wavelength, then the efficiency of the antenna will suffer. Making efficient loops at hf is easier as the capacitances are larger and stray capacitance is. My original plan was to make it a fixed capacitor out of a length of coax for a single 40m frequency. The designation magnetic loop specifies a mainloop circumference necessarily smaller than 0.
Portable magnetic loop antennas ham radios best kept secret eric norris wd6dbm v2. Initial calculations of size, efficiency, required tuning capacitance, voltage, etc. The basic configuration of a small magnetic loop consists of the main loop, coupling loop, and capacitor fixed or variable. You could use a very specific capacitor and not have it variable if you were. The capacitor has been electrically isolated from the tuning knob by means of a nylon shaft. Its easy to build with a soldering iron, a plastic case and a little knowledge of arduino. Design your own tuning capacitor for use with this antenna with the capacitance calculator capacitor design. I played with cutting the coax to the right length and finally decided against. At 12 feet above the ground, the coupling loop needed to be resized to 1. Additionally, one can receive rf burns by touching the copper transmit loop while transmitting.
Ham radio deluxe 5 download about last free version. Magnetic loop antenna calculator resource detail the dxzone. Only when thus configured does the antenna enjoy deep side nulls. There are two basic requirements to make a magnetic loop antenna work. The main category is magnetic loop antennas that is about magnetic loop antenna projects. Homebrew magnetic loop antennas and butterfly capacitors. Magloop, single magnetic loop, fractal shape magnetic loop.
For the case of magnetic loop antenna, this matching is typically achieved by usage of a coupling loop. Many kilovolts can be present across the capacitor, and produce concentrated electromagnetic radiation even at low power levels. A magnetic loop antenna may be the answer and they are not as difficult to build as you might think. Series and parallel fixed coax capacitors were used to compensate for the unknown. The loop antenna element is constructed from 22mm high conductive copper pipe. Nec modeling software does not accurately model this antenna. As shown in the above picture, the main loop formed out of the ecoflex coaxial cable is secured to the top of the pvc pipe using a tjoint.
Antenna tuner sometimes used in each configuration once an swr of 2. The primary design goal was to offer a loop at lower cost than what is available but with better performance, high quality construction and features not found on the currently available loops. This antenna is for the qrp amateur that is looking for a small antenna for home, backyard, portable or the park use, while it is also usable for hiking. Build a magnetic loop antenna controlled by arduino. The main category is antenna design calculators that is about antenna design calculators. Instead, the feed line is connected to a yet smaller loop called coupling loop, which in turn generates.
Loop antennas radiation parameters of a small loop. Magnetic loop py1ahd alex alexandre grimberg py1ahd. Georgia copper source for all sorts of copper products. In part one of this series, i covered the use of one brand of commercially available, small transmitting loop antennas, also known as magnetic loops. Using the atu helped with the narrow bandwidth of the magnetic loop. On the other hand, if loop length were less than lambda8, youd be forced to resonate your antenna using a greater. Listed under the antennas magnetic loop category that is about magnetic loop antennas. This aerial covers the 20, 17, 15, 12 and 10 metre bands and is made from a single 3 metre length of 22 mm copper tube cut into 4 pieces of equal length and joined in the corners with 90 degree elbows.
Loop antenna calculators suggest that a loop of that size can be tune from 40. Jul 24, 2015 magnetic loop antennas for the radio operator with limited space pt. For that article, i bought the very popular alexloop walkham antenna. Loops are usually constructed from aluminum tubing or copper tubing. Of course you can build remote tune circuit, but keep in mind, that small loop have small efficiency and you need very high voltage capacitor. Magnetic loop river city amateur radio communications society.
Here, youll find links for high gain loop antennas covering hf. Homebrew magnetic loop antenna part 1 variable capacitor. Homebrew magnetic loop antenna part 1 variable capacitor getplay. The key to effective magnetic loop operation is keeping the resistance of the loop and electrical connections between the loop and the capacitor to a minimum. To truly be considered a small loop, the loop circumference should be less loss resistance box. This controller doesnt have endstop limit capabilities. This is an absolutely fantastic tool, and if you are working with singleturn magnetic loop antennas, you will need this. Two turn cellflex 12cableloop for 80m 40m, diameter 1.
This link is listed in our web site directory since friday may 9 2008, and till today magnetic loop calculator has been followed for a total of 5642 times. There are many designs and information available on the net concerning magnetic loop antennas even though these antennas are a fraction of the size of a full size resonant antenna, size of the lower frequency loop can still be quite large for a limited sized property. Home made high power magnetic loop antennas amrron. This small magnetic loop antenna was designed for installation on the top of the roof and remotely tuned by a small geared dc motor coupled to the variable air capacitor shaft. Nov 26, 2017 the first simple change ive seen to really make a difference in magnetic loop performance. Magnetic loop antennas resonant loop antennas radioworld uk. An overview of the underestimated magnetic loop hf antenna it seems one of the best kept secrets in the amateur radio community is how well a small diminutive magnetic loop antenna can really perform in practice compared with large traditional hf antennas. This project is for those ham amateurs who dont have a commercial one. This model can be downloaded as an execution file ready to open after download. Loop antenna calculators suggest that a loop of that size can be tune from 40 to 10 mtrs with a variable capacitor of 10180 pf. To be a magnetic loop, the loop circumfrence must be less than 0. Small high efficiency loop antennas for transmitting, the american radio relay league, the arrl antenna handbook, tuning capacitor, farads.460 1389 1437 1493 1560 850 964 731 1205 1150 1012 1107 1673 1119 1540 932 489 355 932 37 1282 558 771 313 525 121 861 630 868 500 1206 378