Magnetic loop antennas for the radio operator with limited space pt. The main category is magnetic loop antennas that is about magnetic loop antenna projects. For that article, i bought the very popular alexloop walkham antenna. Searching on the internet i found an extremely useful site that had an online magnetic loop calculator, something i had not come across before when i constructed my previous loops. 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. So now there are eight ways to feed rf into a loop antenna. The idea for this loop began with my purchase of a new vertical antenna. You start the program magnetic loop antennas calculator by clicking on the.
Magnetic loop antenna is dangerous because of magnetic component it radiates in near field. Its easy to build with a soldering iron, a plastic case and a little knowledge of. Small transmitting loop antennas, commonly called magnetic loops or mag loops, can give surprisingly good performance when they are carefully designed and constructed. I built a prototype today of a high voltage variable capacitor for the 40m magnetic loop antenna i am building. To put this into perspective, with my 24 foot loop, using a 16 turn 5 465pf capacitor. Loop antenna design and construction, magnetic loop antenna. At 12 feet above the ground, the coupling loop needed to be resized to 1. Homebrew magnetic loop antennas and butterfly capacitors. Some time has passed since i worked on the eightshaped magnetic loop by pa0fri. 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. Read his loop article why this software is not valid under that conditions. The death ray some people have claimed that loop antennas emit death rays.
You could use a very specific capacitor and not have it variable if you were. Magnetic loop antenna for 8020 mtrs by frank n4spp. Of course it is possible to use a loop calculator, for example if for some reason the loop. Build a magnetic loop antenna controlled by arduino. This link is listed in our web site directory since monday may 14 2012, and till today magnetic loop software. The tutorial of a diy magnetic loop antenna for the amateur radio band featuring a. 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. The same android application used to control the one capacitor version can be used to control the two capacitors. 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 antenna calculator resource detail the. According to kd7ss article 9, a capacitor large enough to resonate our loop on the low end of 80 meters would require a capacitor. The capacitor is located at either the top or bottom of the main loop, but always opposite the coupling loop.
Choose the units of measurement, english or metric. 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. This link is listed in our web site directory since monday dec 9 20, and till today magnetic loop antenna calculator. 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. The spreadsheet below is a work in progress from a software routine i first wrote about 1990. Working on a new simple basic capacitor controller for two bands, 80 and 40m. Rating capacitors is a challenge, you cannot simply depend on the dielectric strength of dry. Although this online calculator is intended to assist with designing and building homemade, ham radio loop antennas for use in the hf bands, magnetic. This link is listed in our web site directory since monday may 14 2012, and till today magnetic loop software has been followed for a total of 986 times. With 100w to the loop, the current through the capacitor is about 29a rms. I want to make a magnetic loop for hf say 728mhz but i get confused. Magnetic loop antenna calculator magnetic loop calculator v. You simply feed the loop directly across half the capacitor with a series capacitor to match the predominantly inductive load. On the other hand, if loop length were less than lambda8, youd be forced to resonate your antenna.
As shown on the plots published in previous posts, this is the receiving antenna from many i have tried wich provides the. Simple remote tuning control for hf mag loops g8ode. About magnetic loop antenna calculator the resource is currently listed in in 3 categories. Article by w2bri after many requests by ben w4ksy, someone i consider to be my loop mentor, i decided to post a page about my 80 meter magnetic loop. Home made high power magnetic loop antennas amrron. The basic configuration of a small magnetic loop consists of the main loop, coupling loop, and capacitor fixed or variable. A magnetic loop antenna may be the answer and they are not as difficult to build as you might think. Here is a great calculator for sorting out lengths, values, etc. Magnetic loop antenna calculator resource detail the dxzone. Making it any larger, and more efficient at 2m requires too small of a capacitor eg 1pf and. Here is a photo of w2bri with his 12 foot square magnetic loop antenna.
Magnetic loop antenna calculator that helps you compute details about. An answer f rom leigh vk5klt being in the nearfield region of a magnetic loop antenna, or any antenna for that matter while. Magnetic loop river city amateur radio communications. Here is a description of the magnetic loop that i am using for the 160m band.
There are so many designs out there i dont know what is what. Qrp mag loop tuner 80 20m g8ode graphics by g8ode dec 2012 iss 1. Small mag loop capacitor motor bu terf y c ap citor 0. Just be aware that the losses will most likely be greater in this type of capacitor. To understand what i mean, lets talk a little bit about how a magnetic loop is constructed in practice. A second loop, which is one fifth of the diameter of the large loop. I also suggest downloading the ki6gd loop calculator. It is relatively simple to make, does not depend on a good ground and operates well at low heights over short, medium and long. This curve of the measured swr demonstrates the 33 khz 2. The firmware is is free software, released under the. Design considerations loop capacitor zlow loss capacitor means higher loop efficiency zbutterfly capacitors. This is a bigger brother of the previous version of this small portable antenna. 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. A magnetic loop antenna for shortwave listening swl the small single turn magnetic loop sstml antenna consists of a single winding inductor, about 3 feet 1 meter in diameter, and a tuning capacitor.
A magnetic loop antenna for 15 watts can be made fairly inexpensive. This project is for those ham amateurs who dont have a commercial one. The two loops, exactly equal in size and calculated for a certain frequency, are tuned to the frequency band by a capacitor. I am in the planning process for a magnetic loop antenna, and also have a comet cvba500 capacitor. The main category is antenna analysis software that is about software, antenna analysis software, for ham radio operators and hams. There are now eight ways to feed a magnetic or small loop. 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. Small transmitting loop antennas, commonly called magnetic loops or mag. Small magnetic loops made from lmr400 coax cable larry nelson k5ijb. My original plan was to make it a fixed capacitor out of a length of coax for a. The calculators give you theoretical values, your actual construction will also affect the antenna greatly. Although this online calculator is intended to assist with designing and building homemade, ham radio loop antennas for use in the hf bands, magnetic antennas have been.
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. To estimate the rf loss of the flat strip you can use w9cfs calculator. Main loop diameter m conductor diameter mm magnetic loop antenna calculator for round copper construction 1. This should be borne in mind when calculating the size of the coupling loop. A useful mag loop calculation tool has been provided by ki6gds mag loop antenna calculator. Using again an arduino board with a motor controller board from adafruit. Nec modeling software does not accurately model this antenna. I built my 40m loop that size and it works very wellyou might not need to change your capacitor. Portable magnetic loop antennas ham radios best kept secret eric norris wd6dbm v2. I have made small loop antennas using conventional broadcast receiver capacitors and they worked well for qrp use although i know their performance could have been better.
Works either in standard and metric units, and let you choose on material, and loop. I also suggest downloading the ki6gd loop calculator, too. To automatically tune a magnetic loop antenna loftur e. This very easy to do with the controller software i wrote see further below. Homebrew, high voltage variable capacitor for magnetic. The coaxial cable is connected to both sides of the capacitor. Enter the length of the antenna conductor, which is the distance around the loop. Welcome to w2bris magnetic loops images and notes from other loop builders, inventors, and enthusiasts. This controller doesnt have endstop limit capabilities. Great multiband hf antenna for your balcony or vacation. The first antenna to be installed was an old mosley mp31 trap dipole for 10, 15 and 20 meters.
Diy magnetic loop part 1 the capacitor introduction. The circumference of a true magnetic loop should be less than 110th wavelength and the coupling loop at 15 ratio to the main loop. I started to look for places to hang a wire and work some hf but i couldnt find any. The fixed or variable capacitor tunes the loop antenna for lowest swr. 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. A smaller loop is positioned towards the opposite end of the capacitor within the.
732 233 846 846 37 1179 1389 176 966 1295 391 1198 166 84 185 1337 1084 125 721 52 1091 1240 410 1111 1314 768 870 229 761 311 1492 63 1382 451 1035 1132