This 2m yagi uses design data from DK72B’s excellent yagi website. The element to boom mounting used here may be of use to some as it does not use any polamid mounting / insulating clamps at a cost of 2 euro each ( this is a 7 el crossed Yagi so twelve clamps would be needed ).
A windom antenna for 10 to 80 meters band – a design by PU1LHP
Let me first say I make no claims of originality for this item. It is intended as a simple, inexpensive solution for the newcomer to experiment across the 40m band (7.0–7.2MHz) when only restricted space is available. “A picture speaks a thousand words” so by including a couple I’ll keep it as short as possible!
With the rally season upon us, it is an ideal time to pick up those bits and pieces with which to experiment. The antenna described here consists of a 50R coax fed, inductor loaded 5.44m vertical section mounted on a 1m alloy tube driven into the ground and requires no radials although this may well depend on the local soil structure.
The vertical itself is a salvaged unit (probably ex. CB) consisting of 4 telescoping aluminium sections with an extended length of 5.44m and its mounting bracket.
The thick wire in the picture is the coax centre connection from the bracket mounted SO239 connector to the coil. Continue reading
The Grid Yagi (or Grid Quad) is a high performance yagi antenna that can be built with readily obtainable inexpensive materials. Described here is a 6 element 2 meter version with a boom length of about 1 wavelength.
The boom is made of 11?2 inch pvc pipe, although any suitable material can be used, such as steel, aluminum, fiberglass, or wood. The elements are cut from 2 inch by 4 inch galvanized welded wire fencing, with a wire diameter of 0.078 inch, which is what #14 steel wire becomes when it is galvanized. Continue reading
Hear I am sitting in front of the rig listening to everyone working CQ World Wide, and I don’t really have time for this, but I hear a few interesting stations on 20 meters and try to call them. Trying to bust the pile up with 100 watts and my hustler dipole is going to be difficult on this band, so I tune up on 15 meters and there is action, and I have a good wire beam, so I tune up and down the band and can’t find a clear frequency. Then I hear some one say that 10 meters is open. So I tune up there, and there is a world of DX coming in. I choose a few interesting ones to call, but can’t be heard. I should have expected that, as my antenna for this band leaves much to be desired. It is a vertical above my Hustler dipole, but it has no effective ground plane and SWR no better than 3:1 at its best frequency. With no time to assemble a Quad, I start thinking about a better vertical.
The Principles of the Loop Antenna article was in a newsletter of the MDXC. The next three were from a talk that Mike Bates and James Dale gave to the Northland Antique Radio Club’s Radio Workshop at the Pavek Museum of Broadcasting.
2.4 GHz Cubical Quad Antenna – Introduction
The Cubic Quad antenna is a commonly homemade antenna in the range of about 150 odd MHz. Our little project was to design one of these for use in the 2.4GHz range for 802.11 wireless LANs. The reason these are seldomly used for 2.4GHz is the size.
The picture below is a 4 element cubic quad for the 147MHz range. Large isn’t it.
The one we are going to build for 2.4GHz will only be 6cm long!
An antenna is known as “directional” if its pattern strongly favors a certain direction. A directional works by concentrating the signal in one direction at the expense of other directions. It is also commonly referred to as the “Beam” antenna. I am going to start with the earliest type of beam discovered, the “Yagi” Beam. This type of beam was discover by Professor Uda but the english translation was done by Hidetsuga Yagi. This design goes back to the 1920s! One would think today there would be better designs. I believe there is, and that’s why I am so interested in antennas!
The Yagi Beam
The yagi is very simple. The basic yagi consists of three elements, as shown in figure 1. The middle element is an antenna you are already familiar with, the simple 1/2 wave dipole antenna. This element is generically called the “driven element”. This is because this is the only element that is connected directly to the radio, it actually drives the whole antenna. The other two outer elements are generically called parasitic elements. One is called the Reflector (some CBers call it the “back door”) and the other one is called the director element. These elements get their name from the job they do. The reflector reflects RF energy, the director directs RF energy. There is no magic circuit located inside the elements, they are simply straight rods! The reflector element is typically 5 % longer than the driven element and the director is typically 5 % shorted than the driven element. How it works. See figure 1. As signal A comes in it strikes all three elements hence generates a current on each element. Remember we said that current on a wire causes it to radiate? Even though the current is very low, this current induced on the antenna actually re-radiates off the antenna again! Ok, back to the action, the signals are re-radiated by the director and reflector and arrive at the driven element in-phase with one another (the two re-radiated signals and the original signal). This basically means, the signals reinforce each other…and make the incoming signal much stronger coming from direction A. Continue reading
This is an area of hot competition among antenna manufactures. I am not going to cover how to mount your mobile antenna (Radio Shack sells everything you need to mount antennas), but the basic mobile antenna designs that most mobile antennas manufactures are using today. If you have just started reading my page and are new to antennas, you are going to be confused. You cannot just jump right into putting together an antenna without learning a few things about them first. You have to read “Antennas Basics”, “Coax Basics” and the “Verticals” sections first before you tackle this section. First we need to introduce a new term that we will be using to rate mobile antennas (gain really isn’t a good thing to use, since mobile antennas generally have no gain), “antenna efficiency”. This is how well the antenna converts your power (watts) to signal instead of wasting it as heat. An efficient antenna puts most of the power out as signal, so the range of 95-99% is a perfectly efficient radiator (all antennas waste some power, none are 100% efficient). Most base station antennas are 95-99% efficient. Say you are using 100 watts, and your antenna converts 95 watts to signal and turns the remaining 5 watts into heat, this is a 95% efficient antenna. Continue reading
4 Element Yagi Building
This article contains discussion of all the different antenna principles previously described elsewhere on this website. A thorough reading and understanding of the other sections are necessary to comprehend all the terms used on this page. It is not necessary to understand all the terms and theories described to build and enjoy this 4 element Yagi however. This particular section is geared towards the “freeband” CB operator – that is one who uses CB channels above (or below) the standard 40 CB channels. These CB “channels” are not legal for use in the United States – but they are quite popular any ways! The frequencies mentioned in this article are legal CB channels in some countries, check your local laws and act responsibly. This article shines little light on finding cheap aluminum or alternative methods of construction materials for Yagi antennas. It is also devoid of information on the physical design of Yagis. Sad but true, useable aluminum tubing in small quantities is expensive. And the physical design of Yagis is a subject beyond my limitations! What this article does do is provide a truly optimized 4 element Yagi design for the 11 meter “freeband” DX operator. Careful consideration was given the operating frequency and “rejection” needs of most 11 meter freeband DXers (CB operators who communicate with other CB operators more than 150 miles away). Continue reading