Tuesday, 11 February 2020

Ham Radio The Cubical Quad Aerial

Ham Radio The Cubical Quad Aerial

Ham Radio The Cubical Quad Aerial

A two-element cubical quad aerial

Ham Radio The Cubical Quad Aerial.  The cubical quad aerial is another of my favorite aerials which are very easy to build with a little time and patience. The Quad aerial has been used for many years by Radio Ham's to increase their output power from their transmitters and because an aerial has the properties of amplifying the received signal, weaker signals can now be received where they may have been buried in the noise before building your aerial. 

I have also found the Ham radio Quad to be better, a quieter aerial due to the fact that it is a closed-loop.

A Quad also has a good front to back ratio, but what does that mean and how can this property be utilized. Quite simply pointing the back of the Quad, the reflector, to the direction where stations may be causing some interference to the signal you wish to receive reduces their signal strength.

Your quad aerial will reduce these signals by a certain degree, this percentage of attenuation of the signal is dependent on the gain which is produced in the forward direction may be four signal points down. Element spacing forms the ratio of forwarding gain.

It may seem confusing and new radio Hams often struggle with these concepts, after all, Radio, is Physics, but stay with your studies and you will become proficient in this fascinating hobby.

Building the Quad aerial is not too difficult and it can be made using material sourced from local stores specializing in Do It Yourself products. The Boom of the Quad aerial can be made from plastic tubing, the type used for plumbing or wood. Wood is a good choice because it is stronger than plastic. The spreaders used to form the squares to form the cubical quad can be made from plastic tubing or wooden slats one-inch square or a combination of both. Spreaders made from plastic allow you to bend them to add a little tension when fixing the wire to form the square loops.

An advantage of building an aerial is that it not only works out cheaper but you learn from the building, as you make the aerial you start to understand how the theory of aerials work, after all, it is a well-known fact that knowledge comes from doing. The building gives you more control too, you decide on the design frequency, how many elements you wish to use and how you will space the elements, spacing affects the gain of an aerial and building puts you in control of this factor. Elements are spaced between.14 and.25 of a wavelength, the wavelength is calculated by dividing the frequency into 300,000,000, the speed of light.

The Quad, unlike a dipole, is made from square loops of wire which are approximately a full-wave long as opposed to a dipole where we use 468 feet to calculate element length. There are many calculators on the internet now where you simply input the frequency of where you wish the Quad aerial to work and it calculates the dimensions for you.

When I sat the radio Amateurs Examination, it was a requirement to know certain formulas for calculating aerial elements and other electronic components but now you have the internet where formulas are built into online calculators. The Quads that I have built successfully over the many years I have been interested in Ham Radio have all been built using these easy to learn calculations.

The reflector on a Quad aerial is calculated by dividing the deign frequency into 1030 feet, if you are considering building a Quad aerial for the two-meter band or 144 Megahertz, your reflector length will be 1030 feet divided by 144.5, this equals 7.12 feet.

The driven element is the next element you construct; this is number two-element if you are making a three-element Cubical Quad. By diving 144.5 into 1005 feet we get a figure of 6.95 feet for the driven element, this is the element where we connect our 50-ohm coax.

The next and final element is called the director and it is calculated from 975 feet, dividing 144.5 gives the answer of 6.74 feet. To make life easier with this number, multiply them by 12 to five inches they are easier to work with. 6.74 feet now becomes 80.88 inches, using a tape measure marked off in tenths of an inch makes it easy to measure your wire for the Ham Radio Cubical Quad aerial,.88 becomes approximately 9 tenths of an inch, this is easy to see on a tape measure.

Spreader lengths are calculated using simple trigonometry, the quad has four equal sides, drawing a line from the top right-hand corner of a square to the bottom left-hand corner forms a triangle this is called the hypotenuse.

Place your square piece of wire on the floor it is easier to measure these lengths. If we call the equal sides, side A and side B the hypotenuse is the line you have drawn from corner to corner and this is the length of your spreader.

The formulae is A squared plus B squared, the hypotenuse is the square root of this answer. this calculation gives the answer of 30.24 inches for our spreader, using our reflector length of 7.12 feet, 7.12 feet multiplied by 12 equals 85.44 inches, or approximately 85 inches and four-tenths of an inch. 85.44 divided by 4 equals 21.36 inches per element side.

Play around with these numbers, but different frequencies into your formulae, for example, a local air-band frequency and calculate the loop sizes. I have constructed many three-element Quad aerials for the air-band, if you turn the quad where the feed point of the aerial is on one of the sides, it becomes vertically polarised, turning it again to a point where the feeder is along the bottom or top of the quad changes the polarity to horizontal polarisation.

Ham radio beacons are usually horizontally polarised and found in the lower part of the 144 Megahertz spectrum, experiment with your two meter or air-band quad aerial by turning it through ninety degrees, you will hear that the signals increase or decrease depending on the polarity of the transmitted signal.

Ham Radio The Cubical Quad Aerial

Ham Radio aerials-Half square

Ham Radio aerials-Half square

Ham radio aerials-half square is a simple to build wire aerial which offers gain and relatively low angle of radiation in both directions broadside to the wire.

The half-square aerial consists of two-quarter wavelengths of copper wire vertically polarised with a half wavelength of wire connecting them along the top, one of the corners are fed with coax the center going to the long half-wave portion the braid connected to the quarter-wave section.

I used a small plastic box fitted with a so-239 connector at one of the corners of the aerial this allows your coax cable to be attached to the wire and then back to your transceiver.

Modeling the aerial with mmana a free aerial program gives us about 4db over a single vertical radiator, the feed point is, of course, higher than a bottom-fed vertical aerial.

I found I could achieve an SWR of about 1:5:1 ratio using this aerial after a little tuning according to the software mmana shows a beamwidth of about 60 degrees and about -1.9 dB at around 5 degrees off the horizon, with no radiation of signal developing at 90 degrees to the top wire, a good simple cheap aerial for DX

Running the aerial in a north-south direction will give you gain over a single vertical radiator in the east-west direction ideal if you wish to target the U.S.A. from the U.K.

The half-square is easily made but if you feel that you wish to purchase one this link will take you to a Ham Radio supplier.


Ham Radio aerials-Half square

Ham Radio aerials-Half square

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Ham Radio-Operator caught in oil

Ham Radio-Operator caught in oil

By John G4YDM

Portraits in oil hand painted on canvas by Artist John Allsopp

Ham radio-Operator caught in oil. Oil portraits were once the possession of the Rich & Famous, however, times have changed and most people can afford a painting nowadays.

This work of art shows two delighted people enjoying a life long dream to go on a cruise, around the world. I sent in a press release to RadComm magazine it is sent to all Radio Amateurs here in the U.K. when you join the Radio Society of Great Britain.

Don, the gentleman in my picture called me and said he would like a painting featuring his wife and himself enjoying a trip of a lifetime around the world on a cruise ship. You never know who and how people get to contact you. 

He was unsure what I needed to paint a portrait, photographs as many as possible was my reply. Don sent several good clear colored photographs and I set to work in drawing up a portrait style which I thought he would like. He chose the style suggested below and I set to work preparing a "Happy Couple" portrait. It took about three months to finish, painted on the best linen canvas, Don was simply beside himself when he saw it.

Many artists work from photographs, I do sit with subjects from time to time and sketch material for reference purposes but I prefer to work alone working from pictures, I relax better that way and can focus and concentrate on the job in hand.

People often ask what size is the best for a portrait or a painting, it depends really on the subject, if it was too small you lose the perspective, too large and it overpowers you especially if you hang it in a small room, it's not a law when it comes to size you ask what size you want and I will advise.

The largest painting I have created up to now was four-foot square it featured a couple's wedding they have a big open wall in their house, it sits in the middle and looks great. I once saw an artist who painted a lion head six foot by six foot, it looked absolutely stunning but he did have a large wall to display the work, one day I am sure I, ll get round to painting a wildlife scene, they are very popular. You simply can't keep your eyes off them.

I may combine my parent's portraits into a similar work as you see below, I think it would be interesting to paint their portraits again after twenty-five years, I have many reference pictures of my parents like most people, I may combine my grandparents into a new work, that would be interesting to see several generations of my family in a single portrait. 

This is not a new idea many Royal family portraits have several generations combined into a work.

Ham radio-Operator caught in oil

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