Vertical aerials for the Ham radio operator have several distinct advantages over wire dipoles which we string up in the air. Here is a list of the verticals I have used on the upper High frequency bands, i.e. twenty metres and above, they all work efficiently but one works better than the others.

Do you like many other Radio Hams suffer from a lack of what is commonly called free space, a part of the sky where nothing exists, where you can erect a dipole at an optimum height, this is usually at least a full wave length above ground. We all have small back gardens nowadays and room is at a premium when it comes to aerials, they often take second place, a washing line or children's play area maintaining the prime position.

I passed the Radio Amateurs license in the early nineteen eighties and have enjoyed building and testing many aerial designs over the years including verticals, but which one works best.

There are three vertical designs which I have found to work well, they all occupy a small area of ground and with a little bit of care and attention matching to an unbalance coaxial cable with a good match as near to one to one is possible.

A quarter wave length radiating element made from plumbers pipe is a good element, weather can turn it black in a few weeks but a coating of paint helps protect the element from the worst of the weather and I have found that no appreciable effect in radiation occurs.

A quarter wave aerial element is constructed from the formulae of 234 feet divided by the frequency. Your radiator is only one part of the aerial and you need to attach radial wires to complete the circuit. As an alternative to copper pip, 10mm earth cable will work well, however it will need to be supported by a wooden mast or you could create a sloping vertical with one end secured near the chimney.

Try to keep the vertical as far away as you can from your house, verticals radiate at long angles and can induce Radio Frequency currents into house wiring creating interference to Television sets.

Having secured the copper plumbers pipe to the ground, a length of wooden post driven into soft soil will accomplish this job. I have found it easier to dig soil out first and then drive the post into the soil with a heavy hammer. Solder the inner of your coax to the copper pipe making sure that you water proof the connection, self-amalgamating tape or duct tape works well, my aerials have stood the test of time and inclement weather using this simple but highly effective water proofing method has not affected the connections.

A quarter wave length radiating element cut for the twenty metre ham band at 14 Megahertz is approximately 16.5 feet long. Radial wires cut to the same length and attached to the braid of the coax complete this circuit.

You will need to prune the radial wire lengths to get a good match, one to one is possible with a little patience. Bury the radial wires a couple of inches down into the surrounding soil. Three radial wires will probably work but it all depends on your soil, soil is varies from town to town. If you find that your Standing Wave Ratio is too high, try adding another radial, this has worked for me in the past and an acceptable match has resulted. A good tip is to keep the surrounding soil moist if you live in a dry part of the Country, I live in the North East of England and the soil is very rarely dry. If at all possible run your coax back to your radio shack in a pipe buried into the ground, this protects the coaxial lead.

A half wave vertical has a the advantage of a little more gain than a quarter wave, the angle of maximum current is also moved up from ground level which we experience in a quarter wave vertical. A vertical on twenty metres will now be 33 feet long approximately, and the input impedance is now going to be high due to the fact that we are voltage feeding the aerial. A five eighths wavelength vertical has more gain; however the length is now 41 feet which may be too high for your location.

A coil made from enamelled copper wire will be required with tapping points, tap the coil every ten turns, wind 100 turns, use 2mm copper wire wound on a plastic pipe, the type used for drain pipe. A roller coaster is a continuous coil usually made from silver coated copper wire, it has the advantage of being continuously variable inductance, this is achieved by turning a shaft that moves a wheel across the total length of the coil, the inductance is in the order of 30 uh.

A suitable tuning capacitor will be needed to match your coil and aerial on the 14 Megahertz or twenty metre band. Auction websites is where you will find a tuning capacitor for your matching network, to find the correct tuning capacitor needed to resonate your network measure the total inductance of your aerial and coil, this can be done with a Multimeter capable of Inductance and Capacitance measurement or an A.V.O. metre, Amps Volts Ohms. The total amount of capacitance needed is found from this equation 4 x pi squared x frequency squared x L or inductance, divide this answer into one; you will now know the capacitance needed to resonate your aerial network.

To set up the tuning of the vertical, apply a small amount of power to the aerial; adjust the coils by selecting different taps until you obtain the best match on your S.W.R. metre, the capacitor is placed in parallel with your coil. I use a short length of wire from the bottom of the coil to a suitable earth rod.

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