Ham Radio-aerials

Ham Radio-aerials

Ham Radio-aerials are easily constructed with items found at a local do it yourself store, such as copper wire wooden posts for their support, its fun and educational to build aerials, you don't have too but when you are starting off it's better to get the practical skills under your belt. Some Radio Hams build every single part of their radio station, the transmitter the receiver test equipment and aerials, when I started in Ham radio I did just that, building and modifying ex transceivers used by utility companies for use within the Ham bands.

Ham Radio-aerials

This is a QSL card used to verify contact with another Ham Radio station

A simple aerial for listening and transmitting is a dipole, the length is calculated by dividing your frequency in megahertz into 468 feet, as an example if we wish to work on the twenty-meter band frequency 14 Mhz we divide 468 by 14, which equals thirty-three feet approximately. 

In ham radio we often round off numbers to the nearest whole number to make things easy, 20 meters is 14 MHZ roughly, 15 Mhz is 20 meters, divide the frequency in our case 15 MHZ into the speed of light which is approximately 300,000000 meters per second, it equals the wavelength of 20 meters roughly. 

The Ham band we call two meters up on 144 MHZ, is roughly two meters in wavelength using 300,000000 again and dividing our frequency of 144,000000 we have approximately 2, 150 MHZ is more like 2 but we round things for ease.

Our 33 feet is fed in the middle using a centerpiece, coax is attached here, to deliver power from our transmitter to the aerial and from the radio wave passing our aerial down into the receiver.

An aerial cut for 33 feet needs to be high if we want to achieve gain, the nearer the ground a horizontal aerial is the more the power is directed up towards the clouds.

Vertical aerials give low angle radiation when mounted at ground level they are calculated using 234 feet divided by our frequency, in our case 14 MHZ, it results in a radiator of approximately 16.5 feet, we need the other part of the aerial for this model to work, we attach about 32 radials to the coax braid all cut to 16.5 feet and fan them out at the aerial base, radials counteract the absorption by the ground of our radio wave, you can use less but I find 32 to be ideal, 16, if you cant, get 32 is good too, 16 is about four wave-lengths using the formulae above, have fun building aerials.

Ham Radio-aerials

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