For example, let's calculate the length of a radio wave at 28.5 MHz. The formula is 300,000,000 / 28,500,000 = 10.526316

Even more rounding occurs when describing which band of frequencies you are listening to. Hams are familar with bands such as 160, 80, 40, etc. and these are of course rounded numbers too. We've just seen above that when on a frequency of 28.5 you are really on the 10.526316 meter band! But of course we all call that the 10 meter band for short (thank goodness!) If you'd prefer, I suspose you could even call it the 34 feet band! No, let's not!!!

Another use of the length of a radio signal is in using transmission line sections (1/2 wave, 1/4 wave, etc.) in order to provide various impedance transformations. The quarter wave transformer is one popular such use. Now you might think that you would just take 300 / Frequency (Mhz) and divide by four to get a quarter wave line. Don't do it! You'd be off. You see, radio waves travel slower through different mediums. Which means the distance they can travel (wavelength) for a full wave is less than in free space. The coax cable you are using might for example, have a velocity factor of 66%. This indicates that the electrical length is actually 66 percent of the

To calculate the

Switch to:

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Your line length should be cut to