Frequencies and the Spectrum

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Hello everybody and thanks for coming back again! Today we are going to be talking about frequencies and the radio spectrum in general. First off lets talk a little bit about the radio spectrum in general. The spectrum ranges 1 Hertz(Hz) to 10 to the 26th power Hz. Before we go any further, what is a Hertz? Hertz is the unit of measurement for determining the frequency of a wave. It is how many times a wave will pass in one second.

sine_wave

One wave or Hertz is from the point where the wave crosses the center line, goes up then down below the line and back to the center line, as you can see what it says Wavelength on the image above. 1 Hz means that the wave will pass one time in a second. At 146 MHz, which is right in the middle of the 2 meter amateur band, the 146 Million waves will pass in one second!

The easiest way to remember on how frequencies work in relation to distance is, Lower Longer, Higher Shorter! the Lower the frequency the farther or longer the wave will travel in one cycle. Lets look at a couple examples on both ends of the spectrum. The 20 Meter amateur band, has a wavelength of approximately 20 meters or 65.6 feet per cycle. On the 70 centimeter band, one wavelength is about 27.5 inches long in one cycle.

 

FrequencySpectrum

 

The audio portion of the spectrum is from 20 Hz to 20,000 Hz. Anything below 20Hz is generally felt rather than heard. The radio portion of the spectrum is from 20KHz to 30 GHz. Above 30GHz is where infrared, visible light, ultraviolet light, X-Rays and Gamma Rays reside. For the purposes of amateur radio, we are mainly just concerned with the 20KHz to 30 GHz range.

 

Category  Abbrev.  Frequency  Amateur Band Wavelength
Audio  AF  20Hz to 20 kHz None
Very Low Frequency  VLF  3 to 30 kHz None
Low Frequency  LF  20 to 300 kHz None
Medium Frequency  MF  300 to 3000 kHz 160 Meters
High Frequency  HF 3 to 30 MHz 80,40,30,20,17,15,12 and 10 Meters
Very High Frequency  VHF  30 to 300 MHz 6, 2m 1.25 meters
Ultrahigh Frequency  UHF  300 to 3000 MHz 70,33,23, and 13 centimeters
Superhigh Frequency  SHF  3 to 30 GHz 9,5,3, and 1.2 centimeters
Extremely High Frequency  EHF  Above 30 GHz  6,4,2.5,2, and 1 millimeter

So lets talk about a little math.

You can figure out the frequency or wavelength if you have one or the other using this formula:

f = 1 divided by T

f is Frequency
T is Time

To figure out a frequency from the wavelength:

f (in Mhz) = 300 divided by wavelength

example:

f = 300 / 2 (meters)

f = 150 MHz

The technical wavelength of the 2 meter band is a little more that 2 meters so its a little bit off of the 146-148 MHz

To figure out a wavelength from a frequency:

Wavelength (in meters) = 300 divided by f (in MHz)

example:

Wavelength = 300 / 146 (MHz)

Wavelength = 2.05 Meters

I hope that yall have found this information interesting, or at least helped you remember a little bit more about basic amateur radio information.

If anyone has any questions over what we have covered today, please leave a comment below. Thank you all for visiting my blog today and I hope that you will return for my next post. If you haven’t already, please like my facebook page, and/or follow me on Twitter, Google+ or LinkedIn.

Until next time…

73 de Curtis, K5CLM

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  • sdorttuiiplmnr

    I’ve been absent for some time, but now I remember why I used to love this blog. Thanks , I’ll try and check back more often. How frequently you update your website?

  • I normally post three times a week…sun, ties and sat with a throw back Thursday post on my Facebook page on Thursdays…