Chaz Cone

Ham "Bands"

    By international agreement Hams are permitted to operate their stations anywhere they wish within "bands" of assigned frequencies.  By contrast, commercial radio and TV stations have a single assigned frequency on which to transmit. For example, WSB radio in Atlanta broadcasts on 750 Khz. Also, commercial stations are one-way services (indicated by the word "broadcast"). They broadcast, users listen.

    In Ham Radio we're allowed to make two-way contacts with other Hams world-wide -- and across a relatively wide range of frequencies (not just one as with commercial stations). These frequency "bands" have different properties.

    Radio signals have a range that is governed by a number of geophysical properties; among them, the frequency the signal is transmitted on, the number of spots on the face of the sun (sunspots), the relative opacity of the ionosphere and daylight/darkness between the stations at each end of the contact.  Because of these variables, some frequency bands are useful for local communications, some for mid-range and some for long-distance communications -- at different times of the day, season and year.  This is NOT an issue of governments, licenses or regulations -- it's just the way that radio works.

    I once heard radio explained this way:

      To understand radio, you first have to understand telegraphy (wired communications).  Imagine a long dog that reaches from New York to Chicago (a very long dog!).  If you step on his tail in New York, he barks in Chicago.  That's telegraphy.

      Radio is the same thing without the dog.

    Ham bands are roughly divided by frequency, from the lowest permitted frequency to the highest. The lowest group are called (curiously) "High Frequency or HF". That's because commercial AM broadcast stations transmit on "Low Frequency").

    Above HF comes VHF (for "Very High Frequency") and then UHF (for "Ultra High Frequency").

    Radio signals can be described by their wavelength and/or by their frequency; Hams use these methods interchangeably. Here are the bands currently allocated to the US Amateur Radio Service:

    HF160 meters1.8Mhz
      80 meters3.5Mhz
      60 meters5.3Mhz
      40 meters7.0Mhz
      30 meters10.1Mhz
      20 meters14.0Mhz
      17 meters18.0Mhz
      15 meters21.0Mhz
      12 meters24.8Mhz
      10 meters28.0Mhz
    VHF6 meters50.1Mhz
      2 meters144.0Mhz
    UHF1.25 meters222.0Mhz
      70 centimeters420.0Mhz
      33 centimeters902.0Mhz
      23 centimeters1240.0Mhz

    I don't want to say much more here (without getting tons more technical) but the size of the antenna used on each band gets smaller as Frequency increases.