Reply To: Radio Q&A

  • Farm-Ranch-Homestead

    March 1, 2024 at 1:43 am

    What is the “radio spectrum?” Part 2

    In part 1, I discussed the radio spectrum in general terms, and provided some specific information about a few of the radio services that are available for the civilian population. In this part, I will discuss a few other services including the Amateur Radio Service and a few “broadcast” services.

    The Amateur Radio Service (also called “Ham” radio) covers numerous parts of the radio spectrum, with privileges to the various parts permitted by different classes of Amateur Radio Licenses. Most Ham radio bands are referred to with a “meter” designation. When you see a band identified in meters or centimeters, that is a reference to the approximate wavelength of the radio waves in that band. It is a function of the band’s frequency. I will discuss the relationship between wavelength and frequency further in a future post.

    The most common class of license is the “Technician” class. This is the entry level license for Ham radio. This license grants privileges primarily to specific parts of the VHF (Very High Frequency – 30 to 300 MHz) and UHF (Ultra High Frequency – 300 to 3000 MHz) bands, and a few other limited bands using specific modes.

    The most common bands used by licensees of the Technician class are the “2 Meter” (144 MHz) band and the “70 Centimeter” (420 MHz) band. These bands are often accessed using a “dual-band” hand-held transceiver (HT). A very common radio of this type is the typical Baofeng radio, such as the UV-5R or the UV-82. There are many variants of these radios that are often found very inexpensively on Amazon and other websites.

    Technician licensees also have privileges on the “6 Meter” band and a portion of the “10 Meter” band, but access to these bands requires a different type of radio than that used for the “2 Meter” and “70 Centimeter” bands.

    The second class of Ham radio license is the “General” class license. This license grants privileges to everything the Technician license allows, but also adds significant portions of the “HF” (High Frequency – 3 to 30 MHz) bands. HF includes the 80, 40, 20, 17, 15, 12, and 10 Meter bands (3.5, 7, 10.1, 14, 18, 21, 24, and 28 MHz, respectively). These are the more common bands that General class licensees gain access to, although privileges are also granted to several other bands.

    The third class of Ham radio license is the “Amateur Extra” class license. It grants privileges on all available Ham radio bands and all permitted modes of operation on each band.

    The “HF” bands, and the aforementioned “6 Meter” (50 MHz) band, are typically accessed using an “HF+6M” radio, which simply means a “High Frequency plus 6 Meters” radio. Some other radios are HF only, without 6 Meter coverage. Most radios of this type fall into the “mobile” radio category, although there are also both “base station” and “portable” radios of this type also. These radios generally require sophisticated antenna systems to allow them to be used across the permitted bands. These radios typically cover all or most of the Ham radio bands below 50 MHz.

    Besides the two-way radio services mentioned above and in the Part 1 post, there are also some broadcast frequencies you may already be familiar with, as well as others you may not be. For broadcast radio, you only need a receiver to be able to listen to the broadcast transmissions.

    I’m sure most who read this post will be familiar with the typical AM/FM radio such as those installed in most cars manufactured in the last 50 years.

    AM radio has fallen out of favor, but is still a very useful service. In the U.S., the most common AM band, and the one used by car radios, is between about 550 Kilohertz (KHz) and 1650 KHz. On the AM band, under ideal conditions, you may be able to receive broadcasts from hundreds of miles away. I remember years ago listening to a station from Boise, Idaho while I was sitting at home in Los Angeles. AM radio can still be a good source of news and information from your local area or somewhere far outside your local area.

    FM radio generally has better audio quality, but does not provide the range that AM radio does. The common FM band in use in the U.S. is from approximately 88 MHz to 108 MHz. This is the band that is commonly used for broadcast of musical content, but can also be a good source of news and other relevant information.

    Other broadcast bands that are far less familiar to most are the “shortwave” bands. Shortwave listening was popular following WWII, and remained popular through the cold war era. While shortwave radio has fallen out of favor somewhat, it could still provide a good source of news and information from around the world. Typically, you need a radio that is specifically designed for shortwave reception. The shortwave bands generally fall within the same range as “HF” (3 – 30 MHz).