Basics of Very High Frequency (VHF) and Ultra High Frequency (UHF) radios - dummies

Basics of Very High Frequency (VHF) and Ultra High Frequency (UHF) radios

By H. Ward Silver

Many high frequency (HF) ham radios include 50, 144, and 440 MHz operations. The Kenwood 2000 series goes all the way to 1200 MHz. This power makes purchasing a second radio just for VHF/UHF operating less a necessity for the casual operator. Many ham radio shacks have an all-band HF/VHF/UHF radio backed up with a VHF/UHF FM rig for using the local repeaters.

VHF/UHF radios that operate in single sideband (SSB), Morse code (CW), and FM modes are known as all-mode or multimode to distinguish them from FM-only radios. Many of the VHF/UHF all-mode radios have special features, such as full duplex operation and automatic compensation for transponder offsets, that make using amateur satellites easier.

An all-mode radio can also form the basis for operating on the amateur microwave bands. Commercial radios aren’t available for these bands (900 MHz; 2.3, 3.4, 5.6, 10, and 24 GHz; and up), so you can use a transverter instead. A transverter converts a signal received on the microwave bands to the 28, 144, or 440 MHz band, where the radio treats it just like any other signal.

Similarly, a transverter converts a low-power (100 milliwatts or so) output from the radio back up to the higher band. Bringing the output signal up to 10 watts or more requires an external amplifier.

Multimode radios are very popular for the special type of mobile contesting called roving. One of these small rigs and a transverter or two makes for a lot of fun as you rove from grid square to grid square, racking up points on all the bands.

FM-only radios

Nearly every ham uses FM on the VHF and UHF bands regardless of his or her favorite operating style or mode. A newly minted Technician licensee can likely use an FM mobile or handheld radio as his or her first radio. FM is available on the all-mode rigs, but because of the mode’s popularity and utility, FM-only rigs are very popular.

FM radios come in two basic styles: mobile and handheld. You can use mobile rigs as base stations at home, too. Both mobile and handheld radios offer a wide set of features, including loads of memory channels to store all your region’s repeater information, powerful scanning modes, and several types of squelch systems.

Mobile FM radios

The more-powerful transmitters used with an external antenna extend your range dramatically. Receivers in mobile radios often have better performance than those in handheld radios; they’re capable of rejecting the strong signals from commercial transmitters on nearby frequencies.

Although most people expect a new ham to buy a handheld radio, you should start with a mobile radio shared between your car and at home. Assuming you live in an area with average or better repeater coverage, you can simply pop a magnetic-mount antenna on top of the refrigerator, and you’re in business. (If you live in a rural area, you probably need an outdoor antenna.)

The stronger signal from the mobile allows you to operate more successfully over a wider range, which is important at first. When you know more about what type of FM operating you want to do, you can buy a handheld radio with the right features and save money.

You can often use mobile radios for digital data operation on the VHF/UHF bands. As radio modem technology has advanced, hams have begun to use 9600-baud data. If you plan to use your mobile rig for digital data, make sure that it’s data-ready and rated for 9600 baud without modification.

Handheld FM radios

Handheld radios come in single-band, dual-band, and multiband models. The single-band models, particularly for 2 meters, cost less than half the price of a multiband model. You’ll do the lion’s share of your operating on the 2 meter (VHF 144–148 MHz) and 70 cm (UHF 420–440 MHz) bands, so the extra bands may not get much use.

You can expect the radio to include as standard features encoding and decoding of CTCSS subaudible tones (tones used to restrict access to repeaters), variable repeater offsets, at least a dozen memory channels, and a numeric keypad for entering control tones (the same tones used to dial a telephone). A rechargeable battery and simple charger come with the radio. Be sure to get a spare battery and the base charger.

Extended-coverage receiving is a useful feature because being able to listen to commercial FM broadcast and weather alert stations around 2 meters is very useful.

Programming a radio with dozens (if not hundreds) of memory channels can be a chore if you do it all with the front-panel controls. Ask around to see whether someone has programming software and a cable to connect your radio to a computer. The software enables to you to quickly set up your radio for the local repeaters and simplex channels, including alphanumeric labels for each channel.

Most radios can also be cloned, meaning that you can transfer the contents of one radio’s memories to another radio of the same model by using a cloning cable. This method can save a lot of time if a friend has the same model already programmed.

VHF/UHF amplifiers

Increasing the transmitted power from a handheld or low-power mobile radio is common. Amplifiers can turn a few watts of input into more than 100 watts of output. Solid-state commercial units are known as bricks because they’re about the size of large bricks, with heat-sinking fins on the top. A small amp and external antenna can improve the performance of a handheld radio to nearly that of a mobile rig.

Amplifiers are either FM-only or SSB/FM models. Amplifiers just for FM use cause severe distortion of a SSB signal. An amplifier designed for SSB use is called a linear amplifier, and SSB/FM models have a switch that changes between the modes. You can amplify Morse code signals in either mode, with more gain available in FM mode.

RF safety issues are much more pronounced above 30 MHz because the human body absorbs energy more readily at those frequencies. An amplifier outputs enough power to pose a hazard, particularly if you use a beam antenna. Don’t use an amplifier at 50 MHz or above if the antenna is close to people.