Antennas for ham radio stations is a very big topic, and one that you will learn about in study for the license exam and for practical implementation. In this article I will describe the most basic concepts for antennas in order to give you a general idea of what you may want to erect for your future radio station, and I will focus on antenna concerns for the new Technician Licensee. Additional articles referenced at the end of this post provide additional details regarding the challenges of getting antennas right.
Antenna for Your First Radio
HT will be sold with a short integrated antenna often referred to as a rubber duck due to the common rubberized exterior and short length. You can use the rubber duck sold with your new HT, or you can improve performance by replacing it with a longer, more effective antenna such as a 19-inch HT antenna that easily screws onto the antenna connector after the rubber duck is removed.
With an HT, you do not need to erect any permanent structure on your home or route any coaxial cable. The antenna is attached directly onto your radio and you can communicate with other stations quite well within a radius of a few miles, depending on your specific location and local terrain features. If you are within range of an Amateur Radio Service repeater station, you can use the HT with its integrated antenna to communicate much greater distances through the repeater station relay.
If your new HT operates on two bands, be sure to select a replacement antenna designed to operate on those two bands. The 2-meter band + 70-centimeter band combination is the most common dual-band HT, and many 19-inch antenna options are available for this combo. You may expect to spend $25 - $40 on an extended dual-band antenna for an HT.
Mobile Antenna for Your Vehicle
For mobile operations using an HT, your transmit and receive performance will be greatly enhanced by the use of an external antenna mounted on your vehicle and connected to your HT by a narrow coaxial cable. This gets your antenna outside of the metal cabin of the vehicle, allowing radio signals to propagate much more effectively than from inside that cavity.
A magnetically mounted antenna is a popular option that simply sticks to your rooftop using strong magnets and with the narrow coaxial cable slipped between your vehicle's door or window seal. Lip-mounted antennas are similar, but use a narrow clamp to mount onto the lip of one of your vehicles seams, such as a trunk, hatch, or door seam. Again, a narrow coaxial cable is routed inside the vehicle between the seals. With either of these simple-to-implement antenna mount types, your HT can serve as an effective mobile station.
The range of options for magnetic- and lip-mounted antennas is large, but you may expect to spend upwards of $100 for the combination of mount and dual-band antenna.
VHF/UHF Antenna Specifications
The Technician License provides transmitting privileges across the VHF and UHF range of bands allocated to Amateur Radio, but to only a small portion of the HF bands that affect long-distance, over-the-horizon communications. As such, the antenna types discussed here are for VHF and UHF bands. An antenna is designed for use on one or more specific ham bands, such as the 2-meter and/or 70-centimeter bands mentioned above, with these names referring to the approximate wavelength of the signals in the band. When selecting an antenna for your VHF/UHF transceiver, there are a couple of specifications that you must examine to ensure proper compatibility with your radio.
Bands -- as you have surmised, make sure the antenna is designed to work well with the bands transmitted by your radio. For instance, if you have a single-band transceiver for the 2-meter band, make sure your antenna is specified as a 2-meter band antenna. If you acquire one of the popular dual-band transceivers, perhaps with the 2m+70cm combination, be sure your antenna specification indicates it is a dual-band antenna for those two specific bands. This applies to any type of antenna, including the 19-inch HT extended type and the mobile antenna types described above.
Connector -- your antenna needs to have a connector type that matches the antenna connector on your transceiver. For HTs, the SMA connector is most commonly found on newer models. Older models may have a BNC connector. Beyond the connector type you must also confirm the required connector polarity, usually referred to as male or female for the obvious physical configuration reasons. Especially with the SMA connector that is most common, some manufacturers will install a male SMA connector on the HT, requiring a female SMA antenna or coaxial connector. Other manufacturers will reverse this convention, installing a female SMA on the radio that requires a male SMA antenna or coaxial cable connector. Carefully check the required polarity before purchasing an add-on antenna for your radio. For more information on these connectors, see Bob KØNR's article, What's That Connector on My HT?
Gain -- antenna gain refers to the way that an antenna radiates signals with higher power in given directions at the expense of radiated power in other directions. For instance, a vertical 1/2-wave mobile antenna may state a gain of "3.2 dBi." This antenna will radiate an expanding disk-like pattern of energy in all radial directions around the antenna's axis, but little power will be directed up or down. The antenna is said to produce gain in the radiated disk pattern, and the power of the signal in the disk pattern is estimated to be 3.2 decibels greater than it would be if the antenna were radiating equally in all spherical directions (isotropic pattern, hence the "dBi" comparison reference). You can use the gain values of product antennas to compare performance, making sure the comparison references are the same (dBi). Generally, higher gain is more desirable, producing improved performance.
More Information
Getting an enhanced antenna installed on your HT or on your vehicle for mobile ops is quite simple, and practically anyone can easily implement these add-ons with a little investigation into product specifics. More permanent antenna installations for a home base station or for enhancing HT performance offer a little more challenge, and you can read more about that topic is some of the articles listed below.
Stu WØSTU
For additional insight on antennas, check out these HamRadioSchool.com articles:
How Many Antennas Do I Need? An examination of antenna types and models beyond the HT and beyond VHF/UHF bands, including permanent installations for the home. Wire dipoles for HF, verticals for VHF/UHF, other considerations.
Considering a VHF/UHF Antenna for Your Home? A look at various options and considerations for home installations of VHF/UHF antennas, including installation locations, coaxial cable types, connectors and more.
A VHF FM Station at Home. VHF/UHF base station installation considerations and recommendations, including antennas, coaxial cable, and power supplies.
Ham Radio Mobile Installation -- Going Mobile. A two-part post outlining considerations for installing a station in your vehicle with example. Includes VHF/UHF station considerations plus HF station considerations (some advanced concepts), antenna mounting, power connections, and more.
dBi vs. dBd (G9C04) A review of a General License question that explains these two antenna gain references and helps you to ensure you are properly interpreting manufacturer-stated gain figures for antenna products.