About Aviation Radios
Sooner or later, most sport pilots get interested in having a radio on board the aircraft. It doesn’t matter whether you’re flying an ultralight or a 747, there are lots of good reasons for having radio gear, and lots of choices. So let’s get started!
This article deals with these important questions:
1. What kind of radios do pilots use?
Sport pilots use many types of radios. Generally, they fall into two broad categories: receivers and transceivers. A receiver only receives or “hears” broadcasts from other radios, it cannot transmit. Still, a few pilots like receivers because they are inexpensive. A good digital receiver can be bought for under $100. These units can be handy for monitoring traffic in the pattern at a nearby airport, or for listening to weather broadcasts.
Most pilots prefer transceivers, so they can actually communicate with other pilots and ground stations. Sport pilots generally use aviation band transceivers. These radios transmit and receive in the AM frequency band of 118.000 MHz to 136.975 MHz, the so-called “Communication (COM) Range”. Most also receive the108.000-117.975 MHz AM band on which special navigation (NAV) signals are broadcast. These NAV signals often contain continuously updated weather information. Also, many transceivers can decode the hidden NAV signal and display the direction from your aircraft to the navigation transmitter, called a VOR station.
Handheld COM radios can cost as little as $300, those with NAV decoding displays cost much more, maybe $500+. Panel mounted COM radios can be found for between $800 and $1500. A handheld unit puts out about 1 watt of power, a panel mount radio puts out between 4 and 10 watts. Higher power means that your transmission will be heard further away.
Many ultralight pilots use CB radios instead of aircraft radios. These have the advantage of usable range and very low cost. Unfortunately, CB radios caan’t talk to aviation radios. So, CB radios make sense only if your primary interest is to talk to your CB-equipped pilot and ground-dwelling pals.
Most paraglider and hang gllider pilots use “Business Band” hand-held transceivers. These radios are as common as CB, but transmit and receive in the 148 to 158 MHz range. Unfortunately, many business band radios have only one or two frequency selections, and different frequencies are in common use at different flying sites. So, many of these pilots use the so called “Two-meter” band radios designed for licensed ham radio operators in the 144-148 MHz range, and “tweak” the radios so they cover the business band as well. Though not legal, it is very easy to do, allowing a two-meter transceiver to operate in a wide frequency range, from 140 MHz to 160 MHz.
2. Are there legal requirements regarding radio use?
The FCC publishes a set of rules for radio operation, and counts on the honor system. Aviation band, CB and business band radios no longer require any license, but operating in the ham bands does. Basically, whatever radio is used, the operator is supposed to keep communications brief and to the point, keep the radio properly tuned so that it transmits only in the required band, use no profanity and use the correct frequency for communications.
This last point is crucial, especially for aviation radios. The FCC and FAA government agencies have carefully assigned frequencies for aviation use. You can’t just pick up your radio and tune in any old frequency and start talking. Say you live in Detroit and start having a chat on 124.900 MHz - whoops, you’re using the Detroit Metro Airport Approach Control frequency. Never, except in a true emergency, transmit anything on 121.500 MHz, If you do, you will trigger alarms within 100 mile radius, and search planes, police, and all sorts of official people will start hunting for you: that’s the international distress frequency. The frequencies 123.000 MHz, 122.8 Mhz and a few others are reserved for “Unicom” transmissions, a kind of a party-line frequency used near airports without control towers. There are dedicated frequencies for air-to-air discussions between pilots as well. If you’re going to use an aircraft radio, learn the rules!
3. What if I want an intercom?
Most radios can be easily interfaced to intercoms, usually with a simple adapter cable.
4. What about headsets, i.e., earphones and microphones?
While it is possible to operate a radio inside an aircraft using a speaker and a handheld microphone, it is not a good idea. Most aircraft engines and propellers are dangerously loud and will permanently damage the pilot’s hearing in short order. Turning up radio volume to be heard over this already load roar only adds to the problem. The solution is a good quality headset, with two snug-fitting earcups and a boom microphone. These type of units are also available integrated with safety helmets
5. How do I power my radio?
Handheld radios come with either rechargeable or alkaline battery packs, and most can be powered directly from 12 volt aircraft power. Most panel mount radios and CBs require a standard 12 volt DC power input.
6. What do I say when using the radio?
Aviation radios are primarily aids to flight safety. Let’s say you’re landing at a small airport (with no control tower) used by lots of general avaition aircraft. These planes are probably using the Unicom (e.g. 122.800 MHz) frequency. As you approach, you might hear something like this :
-Smallville traffic, Cessna 1234 Romeo is 3 miles south, inbound for
landing......
(a minute later)
-Smallville traffic 34 Romeo is entering downwind for runway 27.....
(a minute later):
-Smallville traffic, 34 Romeo is turning base for runway 27....
(then)
-Smallville traffic, 34 Romeo is on final approach for runway 27....
You get the idea, our Cessna’s pilot is periodically announcing his whereabouts to the whole world; those of us in the vicinity of Smallville Airport will know there is approaching traffic, and where it is. This, of course, assumes that you know what a downwind,base and final approach leg is. A primary use of the radio is to broadcast our position and intentions. If we are legally alllowed into tower-controlled airspace, we use the radio to talk to the contollers. On a cross-country flight with friends, we might use the air-to-air frequency to chat. Keep in mind that there are a limited number of available frequencies, so don’t be gabby.
7. What do I listen for on the radio?
In addition to the previous type radio traffic, the radio offers a lot of resources to listen to. In our example, Smallville is. let’s say, a suburb of Metropolis, which has a huge commercial airport. As such, it will have an ATIS (Air Traffic Information System) automatic broadcast, updated at least every hour. Tune to its assigned frequency, and you’ll hear:
-Metropolis International Airport information Delta, 1800 Zulu
weather: Sky 1800 overcast, 1200 scattered, visibility 1 mile in haze
wind 270 at 13 gusting to 20, light rain. Temperature 20, dewpoint 18,
altimeter 29.92. Visual approach to runway 18 in use. Numerous birds in the vicinity of the airport, runway 27 closed. Arriving aircraft and overflights contact approach control on 123.4, departing aircraft contact clearance delivery on 121.9.Advise you have information Delta.
The “Delta” (for “D”) is the code word for the recording; it tells you how current the data is. Next hour, the code will be Echo (for “E”), and so on. Since Smallville is close, you can be pretty sure that the weather at Metropolis is a lot like the weather at Smallville. This ATIS broaadcast tells you that it’s windy, gusty and rainy near Smallville, and that visibility is poor
8. What frequencies do I use?
For aviation band radios, get your hands on a copy of the Federal Aviation Administration Regulations (FARs) and the Airman’s Information Manual (AIM), available at most bookstores. They contain a list of commonly used frequencies. Get a local Sectional aviation chart to learn the frequencies of airports near your flying sites.
The CB users generally “hail” (establish contact) on channel 16, then switch to another frequency to chat. On the business band, the USHGA (United States Hang Gliding Association) uses three approved frquencies: 151.925, 151.625 and 151.955 MHz.