Go HAM

When you combine the cool factor of being a pilot with the nerd factor of being an amateur (HAM) radio operator, they cancel out. At least, that’s how it has worked out in my case.

Despite engaging in the nerdiest hobby in the world, I’ve managed to avoid getting stuffed in lockers. In fact, many “cool” pilots pepper me with questions when I reveal my geeky hobby.

If you’re interested in how HAM radio knowledge can be applied in general aviation, what follows is some hard-won experience that can help you diagnose and (in some cases) repair radio issues in your aircraft. 

But first, a quick refresher and knowledge gap filler.

GA and other civilians transmit and receive in the Very High Frequency (VHF) band—118.000 MHz through 136.975 MHz for COM radios, and our NAV radios receive VOR and Localizer transmissions on 108.000 MHz through 117.95 MHz. Military aviators use the Ultra High Frequency (UHF) band, 225.000 MHz through 399.950 MHz. ATC can transmit and receive on civilian and military voice bands, and it can even listen to both simultaneously but transmit only on civilian or military as desired.

Other radio wave-dependent technologies use different frequency bands: Glide slope transmitters, DME, GPS/WAAS, ATC, WX Radar, and NDB all use their own sections of the radio frequency spectrum. COM and NAV radios use Amplitude Modulation (AM) radio as opposed to Frequency Modulation (FM) radio. However, even though your COM radio is built for AM, it can still pick up noise from an FM signal transmitted on a nearby frequency—such as an FM broadcast radio station at 107.9 FM—potentially making the reception of a VOR signal at 108.000 MHz difficult.

Radio altimeters (50, 40 30, retard, retard) are why the FAA doesn’t care for new 5G cellphones, as those are the avionics systems most sensitive to that technology’s interference. You probably knew most of that information already, but it's a useful reminder of how and why radios sometimes get finicky.  

Of course, radios don’t just suffer from a bombardment of ill-tuned signals from beyond; they also experience internal problems that, unfortunately, often mimic external causes. Airplanes are a terrible environment for electronics because of the wide variations of conditions they experience. As such, internal problems are likely to occur, no matter how well-engineered your stack.  

If your radio is on the fritz, here is a helpful list of things to consider and do. 

Remember, the radio box is just one of three major components. Plenty of radio issues can be found in the cable connecting your radios to the antenna, the antenna itself, and the connections between them. Check for corrosion and loose fittings.

HAM radio operators frequently use simple and inexpensive tools to help diagnose a problem on the ground.

• A frequency counter tells if you’re transmitting on the frequencies your display shows.
• A field strength meter can verify the power of your signal outside the airplane.
• And a regular ol’ multimeter can sometimes be used to test accessible connection points in your radio/cable/antenna system.

However, the best diagnostic tool is a handheld COM radio. If you can send and receive with it, but your panel-mounted radio can’t, you know there’s an internal problem somewhere.

At this point, it’s important to remind you about 14 CFR Part 43. To paraphrase, don’t mess with any part of the radio except the knobs and buttons, or the FAA will get angry. Unless you’re an A&P, have the proper commercial license from the FCC, or your airplane is an experimental, there’s only so far you can go in diagnosing issues, let alone fixing them.

Here are a few of the most common causes of radio problems and what you can do about them.

• Squelch is too high or too low — fixable by you.
• An unused headset is plugged in somewhere, and the mic is hot (vox or a stuck transmit button) — fixable by you.
• You have a 12V power source (cigarette lighter socket) that has started causing noise on some/all frequencies, even when nothing is plugged in — probably not fixable by you, but it’s a simple and cheap fix for an A&P.
• The sun and its darn sunspots — fixable by no one.

That list is mostly full of good news. You can identify and fix most common issues yourself, even in flight, and the ones you can’t are either a quick visit to the A&P or will pass in a few hours. The sun’s gotta go down sometime, right?

Know Before You Go