Section 7.1: FM Operation #

Alright, new hams, welcome to the world of FM (Frequency Modulation)—the go-to mode for many Technician class operators. FM offers clear, crisp, and relatively noise-free communication, which makes it ideal for everyday local contacts.

Key Information: FM is the most common voice mode for VHF/UHF communications. It provides clear audio with resistance to noise, but uses more bandwidth than other modes. When tuning an FM receiver, you must be precisely on frequency or the audio will be distorted.

Why FM? #

FM is the default mode for most local communications, especially on VHF and UHF bands. While AM (Amplitude Modulation) gets jittery when there’s electrical interference, FM keeps its cool, delivering clean audio even in noisy environments.

A disadvantage of FM compared to single sideband is that only one signal can be received at a time, even when two signals are on the same frequency. This is due to the “capture effect” we’ll discuss shortly.

How FM Works #

Here’s how it works: instead of varying the strength of the signal (like AM does), FM varies the frequency slightly. It’s like changing the pitch of your voice rather than the volume. This is why FM sounds so clear on your car radio—and why it’s perfect for local ham chats.

As we discussed in Section 3.5, there is also PM (Phase Modulation), which is so similar to FM in practical use that most hams don’t know the difference. For convenience, we just refer to it as FM since the main difference lies in how the transmitter generates the signal.

Types of FM Operation #

Now, let’s talk about using FM in the ham world:

Simplex Operation: This is direct radio-to-radio communication. You and your buddy are on the same frequency, taking turns to transmit and receive. It’s great for local chats or emergency communications when repeaters might be down.
Handy tip: 146.520 MHz is the national calling frequency for FM simplex operations in the 2 meter band. It’s like the radio equivalent of a public square—used to make initial contact before moving to a different frequency, or just a good place to listen for activity while you’re on the road.
Repeater Operation: Remember those range-extending marvels we talked about earlier? Most VHF and UHF repeaters use FM. They listen on one frequency and transmit on another, vastly increasing your coverage area.
Narrow Band FM: Many modern radios use Narrow Band FM to allow more channels in the same frequency space. Think of it like fitting more cars into a parking lot by shrinking the spaces just a little.

Key Information: Simplex means transmitting and receiving on the same frequency. The national FM simplex calling frequency for 2 meters is 146.520 MHz. When using a repeater, you’re operating in duplex mode (transmitting and receiving on different frequencies).

FM Operating Tips #

When operating FM, keep these tips in mind:

Speak clearly and at a normal pace. No need to shout—the mic is right there!
Leave a pause between transmissions. This gives others a chance to break in or call for help.
Use simplex when possible. It keeps repeaters available for those who truly need the extended range.
Tune accurately: If you tune an FM receiver above or below a signal’s frequency, the result will be distortion of the signal’s audio. Other modes may sound off-pitch when you’re slightly off frequency, but FM just sounds bad.

Key Information: Over-deviation in FM transmission happens when you talk too loudly into the microphone, causing distortion on voice peaks. The solution is to talk farther away from the microphone, not louder.

FM Quirks #

FM has some quirks you should be aware of:

Capture Effect: The strongest signal wins. If two stations transmit at the same time on the same frequency, you’ll usually only hear the stronger one. If they’re close in strength, you may hear garbled audio—or nothing at all.
Near-Far Problem: A nearby station can overpower a more distant repeater, especially if their frequency is close. Try repositioning or using a directional antenna to help.

Common Radio Codes #

Historically, operators using Morse code (CW) needed quick, standardized ways to express common messages. While these shortcuts aren’t necessary in voice communication, they’ve become a lasting part of ham radio culture. We won’t cover all of them here, but these are some of the most common— including a few you’ll need to recognize for your exam:

QSY – “I’m changing frequency” or “Change your frequency to…”
QTH – “My location is…” Used to tell others where you are.
QRM – “I’m getting interference from other stations.”
QRN – “I’m getting interference from atmospheric noise.” Think thunderstorm static.
QSL – “I confirm” or “I understand.” Like saying “roger” or “copy.”
QRZ – “Who is calling me?” Used when someone is calling but you didn’t catch the callsign.
73 – “Best regards” or “Goodbye.”
88 – “Love and kisses.” (Often used by ham couples or close friends.)
CQ – “Calling any station.” Use this when you want someone—anyone—to come back to you.
DX – Refers to distance. “Working DX” means you’re trying to make long-distance or foreign contacts.

Key Information: The procedural signal “CQ” means “calling any station”—it’s how you start a conversation. “QSY” means to change frequency, and “QRM” refers to interference from other stations.

These codes and abbreviations are part of ham radio’s unique language. They help streamline communication and are understood globally. Knowing them will make you sound like a pro—and they also show up on the test!

So there you have it—FM in a nutshell. It’s beginner-friendly, reliable, and perfect for everyday conversations. Whether you’re checking into a net or chatting across town, FM is probably your go-to. Enjoy it!