Transmission and Reception

The frequency is a conversation, not a phone call

The first mistake of those starting with aviation radio is thinking they're "making a phone call". The VHF frequency is a half-duplex channel shared by all tuned in: when one speaks, the others listen. Two people can't speak simultaneously — transmissions overlap and destroy each other (the technical phenomenon is called heterodyne).

So before thinking about what to say, think about when to say it. The rule is: listen first, then talk.

The standard call cycle

Every ATC radio communication follows the same four-phase cycle:

1. Listen — tune the frequency and listen for 10-15 seconds. Understand if the frequency is busy, who's talking, what traffic is in progress.
2. Transmit — when there's a pause, press PTT, wait 0.3 seconds, make your call.
3. Receive — release PTT immediately after the last syllable, listen for the controller's response.
4. Readback — repeat the essential elements of the received clearance.

Only after the controller has confirmed your readback (with silence or a correction) is the cycle closed.

The standard call structure

Every standard call has two parts: the contact and the request.

Part 1 — The contact

Just two elements in this order:

1. Whom you're calling (station name)
2. Who you are (your callsign)

Example: "Lugano Tower, HB-PMR."

The controller will reply with the same formula reversed: "HB-PMR, Lugano Tower." This means: "I heard you, the mic is yours, tell me what you need."

Part 2 — The request

Only after the controller has responded to the contact, state the request. Typically follows this structure:

1. Current position and altitude (if relevant)
2. What you want (clearance, information, authorization)
3. Any details (intentions, ATIS received, etc.)

The exception: the "compact" call

On low-traffic frequencies or when you've already established contact recently, it's allowed to compress contact and request into a single turn:

"Lugano Tower, HB-PMR, holding point runway 19, ready for departure."

In this case the controller responds directly with the clearance, skipping the "back-handshake". It's more efficient and frees the frequency, but should only be used when you have reason to believe the controller isn't in another conversation.

Abbreviating your callsign

Once the controller has called you, and only then, you can abbreviate your callsign to the last 3 characters.

• First time: full callsign ("HB-PMR")
• After the controller has abbreviated first: you can also abbreviate ("PMR")

Example: - HB-PMR: Lugano Tower, HB-PMR. - TWR: HB-PMR, Lugano Tower. - HB-PMR: PMR, request descent.

The controller may choose never to abbreviate (if there are similar callsigns on frequency). In that case you keep the full callsign too.

Reception: what to do when called

When you hear your callsign, you have 3-4 seconds to reply before the controller repeats. What to do:

1. Acknowledge with a brief "Go ahead" or by repeating your callsign.
2. If it's an instruction, do a complete readback (see Readback).
3. If it's a question, answer directly.

When the frequency is too busy

On saturated frequencies (Zurich Approach during evening arrivals, for example) you may not find space to call. What to do:

• Be patient: 30-second waits are normal on saturated frequencies.
• Don't interrupt: if you transmit over another transmission, you destroy both.
• If urgent, use "Standby" when the controller calls you, to ask for a moment. If it's truly urgent (emergency situation incoming), trigger with "PAN PAN" or "MAYDAY" — see dedicated entries.

Swiss specifics

Summary — to remember

1. Listen 10-15 seconds before transmitting on a new frequency.
2. Contact + Request are two distinct phases. Wait for the contact reply.
3. Structure: whom you call, who you are, where you are, what you want.
4. Abbreviate the callsign only after the controller has.
5. "Roger" is not a readback. Instructions are repeated in full.
6. One transmission at a time: if you hear voices, wait.

Sources

• ICAO Doc 9432 — Manual of Radiotelephony, Chapters 2 and 3
• ICAO Annex 10 — Aeronautical Telecommunications, Volume II
• Aero Locarno · Subject 090 — VFR Communications, "Technique" and "Call category" chapters