Microphones:

Are imperfect reproducers of the human voice and will distort the voice in ways that make it unintelligible unless a set of techniques are used to avoid problems. 

Hold the microphone close to your cheek, just off to the side of your mouth, positioned so that you talk across, and not into, the microphone. This reduces plosives (popping sounds from letters such as "P").

Speak in a normal, clear, calm voice. Talking loudly or shouting does not increase the volume of your voice at the receiving radios but will distort the audio because loud sounds result in over-modulation.

Slow down.  Not leaving gaps between words causes problems with radio transmissions that are not as noticeable when one is talking face-to-face.

Pronounce words carefully, making each syllable and sound clearly distinguishable.

If there is wind, face into the wind so the microphone is shielded by the back of the radio.

Repeaters:

Radios that use a repeater can only receive signals from the repeater. You might be in sight of the other person but the signal still has to go to the repeater and be rebroadcast before you can hear it which causes a slight delay.

After depressing the talk button pause, smile, then speak. While this is less than one second's time, there are many words that could be missed in their entirety if the operator does not delay slightly before beginning their message. 

Why smile?  Radio communication is not the same as natural face-to-face communication.  Your mode of speech is clipped and declarative.  It’s very easy to sound mad or rude or demanding. You might also be in a stressful situation. You have to wait for the repeaters anyway so use the time to smile. It instantly calms you and positively changes your communication.

Speech distortion:

The human voice is changed dramatically by radio, cutting off important audio at both the low and high ends of the spectrum, reducing it by at least half. More distortions occur in the microphone, transmitter, receiver, and speaker and the signal itself is subject to fading, interruptions, and interference. All of these make human speech more difficult to recognize, particularly when momentary disruptions or distortions block the transmission of entire syllables. 

Overcome these problems by greatly reducing the number of single-syllable words used. This is very much counter to the human nature of taking shortcuts in speech, so it takes training and discipline. 

Examples:  Contractions such as “don’t” or “won’t” sound alike. Instead, use “do not” and “will not.” Use “negative” instead of “no.” Use “affirmative” instead of “yes.” The use of single letters and numbers is hard to distinguish.  Use “A-Alpha, B-Boy,” and “Five-oh” instead of “fifty.”

Method of speech

Use the mnemonic RSVP:

• Rhythm—Use short sentences divided into sensible phrases which maintain a natural rhythm. (group things in 3’s)
• Speed—Speak slightly slower than for normal conversation. 
• Volume—Volume should be as for normal conversation. Shouting causes distortion.
• Pitch—The voice should be pitched slightly higher than for normal conversation to improve clarity.

The Five Ws

• Who—needs something
• What—do they need
• Why—do they need it
• When—do they need it
• Where—do they need it

You are ready to talk let’s go through it step by step.

• Listen (you don’t want to interrupt someone else).
• Push the talk button.
• Smile.
• “Robert…Robert, this is Billy.”
• Response, “Go ahead Billy.”
• Insert your declarative sentence here (ie: “I need help at the front door”).
• The response should consist of: I heard you. I understand what you want. This is what I plan to do about it (ie: “Affirmative, on my way.”)

Smile.

Why smile?  Radio communication is not the same as natural face-to-face communication.  Your mode of speech is clipped and declarative.  It’s very easy to sound mad or rude or demanding. You might also be calling because you are in a stressful situation. You have to wait for the repeaters anyway so use the time to smile. It instantly calms you and positively changes your communication. 

Most radio communication problems come down to haste. Listen before you speak to make sure the channel is not in use. Take a moment to compose your message. Push & pause so you don’t cut yourself off. Allow a slight gap between messages. Be sure you don’t talk over someone else. 

Confidentiality.

The same rules and laws of confidentiality apply to the radio as to any other professional communication.  Your words are literally being broadcast, choose them with care.