Sounds like a funny title for a Ham Radio article doesn't it? Certainly anyone who gets on the radio these days probably does it first through the use of a microphone. But what is that microphone connected to, and how does it really work? We might even ask, how does the human ear work?

If the radio being used is operating Single Sideband (SSB), than that microphone is probably connected to a linear balanced modulator. If the radio is operating on the mode of phase modulation (PM) or frequency modulation (FM), the form of the modulation envelope, and the ways it is heard, are completely different! We tend not to think about this when we are involved in a conversation (QSO) with another Ham on the radio. We should be thinking about this, its important!

When we operate a linear mode that is being detected within an amplitude waveform the content of the signal as it mixes with ambient noise is quite different from the modulation envelope or modulation index as it is seen or detected by a non-linear discriminator detector, as in the case of FM. The FM detector will discriminate against noise. Well, this is at least true if adequate signal power is used from the transmitter! The linear SSB or Amplitude Modulated (AM) signal depends on the ability of the human ear to discriminate the shape and form of syllables and verbiage where this audio signal is mixed within the ambient noise of the receivers bandpass window. We have to be cognizant of this, and think about the way and manner we are speaking into a microphone!

I was taken by and impressed with this idea recently while I listened to a detailed broadcast discussion of a highly detailed and technical subject. The broadcast was about various cancers and there cures, a subject of which I have only the most peripheral knowledge. The signal quality was excellent with none of the discussion participants comments being obscured "within the noise", yet at times it was difficult for me to understand all of what was being said. The reason for this was that of the three contributors to the discussion, they each had specific, often bad, speech mannerisms.

One was a clinical person who was expressing specific data, and thinking about what he was saying, and NOT how he was saying it. Another person was a recovering cancer victim in remission who was personalizing her comments in a way and with mannerisms that sometimes made her difficult to understand. The third person had written a book on this subject, and spoke in a way that suggested he verbally addressed or lectured before people often. This last person was easy to understand all of the time. He always spoke while clearly enunciating his syllables, and raised or lowed the level and cadence of his voice as he emphasized individual points of interest. He never mumbled or spoke raucously. He was easy to fully understand and follow his line of thought, even though I knew almost nothing of the details of his topic subject.

Similarly when we speak on the radio, we must think about how we sound on the other end. If the individual is using an amplitude mode, we can have an idea or clue by the signal report he has given us. Likewise if he is using FM, we can interpret this from the level of signal "quieting" he tells us that he is hearing. In this last case if a repeater is being utilized you might want to ask, "how well am I quieting the repeaters receiver, and how well is the repeaters transmitter quieting your receiver"!

Beyond this we must learn how to speak! If the signal is conveyed via FM and the signal is full or nearly full quieting, speak at a moderate level with your mouth close to the microphone. If using FM and the signal is less than full quieting, you should back away from the microphone speaking more gently, you should repeat words or expressions to carry your point. If you are using a linear mode such as AM or SSB, you should speak loudly yet not raucously. In other words speak loudly but evenly. You should also of course be aware that you are not driving your modulator into clipping, and that the ALC (Automatic Limiting Control) level is not exceeded.

An analog to this same practice should be done on FM. Make sure to ask the repeater owner of the repeater you use what the acceptable or common deviation level is. Get together with the other repeater users and adjust your deviation to the same level. This will probably never exceed 5 KiloHertz (KHz.) but may by convention be held down to 4 KHz. or less.

Beyond this and lastly, speak carefully. Be conscious of each syllable in every word you use. With some practice you will learn to stop slurring words that you use more commonly. This is a practice that you might compare to handling emergency traffic on the radio. You would never shout or be unclear if someone's life was at stake. In such an emergency and hectic condition, you must keep your head and speak clearly, calmly, and using only those words needed to make your point. Similarly, when we are speaking about some detailed point in a more conversational QSO, you must still speak clearly, calmly, and with just the right amount of emphasis. If you don't do this, no one will want to speak with you. They may not even be able to understand you at all!

Terms used in this article

Linear: This term is used to describe the physical nature of the transmitted or received signal. Any non-linearity that is imposed by "over-driving" the modulator, or otherwise imposed upon an Amplitude Modulated (AM) or Single Sideband (SSB) causes distortion and a deterioration of modulation quality.

Balanced Modulator: This is the most popular or typical method of producing a Single Sideband modulated signal. The balanced modulator provides the "sidebands" of energy that exist on either side of the carrier frequency but, eliminates the RF carrier.

This is done because it is the sidebands that provide the means of communicating the intelligence within the modulation envelop. These two sidebands, or the one remaining that is not removed by a filter in the case of Single Sideband, provide the nuances of the speech index and mannerisms. SSB is the most efficient use of Radio Frequency (RF) energy for human speech! It provides almost 9 Decibels (dB's) of signal gain over an Amplitude Modulated signal that includes an RF "carrier" of the same power level!

Frequency Modulation (FM): This modulation method on the other hand is by its general nature a "non-linear" form of modulation. It can utilize "Class C" amplification, and the non-linearity of the "modulation index" does not by itself degrade modulation quality. You still must not "over drive" the strictly audio portion of the modulator but, at the radio frequency (RF) end of the transmitted signal carrier, non-linearity is quite all right (Hint: Look up Bessel functions or Bessel nulls in FM!)

Modulation Envelop: The concept of the existence of an "envelop" or zone of radio frequency energy is one of the most important concepts you need to learn in the study of radio physics! This "envelop" of energy exists at some proportionate "point or space in time" on an "instant to instant" basis as the RF energy is modulated. (Hint: High speed code has a wider "modulation envelop" than does slower speed Morse code!)

Phase Modulation: This is a sort of "compromised FM". It provides both Amplitude and Phase (or frequency shift) modulation simultaneously. This might be considered a great advantage over "Direct FM". It can have some applicational benefits, if the modulation "waveform" is kept nicely "symmetric".

Motorola used this method to great advantage by using very low starting (or fundamental) frequencies at the first oscillator of there transmitter. By this method, along with the use of very stable frequency control utilizing high quality crystals, they achieved rich beautiful sounding audio! This sort of modulation at the transmitter, along with good limiter/discriminator receiver made for an excellent high quality communications signal. (Hint: Many modern day FM radio transmitters provide rather non-symmetric modulated signals! Also, the receivers in these transceivers often only provide a fraction of the receiver "noise limiting" of older designed receivers! Discriminator: This is the oldest and best form of detector technology that was used in the earliest FM receivers. An interesting history and debate about Discriminators vs. Ratio Detectors can be found within the history of the development of FM. To look into this, read Lawrence Lessings book, "Man Of High Fidelity". This is the story about the life of Edwin Howard Armstrong, the inventor of FM. He was a wonderful Ham, by anyones judgment! A real John Galt!

Bandpass window: This is another important concept to learn. Radio energy fills a "point or time in space". This space is referred to as the "bandpass" or "bandpass window".

Think of this by imagining the view that you take in as you look out of a glass window. All that your eyes can take in, is the reflected light frequency energy at or around 70,000 GigiHertz (GHz.). This GigiHertz range energy is getting to your eyes, the ultimate "bandpass filters" at this frequency, by the modicum of entering the first filter, your glass picture window! (Hint: Look up bandpass filter "skirts", or the "slope factor" of mechanical or crystal and ceramic Intermediate Frequency filters.)

Quieting: This reference refers to the relative quieting, or noise quenching, that comes about as a radio frequency carrier sufficiently fills the bandpass window.

Clipping: This term refers to a filtering technique whereby audio peak values can be averaged to form a more consistently high level averaged audio driving signal.

Modulator performance is based upon peak level values, however, average levels must be maintained at a serviceably high level since average speech falls well below the peak values. Excess audio drive values must be controlled, otherwise these excess peak values would cause spikes of non-linear modulation distortion.

Traffic: Within the context of this article, "traffic" refers to that message content that forms the framework or substance of the intended communication.

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