Homebrew projects for radio & electronics enthusiasts


How to adjust your rig for the best transmitting audio.

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MIC POSITION - For best audio pickup, turn the mic sideways and park it right next to the corner of your mouth, so that you are speaking across the pickup element. Speak using your normal, conversational volume voice. The fullest range of your voice is available to the microphone, especially the higher-frequency sibilance, which does not rise in the same proportion with the rest of your voice when you talk loudly. This is the part of speech that makes you easily understood. Ask somebody with a hearing aid just how important this speech component is!

When you are mobile, develop the habit of touching your cheek with part of the mic or the hand holding the mic so that as your head turns or moves around, the mic follows, maintaining a consistent audio pickup. Letting the mic drift away definitely drops off your volume and intelligibility

DO NOT put the mic directly in front of your mouth or you will create that obnoxious-sounding breath noise as puffs of air from your lips during speech produce annoying bursts of white noise. This will destroy your clean sound.

Headsets with boom mics, unfortunately, seem to be designed to place the pickup in the worst place: right in front of your lips. In the case of the Heil headset, however, the boom is bendable and by forming a gentle curve into it, and you can place the pickup at the corner of your mouth, out of the way of your breath.

MIC GRIP - Yes, that's right! The way you grip your mic can have an effect. Many hand mics are made completely of plastic and they can get creaky! Plastic rubbing on plastic causes sticktion: as the strength of your finger varies on your plastic key, or if you roll it back and forth a little while you are keying, it will produce an annoying creaking sound. You can even feel the vibrations sometimes in the body of the mic when it occurs. This can be quieted somewhat with a tiny dab of grease. All mics will be sensitive to any vibrations conducted to the mic body. Try not to move your mic hand or cord around too much while you are transmitting, if you can help it. Sometimes, you can carefully trim plastic parts in the mic, such as the key and the housing, to keep them from rubbing together.

KEYING TECHNIQUE - Some microphones introduce an audible transient ('key clunk') when you press and release the key quickly. This is typically mechanical in nature, and is the result of the key hitting its limit of travel, causing an impact that is picked up by the element and often described as a 'clunk' When you are involved in a qso and are anxious to speak, you naturally tend to key your mic quickly. Keying your mic slowly will help reduce this problem. Gluing a piece of felt on the key stop(s) can also help reduce the impact. Some amplified microphones will produce a transient when you key them that is generated in the circuit of the mic itself when the key switch connects the battery to the circuit. In this case, there is not much you can do unless you can modify the internal circuitry.

MIC GAIN - Set up the gain for the 'close talking' position described above. This is so important to reject background noise. That is, of course, unless you want listeners to hear your kids or TV playing, dogs barking, or the vehicle engine or blower fan whining. This is especially important in mobile situations with one or more windows down or inside the cabin of a commercial vehicle or boat. If you are using an amplified microphone having an adjustable output power, set it to the minimum output that will give you full drive (determined below) when the mic gain adjustment on the radio itself is set to its maximum. This will extend the microphone's battery life and help insure that you never accidentally overdrive the radio's input if you inadvertantly move the adjustment pot on the mic. Fine drive adjustments can be made with the mic gain on the radio.

It is a law of physics and acoustics: If you set up the gain for adequate drive with the mic more than a few inches away you will start picking up other sounds around you. If you set it up for 12-18 inches away in the average room, people will eventually say you sound like you're "talking in a barrel!"

Tune your radio to your voice. Every voice waveform is unique. Most men's voices have more noise, less pure waveforms, and are somewhat loud. Most women's voices have a more pure (more like a sine wave) waveform and are quieter. Regardless of gender, some people talk louder or quieter than others. Each nuance of voice will modulate the same radio differently.

FOLLOW-UP ADJUSTMENT. If you operate your radio in a noisy environment, or you are excitable, don't be surprised if your friends say that you are over-driving your rig. Again, it's a natural tendency to raise your voice in a noisy environment without even realizing it. Tweak the gain back down as necessary, or try to develop an awareness of your speech and hold it down. Another technique is to simply pull the mic away from your mouth a few inches momentarily during loud comments (such as laughter) that you are aware of <*grin*>. Singers who use this technique, for instance, call this "working a mic."


SSB TONE ADJUSTMENT. Many single-sideband rigs have an adjustment that you may not be aware of that can have a major effect on the tonal response of your transmitted audio. Look in your owner's manual and see if you can find any references to "carrier insertion point" or "RF processor shift." Once you have the close-talk mic position and the gain set appropriately, as described above, this remaining adjustment will really fine-tune your audio. If you haven't yet discovered this trick, you're not getting the most from your rig. In effect, this adjustment shifts the overal tone response of your voice from bass to treble. There is usually a numeric setting, available in a range, and there are separate adjustments for the upper and lower sidebands. Some microphones have tone adjustments built into them, and it can be difficult to decide which to adjust first: the rig or the mic. It's much more convenient to adjust your mic on the fly, for instance, when you want to work DX or any station that has a poor copy on you, and you need to add 'punch' (see below). Each setting will have an optimum mic gain level, too.

Near one end of the adjustment range, the higher frequencies (fricatives and sibilants) of your speech will be emphasized, and the bass will be rolled off. This can be excellent for working DX stations when your signal may be just barely above their noise level. This setting, along with the speech processor, helps deliver that 'punchy' sound that cuts through noise. However, if you go too far, you will sound thin and nasal, or 'cold', as more and more bass and midrange frequencies are lost. Typically, when you emphasize treble response, the peak power drops slightly. You can add more mic gain to compensate without causing flat-topping (see mic gain section), maximizing the high frequency boost effect.

At the other end of the range, as you might expect, your voice sounds 'warmer' and has more bass, at the expense of some intelligibility. Remember, the intelligibility comes from the higher frequencies. This setting is usually more pleasing for ragchewing with friends when they have a good copy on your station. Again, your voice quality degrades as you go too far, and you begin to sound muffled from the loss of high frequency content. Some people make a note of the settings for DX and ragchew, and actively readjust their audio for their intended mode of operation. Others pick one setting for good, all-around use. It helps to have a nearby friend, who is familiar with your voice in-person, to listen to you and guide your adjustments.


HIGH FREQUENCY RESPONSE AND KEYING TRANSIENT TESTS. Here's an easy way to see if your rig has good high frequency response, and therefore, good intelligibility. For SSB and AM testing, you will need the dummy load and peak-reading wattmeter as described earlier. For an FM rig, you will need a service monitor, deviation meter or oscilloscope. Without these instruments, you can still conduct a test, but you will have to rely on another person's subjective perception and description of how you sound (see the section on soliciting a meaningful audio report).


MEANINGFUL AUDIO REPORT - This is not to be confused with a signal report, where signal strength or FM quieting is all that is required. An audio report is best given by someone who is familiar with the transmitting operator's voice in person, but this is not absolutely necessary to determine if there is any distortion. A solid copy of the ransmitting operator is a must: 5X9 on sideband or AM and full quieting on FM simplex. On an FM repeater, the listener should have a full quieting copy on the repeater itself, which can be determined by listening to the repeater tail, after the coutesy tone, and before it drops out. The typical speech passband for communications is 300 Hz to 3000 Hz. This doesn't fully capture the entire range of human speech, but it is enough for good communications.

A meaningful audio report should include the following:

Good luck with your rig!

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