Telex BTR-800, TR-825 dimensions Tech Tips, Frequency Interaction, Microphone Gain Adjustment

Section

10

Tech Tips

Frequency Interaction

Unfortunately, radio frequency (RF) channels cannot be ran- domly selected for use in radio devices. They must be selected to avoid known frequencies in use, FCC restrictions on the lo- cation of devices, and even interference between your own RF devices. The factory defined frequencies (Groups 01A-24) se- lected by Telex for this RadioCom™ system are chosen to minimize possible interference.

Microphone Gain Adjustment

The microphone gain controls on the base station and beltpack are set to mid-levels by the factory. In most cases this setting w i ll w o r k f in e a n d o n ly o n lo u d s p e ec h w il l t h e overmodulation (OM) indicator light. However, in environ- ments where the background noise is loud or the user has a strong/quiet voice, the gain control will need to be adjusted. In Figure33 the gain is set correctly. The user’s root-mean-square (RMS) sound level is well below the OM threshold and only on peaks does his or her voice flash the OM indicator light.

Figure 34 displays the same gain setting as in Figure 33 but brought into a high noise environment. The user’s voice now lights the OM indicator all the time he or she speaks due to the higher noise plus the user speaking louder. The result on the system is distortion on louder speech. The microphone gain must be reduced. The same applies to a user with a powerful voice. If someone sets the system mic gain to their voice and user has a much stronger voice, then the gain will need to be reduced, even if the background noise is the same.

Always remember to set the microphone gain based on the sit- uation and location in which the equipment will be used. If the equipment is used on the field during a football game, set the gain based upon a loud stadium, NOT the quiet stadium 2 hours before a game. If a production studio user has a quiet voice, set the gain to their voice and NOT the stage hand’s loud voice who helped set up the system.

SOUND LEVEL, RMS

OM THRESHOLD

USER'S VOICE

NOISE

SOUND LEVEL, RMS

USER'S VOICE OM THRESHOLD

NOISE

Figure 33	Figure 34
Low Noise Environment	High Noise Environment
Microphone Gain Set Correctly	Microphone Gain Set Too High

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