AKG Acoustics WMS 4000 manual Bandwidth, Frequency Modulation FM, Interference

AKG WMS BASICS

Bandwidth

Every frequency-modulated carrier signal does not oscillate entirely within the frequency allocated to it, but also occu- pies frequencies in the adjoining range. This range is known as “bandwidth”. The wider the available bandwidth is, the better the transmission quality. Ideally, different carrier sig- nals should therefore be far enough apart to prevent their bandwidths from overlapping.

Frequency Modulation (FM)

Transforming an audio signal into a radio-frequency one and back again is achieved by means of frequency modulation (FM). This technology has also been used for decades in UHF radio to ensure reliable transmission and high signal quali- ty. This involves imposing an audio signal on a radio-fre- quency (RF) sine-wave carrier that now begins to oscillate in time with the audio signal. Variations in the level of the audio signal (changes in volume) produce frequency chan- ges in the RF carrier signal (transmission frequency). Therefore, this technique is known as “frequency modulation”.

Interference

Overlapping (interference) occurs when the bandwidths of adjacent signals are too wide, or the carrier frequencies are too close together. Parts of the signals transmitted lying in this range are no longer clearly recognized by the receiver, resulting in noise or dropouts. For this reason it is not pos- sible for two or more systems to work on the same frequen- cy. Even if the frequencies are different, one must always ensure that there is sufficient separation between the fre- quencies used.

Example of AKG WMS 40 carrier frequencies

AKG has selected fourteen different frequencies as carrier frequencies for wireless transmission by WMS 40 wireless systems. There is sufficient separation between them to ensure trouble-free operation and optimal signal quality. A maximum of four WMS 40 systems can be operated at any one time, and care must be taken to ensure that none of the frequencies are used twice! If more than four radio links are required simultaneously, AKG offers a series of wireless systems that make it possible to use a higher number of channels at once. Please refer to pp. 30 for detailed infor- mation. The maximum permissible number of channels may vary depending on national frequency plans.

					Color coded for easy identification
					It is easy to match up transmitters and receivers thanks to
					their color coding system. At the same time, the colors also
					tell you the carrier frequency used for the radio link.
➜	➜		➜	➜	Transmitters and receivers using the same carrier frequency
		➜			are coded with the same color. The color code clips on the
					HT 40, SO 40, MP 40, and GB 40 transmitters are removable,
					and can be replaced by the black clip provided.
				➜	➜
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