AKG Acoustics WMS 4000 manual Rule no, Wavelength

AKG WMS BASICS

HOW WIRELESS TECHNOLOGY WORKS

HOW RADIO SIGNALS ARE TRANSMITTED

Wireless transmission technology is based on the physical principles governing the propa- gation of electromagnetic waves. Radio, tele- vision, mobile telephone communications, mi- crowaves, and light are all based on electro- magnetic waves with different wavelengths.

Short waves have completely different cha- racteristics, and are propagated as high-fre- quency signals in the form of radio waves or X-rays, for instance, traveling incredible distances through the universe and still detectable after millions of years.

Speech and other sound signals, on the other hand, are not electromagnetic waves, and require a high-frequency carrier signal for wireless transmission: it is this carrier signal that serves to transport the audio signal through the air. The process that does the trick is called modulation: this is similar to the audio signal getting into a taxi in a scien- ce-fiction movie (climbing into a radio-fre- quency signal), because the physical laws that now come into effect are similar to the highway code of the future! This metaphori- cal example is not entirely analogous to the physical reality, but it may give a clearer pic- ture.

What happens to our audio signal once it has entered our metaphorical taxi in order to tra- vel from the transmitter to the receiver? First it has to tell the driver its destination, for example: “Please take me the fastest way

from transmitter to receiver.” Since he has been asked to take the fastest route, the taxi driver will try to select this route. However, the thing is that we are not alone on our jour- ney, but have to share the roads with a num- ber of other (wireless) road users: in this situation the following rules apply:

Rule no. 1:

The stronger your radio signal is, the better chance it has of reaching its destination. In our metaphorical example, TV stations do not travel in radio-wave taxis in one lane, but in gigantic trucks occupying several lanes at once. The only solution here is to avoid them by selecting another frequency band, in our example by taking another road so as not to be run over by them!

Rule no. 2:

Keep your distance and stay in your lane! Our taxi needs a road lane on which it can travel, and must keep its distance from vehicles in the adjacent lanes so as to avoid a collision, which we refer to in technical terms as radio interference. Unfortunately, however, we are also obliged to share our lane with signal waves from mobile telephones, television sets, microwave ovens and radio sets, and are permanently faced with congestion and traf- fic jams. These other signal waves continual- ly come dangerously close to our taxi, and we are continually in danger of colliding with other road users: it is therefore essential that we keep our distance!

Rule no. 3:

The higher the frequency, the more “lanes” there are available, and the risk of various radio signals colliding with one another is correspondingly lower. This is why all WMS 40 systems work in the short-wave UHF range, which ensures extremely reliable transmission and optimal signal quality.

AKG has specified various radio frequencies for its WMS 40 wireless systems in order to ensure secure and reliable transmission in the UHF range, normally enabling four systems to be operated simultaneously. This means that we are able, as it were, to send our audio signals from transmitter to receiver using very fast taxis on four safe road lanes.

This is particularly important when transmit- ting speech and music in order to avoid unwanted signal dropouts (see illustrations on facing page and also the illustration of signal characteristics on page 7). The maxi- mum number of channels that can be opera- ted simultaneously varies depending on national licensing regulations.

The licensing regulations issued by the rele- vant regulatory authorities for telecommuni- cations systems also vary from country to country. Your local AKG supplier will be able to tell you whether you require a license to operate a WMS 40 wireless system in your country.

Wavelength

The properties of a wave depend primary on its wavelength. Wavelength is the term used to refer to the distance between points at which the wave has the same phase in two consecutive cycles. The radio waves of wireless microphone systems, and also television and radio sets, mobile telephones and microwave ovens, have a wavelength of about a meter. The wavelength of visible light varies between 770 and 400 nm (1 nm = 1 thousandth of a meter), whilst X-rays, gamma rays, and cosmic radiation have even shorter wavelengths.

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