RADIO NOTES.

Northland Age, Volume 25, Issue 15, 6 August 1925, Page 7

RADIO NOTES.

(By “Electron)” The technical side of wireless seems to be what puzzles most people. A question often asked is “How do you change from one station to another?” To say “Simply by-turning a number of dials to a different setting,” does not enlighten people much so I will endeavour to make clear how j this is done.

The transmitting station has what is known as an aerial hoisted in the air, which usually comprizes about six wires on two spreaders, each wire the same length as the others and from one end of each wire a lead in is taken to the transmitting plant. Also leading to the transmitting plant are the leads from the microplane which is placed where it will pick up the music, speech or whatever is to be broadcast. Wireless waves travel with the speed of light which is roughly 186,000 miles a second. Part of the transmitter is used to generate electric or wireless waves. These waves surge first to one end of the aerial and then to the other and down to the transmitter. In the transmitter there is usually a coil of wire often shunted by a condenser, which is two sets of copper or alluminium plates. Between each two plates of one set one of the other set is placed, one set being highly insulated from the other. The effect of the coil and condenser is to make the waves travel further in their journey from the far end of the aerial to the earth than they otherwise would have done. The real end of the aerial is the earth to which a wire is connected from the other end of the coil. The number of times a wave can travel from one end of the aerial to the transmitter through the coil and to the earth in one second determines the wavelength of the station. Suppose the wave surges back and forward 1,000,000 times a second, the speed of the waves is 300,000,000 metres a second. By dividing the first number into the second we get 300, which means that the wave length of this station is 300 metres. This wave does not leave the aerial as is sometimes supposed but simply makes an impression in the ether which surges out in all directions much the same as throwing a stone into a pond causes ripples to spread out in all directions in ever widening circles. The music or speech to be broadcasted is first amplified by a number of valves and is then impressed on the carrier wave. When impressed on the carrier wave the speech or music takes a different form and is no longer audible. The carrier wave might be likened to a piece of paper on which the message is written and from a listeners-in point of view is of no real importance. The message is also written in code and the detector valve or crystal is the part of the receiver which deciphers the message for you. More about receivers next time).