The Radio World

Hawke's Bay Tribune, Volume XVIII, Issue 225, 5 September 1928, Page 7

The Radio World

NEWS FOR LISTENERS

VOLUME OR MUSIC. OVERLOADING THE SPEAKER. Sonic people, when using a radio receiver, appear to make a practice of employing every available degree of amplification, so that music or speech frequently bellows from the loud speaker in a quite unnecessary and often unnatural volume of sound. These people are to bo found both among those who listen in at home, often to the discomfort of their neighbours ,nnd those who demonstrate in the radio shops to the dismay of possible customers. It is to be doubted whether sounds amplified beyond their normal volume are ever natural, however faithful may be their reproduction. But when, as usually happens, the reproduction is not perfect, the effect is far from pleasant. Yet these operators sit back quite content with the wonderful volume they are producing, and do not give a thought to anyone else who may be listening. As a matter of fact, the roaring of a harsh superamplified voice from an over-strained speaker diaphram can do a great deal of harm to radio by creating an impression that at best the reproduction of a receiving set is but a cariaturo of the real thing, and that radio is tot worth the attention of people who appreciate good entertainment. For reception of band music and other naturally loud transmissions considerable volume is often justifiable though it should be carefully regulated. But when vocal and other items are received tho volume should be reduced >o that tho effect is natural. Attention to these details will enable the average listener to get a greater amount of pleasure from his set. and nt I he same time not bring radio into disrepute.

ADVANTAGES OF A WAVEMETER, Some kind of wave-meter should, in fact, be possessed by every owner of a receiver which is capable of picking up a number of stations. Not only does it aid him in tuning his set exactly to the wave-length of the station it is desired to receive, but it alto assists him to identify transmissions picked up when searching casuallj. With tho wavc-tneter the wave .ength of the station'picked up can be measured more or less accurately, which will show that the transmission' mus’. emanate from oho of a small group of station using ■wave-lengths closely approximately to that recorded by tho wavc-mcter. A slight knowledge of languages will then usually be sufficient to indicate the exact source of the transmission picked up. The simplest form of wave-meter, but one which is accurate enough for all oidinary purposes, requires only a tuning coil, variable condenser, buzzer, battery ,and switch for its construction (says “Magna Vox” in the Otago “Daily Times.”) The coil and condenser are connected in parallel with each other, and tho buzzer battery, and switch in series with each other—across tho coil and condenser.

When the switch is closed the batUry operates tho buzzar, tho necessary current flowing through tho coil. Tire causes oscillations to bo set up in the tuned circuit, consisting of coil and variable condenser, tho frequency of these oscillations being the same as tho natural frequency of the tuned circuit. By altering the inductance of the coil, or the capacity of the variable condenser, the frequency of tho oscillations can be adjusted. Very foebio “wireless” waves are radiated from tho coil when oscillatory currents arc flowing through it, which can be detected by a receiving set In the vicinity, provided that the receiver is accurately tuned to tho same frequency as the wave-meter. A wavemeter is of little use, of course, until it has been calibrated—that is, lit til a record has been made of the wavelengths corresponding to various settings of tho wave-meter condenser. To calibrate a wave-meter, various transmissions, of known origin, should bo tuned in on the receiver in the usual way. Each time a station is tuned in to maximum strength the buzzer of the wave meter should be set in operation and the wave-meter condenser adjusted until the “buzz” of tho wave-meter is hoard in the ’phones of the receiver with the greatest intensity. Tho reading of the condenser dial on the wave-meter will then correspond to tho wave-length of the sta< tion which has been tuned in. As tho identity of this station is known, th.i ncutnl wave-length corresponding to the wave-meter reading can bo at enco jotted down. The procedure is to bo gone through with as many stations as can be identified when a curve can be plotted out on squared paper, showing tho relationship between the wave-meter readings and lha yravo-lengths of tho stations which have boon used for the calibration process. From this curve the win<-meter settings corresponding to intermediate wave-lengths can also bo seen. To use tho wave-motor in ordel to tune the set accurately to a station whose wave-length is known, tie wave-motor condenser is first sot to the reading corresponding to tho wave-length of the desired station, and the wave-meter switch closed. AH that remains to be done Is to alter th.) tuning adjustments of the sot until the wave-meter signals are pickel up with the greatest Intensity when the wave-meter buzzer can be shut off and the station itself received. If a transmission from an unknown Sts t ; on is picked up. and it is desired to identify tho station, the procedure is as follows: —The station is tuned in as well as possible, and then the wave m°ter switch is put in tho “on” position. The wave-meter is adjusted until tho “buzz” in the ’phones is at its maximum strength, when the wavelength of the transmitting station is easily ascertained from the curve.

FITTING TERMINALS AND SOCKETS. It is remarkable tho number of amateur constructors who find difficulty in the fitting of terminals and valve sockets, particularly the latter. Yet the tusk is easy,-and couzistsi simply

in drilling a plain holo at least one drill size larger than the clearing size of the screwed stem of the terminal or socket. The result is, of course, a very loose fit, so one must depend on two tightly-locked nuts for security. In the case of valve sockets, one nut is sufficient, as they are not subject to any twisting action tending to unscrew them. Now the advantage, of this method are that it is easier and takes less time to drill a plain hole too largo than to drill a tapping size and afterwards tap; and it matters very little if the hole is criiled obliquely (as happens usually with most home constructors). In the case of valve sockets, which require the greatest accuracy in fitting, if a hole is slightly out of truth, through too drill slipping, the looseness of fit allows the necessary lateral movemoat to bring the sockets into their '.rile position, and a valve plugged in will keep them in place whilst tightening up the nuts.