BAD NEUTRALISATION

Radio Record, Volume I, Issue 14, 21 October 1927, Page 2

BAD NEUTRALISATION

CAUSES INTERFERENCE There is not the slightest donbt that much of the howling valve nuisance in New Zealand is due to badly adjusted "neutralising condensers of nentrodyne sets. A neutralised receiver, also, unless it is carefully adjusted, can be less efficient than one in which neutralisation -is not employed. There are (says Syd- | ey Radio") three chief ills of improper nentralisation. The first and most obvious manifestation of incorrect adjustment of the neutralising device is oscillation in’ some or all of the radio-frequency circuits. ‘These oscillations, as a general rule, become more severe as the frequency is increased, and a lond squeal or whistle will be heard as the tuning controls are adjusted to receive some. station that is transinitting. Causes Interference. Such an effect will make it dificult for the user of the receiver to obtain satisfactory reception, and the osvillations will be radiated from the antenna attached to the receiver, and cause interference on other receivers located in the neighbourhood. Such oscillations can be prevented by correct adjustment, and it is essential that the proper setting be determined in order to make it possible to obtain best results from the receiver. : Distortion Results. A second detrimental effect of maladjustment of the neutralisers is poor quality, which is generally due to the existence of too much regeneration, The quality, under these conditions, will generally sound drummy, indicating that the various frequencies in the earrier are being unequally amplified by the radio-frequency amplifiers. To preserve good quality, the radio-fre-quency amplifiers must amplify without distortion a band of frequencies extendinig about 5000 cycles above and 5000 cycles below the carrier frequency, and this condition does not exist unless proper neutralisation is obtained. Loss of Sensitivity. Another effect of improper neutralisation is to cause one or more of the tuned circuits in a single-control receiver to be thrown out of synchronism, so that the set loses a great deal of its setisitivity, and, as a result, it is not possible to tune-in distant stations with satisfactory volume. ‘These three major effects of improper neutralisation indicate how essential it is that neutralisation be always carefully and complete ly accomplished. ee