A turn of this kind, giving wide contrasts of light and shade, was thought to provide 'genuine entertainment value' on 30-line television
Paving the way for a better understanding of short-wave propagation, Appleton showed for the first time in our pages that there was more than one reflecting layer in the upper atmosphere. He had earlier sought the help of our readers in reporting distortion of the Baird 30-line television picture brought about by multi-path propagation and reproduced a reader's sketch of a picture which clearly showed the effect.
Sketch by a reader (W B Weber) showing observed effect of multi-path propagation on a 30-line television picture
Short-wave telegraph and telephone services had by now linked many, if not most, of the more advanced countries of the world and lack of secrecy, a handicap of wireless since the earliest days, was overcome by 'scrambling'.
The NPL was taking steps to develop a standardised form of test for the sensitivity, selectivity and fidelity of receivers. The decibel scale began to come into general use in place of such expressions as 'times amplification', etc.
A highly-developed broadcast receiver of the late 'straight-set' period: the Murphy A3 (1931)
So far as receivers were concerned, the introduction of the variable-mu valve with linear characteristics largely overcoming the difficulties of cross-modulation, was an important development. 'Straight versus superhet' became a burning issue, but the outcome was not in much doubt. Realizing that ganged tuning with 'potted' coils would soon become universal, we commissioned a special investigation of the characteristics of coils. Moving-coil speakers, now generally built into the receiver, were almost universal: during this and the preceding year the finer points of their design were discussed in a long series of important articles by Dr N W McLachlan.