Patent GB-543602-A (GB)
Title: Improvements in or relating to electrical phase or time delay indicating or controlling circuits
IPC: H04B7/08
Filed: 1939-06-21
Abstract: 543,602. Radio receiving systems. BLUMLEIN, A. D. June 21, 1939, No. 18034. [Class 40 (v) ] [Also in Group XXXVI] An electrical system for indicating the relative time delay of two similar primary complex electrical waves comprises means for producing from these waves two auxiliary waves, the first representing their sum and the second the integral of their difference, and means for indicating the relative time delay in accordance with the product of the two auxiliary waves. Where the primary waves contain component frequencies which are liable to differ in phase by more than 180 degrees, the primary waves are rectified and smoothed or filtered so as to produce two secondary complex waves representative of the amplitude variations of the primary waves and having the same relative timing but not containing component frequencies with phase differences of more than 180 degrees. The auxiliary waves are then produced from these secondary waves. The application shown is to a, short wave radio receiver-wherein a number of receiving channels receive the same transmitted signal, the various channels being fed from spaced aerials so phased that each receiver channel represents the transmission due to a single sky wave. It is required to combine the modulation frequency outputs of the various channels so that if one channel loses signal due to fading the signals will be heard from the other channels. These outputs are liable to differ in relative timing owing to the sky waves travelling different paths. By delaying the outputs from the shorter sky paths all outputs may be brought to a similar timing and may then be mixed. Two complex waves comprising the modulation outputs of two receiving channels A1, A2 are passed through corresponding delay networks T1, T2 having tappings taken to, studs over which contacts are driven by one or more small electric motors E. The contacts feed into a mixing stage M which may include a pair of valves to the grids of which the outputs from the delay networks are applied and in whose anodes the signals from the different channels are mixed. Fed also from the contacts are the grids of valves (not shown) which feed the summing, differencing, and integrating circuits S, D, N which produce the auxiliary waves. The outputs from these circuits are fed to two valves whose anodes feed, through transformers, the coils of a dynamometer R which closes contacts controlling the motors E which adjust the delay networks so as to reduce the delay in one channel and increase it in the other until the outputs of the delay networks are similarly timed. The dynamometer may include two coils fixed at an angle with respect to each other and a third coil, the fixed coils and the third coil being relatively movable and one auxiliary wave being applied to one of the fixed coils and the third coil and the other auxiliary wave being applied to the other fixed coil. When more than two complex waves are employed a plurality of waves are derived therefrom each linearly expressible in terms of the complex waves. These derived waves and one or more waves representative of a sum formed from the complex waves are used to form one or more products constituting an indication of relative delay. This indication is utilized to insert delay in one or more of the channels. The product of a plurality of auxiliary waves may be employed to effect a coarse adjustment of delay while an indication for fine control is obtained from the primary waves or a predetermined part of the band width of the primary waves. Specification 394,325 is referred to.