"FADING"

Radio Record, Volume I, Issue 7, 2 September 1927, Page 3

"FADING"

The Editor, "Radio Record." S?r,-All wireless workers are familiar with fading trouble when working with distant stations. From the home station it is unnoticed, therefore it is safe to look afield for the cause. Various theories have been advanced, but as an old telegraphist I would like to recount some of the experiences affecting the telegraph system that have come under my own observation, by way of suggesting that our ‘wireless broadcasting is also subject to similar influences. I refer to magnetic storms, originating in certain conditions of the sun, the presence of which are often indicated by the aurora borealis, or southern lights. A telegraph wire with its ends earthed at Wellington and Christchurch, carrying a galyanometer and battery, so that a constant needle deflection of, say, 50 degrees is made, will act im a curious inanner on the approach of one of these magnetic storms. The needle of the galyvanometer will every few minntes rise steadily to zero -sometimes beyond. In a few moments it will recede to its first position These peculiar moyvemenis have sometimes started in late afternoon and lasted untif miduight. My observation is that the time intervals covering the peaks of these movements agree with those noticed in wireless fading. | It is obyions that the galyanometer’s deflection to zero is caused by an opposing current. In telegraphy this leads to serious interruption of trafic, and can only be obviated by substitnting a second wire for the earth return. It should be stated that the telegraph system is subject to this form of interruption at amuch longer interyalsmonths often elapse--than in the case with wireless broadcasting, where it is usually of weekly occurrence. ‘There is reason for this in the fact that the telegraph is only susceptible to magnetic storms of considerable strength, whereas wireless being extremely sensitive is influenced by sources of energy haying no effect on telegraph ¢pparatus. Readers of Arctic and Antarctic literature will have noted thta aurorae are very frequently observed in polar latitudes -in fact, are of almost niglitly occurtence. It may, therefore, be asserted that magnetic storms in varying strength are making their power felt; that their electrical energy is being broadeast through the cther, chiefiv in Jongitudinal direction, with earth return; anl that this energy-Nature’s hroadcast-imeeting and opposing that directed by 2YA and his coutentporar- ies, is the true source of fading trouble. It would appear that uo remedy is in sight, It is interesting, liowever, in view of the fact that a return wire removes the interruption in telegraphy, to conSider whether the provision of suitable counterpoises at the broadcasting and listeners’ stations replacing the present earths, would have the right effect.-I ai, ete.,

EX-TEL. ENGR.