LONG DISTANCE CABLE CIRCUIT 571 



8,000 cycles is transmitted with very little distortion within the band 

 the results obtained are very pleasing. The ordinary observer without 

 making direct comparison tests is unlikely to detect the absence of 

 the higher frequencies. 



From the standpoint of radio transmission there will probably be 

 some difficulties in handling the 8,000-cycle range which has been 

 tentatively set as a standard for the cable line. Each radio station, 

 theoretically at least, is now being allowed only a 10,000-cycle band 

 of frequencies and, since both sidebands are transmitted, each band 

 is fully occupied when transmitting 5,000 cycles. Since adjacent 

 frequency ranges are not assigned to stations in the same locality, 

 a certain amount of spreading out is, no doubt, tolerable, so that 

 those listeners who are close to broadcasting stations should, in gen- 

 eral, be able to pick up the 8,000-cycle range without undue inter- 

 ference from other stations. The more distant listeners will have 

 trouble if their sets take in the complete 16,000-cycle band required 

 to handle, on a double-sideband basis, the 8,000-cycle program range. 

 Letting in this wide frequency range will bring in increased interference 

 from other stations and will also increase the atmospheric interference. 



In spite of this increased trouble which the distant listeners will 

 have, it can no doubt be argued that it will do little harm for the 

 radio stations to put out the full 8,000-cycle band. The nearby 

 listeners, if they have very good sets, will in general be able to appre- 

 ciate this, while the distant listeners, if their sets are arranged to 

 receive only a 5,000-cycle band, should receive only slightly more 

 interference from wide-band stations occupying adjacent frequency 

 bands. 



Evidently, if the frequency range were doubled so as to furnish 

 the listener with practically the whole audible range of frequencies, 

 these radio difficulties would be exaggerated. It seems certain that, 

 if radio stations were to handle the whole audible band of frequencies, 

 a reassignment of frequency bands to these broad-band broadcasting 

 stations would be called for and also quite probably these radio stations 

 would be forced to resort to single sideband transmission. 



It is not sufficient merely to fix the limits of the frequency band. 

 Limits to the allowable distortion within it must be established. 

 Tests have indicated that it is desirable that different frequencies 

 within the transmitted band should not suffer attenuations differing 

 by more than about 5 db corresponding to power differences of about 

 three-fold. 



The transmission delay* suffered by different portions of the fre- 



* "Delay" as used in this paper has the same significance as "envelope delay" used 

 in literature on phase distortion. It is defined as d^jdu where /3 is the phase shift 

 and CO is 2 7r times the frequency. 



