RADIO TRANSMISSION SYSTEM FOR TELEVISION 



635 



substitute for the ordinary type of tuned circuit was at hand and such 

 circuits discriminate seriously against side frequencies differing by 

 more than a few per cent from the frequency to which they are 

 adjusted. 



The results of the survey disclosed two bands somewhat wider 

 than that required centering approximately about 1575 and 1750 

 kilocycles. It was also conclusively demonstrated that the operation 

 of the synchronizing channel at a frequency above the broadcasting 



Fig. 1 — General view of the Whippany Station, 3XN 



band was entirely out of the question. With two broadcasting 

 stations located in the immediate neighborhood, one producing a 

 field strength of perhaps 50 millivolts per meter and the other several 

 volts per meter, the operation of a third transmitter on an adjoining 

 frequency with the maximum obtainable separation between antennae, 

 resulted in an almost continuous interference spectrum. It was 

 decided, therefore, to transfer the synchronizing channel to a fre- 

 quency of the order of 185 kilocycles, which would be sufficiently 

 remote to remove interference from this source, and to make further 

 studies in the regions about 1575 and 1750 kilocycles based on trans- 

 mission from Whippany. No difficulty was anticipated in making 

 suitable arrangements for the speech channel on account of the 

 narrower band required and the well-known nature of the problem. 



