MOBILK RADIO TRANSMISSION 



1071 



Transmitter power reqiiiretl to a^'hic^'e the same service result at 

 various frequencies has been derivetl by taking into account the clianges 

 of path loss with frequency and also the changes of signal required with 

 frequency. Fig. 3 shows the amounts of power that are rcciuired in order 

 to achieve the same coverage in all cases as is now obtained at 150 mc 

 with 250 watts of land transmitter power radiated from a dipole. As 

 shown, the use of an antenna having gain can appreciably lower the 

 land transmitter power that is requiretl. The mobile transmitter power is 

 much less than required of a land transmitter due to the assumption 

 that there are six land receivers located appropriately in the coverage 

 area, rather than just one. 



It is apparent from Fig. 3 that the required transmitter power is a 

 minimum in both directions of transmission at around 500 mc. It is also 

 apparent that above this point the required transmitter power increases 

 rapidly with frequency. 



5 



Q -115 



300 400 500 600 800 1000 1500 2000 



FREQUENCY IN MEGACYCLES PER SECOND 



3000 4000 5000 



Fig. 2 — Median value of signal required to over-ride noise. 



