AMPLICATION 01' WIRI- I'RAXSMISSION TO RADIO 121 



itself is the very considerable one which is characteristic of logarithms, 

 namely, that when thus expressed the individual losses and gains 

 thruout a system may be summed up algebraically, and the over- 

 all transmission equivalent of the system thus readily determined. 



It should be noted that the transmission loss given in the radio 

 curves is that obtaining between the point at which power is delivered 

 to the ether at the sending end and that at which it is delivered to the 

 dissipative load of the receiving antenna circuit. In Fig. 1 these 

 points are represented by Ry at the transmitter and /?, at the receiver. 

 If at the sending end, we start with the power developed within the 

 generator, meaning in Ri instead of R^, then the power ratio is sim- 

 ply doubled, for the conditions assumed, and the attenuation is 

 0.15 units or about 3 miles greater than given in the curves. The 

 curves can be used for obtaining the loss in any practical case simply 

 by taking the minimum loss as given by the curves and adding thereto 

 the additional loss obtaining in the actual antenna. 



Referring now to Fig. 2 — the transmission losses in the two cases 

 are given for distances up to 200 miles (320 km.). The straight 

 lines represent the wire losses, the bending-over curves the radio 

 losses. Of the radio curves, the dash lines give the spreading-out 

 losses alone, while the full lines give the total losses, including ab- 

 sorption. 



The first thing one observes is the difference in the nature of the 

 two sets of curves — the wire losses being represented by straight 

 lines, because of their exponential law and the fact that it is the 

 logarithm or the exponent itself which is being plotted, while the radio 

 curves jump up rapidly at first and then straighten out, in accordance 

 with the " inverse-with-distance " law. 



The second thing one notes is the fact that as a result of the large 

 initial (or " jump off ") loss, the radio values run on the whole higher 

 than do the wire for the more usable wire frequencies, and very much 

 greater than the wire losses at telephone frequencies (1 k.c.).'* For 

 the wire case the number 8 Birmingham wire gauge open wire circuit is 

 taken.^ This is the standard long distance telephone circuit of the 

 United States. The constants are given in the appendix. 



A third characteristic which one notes in the radio curves is that 

 the losses are greater for the higher frequencies or, conversely, lower 

 for the lower frequencies. This is because the efficiency of the an- 

 tenna has been kept constant for all frequencies. In practice the 



* 1 k.c. is 1 kilocycle per second or 1,000 cycles per second. 



' Diameter of number 8 Birmingham wire gauge wire = 0.165 in. = 0.42 cm. 



