FIRE-CONTROL RADARS FOR NAVAL VESSELS 37 



tubes was rushed through development and produced in lime to go with 

 the first accurate fire control radars. This transmitter provided a peak. 

 j)ower output of about 40 kw with a pulse duration of 2 microseconds. It 

 resulted in a material increase in reliable range, with satisfactory tube life. 

 The new transmitter, shown in Fig. 30, was made mechanically inter- 

 changeable with the old and was applied retroactively also to the Mark 1 

 Radars. 



Duplexing 



The use of the high-power transmitter required additional protection 

 for the receiver during the transmitted pulse in order to prevent damage 



Fig. 31— VV. E. 702— TR tul)e 



and to permit the receiver to recover rapidly for reception of nearby echoes. 

 The duplexing equipment was therefore modified to inclu de a gas switching 

 tube in the receiving transmission line. This was a refnicment of the 

 method used earlier by the Naval Research Laboratory. 



The switching tube (W.E. 702A) was developed specifically for this 

 purpose and is shown in Fig. 31. It was the first of the "TR" tubes of this 

 general form and consists of a hydrogen-water vapor filled glass chamber 

 with three copper electrodes.*^ This tube was mounted in the center of a 

 half-wavelength coaxial line short circuited at each end, the outer con- 

 ductor being connected to the outer electrodes and the center conductor 



« "The Gas Discharge Transmit-Receive Switch," A. L. Samuel, J. W. Clark, and W. W. 

 Mumford, this issue of B. S. T. J, 



