Radio Construction Notes 



A New Aerial Supporter 



AAIATEURS having high masts are 

 often troubled by having their 

 hoisting ropes shrink in wet weather. A 

 remedy which also prevents the spread- 

 er from tilting is shown herewith, Re- 



^M ^ ,s 



Sketch and construction of a steady 

 aerial supporter 



ferring to the sketch, piece A is of ^- 

 inch strap iron, 3/2-inch wide and 2 feet 

 4 inches long. Have a blacksmith bend 

 it as shown and drill two 34"inch holes, 

 one on either side, 3 inches from the 

 bent end. 



In mounting it on the mast it should 

 be on the same level as the pulley. The 

 closed end must clear the mast by about 

 an inch when it is in the horizontal po- 

 sition. Long screws should be used to 

 fasten it to the mast and it should be so 

 loose that the ends with the hooks on 

 will drop down when the light cord C is 

 released. About ^-inch diameter is a 

 good size for this cord. 



Piece B may be either an iron or 

 wooden rod 6 inches long. It is fast- 

 ened to the spreader with two No. 14 

 galvanized wires. The rope R passes 

 through pulley F and is fastened to the 

 middle of piece B. 



The aerial is raised by means of hoist- 

 ing rope R until piece B is against the 

 pulley D, and then the hooks on A are 

 raised by pulling on cord C. Rope R 

 is then slackened until piece A alone 

 supports the aerial. To lower the aerial 

 simply pull on rope R until the hooks 

 disarrange themselves and then lower 

 away. 



A Simple Change-Over Switch 



A GOOD many cases of poor send- 

 ing and receiving results may be 

 traced to a poorly insulated change-over 

 switch. One that will cost less than 

 fifty cents and will give as good results 

 as a more expensive one is an ordin- 

 ary double-pole, single throw switch 

 such as is used in the lighting circuit. 

 This is connected as in the diagram. 

 When the switch is open, the incoming 

 waves will go through the loose coupler ; 

 when the switch is in, the receiving set 

 is short circuited, and the power circuit 

 is closed. Thus, when receiving, an ac- 

 cidental touch of the key will do no 

 harm, as the power circuit is broken. 



If the station has a rotary gap. a 

 triple pole switch may be used, the ex- 

 tra blade connected in the gap motor 

 circuit as in Fig. 2. Thus, throwing the 

 switch will start the rotary gap. 



rig.2 



Connection diagrams for ordinary 

 switch used as change-over 



A Condenser's Power 



AT 60 cycles a condenser will store 

 1 kw. of power if its value is 0.019 

 microbarad and it is charged to a volt- 

 age of 30,000. This e. m. f. corresponds 

 to a spark gap slightly under one-half 

 inch in Icnirth. 



157 



