Page:Popular Science Monthly Volume 88.djvu/185

 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-

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���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.

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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.

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