Next bore a hole through the frame of the window at a point nearest your receiving set and push a porcelain tube 5/8 inch in diameter and 5 or 6 inches long, through it. Connect a length of wire to the top post of the arrester or just above it to the wire, run this through the leading-in insulator and connect it to the slider of your tuning coil. Screw the end of a piece of heavy copper wire to the lower post of the arrester and run it to the ground, on porcelain knobs if necessary, and solder it to an iron rod or pipe which you have driven into the earth. Finally connect the fixed terminal of your tuning coil with the water pipe or radiator inside of the house by means of the ground clamp as shown in the diagrammatic sketch at B in Fig. 6 and you are ready to tune in.
If you want to use a lightning switch instead of the air-gap arrester then fasten it to the outside wall instead of the latter and screw the free end of the leading-in wire from the aerial to the middle post of it as shown at C in Fig. 6. Run a wire from the top post through the leading-in insulator and connect it with the slider of your tuning coil. Next screw one end of a length of heavy copper wire to the lower post of the aerial switch and run it to an iron pipe in the ground as described above in connection with the spark-gap lightning arrester; then connect the fixed terminal of your tuning coil with the radiator or water pipe and your aerial wire system will be complete as shown at C in Fig. 6.
A Two-wire Aerial.--An aerial with two wires will give better results than a single wire and three wires are better than two, but you must keep them well apart. To put up a two-wire aerial get (1) enough No. 16, or preferably No. 14, solid or stranded copper or aluminum wire, (2) four porcelain insulators, see B in Fig. 5, and (3) two sticks about 1 inch thick, 3 inches wide and 3 or 4 feet long, for the spreaders, and bore 1/8-inch hole through each end of each one. Now twist the ends of the wires to the insulators and then cut off four pieces of wire about 6 feet long and run them through the holes in the wood spreaders. Finally twist the ends of each pair of short wires to the free ends of the insulators and then twist the free ends of the wires together.
For the leading-in wire that goes to the lightning switch take two lengths of wire and twist one end of each one around the aerial wires and solder them there. Twist the short wire around the long wire and solder this joint also when the aerial will look like Fig. 7. Bring the free end of the leading-in wire down to the middle post of the lightning switch and fasten it there and connect up the receiver to it and the ground as described under the caption of A Single Wire Aerial.
Connecting in the Ground.--If there is a gas or water system or a steam-heating plant in your house you can make your ground connection by clamping a ground clamp to the nearest pipe as has been previously described. Connect a length of bare or insulated copper wire with it and bring this up to the table on which you have your receiving set. If there are no grounded pipes available then you will have to make a good ground which we shall describe presently and lead the ground wire from your receiving set out of the window and down to it.
How to Put Up a Good Aerial.--While you can use the cheap aerial already described for a small spark-coil sending set you should have a better insulated one for a 1/2 or a 1 kilowatt transformer set. The cost for the materials for a good aerial is small and when properly made and well insulated it will give results that are all out of proportion to the cost of it.