Most amateurs support their aerials from a pole placed on the top of the house, in a tree, or erected in the yard. Many use two supports, since such an aerial has many advantages. The facilities to be had for supporting the aerial will largely determine which form to use. [Illustration: Fig. 198.—Method of Arranging the Wires and Insulating them from the Cross Arm or Spreader.] The grid aerial has no particular advantages or disadvantages. The “V” aerial receives waves much better when they come from a direction opposite to that in which the free end points. The "free" end of the aerial is the one not leading into the station. The inverted “L” aerial possesses the same characteristics as the “V” type. The “T” aerial is the best “all around" and is to be recommended whenever it is possible to put up an aerial of this sort. Much of the detail of actually putting up an aerial or antenna must be omitted, because each experimenter will usually meet different conditions. It should be remembered, however, that the success of the whole undertaking will rest largely upon the construction of a proper aerial. The most excellent instruments will not give very good results if connected to a poor aerial, while, on the other hand, inferior instruments will often give fair results when connected to a good aerial. [Illustration: Fig. 199.—Various Types of Aerials.] The aerial should be at least thirty feet high. The wire should not be smaller than No. 14 B. & S. The masts which support the aerial should be of wood and provided with pulleys so that the wires may be lowered any time it may be necessary. The mast should be thoroughly braced with stays or guys so as to counteract the strain of the aerial. The aerial should not be hoisted up perfectly tight, but should be allowed to hang somewhat loose, as it will then put less strain on the ropes and poles that support it. When an aerial is to be fastened in a tree, it is best to attach it to a pole placed in the top of the tree, so that it will come well above any possible interference from the branches. The wires leading from the aerial to the instruments should be very carefully insulated throughout their length. This part of the aerial is called the "rat-tail" or lead-in. The illustrations in Figure 199 show the proper place to attach the “lead-in" form of aerial. The wires should gradually converge. [Illustration: Fig. 200.—A Ground Clamp for Pipes.] It is very important that a good ground connection be secured for wireless instruments. A good ground is absolutely necessary for the proper working of the apparatus. Amateur experimenters usually use the water or gas-pipes for a ground, and fasten the wires by means of a ground clamp such as shown in Figure 200. In the country, where such pipes are not available, it is necessary to bury a sheet of copper, three or four feet square, in a moist spot in the earth and connect a wire to it. *The Receiving Apparatus*