. An elementary manual of radiotelegraphy and radiotelephony for students and operators . itshigh frequency resistance. It decreases, therefore, the time periodof in so far as inductance is concerned, although on thewhole there is generally an increase in the time period. Its chief advantage is that it enables us to accumulate moreenergy in the antenna in virtue of the greater capacity. It is anadvantage to increase this capacity without adding to the heightof the wires, because an increase in height involves more cost insupporting them. One way of doing this is to carry the wire
. An elementary manual of radiotelegraphy and radiotelephony for students and operators . itshigh frequency resistance. It decreases, therefore, the time periodof in so far as inductance is concerned, although on thewhole there is generally an increase in the time period. Its chief advantage is that it enables us to accumulate moreenergy in the antenna in virtue of the greater capacity. It is anadvantage to increase this capacity without adding to the heightof the wires, because an increase in height involves more cost insupporting them. One way of doing this is to carry the wire upvertically for a certain height, and then extend it may be done in one, two, or more directions, and we have agallows-shaped, or T-shaped, or umbrella-shaped antenna. M l62 RADIO TELEGRAPHY This last form, with the radiating wires inclining downwards,is a favourite form, since it is easy to erect, and the wires them-selves can act as stays for the central support. It is also aconvenient form for the portable antennte used for militaryradiotelegraphy (see Fig. 11).. Fig. 11. There are certain forms of antennae which have the propertyof sending out electromagnetic waves more in one direction thanothers, and these are called directive antennce. They will beconsidered in a later section. For ship antenna, a special gaff or sprit is attached to a mastto give greater height, and a multiple antenna may be suspendedfrom it, or, for some purposes, horizontal wires may be carriedbetween masts, and vertical wires brought down from them fromthe middle or from both ends. 7. Earthed and Non-earthed Antennae.—From what has beenalready stated it will be evident that in addition to classificationinto open and closed antennae, we must distinguish betweenearthed and non-earthed antennae. If, for instance, we stretch aninsulated wire horizontally, cut it in the centre and introduce aspark gap, we construct a non-earthed horizontal antenna. Whentraversed by oscillations the l
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Keywords: ., bookcentury1900, bookdecade1910, booksubjecttelegra, bookyear1916
