The Home Radio; How to Make and Use It

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated.1922 Excerpt: ... THE SIMPLEST SENDING SET ALTHOUGH it may be possible to L devise a transmission set or radiophone which is simpler than that shown in Fig. 58, it is questionable if anything simpler would really be efficient. At any rate, this is so extremely simple that the veriest amateur should have no difficulty in setting it up. It has only two adjustments, the rheostat and the variable condenser. Moreover, it is a very cheap set and, aside from the batteries, there is nothing which need be purchased ready-made (except wire) other than the following: 1 Variable condenser of.0005 mfds. 1 Microphone or telephone transmitter. 1 Rheostat. 1 Vacuum tube and socket. 1 Cardboard tube about two inches in diameter and about three inches long. The diagram needs no explanation as to details; A being the aerial, B the ground, C the tap-off of inductance, D the variable condenser, E the B. battery of from 60 to 120 volts, F the six volt battery, G the rheostat, H the tube plate, I the grid, J the phone transmitter. To make the inductance, wind the two inch cardboard tube with thirty-eight turns of No. 16 double cotton covered wire or B. & S. wire. When twenty turns have been taken, twist a loop in the wire as a tap-off and then continue winding the other eighteen turns. The tap-off should have the insulation scraped off in making the connection at C, after which the joint should be covered with adhesive tape. If, when using the set, any difficulty is experienced it may be tuned to a different wave length by taking off one or two turns of the wire at top or bottom, or both, of the inductance. For an aerial use No. 14 phosphor bronze 7 strand or No. 14 plain copper, using an aerial at least 150 feet long and of several wires and, if possible, use a counterpoise as described under "Ae...