5 Watt Transmitter (USA - 1922)

 AN EFFICIENT 5 WATT TRANSMITTER (Alpheus Hyatt Verrill - 1922)

For those who wish a more powerful and efficient set for sending this is to be highly recommended. Under favorable conditions it should have a range of from 25 to 40 miles. Moreover, it is not an expensive set to make and, exclusive of batteries, should not cost over $35.00 to $45.00. ($45 = to $800 2024)

The accompanying diagram Fig. 60, makes the wiring very plain, A being the aerial, B the ground, C the ammeter, D the inductance, E the variable condenser, F the fixed condenser, G the grid-leak, H the modulation transformer, I the 6 volt battery, J the microphone, K the grid, L the plate, M the rheostat, N the choke-coil, O the rectifier, P the current transformer.

Although practically every part of this set can be made, with the exception of the ammeter, rheostat, microphone, and modulation transformer coil, still it is almost as cheap and much more satisfactory to purchase the current transformer, the variable condenser and the choke-coil. The inductance D is easily made, the plate coil being wound with No.18 cotton insulated wire on a cardboard tube three and one-half inches in diameter, using twenty-six turns and is tapped at the thirteenth turn. The aerial coil is the same size of wire, but with only eight turns. The space between windings or turns should be about one-half inch. The choke-coil may be purchased as such, but an ordinary spark coil—using the secondary winding —may be used and an old Ford spark coil with contact-breaker screwed down may be used for the modulation transformer. The ammeter used should be one of low reading scale or, if desired, an ordinary 3 volt flashlight bulb may be used instead. The ammeter, however, will give far better results. 

The grid-leak is an ordinary lead pencil leak of medium soft lead. The most difficult part to make is the current rectifier, but even this is very simple and consists merely of eight pint fruit jars filled with a solution of ordinary borax in the proportion of half a pound of borax to ten pints of water. In filling the jars avoid having any undissolved borax or sediment in them, and fill only about three-fourths full. 

Borax bridge rectifier (shown Fig. 61)

The plates consist of alternate lead and aluminum strips, eight of each alternating as shown in Fig. 61, and with each plate 5 x 3/4 inches. With this rectifier and the current transformer P, an ordinary 110 volt, 60 cycle electric current may be used, or without these, two or three B-batteries may be used instead, but this is far more expensive and does not give as good results. Before using this outfit the rectifier must be treated to form the plates, which is accomplished by connecting an ordinary 50 watt incandescent bulb and letting the 110 volt current run through it for ten or twelve hours.

Another point to remember is always to disconnect the high voltage current from the plate when not in use and when using the set always light the filament in the tube with the low voltage battery before turning on the high voltage current. The switch on the microphone circuit also should always be thrown off, thus disconnecting the phone from the battery, when not in use. To tune this set it is only necessary to adjust the variable condenser until the ammeter or flashlight shows the highest reading.

The author:-

Alpheus Hyatt Verrill, known as Hyatt Verrill, (23 July 1871 – 14 November 1954) was an American zoologist, explorer, inventor, illustrator and author. He was the son of Addison Emery Verrill, the first professor of zoology at Yale University. He authored numerous works on natural history and science fiction.