Mohave County miner and our mineral wealth., 1922-06-23


 direct current pulsations are smoothed
 out so that the 60 pulses of direct
 current per wave train of 60 oscilla-
 tions is transformed into one pulse
 through the telephones. Since the os-
 cillations have frequency of 1,500,-
 900, and 60 oscillations per wave train,
 it is seen that there are 1,500,00O di-
 vided by 60 equals 25,00O wave trains
 per second. Since each wave train
 causes one pulse through the tele-
 phones, there are 25,000 pulses of di-
 rect current passed through the tele-
 phones. A Morse dot is composed of 1 30 to 50 pulsations. These pulsations the diaphragm of the telephone to be
 drawn in with rapidity of 30 to 50
 times which forms an audible note. It is thus seen how the "detector and
 the telephones change the radio ire
 quency to audible frequency. Because
 the action noted depends upon suc-
 cession of wave trains, this method
 cannot be used for the reception of
 undamped waves, since undamped
 waves are not composed of wave
 trains but are continuous waves.
 If this same method, the use of a
 crystal detector, were used for the re-
 ception of. damped waves, the tele-
 phone diaphragm would be distorted at rthe beginning of each signal and re-
 leased at the end of the signal, no
 sound being heard during the length
 of the signal. The only sound heard
 would be click at the beginning and
 at the. end of the signal, and this
 would be too weak to be- recognized. Therefore some other method must
 be used for undamped wave reception.
 The most common method now in use is that of utilizing the action of the vacuum tube. The action of the vacuum tube was explained in the last article. We will now see how it is used as detector of undamped waves. Assuming the same circuit as used in the reception of damped waves, make the following changes and ad-
 ditions: Remove the telephone receiv- !, CTS. and the crystal detector, and con- meet the terminals of the condenser to , the terminals of the secondary wind- :. ing of the oscillation transformer.
 The secondary circuit is now simple oscillatory circuit. From one terminal of the condenser (for convenience let
 us call it the upper terminal) connect : a small condenser in series with the
 grid element of the vacuum tube , Across the terminals of the small con
 Edenser, which is called the grid con.
 denser, shunt high resistance, about !, one million ohms. This resistance is , called. the grid leak. Connect the ! plate element of the vacuum tube to one terminal of the telephone receiv. n CTS. The other terminal of the tel. f ephone is connected to high voltage battery, about 422 volts, called the b. f battery. The negative terminal of the , B-Battery is connected to the positive n terminal of six volt storage battery called the A-battery. The two ter e minals of the filament of the vacuum h tube are connected to the two termin e als of the A-battery. The lower ter l. minal of the main secondary conden ! ser IS connected to the junction of tn, e B-battery and the A-battery. From a this hook-up it is seen that variatio, t of the plate current will cause a var . iation or the current flowing through V the telephones, with a resulting aud Q ible sound.
 " The incoming signals cause the an IT tenna Circuit to oscillate. These os l. Icillations are transferred to the sec l. ondary circuit by the oscillation trans e former. During one half of an os d cillation the plate of the grid con n denser which is connected to the mail 2 condenser is electrically positive. Thi n causes the other plate of the grid con e denser to become negative. Thi n means that an excess of electrons ha j. been drawn to this latter plate, an, l. these electrons were drawn from tn e grid itself, causing a deficiency O e electrons on the grid. This cause IT the grid to become positive. If tn e filament of the vacuum tube is heat Q. ed, 1t throws off electrons. The gri d being positive attracts these electron ,- and increases the flow of electron IS from the filament to the plate. Thi 1t increases the current flowing throug e the plate circuit. During the nex le half of the oscillation the grill is neg d. atively charged. It is seen that du1 e, ing the first half of the oscillation is some electrons which hit the gric
 were held there, that is, trapped O. l. the grid. During the second half 0 g the oscillation no more electrons wer in trapped because the grid was negative le but during the first half of the fol n- lowing oscillation more electrons wer ,f trapped in the same manner. If re damped signal were being received, lg is seen that during half of way Jf train thu ur;d u,o,lJ ot+root oul +,,,