86.  How  TO  PLACE  A  CHARGE  IN  A  CONDENSER.     87.  ANALYSIS
OF  A  SPARK  DISCHARGE.     88.  EFFECT  OF  RESISTANCE  ON  OSCIL-
LATIONS.    89.  ELECTRICAL  RESONANCE.     90.  THE  OPEN   CIR-
CUIT OSCILLATOR.     91.  THE  LENGTH  OF  THE  ELECTRIC  WAVE.
92.  THE  DETERMINATION  OF  WAVE  LENGTH  FROM  THE  INDUC-
TANCE AND  CAPACITY.     93.  LOGARITHMIC  DECREMENT  OF  THE
OSCILLATIONS.     94.  METHODS  OF  EXCITING  OSCILLATIONS  IN
AN  AERIAL.     95.  THE  REACTION  OF  COUPLED  CIRCUITS.     96.
THE  STANDARD  WAVES  OF  COMMERCIAL  WIRELESS  TELEGRAPHY.
97.  FUNDAMENTAL   CIRCUIT   OF   A   COMPLETE   RADIO   TRANS-
MITTER.   98.  SIMPLE    EXPLANATION    OF   THE    CIRCUITS.    99.
NUMERICAL  VALUES  FOR  A  STANDARD  RADIO  SET.
Fig.  88 — Oscillations  of  Constant  Amplitude.
CONSTANT   AMPLITUDE


The  electric  waves  for  commercial  wireless  telegraphy  are  set  into  motion  by
alternating  currents  or  electrical  oscillations  at  frequencies  varying  from  25,000
to  1,000,000  cycles  per  second.  We  shall  confine  this  chapter  to  an  explanation
of  the  apparatus  for  the  production  of  damped  electrical  oscillations  which  are
employed  almost  universally  for  wireless  ship  to  shore  communication.
83.  Methods  of  Generating  Radio  Frequency  Current. — In  order  to  distin-
guish alternating  currents  of  the  order  of  frequency  employed  in  wireless  teleg-
raphy from  those  of  a  lower  frequency  corresponding  to  audible  vibrations,

the  following  arbitrary  terms  are  in
use;  an  alternating  current  of  fre-
quency in  excess  of  10,000  cycles  per
second  is  termed  a  current  of  radio-
frequency;  below  10,000  cycles  per
second,  it  is  called  a  current  of
au  dio-frequency.
A  current  of  radio-frequency
may  consist  of  either  continuous  or
discontinuous  oscillations.  A  group
of  oscillations  of  continuous  ampli-
tude are  shown  in  Fig.  88;  a  group
of  discontinuous  oscillations  appear
in  Fig.  89.
Continuous  oscillations  are  gen-
Fig.  89— Oscillations  of  Decreasing  Amplitude.  Crated  :


DECREtolNQ    AMPLITUDE


THE  RADIO  TRANSMITTER.
