Evening public ledger. [volume] (Philadelphia [Pa.]) 1914-1942, 1922-06-20
RADIO IN THE HOME
.., s" BY HENRY M NEELY
There Are Two Kinds of Ampli ifcasion

Whenever I pick up radio magazine
find myself very much in sympathy
with the average beginner who is try
ing TO get an idea Of what kind Of ap-
paratus to get for his receiving set.
The magazines bury him under such II
de!uge Of technical terms that / some.
times wonder how lie gets out vt all.
Almost everybody who insthls radio
receiving set dreams OF the day when
one Of those attachments which makes
the music come right out OF his phono.
graph just rs though he had a record
playing. He knows, however. that this
result cannot be achieved with a crystal
detector and that, II he Is using an
/ audion bulb. he will in most cases
have to have extra bulbs. which arc
known rs ampliRers and which serve
to increase the strength Of the signals
so much that the addition Of a horn
will make them sound all through the
| house.
Knowing that he needs AmpliAers he
turns to his radio magazine and, in
nine cases out Of ten. he finds himself
plunged into a puzzling discussion Of
the relative merits Of "audio' and
radio" frequency application. Nat.
'uraliy he doesn't know what this II al!
about. He IL under the impression that
amplifers are amplifcrs. and when he
finds that there is difference. he Is
inclined to be discouraged.
But he need not be. In mbst cases
the amateur will find audiO frequency
the best for him to handle and when.
ever he sees transformers advertised he
can be fairly sure that they are audto
frequency, because If they were radio
frequency the advertiser would be sure
to boast about 1t.
The difference between the two, how
ever, is really very easy to understand.
Let us spend few minutes today
studying this difference and then the
discussions in the radio magazines will
mean something to us.
Everybody knows by this time that
wireless work is carried on by means
of extremely rapid vibrations OF elec-
trio energy. The rnpidity Of these VI
brations governs the difference between
these two forms of amplification.
Radio waves are made so fnst that.
in the signals sent from broadcasting
stations. there nre over three quarters
Of a million vibrations In n single Sec
ond. This is much too rapid to work
the diaphragm Of the telephone ano.
even if the diaphragm did respond. the
mechanism of the human ear Is not
capable Of translating them into sound.
Il When we get 10 II frequency Oh Ten
thousand second or more we are be.
yond the power Of the average ear.
Signals which vibrate faster than that
are not audible-they cannot be heard
and therefore arc not Of "audio fire.
quency." SO we class vibrations above
ten thousand as "radio frequency"
To turn radio frequency current
into an audio frequency one. we insert
the grid condepser and grid leak.
These two instruments. rs we pointed
out sOme time ago. store up a quantity
i Of the current and release 1t about Il
. thousand times n second and SO we get
one thousand groups OF pulsatiOns and
the car can respond readily to this
number. In other words. the vibra
tions are of radio frequency when they
come from the aerial, but the con
dcnser and leak turn them into aud!C
frequency groups.
Naturally the signals as received
must be Of n certain strength or else
, they will not be able to fiji the con
dcnser and overflow through the leak
t 1t is here that radio frequency ampli.
: tication becomes valuable. Let us SCI
r how 1t works.
! The extremely rapid vibrations tina