New-York tribune., 1922-09-17
Analogy Shows
4 junction. oil
The Aerial
Currents Built Up in 1, by
Incoming Wave just Like
Wave Moiiou Caused by
Paddle in Wafer Trough
Aerial Must Be Insulated
Ucieclor Must Be Connected
Across Enducsancc and
MOI OH Series Condenser


Not OH Series CoutIcnsc-
hy Is it necessary to have an out
side aerial in order to receive tho
raidophorc concerts? This is a cues.
, tion that is beng frequently asked
these days, particularly in view of
the development o. super-rcgcnclation.
radio frequency amplihcation and
ether complicated systems, which win
function satisfactorily on p small loop
aerial chat can be placed anywhere in
side house
The answer to this question is very
important because it is upon the aerial
that the success of The receiver abb
solutcly depends, and more thorough
understanding o, the manner in which
IT operates Will ssist the radio fan in
getting The best out OF his set with
the ordinary t pc OF receiver on the
market an aerial is absolutely noces-
sary Furthermore, in order TO obtain
absolutely the best possible results
this aerial should be an outdoor affair.
clear as possible from all surround
! ing objects.
Now. in order to illustrate the
! operation OF an aerial it is perhaps
best to take the hydraulic analogy that
| has been developed by The radio
engineers as q means OF describing
an aerial, In the first place it must
be clearly understood that the aerial
! and ground are, in reality. con-
deneer. the aerial being one plate and
the ground the other. The tuner,
which after all is variable Undue
tancc, is merel" an arrangement that
| will permit us to increase the length
Of the aerial itself
Wave Motion in Water Trough
If we look upon the aerial circuit
| as large trough in which water is
! held, we can understand its function
ing little more clearly. If in this
trough of water we insert paddle
wheel and commence steady dis
turbance. tho water viii be set into
/ wave motion and will oscilate be-
! tween the two ends OF the trough,
according to the length Of the trough;
or, in other words. the natural fire.
quency Of the trough.
If this paddle. is moved back and
forth at the cvrrect rate OF speed
equal to the natural period OF the
! trough. it will set up waves Of maxi
mum height which will in time s'op
! ever the ends OF the tub. If. hoWevcr .
/. the rate of movement is too fast or
! too slow, the maximum wave motion
will not be attained
! If we study the wave motion +"
trough VIC will find that the maximum
height of the wave is reached at either
/ end of the trough and that as the
water flows back and forth in ar
oscillatory manner The greatest height
is reached at each end Of the trough.
In our aerial circuit this action is
reproduced when tie incoming wave
sets up an oscillatory current in the
aerial circuit 1t Will be found that
the highest voltage is at either end Of
! the aerial wire. and 1t Is nccessa Ify.
/ therefore. tha" these two ends be.
thoroughly and completely insulated
in order to prevent any losses.
Aerial Must Be Clear
Now. we have exactly the same con-
dition in the aerial circuit as we have
| in the trough. If the incoming wave
| length is too small, it will not set up
an oscillatory current in the aerial
circuit, and also if it is too large, the
same results viii obtain.
natural frequency of the aerial we can
make up for any small difference by
/ means of an inductance that is con-
nected in series to it. 1t is for this
| rehson. therefore. that il is necessary
to have a we'll constructed aerial, free
and clear of all other objects, where
the ordinary normal circuit is used IN
order to get best results.
Roughly speaking, the inductance in
the circuit will enable you to increase
the range Of your set so far as wave
length is concerned, which is equivalent
to varying the length of the trough in
the analogy. while the addition Of
condenser in series with the aerial re-
| duce the wave-l length range Of the set
within certain limits and is equivalent
to shortening the trough. The con-
| denser in series with the aerial can
also be used for more flexible tuning
purposes in the aerial. There is very
important point, however, that should
| be taken into consideration in copjunc
| tion with using a series condenser in
the antenna. In the first place, it is a
| fundamental fact in electricity that
condensers placed in series with each
other reduce the total capacity OF the
circuit and that is exactly just what
| happeAs when you place the tuning
condenser in series with the aerial, be-
cause the latter is also a condenser
! Detector Is Joined Across Enductance
II this connection there is very
peculiar situation: if The detector cir
cult is connected to the aerial cir
cult in such way that the condenser is
! included. there will be a great reduc-
/ ton in the amount of voltag9 impressed
upon The de.ector, and consequently
the efficiency o. the receiver viii be
materially reduced.
Ii is necessary, therefore. to connect
| the detectors circuit around the aerial
! tuning inductance only. Whether this
aerial tuning inductance consists of q
straight tuning coil, q honeycomb coil
or any other form of ..ductance does
not make any difference. The detec-
tors circuit should be connected
! around it in such way that the series
condenser in the aerial is not included.
Radio Society in Paris
A society has been formed in the
French capital for the purpose Of
broa iea ting al least three times q
dag ALL new; m atter fear "a +hn. ~ q t;.,c.