New-York tribune., 1922-04-02
Loop Aerial
Cuts Down
Interference
Can Be Used in Apartments
When Impossible to Erect
Outdoor Aerial; Needs
.Amplification for Results
Easily ConstructedatHome
viii Not Respond to Music
Unless Edge Is Pointed
Toward Sending Station

Toward Sendlng StauOn
How can any one living in an apart
IAN. house install a radiophone when
y. landlord refuses permission to
.r. nm an aerial on the roof? This is
a. most serious question that has
.,,sronted the radio fan since the big
,roadcas.ing stations commenced send
wv nut daily program of entertain
rent.
There are just two answers TO this
.,...ion. and both depend great deal
.nor the location Of the apartment
srrse its distance from the broad
s.st;np station and the general con-
si.ions surrounding it. One is by
Means of an indoor aerial and the
other by utilizing so-called "loop"
or coil aerial
The latter is by far the best, because
!. not only can be used indoors, but
4 also has the property of cutting out
Interference to maximum degree
through its peculiar property of only
,ecrding signals when one of its edges
Is pointed directly at the transmitting
station.
It's drawback lies in the fact that
onlv very small amount of current
!. picked up by it, and consequently
il is necessary to use amplification in
order to build up that current until it
bscorncs audible in the telephone re-
seivers.
The natural question which now
arises in your mind is. How can build
loop aerial? l propose to answer
this and then follow it up with de-
tcription of the manner in which a
loop aerial is used. Before doing SO,
however, | want TO point out that
owing to the fact that most broad
casting stations are operating on 800
meter wave there are many things
which prevent US from taking the full
connection with loop, because Of the
litheulty Of handling short waves and
their terrific, high frequency.
How to Make Loop
A loop aerial suitable for reception
ei short-wave broadcasted music is
best made in the following manner:
Take two pieces of hard wood, six feet
long and about three inches wide
Iasten them together in the middle, so
that they are at right angles to each
other. Next fasten a piece OF hard
rubber at each of the four ends, and
groove the hard rubber SO that it will
hold the wire which is to be wound
around it.
Upon the frame that you have now
constructed it will be necessary to
wind four turns of wire. For this pur-
pose you will need seventy feet Of
SY16x38 litzendraht cable. 1t will be
So y -
50 that each of the four turns Is spaced
This can be controlled by the grooves
in the hard rubber.
When you have finished wiring this
frame your wire will be square In
shape. The two ends of tho loop will
come together at one corner Of the
loop. Cut of all the excess wire, leav-
ing about three inches at each end for
making connections.
You have now not only an aerial, but
sso an aerial tuning inductance Of a
nxed value. If you now place a varia-
Ole condenser Of .001 micro-farad ca
paeity across the two ends of the loop
Your tuning circuit will be complete,
although little closer tuning can be
obtained by placing small variable
inductance in series with the con-
d.nser.
The next thing for you to do is to
er'll hole through the center of your
frame, where the two cross-arms are
connected. This should be large
enough to carry spindle which will
support the loop on stand and permit
you to turn the loop around in a COM
p.e'e circle. This is very necessary,
as you will have to turn the loop
:round until one of it's edges is point
Ing directly toward the station you
wish to listen to.
use Regular Amplifier
after you have done this you will
nave TO connect q vacuum tube de-
'eeSor and two stages Of audio-fre-
guency amplifcation to the two ends of
;ne loop where you have the condenser
!o.neo across. The regular cabinet
eor"i CT detector and two-stage ampli-
"er can be used for this purpose.
.,ror persons living within twenty
I've miles OF the broadcasting station,
VIII probably be found that salts
."s.ofy results can be obtained with
,oop aer'al using only q vacuum tube
Il.'eetor and without ampli6cation, but
local conditions will determine this to
great extent.
oi"S ducoIICH ABOUT CNe
~ovantages of loop aerial. 1t elimi-
.s ,a'es all interference. except that
which emanates from some point in
dlrect lire with the transmitting
san sd.sson 1t also eliminates a great
deal of static.
"nere il is impossible to put up a
otP because Of the amount Of ampiifi-
hNoh needed results may be obtained
!. using an indoor aerial This can
se Done by laying 100 feet of No. is
,uvered so',,d bell wire around the picture
'na ~va'aIng OF room and joining one
aa 10 the instruments where the out
wv wv. aerial is usually attached. In this
b,ps of aerial a ground connection will
necessary. which, by the way, is not
pessary with loop aerial.
viii mmeGseption by means of a loop aerial
ssn.e rsa De greatly improved as soon as
imee,Ive ios ~ means have been discovered
an.,!. ,he application of radio frequency
asn"pi,iincation on short waves. Radio
Ilo,ap'ihcation is very simple with very
,,.e waves, but no great success has
nj NJ been obtained with short waves.
,"nen a.a It has it will be possible to
ss.a an indoor loop aerial almost any
'fc In the country.
nm ------A "
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