Evening star., 1925-03-22
No. 8, TnekIing the Tuner.

Times are certainly changing. Fa-
theirs used to hold a gTudge against
their young sons because the latter
were lazy and stupid. Now the mod
ern father is just a little jealous Of
sonny's capacity for learning.
The radio has done it. That boy
of mine is making n set of his own,
Smith complained, and / don't even
know how my own works. Just now
he's busy building himself an odd
looking coil He says he's going to
get a cats whisker, whatever that Is,
hook the combination to my aerial
and ground and get the local stations
with the ear phones. Can you beat
that? Imagine that young brain of
his holding all that dope about oscil-
lating electro magnetic waves-all
that dope you shot into me the other
day"
That's where the boy has the ad-
vantage on YOU" l explained. He
just assumes that the air is full OF
these waves, each train of them being
at different wave length. He looks
TO the easiest way to catch the waves
he wants. From others he has learned
that the simplest way to do this Is to
employ a detector and q tuning COLL
But what does this coil mean to
him ?" Smith stammered.
THE boys wise" I retorted. He
takes a few things for granted. You
get confused because you want to
know too much at once. He knows
that the frequency of the radio waves,
their rate of oscillation, Is determined
by two things: inductance and ca
pacity. The coil takes care of the in
ductance, while the condensers take
care Of the capacity. He goes at 1t
the same way that you figure interest,
without giving a thought as to who
first thought OF IL and whether the
originator was right.
This little coil he is building is
some form of inductance. It's prob
ably a cardboard core on which he is
winding a number of turns Of bare
copper wire. One end is attached to
the aerial wire, tho other TO the
ground. Probably he's going to tap
the coil at several points so that by
means of a switch he can come closer
| to the wave lengths he tunes for.
You don't have to know any more
about this coil than that the length of
wire used between the aerial and the
ground regulates the inductance and
brings this simple set into resonance
| or tune, with the inductance used in
| the transmitting outfit"
The boys coil is a little different.
| Smith explained. There seem TO be
sliding contacts that will touch the coil
at any one of turns"
That's a tuning COIL said, recog-
| nizing the type. with the sliding con-
facts he can obtain a wider variation
in inductance in his work OF intercept
ing the waves. It also means that he is
| working on two-circuit arrangement
that is a little bit more complicated
than the one you or any other beginner
ought to tackle at the start"
This rubbed Smith the wrong way.
You aren't telling me thing except
| that the boy knows more about IL than
l :" he snapped.
Noting the fever Of the family COM
petition 1 Immediately got out a radio
catalogue and, pointing to a number Of
odd-looking- articles of various shapes
and sizes, said Here's where you can
put something over on him. When he
gets his little tuner all finished just IN
form him that he's using a system that 8
all out of date. That will make him ask
questions and view you as an authority
That will be d nice way for him to
make a monkey out of me- Smith con-
fessed.
"All you've got to tell him is that his
sliding contacts, do not admit of any
neat or convenient form of control, and
that if he wants to have a regular set
like dads with neat-looking dials on a
black panel he'll have to discard the
od-fashioned stuff"
"What'n suggest to take its place ?''
Tell him that by adding a variable
condenser to an inductance coil he can
get a far better variation in the induc-
tance.' Show him q picture of one of
these sets with a dial to- operate a varia-
BILE condenser and the series Of contact
points to make the rough variations of
the turns of coil wire used Or you
might suggest using a variometer, and
give him a present of one so that you
can find out what it does.
I'm telling him this Won will come ia