The Indianapolis times. [volume] (Indianapolis [Ind.]) 1922-1965, 1924-04-25
BUILDING OF
POPULAR SET
IS OUTLINED
Armstrong Regenerative g.
Circuit Tuner Much in
Demand.
BY ISRAEL KLEIN
Times Radio Editor.

ceiving set is the Armstrong
- regenerating three-circuit tun-
er. The principle upon which this
circuit has been designed is that by
which a signal after detection is fed
back" upon the grid circuit, thereby
increasing it's original energy and
greatly simplifying the weaker sig
nails.
This Regeneration" is produced by
means Of a ticker coil or variometer
in the plate circuit which throws
back" the signal from the plate to the
grid. A varlometer in the grid circuit
in turn sends the amplified signal
back to the plate and the phones.
Parts Needed
Following are the parts for such
set:
One dielectric panel, by Is inches.
One wood base, s by II inches.
One vario-coupler.
Two variometers.
One 23-plate, or 0005 variable con-
denser.
One .O0O25 grid condenser and va
riable grid leak.
One 6-ohm vernier rheostat.
One tube socket.
One rotary switch.
Six contact points.
Two switch lever stops.
One closed circuit phone jack.
Six binding posts.
Thin sheet copper for shielding, s
by IS inches.
Bus wire for connections. =
All this. besides the UV2O0 or Cs0o
tube, the 6-volt storage A battery,
the B battery and phones.
This hookUp can be heard only on
phones. If loud speaker is to be used
two-step audio application would
be necessary. In that event also the
battery voltage would have to be
increased from % 13 to As volts.
Special Windings
For The vario coupler, take a piece
Of thin dielectric tubing inches in
diameter and inches long, and wind
As turns Of No. 20 D. c. C. wire. TAX
ing a tap off at every 8 turns. The
secondary consists Of a ball rotor. 3la
inches in diameter. On each side of
wire.
Both variometers are made exactly
alike. Each consists of one piece OF
4-inch tubing 1 inches long and a
rotor 31A inches in diameter. Wind
20 turns of No. 20 D. c. S wire on
the tubing then skip one-half inch
and wind 20 more turns of the same
wire. The halfinch space allows room
for a guarter-inch rod to hold the
rotor in place.
On each side Of the rotor wind 90
turns Of the No. 20 D. C. c. wire.
Wind all coils in same direction.
Connect one end of stator of the
variometers to one end of the rotor.
The variometers should be as far
apart as possible. The tube and the
vario coupler can be placed between
them.
The variable condenser can either
be kept outside the set, or can be at
tached TO the upper left side of the
panel above the first, or grid, vari
ometer. The connection from the grid
variometer to the grid condenser and
leak and thence TO the tube socket
must be as short and direct as pos
sible Make all connections as short
as possible. The grid leak can cary
from one to five megohms.
Operation of Set
Operation Of this set Is extremely
delicate. For this reason, it is sug
gested that a copper shield be applied
to the back of the panel, clear OF all
rods and contact points, except the
center Of the switch lever and the
ground binding post.
A vernier rheostat is called for to
get the tube to an exact position just
before its oscillation point. This is
done by turning the rheostat until
frying noise is heard, then turning
the vernier back until this is cleared.
Then the grid and plate variometer
dials can be turned slowly and equal
ly until a whistling sound is heard.
The variable condenser and the sec
ondary of the vario coupler are then
turned to clear the whistling and bring
out the broadcast program.
For different wavelengths, the pri-
mary switch is moved forward or
backward from one switch point to
another.
Copyright, 1924, NEA Service, Inc.)