The Washington times., 1923-03-18
By II. j. MARX.

BY HI. j. MARX.
81 "HE wave OF popularity that has
greeted this new circuit az
t first announced by the Radio
Digest Illustrated, is a clear indi-
cation of It's efficiency OF opera.
ton. In contrast to the Arm
strong uper-Regenerative circuit,
1t requires no experienced operator,
! but can be handled by the newest
OF Radiophans.
With but q single tube in the
2 hook-up, reports are coming in:
u from ali over the country of the
4 efficiency Of this circuit in long
distance reception. Requests. are
repeatedly coming In for more
detailed information and hook-ups
Tor radio and audio frequency am.
Publication.
The popularity Of the panel and
cabinet iilstallations OF circuits has.
Slecessltated some form OF layout
along similar lines for the Flewell-
ing circuit. In order to make 1t
! easier for the amateur to under
stand, the hook-up is repeated in
: the panel form. Details Of and COM
sa anents on the various pieces of APP,
@ paratus that make up the set are
given.
S. DESCRIPTION OF APPARATUS.
The parts i'm the panel diagram
81 are numbered for Identification.
Numbers and are honeycomb
coils, mounted so q variation in
coupling can be had. The first
3 ssOrs grid coil should have about fifty
= turns although this may. be af-
6ected by the natural wave length
s of the particular type Of antenna
used. The second or plate honey
comb coil can be ordinarily a Is
turn coil, although sometimes
slightly better results have been
obtained with ninety turns. The
question is often asked whether
q variocoupler cannot be substi-
tuted The difficulty lies in the
fact that the winding on the rotor
Z Of yaricoupler has an insufficient
number Of turns. IL, however, the
turns are increased to about seven.
Il fy-fiye or ninety. the results viii
be about the same as with the
h0neycomb coils and will in addi-
tion, simplify the panel mounting
& construction.
The variable condenser, No 8, is
Of the usual 23-plate type L0O05 MID.
preferably with vernier) and is shunt-
ed across the grid coil. The condens-
er No. IL likewise variable but the
capacity is only .0OO25 mid. 11-plate.
This Is placed in series with the an
tenna, but g snap switch, No 5, Is
connected across so that the con-
/ denser can be shunted out IL desired.
The three fixed condensers, No 6,
have a capacity Of .0O6 MID. EACH
4 These apparently have stumped
4. many Of the amateurs because nu-
nerous letters have been received
stating that this particular capacity
Is not obtainable on the market 1t
can be taken care of, however. by
combining in parallel three phone
condensers of .002 mid. each, six of
. OOO1 each, or other combinations.
Condenser No. is the usual grid
condenser and has a capacity of
.0O025 mid. The grid leak, No. 8.
should be Of the variable type as the
adjustment is very critical, running
from / to 1.5 megohms. The pencil
mark leak offers the simplest and
cheapest method. although other
types and forms of variable grid
leaks are obtainable on the market.
& NO. is also a variable grid leak of
very low resistance and is not par
Fl ticularly sensitive. Experiment must
{ determine its value as it will vary
4 with tubes.
TUBE TO USE.
The tube used in this circuit is
! preferably hard. The usual annph-
{ 1er tube, Wv 2O1 or c 301, will give
viii give slightly better results.
I With the ordinary amplifier tubes
the plate voltage should be about
100 volts. With power tubes, how
ever, an increased plato potential
Is possible. The filament rheostat
No. IL can be Of the ordinary type.
but vernier construction is recon.
mended. The usual phone condenser
with capacity of .0O2 mid. is used.
When the loop aerial is used with
Il this circuit the two ends are con-
nected to the binding post on the
left side OF the panel. Under such
conditions condenser No. would
be shorted out by switch No. 5.
When outdoor aerial alone is used
without a ground it should be con-
nected to the upper left binding
post. Under these conditions switch
No. Is left open and the primary
circuit Is first tuned by means Of
condenser No. 4.
81 II the ground connection is lse5
+ instead Of the antenna, it should
also be connected to this upper bind
Ing post. Very often, for short dis
4 lance work, good results viii be
obtained without the use of any
aerial or ground connection at all.
Ine amateur should not overlook
the fact that the natural wave
length. OF his antenna circuit may
necessitate a change in the value
n Of honeycomb coil No. ].
II The operator will find that the
{ coupling between coils No. and
No. 2 is not half as critical as the
adjustment OF grid leak No. 8
Tor best resistance to balance up
the circuit. Condenser No. 3 serves
the purpose OF accurate tuning ad-
jnstment Of the grid circuit for
wave length. The resistance of the
! grid leak No. 8 will be considerably
affected by the position OF the rheo-
stat I'D since the potential and
connection of the grid is dependent
on the heat of the filament. The
three condensers (No. 81 should be
fairly accurate in value in order to
get properly balanced circuit. In
assembling the set 1t is essential to
= bear in mind that short leads will
Z be Of considerable assistance in
eliminating unnecessary bowling.
1 Copyright, 1929. Radio Digest
49, Publishing Coz Chtcsgo.)