New-York tribune., 1922-11-05

designed for radio frequency amplifica-
tion and those for audio.
The tuning element in this system
can be of any standard design, that
is. vario-coupler with variable con-
denser across the secondary, or even u
simple variometer, as shown in the
diagram.
The input from the tuner Is upon
the grid of the first tube. The plate
circuit of this tube is then Joined to
kthe primary of the radio frequency
n sformer. The other side OF this
kAraary is then joined to the primary
OF the second audio frequency trans-
former. The other side of the latter
is Joined to the positive terminal of
the "B'' battery in the usual manner.
Across the primary of the audio-
frequency transformer there is Joined
condenser, and this condenser acts as
bypass for the high frequency cur
rents in the r. F. transformer, while
the audible currents must pass through
the audio-transformer. Another con-
denser of similar character is placed
across the secondary of the audio fre-
quency transformer for the same pur-
pose. 1t will be seen that this system
lie followed throughout.
Crystal Detector Is Best
For the best results with the system
crystal detector should be used for
rectlilcation. The amount of energy
supplied to the crystal will be quite
large, because of the fact that there is
considerable amplifieation of the radio
frequency currents by the two tubes
shown in this particular diagram. The
OUTPUT from the crystal detector is
passed through the first audio-fre-
quency transformer shown connected
tn 1 - s,l
grid of the first tube for further am
plifcation.
So far as the amplifcatien of the
voice currents is concerned the amount
OF wire in the radio frequency trans
formers is negligible in effects, so
Ithere is no interference from them,
facd amplifcation goes on in the same
manner as in tho standard sets.
There is slight difference in the
placing of the transformers The radio
frequency transformers follow the
tubes in both cases. The first audio
transformer follows the crystal de-
tector and the second follows the first
vacuum tube. The telephones are
e IN the plate circuit of the sec
oL IN series with the primary
OF tae sacond radio transformer. A
condenser is placed across the tele-
phones as bypass for the radio
frequency currents from the second
tube.
While the circuit can be assembled
by any amateur, it will require quite a
little experimentation before it is
placed into suitable operation. This
will be because of the different char
acteristics of the vacuum tubes and
the transformers. 1t ia for this reason
that absolutely fixed constants cannot
be given for tha f.5retfif 81
1t will be found, however, that the
capacities of all the bypass conden-
sers can range from ,00o6 to .0oI
Imicrofarads the exact amount Of the
Nspacity, OF course, viii have to be de-
tefmined by experiment The CON
deasers used for this purpose can
either be Of the ordinary variable
type or Of the small fixed type which
will permit easy variation in small
steps. The latter are the best. how
eyer. The exception In capacity is the
condenser across the telephones which
bouid BE- Of u006 rnierosarad.
Ions, bat not st the expense os en-
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