The Ely miner. [volume] (Ely, Minn.) 1895-1986, 1925-01-30

ent Resonance.
losses and suppress oscillations. This
is not true. In fact, 1t is the reverse.
Actual operation shows that the more
resistance one introduces into the pri-
mary circuit the more the set oscillates.
In other words, we have common re-
generation control for the two stages
Of radio frequency.
The action of the variable 100-ohm
resistance may seem uncanny to many
builders, but study of the underlying
theory will take all the mystery out Of
ii. The radio amplifier is built so that
it is highly improbable that any res
onance can take place, making the
amplifier itself non-oscillating. The
resistance may be more properly
termed reactance of variable choke.
1t is conceded fact that choke coil
introduced in the plate circuit will re-
tard the radio frequency currents and
therefore throw the set into oscillation.
Consequently, If the reactor, or choke,
be variable, the oscillation point of the
amplifier can be adjusted to accommo-
date all wave lengths
Actual Results.
Selectivity and sensitivity go hand
in hand. A receiver cannot be really
efficient and not be selective; the re-
verse is true, also. The sensitivity OF
the set may be accounted for by the
ability TO keep the receiver on the hiss
ing point at all wave lengths by SIM
pie control. The selectiyity is far bet
ter than a neutrodyne because of the
lower compiling employed. This is I'M
peratiye because of the fact that the
radio frequency primaries must have
six turns so that resonance cannot be
obtained.
If you are DESTROYS of constructing
set of this type, the circuit diagram of
Fig. should lead you Or the right
track.
A list of the necessary parts used by
the writer follows:
Three spiderweb coils for usual
tuned r. F. amplifiers.
Three 17-plate (.OOO3) variable con-
densers.
One 6-ohm Amsco rheostat for four
tubes.
One 20-ohm rheostat for detector.
One 1O0-ohm rheostat or 200-ohm
potentiometer (Amsco).
One double circuit jack.
One single circuit jack.
One by Is bakelite panel (black or
mahoganite).
One 61s by Il bakelite Dashboard.
Three finch Freshman dials.
One .OO05 fixed condenser.
One .O0025 grid condenser with 2
megohm leak.
One .OO6 MID Dubilier condenser.
One 01 mid. fixed condenser.
Two audio transformers.
One battery switch.
Seven binding posts preferably
marked).
Twelve lengths bus-bar.
Sundries such as screws, nuts, an
giles, etc.
A little confusion might arise about
the spiderweb coils. They may be OBJ
tanned from your radio dealer if you
know what TO ask for. They are called
tuned radio frequency coils of the non
oscillating type. Usually the primaries
have 10 turnS-but no matter how
many turns on the primary they will be
all right.
Make sure that the secondary has 65
turns, for a greater or lesser number
of turns will not cover the band of
wave lengths on the usual coil and con-
denser; of course turn or two out of
the way matters but little. Remove
sufficient turns from the primaries of
two of the coils so that only six turing
will remain on each. the third one re-
manning as purchased.
Coil Supports.
The coils should be fastered with
little pieces of rubber so that the fiat
area is at right angles to the panel, IL
being preferable that the coils be
mounted on top of the condenser. to
make them the highest unit in the set.
The unhampered coil having a 15-turn
primary is fastened to the first con-
denSer, i. e.. the one on the extreme
left of the set facing from the front.
The other two coils should be mounted
in a similar manner, the order OF
mounting making no difference since
they are similar.-New York Telegram.