New-York tribune., 1922-10-29
Problems OF Recepsion

Questlon--None OF the textbooks have
consulted seem to answer the following
questions in manner ccomprehensbls, to
enough to answer them for me In a nom
technical way, 30 that may be better
able to ", Hnderstana my set and learn to
/. which " the better regenerator,
from the view point OF seiectiyity and
reception. one using two variometers and
vario-conpler, or one using = vario-
coupler. secondary condenser and plate
g.. or what capacity should oy-pass
condenser be to give the best results. ana
what os s VI Wsat tuest5aef eapaoty should second
AIRY condenser be7 Which would be the
better; one Of low or one OF high
I. Would a vernier condenser, or, a
vernier ettachment be OF any real value
Il Il. used In connection with a.os secondary
S. Is variable grid condenser essen
tiai for the best operation of a set. or
| can one Of fixed capacity be used equally
6: Is potentiometer necessary when
hard no tube o + II. uSSd e. aod
q tube OF thi. type considered critical in
T.; Would vern!sr . controlled oiled rheostat
using a hard tube as .detector, and BY
Q. Assuming an "a" battery to be in
gr6nn wth The %rnr of s
which might cause this battery to run
down in short time, and would a set
wrongly wired continue to operate for
tuning "a ]. w.
Answer--The answers to the specific
questions you ask are as follows:
/. For the purpose Of selectivity on
short wave lengths, the better of the
two receivers mentioned Is the vario-
coupler two-variometer type. The rea-
son for this is that there are really
tuned circuits for the other type.
Those three circuits are as follows:
The aerial circuit, which consists Of
the aerial and primary Of the vario-
coupler and ground with or without
variable condenser); the second cir
cult, the secondhand Of the vario-coupler,
which Ia tuned by the grid variom-
eter, and the third circuit, the
plate variometer. All three Of these
circuits must be In unison with each
other In order to secure regeneration
by means of the internal capacity Of
the vacuum tube itself. AS you will see
1t is logical that the larger the num-
ber of tuning circuits, the smaller will
be the outside interference from other
wave lengths, In addition to this, the
triple tuned circuit is no more diff
cult to adjust than the double circuit.
2. / cannot answer this question
specifically, as great deal depends
upon the exact work that the bypass
condenser has to do. Its function is
to permit high frequency currents to
pass through, while direct currents are
stopped. An example of this is the
grid condenser, which is bypass con-
denser for high frequency current re-
ceived by the aerial, in that it per-
mits them to. reach the grid. The grid
leak, which is shunted across the con-
denser, permits the negative charge on
age battery, without interrupting the
passage Of the high frequency cur
rent. The higher the frequency OF
a current that is flowing in the circuit
the more easily will it pass through
the condenser. You will see the diff
ticulty Of answering specifically what
the capacity Of bypass condenser
should be, when I state that grid con-
denser can be as low as 900 mid. while
a bypass condenser, used in radio
frequency amplitication around the
negative side of tho potentiometer is
of .002 mid. capacity.
y. AAiSs quSSIioH is also QlffiCutt to |
answer specifically without going into
great detail regarding the quality Of /
resonance in an electrical circuit. II
will depend entirely upon the amount
of inductance in the circuit-tho
larger the inductance of the specific
wave length the smaller will be the /
capacity needed, and vice versa. The /
best thing is to strike balance be- [
tween. the two, always remembering
that the capacity plays a very impor I
ttant, part in the higher frequencies
involved with short wave lengths.
q. a Vernier condenser is of utmost
Importance in tuning the regeneratiya I
sets under all conditions.
5. A variable grid condenser is not
essential for the operation of q sat,
but for those who wish to get absolute.
ly the best results and can spare time
ana expense in experimenting, yari- t
able condenser has distinct advant-
age.
9. Like the variable grid condenser.
the potentiometer is refinement.
rather than necessity The v r
detector tube Is not critical. Only fhe
so-caiied "soft" or "gas content tubes