The Challis messenger. (Challis, Idaho) 1912-current, 1924-04-16
BY ARTHUR Il. EDDY

If you engage yourself In converse
ton with the average amateur con-
corning his radio receiving set 1t will
not be long before he will bring up the
question Of maximum range Of re-
ception, which would be the para
mount topic Of discussion 1t Is thus
that we have grown into the habit Of
judging the relative merit Of a re-
ceiving set by the range that 1t can
cover, and although this method Of
Judgment Is not altogether fair and
just to all types Of outfits. yet for the
average beginner or radio expert
menter It does form a good basis Of
quality. The standard range Of the
regenerative receiver is quite an I'M
known quantity, for amateurs and ex-
perts having almost identical circuits
and antenna conditions give very con-
f1icting claims. But still, II we are
to base most Of our claims on dis
lance, on everyday possibility Of re-
ceiving a certain broadcasting sta
ton, 1t would be very near the truth
II we should limit the regeneratfve re-
ceiver to approximately range Of 100
miles when using a rather sensitive
detector tube
Most amateurs realizing this have
endeavored to augment this distance
by the use Of combination Of audio
and radio frequency amplifers-
other words, the reflex circuit. With
the former type success was assured
where the sensitivity Of the detector
was great enough to detect the signal,
but since the sensitive tube must be a
soft tube-that is, a tube that Kisses
at a critical point-the number OF
audio frequency stages Is somewhat
limited To adapt radio frequency
application to a regenerative re-
ceiver after once 1t has been con-
structed is by no means an easy task.
Yet some amateurs have not only &C
complished this, but have obtained re-
markable results.
For the vast majority Of beginners
the true answer to the problem Of
building long distance receiver is not
the regenerative receiver with audio
and radio frequency ampliflers nor the
superregenerative receiver, but re-
ceiver which Is combination Of audio
and radio frequency units in the cir
cult. This type of circuit will not only
have the desired range, but will be so
compact that 1t will be readily port
able and so simple and efficient in Its
operation that the beginner can oper-
ate it as satisfactorily as the expert.
Reflex Is not new, but is usually
described In peculiar ways with
peculiar names. This is at once an
evidence of evasion. for the simple
reason that at the end Of the story
the whole thing will be found to be
the original reflex circuit
A reflex set can be made from
single tube and crystal detector, the
single tube serving for both audio
and radio frequency application. If
It is desired to operate loud speaker
we must resort to two or three tube
reflex circuit. Here the first two tubes
serve as radio amplifiers and audio am
differs, with the crystal as detector.
The scflematic diagram shows num-
Der Of two-tube reflex circuits.
If amplif1er tubes are used In all
stages the B battery should be regu-
ated so that the proper battery
voltage is applied to their respective
plates. This is accomplished by ex-
pertinent. Usually between forty-five |
md seventy volts are found best for |
he plate voltage.
In the actual application of the cir
.uits there are several difficulties to
,e overcome. The tubes, for instance.
must be coupled for both radio and au-
Ito frequency application, but placing
he audio frequency amplifier In a cir
uit where radio frequency currents are
lowing, the windings of the secondary
ct as a choke coil and prevent the
ado frequency currents from pass
az. To overcome this condenser Is
hunted around the windings so the |