Belt Valley times. [volume] (Armington, Mont.) 1894-1977, 1926-07-22
eY JAMEs E. cARTER


certain definite conclusions about
what makes up a good radio receiver.
These conclusions. In pracawl form,
are embodied In most really Successful
manufactured sets Of today. Some re-
ceivers have greater perfection than
others. Some are Of better design and
construction. A few are outstanding
In achievement
good set, first OF all. whether 1t
be homemade or faetory-bullt, must
be OF correct design. The home con-
structor who is contemplating the
building of a receiving set is natural
~ DESTROYS of obtaining the utmost
in the way Of performance and is
keenly alert to improvements In the
successful manufactured set.
The first point Of Importance to the
home set builder will be the type OF
circuit to use. It is needless to say
that the day OF the regeneratlve
ticker feed-back type OF receiver
without radlo-frequency application
before the detector is over.
There remains the straight radio
frequency circuit with positive con-
trolled oscillation. which is probably
the easiest all-around highly efficient
circuit to construct.
Volume and Distance.
For the set builder who Is situated
fifty or more miles from broadcast
station two stages OF tuned radlo-fre-
quency application, followed by
detector and two or three stages Of
audI0 amplIficatIon, will give ample
satisfaction In the way OF volume and
distance. Where the user is located
within 90 miles of a strong broad
casting station three stages OF tuned
radio-frequency application is neces-
sary to work distant stations as near
as 20 kilocycles either above or below
the nearby station.
In the accompanying diagram the
nve-tube radio receiver 10 be de-
scrIbed In this article ia shown. This
set employs two stages OF transformer
coupled tuned radio-freQuency ampli-
fication, a nOn-regenerative detect0r
and two stages Of transformer coupled
audiO-frequency application. An
examination of this diagram viii show
that there Is nothing unusual In the
wiring OF the circuit. the chief point OF
interest being the way In which one
control tuning is accomplished. A
triple condenser is used to tune the
secondary coils of the three radio
frequency transformers, all OF which
are identical In construction, and
small adjustable fixed compensating
capacity Is connected In shunt with
each of the three units Of the con-
denser to compensate for the varia-
ton in the capacity OF the wiring Of
each Of the circuits. Also a variable
antenna compensating condenser IL
connected in shunt with the unit Of
the condenser tuning the secondary
OF the antenna coupler. This has been !
found necessary TO make possible eff.
Client operation with any type of an.
tenna. Another feature which makes |
the set more flexible Is the small fixed |
condenser, which may be placed In /
series with the antenna. When this
condenser is in use the receiver lie
more seiective and may be operated |
from large antenna without expert
enclng interference.
The Parts Needed.
The following is list Of apparatus
actually employed In the construction
Of this receiver:
One three gang Perisz condenser leach
Hecrf0n .0005b MIDI
Three radio-frequency transformers
matched for use with this condenser
(Perlez or home-made).
Two Thorardson audio-frequency trans
formers.
One Hammariund compensating con-
denser $50 mmfd.).
One 500 ,0O0-ohm Centralab variable re-
aistance
One centralab modulator CoptionaD.
Five Benjamin sockets.
Two Dubllier o0025 mid. fixed condemns
ers.
One Dubiiler .Oof mfd. fixed condenser.
Two Dubllier 1 MID. hxed condensers.
one s meg. Durham grid leak
One e-ohm rheostat.
)ne Carter battery switch.
Eleven Eby binding posts.
One panel 23M x9x3-16 inches.
one panel 10hx4h x3-le inches
Two panels 3x2H xs-1s inches.
)ne Dashboard 23x10xh inches.
The method employed to control the
rolume OF this receiver eliminates
he necessity Of connecting jacks In
he output Of each stage Of amDlihca-