Belt Valley times. [volume] (Armington, Mont.) 1894-1977, 1925-10-08
By J. s. ANDERSON. IN New YORK

! - Es -
Herald Tribune.
One stage Of tuned radio-frequency
amplification, enc stage OF choke coll
coupled. regenerative radio-freQusncy
application. a crystal detector and
two stages OF transformer coupled
audio-freQuency ampllncatlon are the
main elements that make up the pres
ent receiver.
When the diagram Of the receiver,
which is published herewith, was
shown to . radio fan long since past
the novice stage be remarked that ev-
erythlng 10 the receiver was done
backward. Well. not everything Is
done backward, for most OF the circuit
is strictly orthodox, but there Is one
thing which is done in the reverse
order. and 1t ls this fact which makes
the receiver unique This fact Is the
manner in which regeneration Is OBJ
talned in the second tube. Az WIN be
observed, the tuned circuit Is CD OF
this stage Is placed 10 the plate circuit
Of the tube. and the ticker coil Ia
connected In series with the grid lead
OF the tube IL placed In lnductlve re-
lation with the tuned coll LA In this
manner a voltage Ia induced In the
coil Ia. and this Is added to the input
voltage across the resistance r. II
this added voltage is sufficient regen-
Grafton viii be obtained. provided. Of
course. IL IL In the right phase
use Of Crystal Dstsct0y
The tuned coil LS was placed In the
plate circuit for several reasons. In
the flrst place. It was desired to use
crystal for detecting the signals 90
that advantage could be taken Of the
greater Quletnees and economy Of op-
Grafton obtainabIs with this device. II
was also found that the signals could
be increased tremendously BY connect
ing the crystal directly across the
plate coil and tuning Il instead Of con-
Meeting the crystal across tuned sec
ondary. No tube noises go into the
crystal because the audlo frequency
difference OF potential across LS Is en-
ffreiy negligible, and there Is no dan
ger Of injurlng the crystal BY heavy
direct current, because the DC differ
ance OF potential across Is Is even
less than the andio-frequency alter
mating current potential difference.
Hence neither tube noises nor direct
current OF appreciable magnitude viii
20 into the crystal detector circuit.
The fact that the crystal detector cir
cnIt IL connected to the positive side
OF the plate battery does not mean
that the plate battery voltage is In the
crystal circuit
Since the grid coli IA ~ not tuned
Il requires closer coupling between
LS and Ia TO obtain regeneration than
when the grid coil Il tuned and when
the tickler Is IN the plate circuit. For
this reason II viii be necessary TO
use 9 high lnducfnnce In Ia In order
70 obtain satisfactory regeneration. AS
Il Is desirable TO have compact coil |
for ticker, Ia should preferably be |
wound with fine wire. The writer used |
100 turns Of No. 80 double cotton
covered wire wound on diameter Of |
two inches.
since the crystal circuit IL connect
ed across the tuned circuit lib CD and /
takes considerable energy from It, the
latter Is naturally very broad and non
seIectfve. In order to Increase the Sc
Iactivity Of the arrangement I.3 should /
be wound with fairly heavy wire. and
.ha low-Ioas method Of constructing It
may be employed. Two or three taps
should also be provided on Il 30 that
Ehs crystal circuit may be connected
lcroas only q portion Of LS when
greater seIecffvity IN required
Does Not lncrsass SelsetlvIty.
The regeneration does not increase
be selectivlty 70 the same extent In
his case as II does in the ordinary
,iFcuIf. The reason for this Is that
ne grid coli Is apeEiodic and responds
TO eurr@mfs Of all freQuenriest
which are surGlng IN LS CO. That
:. fhe eide hands SIRE Intensified nv
almost to the same extent
- the carrier frequency. The set re-
produces faithfully. but. Of course. the
Tumllsy 10 dependent ON the perform
Incs 81 the andio-frequency trans
ormera. II the choice Of these has
'sen lucky or we'll advised the set win
make pleasant listening.
the anfenna coil 10 and the first
nulnn coli Ii may be the two wind
sRs OF an ordinary radio-frequency
uming unit, which may be purchased
/ amv radio store The coupling be-
ween the two wfndlngs should be
pose. 80 that the selectivity Of the
ct wEll moi be Impaired II made st
osae the primary 10 may consist OF
"a furns and the secondary Ii Of
orfv-shree turns. wOund on a length
I eenposlflon tubing three inches 2 ,
lamefer with about NO 20 double
wire. There should be AZ
sAaf quarter OF an inch separating
Is two wlndEngs. The two tuning
m aud fHH ahnuId each be