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Патент USA US2115871

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May 3, 1938 .
H. PITSCH
2,115,871
AUTOMATIC RECEIVER GAIN CONTROL CIRCUITS
Filed Oct. 9, 1936
70L‘. _
2 Sheets-Sheet 1
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—6 MAX.
lNV ENTOR
HELMUT PITSCH
B?
ATTORNEY
May 3, 1938.
H, P‘TSCH
'
_
2,115,871
AUTOMATIC RECEIVER GAIN CONTROL CIRCUITS
Filed Oct. 9, 1936
2 Sheets-Sheet 2
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SIG/VAL
SOURCE
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INVENTOR
HELMUT PITSCH
BY )QZMW
ATTORNEY
Patented May 3, 1938
2,115,871
UNITED STATES PATENT OFFICE
2,115,871
AUTOMATIC RECEIVER GAIN CONTROL
CIRCUITS
‘
Helmut Pitsch, Berlin, Germany, assignor to Tel
efunken Gesellschaft f-iir Drahtlose Telegraphic
m. b. H., 'Berlin, Germany, a corporation of
Germany
Application October 9, 1936, Serial No. 104,768
‘In Germany October 18, 1935
9 Claims. (Cl. 250-20)
Receivers comprising means adapted to insure
automatic volume control offer the practical ad
vantage that all transmitter stations come in ap
proximately with like intensity, and that the
effects of fading are neutralized. However, there
tuning is secured by that the'loosely coupled os
cillatory circuit with which the recti?er intended
to suppress cracking noises is connected, is en
is the disadvantage that the various stations are
not audible the loudest at a single or de?nite
meant by sharp tuning accomplished automati
point, but that they come in with undiminished
power or strength also at points adjacent the
10 tuning point since the receiver tends to raise the
in those regions adjoining the tuning points.
However, inasmuch as reception in the presence
of inaccurate tuning is distorted because of the
cutting off of portions of the side-bands and re
duction of the strength of the carrier frequency
cally is that the operator, or‘user, of the set need
not pay any particularly close attention to exact’
tuning. While normally enhanced selectance of
reception is achievable by resorting to regenera 10
tion, the ways and means here disclosed operate
in such a way that the transmitter station appears
only at one de?nite sharply and narrowly bounded
place so that optical indicator, or marking, means
compared with the side-bands, optical indicator
become dispensable. The quality of reception is 15
not impaired by resorting to regeneration, on the
means are provided in receivers designed for auto
contrary, it is even improved seeing that errone~
matic volume control by the aid of which the
proper point of tuner setting is made known.
Now, attempts have been made to render such
an accessory device dispensable by suggestions to
ous tuning is precluded.
A number of exempli?ed embodiments of the
idea underlying this invention are shown in the 20
drawings. Figs.‘ 1 to 4 inclusive show di?erent
modifications of the invention. The circuits show
build the receiver in such a way that the receiver
apparatus needs to be set or tuned only proxi
mately, while automatic means become operative
which will e?ect readjustment to the proper
value or point. However, arrangements of the
said kind require considerable expenditure of
money and materials. It is known in the prior
art to couple the tube serving to eliminate crack
ing noises (insure silent tuning) by way of a
sharply tuned or highly selective circuit, the said
tube blocking the ‘reception whenever unduly
small radio frequency amplitudes are coming in;
the result is that in this manner strays and noises
which become thus audible between the stations,
and which are specially emphasized because of
the volume control, will be suppressed. What is
meant by the said highly selective circuit is a
simple tuning circuit rather than a band-pass
?lter. In this manner, reception upon tuning is
rendered operative, or is released, later than
would he the case in the absence of such a cou
pling. l/Vhat is worse is that reception is not yet
permitted or insured at a sharply de?ned and
optimum point, so that the further suggestion has
been made in the earlier art to couple an oscil
lating tube with the recti?er serving to suppress
5
dowed with a more pointed or peaked resonance
curve by. the aid of regeneration. ~ What is here
noise, the said tube serving to suddenly diminish
the suppression potential whenever the incoming
signal oscillation “entrains” the locally‘generated
oscillation inside a small range (or pulls the same
into step). Such a circuit arrangement is quite
complicated, and is not adapted to a simple reg
ulation.
According to this invention automatic sharp
intermediate-frequency (beat) receivers, though
the invention by no means is con?ned to the ap
plication in receivers of the said type. In T. R. F. 25
receivers, to be sure, there arises the disadvan
tage that the loosely coupled oscillation circuit
must also be tuned to the desired transmitter
station.
Referring to Fig. 1, the intermediate-frequency 30
current flows from the oscillatory circuit Z, on the
one hand, to the rectifier vG of the receiver with
resistance W1; and, on the other hand, by way
of the small condenser C (loose coupling) to the
oscillation circuit S. In the presence of sharp 35
tuning to a certain station, a negative biasing
voltage arises across the resistance W2 by recti
?cation between the grid and the ?lament of tube
K so that the blocking voltage for the audio am
pli?er tube N prevailing in quiescent state across 40
the resistance W3 is discontinued. The tube R
is fed with radio frequency energy directly from
the oscillation circuit S, and by the aid of the
tickler (regeneration) coil RK a feedback action
is produced in the oscillation circuit S. With 45
tube K regeneration isnot possible inasmuch as
this tube is blocked when tuning to a transmitter
station. Another exempli?ed embodiment is il“
lustrated in Fig. 2, which offers the special ad~
vantage that the plate current of the'blocked
audio tube will not counteract the arising of an
unblocking potential across resistance W3. In
Fig. 2, when blocking the tube K, there occurs
a shift of point P in a positive direction so that
tube N, by way of resistance W3, is impressed with 55
2
2,116,871
the negative biasing voltage -G, while in blocked
state of the said tube N (tube K unblocked) the
point P is subject almost to the voltage —Gmax.
Also in this instance‘, the tube R serves for feed
back.
tube, means normally operative to block signal
transmission through said tube, a highly selec
tive tuned signal input circuit connected to said
blocking means, means in said input circuit for
rendering the blocking means inoperative when
In Fig. 3, the same circuit is shown except that
for unblocking and for regeneration a tube K’
signals of the frequency of said input circuit are
impressed on the latter, and means, responsive
comprising two plates is used. The left-hand
anode, or plate I serving for feedback must'be
to said signals, for regeneratively feeding back
signals to said input circuit thereby to increase
10 fed with a high plate potential in order that upon - the selectivity of the latter to a substantially 10
the arising of a negative potential across there
greater degree, said blocking means including a
tube provided with a cathode, control grid, plate
yet be blocked so that, if possible, no change in , and one auxiliary- electrode, said auxiliary elec
the slope or mutual conductance occurs as a result trode being regeneratively coupled to said selec
tive input circuit to provide said feedback means.
15 of the shift of the working point. The plate po
5. In combination with a signal transmission
tential for the plate 2 of the right~hand system,
on the contrary, is so proportioned'that blocking tube, means normally operative to block signal
will be produced. This plate potential which’ transmission through said tube, a highly selective
arises between —G and —Gmax is low alone by . tuned signal input circuit connected to said block
sistance We the left-hand tube system will not
20
20 reason of the requisite small blocking potential.
ing means, means in said input circuit for ren
In the case of the scheme in Fig. 4, recourse
is had to a pentode ‘K1. The ?rst grid 3 and the
screen grid it serve for’ the production of the
feedback current, while the third grid 5 and the
25 plate 6 properly so-called are employed for in4
suring the blocking and unblocking actions.
Since, when tuning to a transmitter station, a
negative biasing voltage is set up across the re
sistance We, the stream of electrons will be
dering the blocking ‘means inoperative when sig
nals of the frequency of said input circuit are im
pressed on the latter, and means, responsive to
said signals, for regeneratively feeding back sig
nals to said input circuit vthereby to increase the 25
selectivity of the latter to a substantially greater
degree, a signal source coupled to said input cir
'30 forced more strongly on the screen grid.
There
by the feed-back is raised with the result that
in tuned state the resonance curve is auto
matically rendered still sharper.
35
What I claim is:
1. In combination with a signal transmission
tube, means normally operative to block signal
transmission through said tube, a highly selec
tive tuned signal input circuit connected to said
blocking means, means in said‘input circuit for
rendering the blocking means inoperative when
signals of the frequency of said input circuit are
impressed on the latter, and means, responsive
to said signals, for regeneratively feeding back
signals to said input circuit thereby to increase
45 the selectivity of the latter to a substantially
greater degree.
cuit, a demodulator'coupled to said source, the
input electrodes of the transmission tube being
30
coupled to ‘the demodulator.
6. In combination with a signal transmission
tube, means normally operative to block signal
transmission throughsaid tube, a highly selec
tive tuned signal input circuit connected to said
blocking means, means in said input circuit for 35
rendering the blocking means inoperative when
signals of the frequencyof said input-circuit are
impressed on the latter, means, responsive to said
signals, for regeneratively feeding back signals
to said input circuit thereby to increase the selec 40
tivity of the latter to a substantially greater de
gree, a demodulator coupled to said signal trans
mission tube, and means responsive to signal
amplitude increase for maintaining the signal
amplitude at the demodulator input substantial
ly uniform.
2. In combination with a signal transmission
'7. In combination with a signal transmission
tube, means normally operative to block signal
transmission through said tube, a highly selec
50 tive tuned signal input circuit’connected to said
blocking means, means in said input circuit for
rendering the blocking means inoperative when
signals of the frequency of said input circuit are
impressed on the latter, means, responsive to
55 said signals, for regeneratively feeding back sig
nals to said input circuit thereby to increase the
selectivity of the latter to a substantially greater
tube, means normally operative to block signal
degree, and said feedback means comprising a
tube which is independent of said blocking
means.
3. In combination with a signal transmission
tube, means normally operative to block signal
transmission through said tube, a highly selec
tive tuned signalinput circuit connected to said
65 blocking means, means in said input circuit for
rendering the blocking means inoperative when
signals of the frequency of said input circuit are
impressed on the latter, means, responsive to
said signals, for regeneratively feeding back sig
nals to said input circuit thereby to increase the
selectivity of the latter to a substantially greater
degree, said blocking means comprising a tube,
and said feedback means including a second tube
independent of said blocking tube.
75
4. In combination with a signal transmission
transmission through said tube, a highly selec
tive tuned signal input circuit-connected to said 50
blocking means, means in said input circuit for
rendering the blocking means inoperative when
signals of the frequency of said‘ input circuit are
impressed on the latter, means, responsive to
said signals, for regeneratively feeding back sig
55
nals to said input circuit thereby to increase the
selectivity of the latter to a substantially greater
degree, a signal source coupled relatively loosely
to said input circuit, a signal detector coupled
to said source'and providing audio and direct cur 60
rent voltage, means for impressing the audio volt
age on said transmission tube, and automatic
volume control means utilizing said direct cur
rent voltage.
8. In combination with the intermediate fre
65
quency network of superheterodyne receiver,
means demodulating the intermediate frequency
energy, means for amplifying the demodulated
energy, a tube having its space current path ar
ranged to'provide a normal blocking bias for the 70
amplifying means, said tube having an input cir
cuit tuned to the intermediate frequency, means
for impressing intermediate frequency energy on
said input circuit, means responsive to inter
mediate frequency energy in said input circuit 75
2,115,871
for reducing said space current to an extent such
that said bias is removed, and means including
an electron discharge device, responsive to in
termediate frequency energy in said input cir
cuit, for providing regenerative feedback of the
intermediate energy to said input circuit thereby
greatly to increase its selectivity.
9. In combination with the intermediate fre
quency network of superheterodyne receiver,
means demodulating the intermediate frequency
energy, means for amplifying the demodulated
energy, a tube having its space current path ar
ranged to provide a normal blocking bias for
the amplifying means, said tube having an input
15 circuit tuned to the intermediate frequency,
3
means for impressing intermediate frequency en
ergy on said input circuit, means responsive to
intermediate frequency energy in said input cir
cuit for reducing said space current to an extent
such that said bias, is removed, and means includ Cl
ing an electron discharge device, responsive to
intermediate frequency energy in said input cir
cuit, for providing regenerative feedback of the
intermediate energy to said input circuit thereby
greatly to increase its selectivity, said device in 10
cluding at least one electrode in said blocking tube
which is auxiliary to the normal electrodes
thereof.
HELMUT PITSCH.
15
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