US2159803A - Automatic volume control receiver - Google Patents

Description

May 23, 1939.

E. KLOTZ Filed March 10, 1937 DELAYED A VC I. F. AMPL- l I X i J 4 2 wvosmrsa AI/C J INVENTOR z ERNST KLOTZ ATTORNEY M (AF-NETWORK) m 40 1 ,tential arising across resistance W so that across tion of volume control means oifers the advan- Patented May 23, 1939 PATENT OFFICE AUTOMATIC VOLUME CONTROL RECEIVER 'Ernst Klotz, Berlin, Germany, assignor to Telefunken Gesellschaft fiir Drahtlose Telegraphic m. b. 11., Berlin, Germany, a corporation of Germany Application March 10, 1937, Serial No. 130,082 In Germany March 12, 1936 1 Claim. (01. 250*20) The use of means insuring a lag in the opera- 3 1 tage that the maximum amplification of the re- ;ceiver is not diminished. However, it involves the drawback that the tuning indicator is ren-,

dered operativeonly when the regulation, or

compensation, of the fading, i. e., automatic volume control, becomes operative or is initiated.

In other words, when feeble stations are received the tuning indicator, as a matter of fact, would not be necessary at all in that case seeing that {adjustment by ear is possible.

the volume control means is inoperative, so that However, it is highly desirable for the user, or operator, of the set to be in a position, also in the reception of *feeble stations, to tell from the tuning indicator 1 whether a desired station is being received or not, and to be enabled to adjust the tuning by reading the indicator to the proper value. In case silent tuning is desired the tuning indicator is j absolutely necessary. In other words, there exists Q a certain conflicting situation which is to be eliminated by the ways and means disclosed in the present invention. l 25;

is included in the plate circuit of a tube which is According to the invention, the tuning indicator {not subject todelayed gain regulation, and whose gain isless changed by the regulation than that g j l s ot the other tubes in which a lag of regulation is occasioned. i

The invention shall be explained in more dej-fltail by reference to the drawing wherein there is shown a superheterodyne receiver. In the mixer, or combined oscillator-first detector, tube M, the

l lation circuit E is changed into the intermediate incoming, or signal, oscillation fed to the oscilfrequency, and by way-of the band-pass filters 2F and the I. F. amplifier tubeZ the I. F. energy [is fed to the second detector stage G. The left diodeof tube G isnegatively biased by the podiode load resistanceWr, with small incoming amplitudes, no regulation will as yet be initiated.

fI'he right-hand diode sets up across the resistance W2 a regulator potentialeven when the I. F. carrier amplitudes are small, and this gain regulation voltage is impressed upon the I. F. tube Z. The plate circuit of the latter contains means for controlling the first detector gain with the tuning indicator, which, as will be noticed, is rendered operative also when feeble stations are coming in. The voltage across resistor W1 is used to control the gain of the first detector tube.

The tube which is subject to undelayed regulation should be regulated but little in its gain in order that, when signals from feeble stations are collected by the set, the amplification of the receiver may be but inappreciably reduced. Otherwise, the leg in volume control provided in the other tubes would be illusory. In the instance here shown and discussed, weak regulation of the I. F. tube Z would be required because it is located directly ahead of the diode so that, in case a powerful transmitter is received, distortions due to overload will be avoided, an action that would not happen if the regulation is unduly great. Weak regulation may be insured either by the use of a tube whose characteristic rises slowly, or else by tapping only part of the gain regulation potential.

It would, also, be conceivable to include the tuning indicator in a weak input tube which is not subject to lag in regulation. However, this scheme is less favorable for the reason that it is desirable that a powerful regulator action should be brought upon the first tube. It would, also, be unfavorable to include the tuning indicator in the plate circuitof the mixer tube for the reason that the plate current of the same is a function of the amplitude of the oscillator wave which is subject to slight changes inside the wave band.

What is claimed is:

In a superheterodyne receiver of the type including a first detector tube, an intermediate frequency amplifier and an audio network, a rectifier coupled to the amplifier and providing direct current voltage, a gain control circuit impressingthe direct voltage on the amplifier to reduce its gain as soon as signals are received, a second rectifier coupled to the amplifier to provide a second direct current voltage, means for delaying the rectification of the second rectifier,

the second voltage, and a tuning indicator in the amplifier space current path.

ERNST KLOTZ.

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