GB491693A - Improvements in variable selectivity radio receivers - Google Patents
Improvements in variable selectivity radio receiversInfo
- Publication number
- GB491693A GB491693A GB36168/37A GB3616837A GB491693A GB 491693 A GB491693 A GB 491693A GB 36168/37 A GB36168/37 A GB 36168/37A GB 3616837 A GB3616837 A GB 3616837A GB 491693 A GB491693 A GB 491693A
- Authority
- GB
- United Kingdom
- Prior art keywords
- bias
- limiter
- diode
- valves
- stage
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03G—CONTROL OF AMPLIFICATION
- H03G5/00—Tone control or bandwidth control in amplifiers
- H03G5/16—Automatic control
- H03G5/24—Automatic control in frequency-selective amplifiers
- H03G5/26—Automatic control in frequency-selective amplifiers having discharge tubes
Landscapes
- Circuits Of Receivers In General (AREA)
Abstract
491,693. Wireless receiving circuits. HAZELTINE CORPORATION. Dec. 30, 1937, No. 36168. Convention date, Jan. 21. [Class 40 (v)] The selectivity of a radio receiver is automatically varied in accordance with signal strength by utilizing A.V.C. potentials applied to at least one stage, in conjunction with a limiter to limit the maximum band width of that stage to a value corresponding to the modulation band width of the received signal. The I.F. stage of a superheterodyne receiver comprises a forward amplifier 31 and a triode 37 having a sharp cut-off characteristic and forming part of a reverse feed-back path coupled at 38, 40 to the output and input circuits 27, 26 respectively of amplifier 31. The gain of the preselector 1, frequency changer 3 and I.F. amplifier 31 is controlled by the A.V.C. diode 14 over lead 8, while the biassing resistances 32, 33 which are common to the two valves 31, 37 are such that the reverse feed back valve is biassed to cut-off at inputs at or below the sensitivity limit of the receiver. The A.V.C. voltage thus directly varies the slope of valve 31 which in turn varies that of 37, the selectivity varying in accordance with change of product of the mutual conductances of the two valves. The characteristics of the valves must vary at different rates with variations in A.V.C. bias, and with this system the bandwidth passed increases with applied bias to a maximum and then again falls. To prevent this, an auxiliary control circuit is provided, comprising lead 44 from the junction of resistances 10, 45, a diode limiter 46, the lower part of the voltage divider 47 and through the earth connection and the resistance 33 to the cathode of the A.V.C. diode 14. The limiter 46 is in shunt with the resistance 33 and lower part of divider 47 in series, the voltage across the two latter being opposed to that developed across the A.V.C. resistance 16. Up to a certain value of A.V.C. bias determined by the slider on divider 47, the limiter is inoperative, this bias corresponding to maximum bandwidth. Thereafter, further increase in bias energizes the diode 46 which prevents further change and the ensuing droop in the bandwidth-bias characteristic is eliminated. Specification 426,803 is referred to.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US491693XA | 1937-01-21 | 1937-01-21 |
Publications (1)
Publication Number | Publication Date |
---|---|
GB491693A true GB491693A (en) | 1938-09-07 |
Family
ID=21958382
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB36168/37A Expired GB491693A (en) | 1937-01-21 | 1937-12-30 | Improvements in variable selectivity radio receivers |
Country Status (1)
Country | Link |
---|---|
GB (1) | GB491693A (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2284718A (en) * | 1990-10-10 | 1995-06-14 | Motorola Inc | Adjusting telephone bandwidth using variable integrated transconductance filter |
-
1937
- 1937-12-30 GB GB36168/37A patent/GB491693A/en not_active Expired
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2284718A (en) * | 1990-10-10 | 1995-06-14 | Motorola Inc | Adjusting telephone bandwidth using variable integrated transconductance filter |
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