Varactor tuning system

• US 3,878,466 A
• Filed: 02/12/1973
• Issued: 04/15/1975
• Est. Priority Date: 02/12/1973
• Status: Expired due to Term

• Current Assignee: Melvin C. Henrickson
• Original Assignee: Melvin C. Henrickson
• Inventors: Henrickson, Melvin C.
• Primary Examiner(s): Safourek, Benedict V.
• Application Number:
  US05/331,921
• Time in Patent Office: 792 Days
• Field of Search: 325/464,465 334/14,15 323/79,80 338/92,95,118,120,122,185,191,202
• US Class Current: 455/182.2
• CPC Class Codes: H03J 5/0209 Discontinuous tuning using an electrical variable impedance element, e.g. a voltage variable reactive diode, by selecting the corresponding analogue value between a set of non preset values
• CPC Class Codes: H03J 7/12 Combination of automatic frequency control voltage with stabilised varactor supply voltage

Abstract

A television channel selector includes UHF and VHF tuners each having a varactor as the frequency-determining element. A number of fixed contacts on a rotary switch are respectively associated with different channels in both the VHF and UHF regions of the spectrum; also included on the switch are a pair of selection contacts. Printed on the same substrate which carries the switch contacts are a plurality of resistors which together constitute a voltage divider that has individually different junctions between the resistors connected to respective different ones of the fixed contacts. A fast-tuning shaft drives the selection contacts over the fixed contacts. That shaft is detented each time the selection contacts are moved over a chosen number of the fixed contacts. A slow-tuning shaft is coupled through a gear system to the fast-tuning shaft. The slow-tuning shaft is detented in rotational increments that correspond to movement of the selection contacts, through the gear system and the first shaft, from each one of the fixed contacts to the next. The selection contacts read out a voltage from the divider which is fed to the varactors in determination of frequency. For fine tuning, the varactor control voltage is derived from a tap on a potentiometer the opposite ends of which are connected by the selection contacts across selected individual different ones of the resistors in the voltage divider.

Claims

1. A television channel selector for tuning a plurality of channels of equal bandwidth in unequally spaced frequency bands, said channels being contiguous within each individual band comprising:

tuning means including at least one varactor as the frequencydetermining element, the frequency determined being a function of the voltage presented to a terminal of said varactor;

a source of DC potential;

a voltage divider connected across said DC source and composed of a plurality of resistors connected successively in series with the junctions between successive resistors terminating in stationary contacts;

fine-tuning means including a poTentiometer having a movable tap coupled to said terminal to supply a frequency-determining voltage to said varactor, and a pair of offset movable contacts, each connected to respective opposing ends of said potentiometer;

channel selection means for moving said offset movable contacts sequentially into engagement with adjacent ones of said resistors to adjust the level of said frequency determining voltage; and

means, coupled to said voltage divider, bridging those stationary contact which define adjacent ends of said unequally spaced frequency bands.

2. A television channel selector as set forth in claim 1, wherein said last-mentioned means comprise resistors selected to develop voltage differentials to enable said varactor to tune across the frequency gaps between said unequally spaced frequency bands.

3. A television channel selector as set forth in claim 2, wherein said voltage divider is formed on a ceramic substrate.