Radio Receiver

Abstract

An FM monitor type radio having indicator lights on its front face to indicate the particular channel to which the receiver is tuned. A digital counter driven by a multivibrator cycles the radio in order, through its various channels. The multivibrator is switchable from a free running state to a state in which it is actuated to drive the counter one position by means of a manual selector switch. The number of channels to which the radio tunes can be controlled by opening or closing one or more of a plurality of switches each of which is provided for a respective one of the channels. Each of the channels of the receiver is capable of being pretuned to a desired frequency in one or the other of two separate frequency bands.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a radio receiver.

2. Description of the Prior Art

There are available on the market various types of radios intended for use in monitoring the two way communications of others. Such radios are used, for example, by volunteer firemen, by aircraft pilots, by watercraft operators and by professional newsmen to mention only a few of the many applications. Some of these radios step around from frequency to frequency locking on a frequency only if there is a transmission being received on that frequency. It is desirable that a radio of this type be capable of being preset or pretuned to frequencies which are in widely separate bands, such as, for example, the 30 to 50 Mc band allocated for police, fire, forestry, highway and railroad service purposes and the 122 to 174 Mc band allocated to amateur and other purposes.

SUMMARY OF THE INVENTION

One embodiment of the invention might include a radio receiver apparatus comprising an antenna, a pair of RF amplifiers coupled to said antenna, said RF amplifiers being arranged for receiving separate frequency bands, a pair of mixers each coupled to a respective one of said RF amplifiers, an IF and audio section coupled to said RF amplifiers and mixers, tuning apparatus tunable to a given plurality of channels, means for stepping said tuning apparatus through said given plurality of channels in a regular order, means for locking said tuning apparatus on a given channel as long as a signal is received on that channel, and means for presetting said channels of said tuning apparatus to couple either one or the other of said RF amplifiers and respective mixer to said IF and audio section whereby the frequency received by each channel is pre-selected from one or the other of said bands.

Objects of this invention are to provide an improved radio receiver and to provide a radio receiver which cycles through a predetermined number of frequencies which are pre-selected in separate frequency bands.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic electrical block diagram of a radio receiver embodying this invention;

FIG. 2 is a perspective view of the radio receiver of this invention; and

FIGS. 3 and 4 are schematic electrical diagrams of some of the circuitry of the radio receiver.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring more particularly to the drawings, there is illustrated an FM monitor type radio 10 which has on its front face an on-off switch 11 and a squelch knob 12. The radio is capable of receiving eight different frequencies each of which is associated with a respective one of the lights 1-8, inclusive, and switches 1'-8' inclusive. The radio has a two position switch 15 which permits selection of automatic operation or manual operation and also has a manual channel selector switch 16. As mentioned, the purpose of the radio is to monitor various radio frequencies. This is accomplished by the stepping at a constant rate through the various frequencies. When a frequency has a transmission on it, the radio locks on that frequency until the transmission stops.

Referring to FIG. 1, the IF and audio portion 17 of the receiver is connected to an electronic switch 20 which places a B+ or DC voltage on the terminal 21 when the receiver is tuned to a frequency on which there is no transmission. When the switch 15 is in the illustrated position with the contact 22 in engagement with the contact 21, the B+ is conducted to the multivibrator 25 causing it to run continuously. As the multivibrator runs, it drives the counter 27 causing it to place a signal, in order, on the lines 1"-8" and to cause the receiver to be tuned in order to the various desired frequencies. The electronic sensing switch 20 is connected to the IF and audio portion 17 of the receiver through the squelch circuit of the receiver. When the receiver is tuned to a frequency on which there is a transmission, the electronic sensing switch 20 is operated and no B+ is provided to the terminal 21. Consequently, the multivibrator does not run. Only when the transmission stops does the terminal 21 again receive the B+ so that the multivibrator is again caused to run.

The switch 15 may be operated so that the contact 22 engages and remains in engagement with the terminal 26. In this condition the manual selector switch 16 is used to tune the receiver to the various frequencies. The switch 16 is a push button type spring return switch. When the switch 16 is closed, a pulse of voltage is transmitted from B+ to the terminal 26 causing the multivibrator to move the counter 27 one position. The capacitor 30 causes the voltage at the terminal 26 to quickly drop back so that further running of the multivibrator does not occur until B+ is again provided to the multivibrator.

As shown schematically in FIG. 1, the crystals 1'"-8'" are located between the diode switching circuit 35 and the oscillator 36. Each of the crystals is associated with a respective one of the lines 1"-8", a respective one of the lights 1-8 and a respective one of the switches 1'-8'. When all of the switches 1'-8' are closed, the counter energizes each of the lights in order and places each of the crystals in the circuit of the oscillator so that the receiver is tuned to the frequency determined by each crystal. If one or more of the switches 1'-8' is manually opened, the counter still cycles to and through the particular line 1"-8" but because the particular switch is not closed, the particular light 1-8 is not turned on and the particular crystal 1'"-8'" is not placed in the oscillator circuit. Consequently, that frequency is out of the cycle whether the receiver is manually stepped or automatically stepped.

The manner in which the lights are turned on and the respective associated crystals are simultaneously used will be clear from FIGS. 3 and 4. FIG. 3 may be considered a description of the pre-IF section of the receiver. In FIG. 3 the oscillator 36 has the respective crystals 1'"-8'" connected in its circuit through the line 40, diodes 41, lines 42 and line 45. As long as the lines 42 have a sufficiently high voltage thereon to back bias the diodes 41, no current flows through the crystals. The voltage, for example, at the line 40 in one specific embodiment of the invention is +8.5 volts. Referring to FIG. 4, the voltage supplied at point 46 is +13 volts. FIG. 3 connects to FIG. 4 at the points 1""-8"". Therefore, when the switches 1'-8' are open, the voltage at the lines 42 is also 13 volts because there is no voltage drop through resistor 47 (33.OMEGA. 1/2 watts), or through the light bulbs 1-8 or through the resistors 50'. Whenever any of the switches 1'-8' is closed, there is a voltage on the respective line 42 of approximately 10 volts because of voltage drop through the resistor 47 and the respective bulb 1-8. Still the voltage of 10 volts is not low enough to forward bias the respective diode 41.

As the counter steps along, however, it turns on the respective transistors 1A-8A and transistors 55' and 56' which drops the voltage on the terminal 51' of the respective lights 1-8 to a voltage close to ground so that the respective light is turned on. The turning on of the respective transistor drops the voltage on the respective terminal 51' to approximately 0.3 volts which turns on the respective diode 41 because it is now forward biased. Thus the respective crystal is placed in the oscillator circuit. As regards the counter operation, the transistors 1A and 2A are turned on at the same time through the line 60'; however, the transistors 55 and 56 are alternated in being turned on. It can be appreciated therefore that the voltage at the terminals 51 cycles in order through the lights 1-8.

FIG. 3 also connects or, in other words, the circuit of FIG. 3 can be connected to the circuit of FIG. 4 by the band selector matrix 49 which includes the jacks 1V-8V. The jacks are connected to the collectors of each of the respective transistors 1A-8A through the lines 48 and diodes 49'. Each of the jacks can be inserted in either of two terminal receptacles 1W-8W or 1X-8X. All of the receptacles 1W-8W are connected to the line 50 while all of the receptacles 1X-8X are connected to the line 51. The lines 50 and 51 each are coupled through respective current limiting resistors 52 to first and second band switches 54 and 55 each of which is a PNP transistor with its base 56 connected to the resistor 52. Each of the switch transistors has its emitter 57 connected to a positive constant DC voltage source 58 and has its collector 60 connected to respective lines 61 and 62. The line 61 of switch 54 connects through line 66 to the biasing resistors 67 and 70. The biasing resistor 67 is a part of the first band RF amplifier 71 while the biasing resistor 70 is a part of the first band mixer 72. In like fashion the second band switch 55 is connected through biasing resistors 75 and 76 of the second band RF amplifier 77 and second band mixer 80. Each of the RF amplifiers 71 and 77 is coupled to an antenna 81 through lines 82 and 85. The mixers 72 and 80 include common components 86, 87, 90, 91 and 92 and are coupled through inductance 91 to inductance 95 representing the IF and audio portion of the receiver.

As suggested above, each of the jacks 1V-8V can be inserted into a receptacle which is connected to either the line 50 or the line 51. The first band RF amplifier may be tuned, for example, to the lower frequency band while the second band RF amplifier may be tuned to the higher frequency band. Thus, the radio may be preset by proper selection of the crystals 1'"-8'" and insertion of each jack in an appropriate receptacle so that the radio repeatedly cycles through a predetermined series of frequencies, some or all of which are high band and some or all of which are low band.

Assuming, for example, that the counter has turned on transistors 1A and 55' so that the voltage at the terminal 51' light 1 is 0.3 volts. Assume further that the radio has been preset by the plugging in of the jack 1V in the receptacle 1W. The first band switch 54 is turned on causing biasing current to be supplied through the transistor thereof from the constant DC voltage source 58 to the biasing resistors 67 and 70. The first band RF amplifier and the first band mixer are thereby conditioned for operation. If a signal of appropriate frequency is being received through the antenna 81, the mixer 72 beats it against the output of the oscillator 36 to provide a signal input to the IF and audio portion 17 of the receiver.

While the invention has been disclosed and described in some detail in the drawings and foregoing description, they are to be considered as illustrative and not restrictive in character, as other modifications may readily suggest themselves to persons skilled in this art.

Claims

The invention claimed is:

1. A stepping radio receiver for production of audio signals from radio frequency signals and capable of tuning to a plurality of separate channels on a plurality of bands and which comprises:

a. a pre-IF section having an RF signal receiving means, a plurality of mixers, and an oscillator means;

b. said RF signal receiving means being for providing sufficient RF signal level for said plurality of mixers;

c. said plurality of mixers being coupled to the RF signal receiving means, there being one mixer for each of said plurality of bands;

d. an audio detection means coupled to said mixers for producing an audio signal when an RF signal is being received, said audio detection means including squelch means for preventing the production of an audio signal when an RF signal is not being received;

e. said oscillator means being coupled to said mixers and operable at a given plurality of frequencies, there being one frequency for each channel to which the receiver can tune;

f. stepping means which is defeatable and which has a plurality of outputs which are coupled to said oscillator means for stepping said oscillator means through said given plurality of frequencies;

g. locking means which is connected to the stepping means for defeating said stepping means as long as an RF signal is being received and allowing resumption of operation of said stepping means when no signal is being received;

h. a programmable band-selecting means connected to the pre-IF section of the receiver and to the stepping means for determining which mixer can have an output feeding the audio detection means whereby each channel received can be in any one of the plurality of bands, said programmable band-selecting means including a band selector matrix having

1. a plurality of first connecting elements, each of said first connecting elements coupling to one of said outputs of said stepping means, and

2. a plurality of second connecting elements, said plurality of said second connecting elements coupling to a first enabling means for enabling one of said mixers to have an IF signal at its output, and others of said second connecting elements coupling to a second enabling means for enabling another of said mixers to have an IF signal at its output, whereby the manual connection of one of said first connecting elements to one of said second connecting elements determines the band on which one of the channels will operate;

i. visual indicators connected to the stepping means to indicate the channel to which the receiver is being tuned.

2. The receiver of claim 1 in which the RF signal receiving means includes an antenna and an RF amplifier.

3. The receiver of claim 1 in which the oscillator means includes a plurality of crystals.

4. The receiver of claim 1 in which there is one visual indicator for each channel and the indicators are arranged in a row.

5. The receiver of claim 1 in which there is only one oscillator circuit in said oscillator means, said oscillator circuit producing an output at two frequencies.

6. The receiver of claim 1 in which said first connecting elements are jacks and said second connecting elements are receptacles into which said jacks can be inserted.

7. The receiver of claim 1 in which there are at least twice as many second connecting elements as there are first connecting elements.

8. A stepping radio receiver for production of audio signals from radio frequency signals and capable of tuning to a plurality of separate channels on a plurality of bands and which comprises:

a. a pre-IF section having an RF signal receiving means, a plurality of mixers, and an oscillator means;

b. said RF signal receiving means being for providing sufficient RF signal level for said plurality of mixers;

c. said plurality of mixers being coupled to the RF signal receiving means, there being one mixer for each of said plurality of bands;

d. a audio detection means coupled to said mixers for producing an audio signal when an RF signal is being received, said audio detection means including squelch means for preventing the production of an audio signal when an RF signal is not being received;

e. said oscillator means being coupled to said mixers and operable at a given plurality of frequencies, there being one frequency for each channel to which the receiver can tune;

f. stepping means which is defeatable and which has a plurality of outputs which are coupled to said oscillator means for stepping said oscillator means through said given plurality of frequencies;

g. locking means which is connected to the stepping means for defeating said stepping means as long as an RF signal is being received and allowing resumption of operation of said stepping means when no signal is being received;

h. a programmable band-selecting means connected to the pre-IF section of the receiver and to the stepping means for determining which mixer can have an output feeding the audio detection means whereby each channel received can be in any one of the plurality of bands, said programmable band-selecting means including a band selector matrix having

1. a plurality of first connecting elements, each of said first connecting elements coupling to an output of said stepping means, and

2. a plurality of second connecting elements connected to the pre-IF section of the receiver and being of a design as to mate with said first connecting elements, whereby the manual connection of one of said first connecting elements to one of said second connecting elements determines the band on which one of the channels will operate; and

i. visual indicators connected to the stepping means to indicate the channel to which the receiver is being tuned.