WO1996027949A1

WO1996027949A1 - Computerised radio receiver

Info

Publication number: WO1996027949A1
Application number: PCT/AU1996/000119
Authority: WO
Inventors: Milan Hudecek; Barry Naujok; Peter Nesbit
Original assignee: Rosetta Laboratories Pty. Ltd.
Priority date: 1995-03-06
Filing date: 1996-03-06
Publication date: 1996-09-12
Also published as: AUPN155395A0

Abstract

A radio receiver comprises an RF tuner (10) on a computer card (11) having a frequency selector (19) for determining the current selected frequency. A programmed computer functions as a control system (100) controlling the tuner and a display screen (200) presents data and user selectable inputs to the user. An input peripheral device (101) enables the user to input data or information and commands to the control system. The control system causes a display (220) on the display screen (200) in real time of both digital and analogue indications of the current frequency being passed by the tuner (10); and provides a tuner frequency select control responsive to input of a frequency change command by the user to change the current selected frequency. Features include automatic changing of mode (AM, FM, etc.) when stepping or scanning through frequencies; a simulated analogue tuning dial (225); multiple selectable modes of scanning; slow and fast rates of frequency changes; and compensation for RF background noise from the computer and monitor via local antennas (38, 39).

Description

COMPUTERISED RADIO RECEIVER Field of the invention

This invention relates to radio receivers. Background of the invention Currently available radio receivers include those which are dedicated and specially constructed for domestic, shortwave listening, scanning, amateur radio, and professional applications.

Domestic receivers usually have limited capabilities and performance. Shortwave receivers have better (but still limited) capabilities and performance, at a higher price. Many scanning receivers cover a wide range of frequencies, as much as 500 kHz to 512 MHz or more, and usually include a variety of scanning capabilities. However they are either limited to discrete frequency steps of approximately 5 kHz (which greatly reduces their ability to receive non-channelised signals), or else have mediocre RF performance, or both.

Amateur receivers have medium to high performance, but except for a few expensive units, have a limited frequency range. Professional receivers have high performance and capabilities, but are very expensive and outside the reach of all except professional and government users.

No receivers, which are generally available to the public, are capable of decoding received signals and making intelligent decisions based on the content of those signals. Summary of the invention

It is an object of the present invention to provide a radio receiver having functions and capabilities which incorporate features from better quality radio receivers which are generally available to the public, including those intended for shortwave, scanning, and amateur applications and which can utilize a computer for user interface. It is a further object to provide a radio receiver having a system for user control which can be readily understood and operated

Furthermore, a preferred object is to provide a radio receiver capable of decoding received signals into a form recognizable by a computer, and of utilising the computer to process and store such signals. Further preferred objects include:

(a) the receiver is comparable to currently available high quality and high performance scanners; (b) the receiver can operate in conjunction with a DOS PC or Apple Macintosh computer;

(c) the receiver can comprise a card installed in a PC expansion slot;

(d) the receiver can include means for decoding digitally encoded signals such as morse code and radio teletype; (e) the receiver should be able to be priced less than conventional radio receivers having similar capabilities.

According to the present invention there is provided a radio receiver comprising: an RF tuner which is operative to receive an input RF signal from an antenna, the tuner including a frequency selector for determining the current selected frequency so that the tuner produces an output signal derived from the selected RF frequency and which can be supplied to a peripheral output device; a control system coupled to the tuner so as to control the operation thereof including operation of the frequency selector; a display screen coupled to the control system, the control system being operative to control the presentation of data and the presentation of user selectable inputs by the display screen; an input peripheral device coupled to the control system and by means of which the user can input data or information or commands to the control system; the control system including: a tuner frequency display control operative to cause display on the display screen in real time of the current frequency being passed by the tuner; and a tuner frequency select control responsive to input of a frequency change command by the user via the input peripheral device to cause the frequency selector of the tuner to change the current selected frequency of the tuner in accordance with the frequency change command.

Preferably the control system further includes: a scan control selectively operable to cause the frequency selector of the tuner to change the current selected frequency of the tuner by a first desired incremental frequency step size; a receiver operating mode control operative to cause display on the display screen in real time of the current mode of operation of the tuner, the mode of operation including at least the current frequency band of the tuner operation; a stepping size memory for storing a magnitude of the first frequency step size by which the tuner frequency is to be changed when the scan control is operating and for storing a second desired incremental frequency step size by which the tuner frequency is to be changed when the user inputs the frequency change command to step up or to step down from the instantaneous selected tuner frequency; and a mode and step size switch responsive to the tuner frequency select control and/or to the scan control and operative if the current selected frequency enters a different band when it is being changed to automatically change the tuner to the appropriate mode of operation for the different band and to automatically retrieve from the stepping size memory the appropriate first or second frequency step size for the different band for use in controlling incremental frequency changes of the current selected frequency. These features of the preferred embodiment help make the operation of the receiver simple for the user.

The tuner frequency select control is preferably operative to cause display on the display screen of an image of a user selectable tuner frequency modifier, the control system being operative, firstly, in response to user selection of the tuner frequency modifier image via the input peripheral device, to cause the frequency selector of the tuner to change the current selected frequency of the tuner in accordance with the user selection, the tuner frequency modifier image comprising an image of an analogue tuning dial having markings to indicate a simulated rotational position of the dial and, secondly, when the user selects the dial and inputs the frequency change command via the input peripheral device to cause the frequency selector of the tuner to change the current selected frequency, the tuner frequency select control causes display on the display screen in real time of an animation of rotation of the dial for as long as the frequency change command is being input. Also, the control system preferably further includes a stepping size memory for storing a desired incremental frequency step size by which the tuner frequency is to be changed when the user inputs the frequency change command to step up or to step down from the instantaneous tuner frequency. These features give the user interface by which the user operates the radio receiver a natural operating feel.

The control system may further include: a scan control selectively operable to cause the frequency selector of the tuner to change the current selected frequency of the tuner by scanning through different frequencies; a scan mode control operative to cause display on the display screen of an image of a user selectable scan mode modifier, the control system being operative, in response to user selection of the image of the scan mode modifier via the input peripheral device to enable the frequency selector of the tuner to commence to automatically scan through frequencies different from the current selected frequency of the tuner when the scan control is operated, the scanning occurring according to a mode of scanning selected by the user from the modes

(i) a first mode consisting of scanning of the frequency up or down from the current selected frequency in steps of a first desired incremental frequency step size, (ii) a second mode consisting of scanning of the frequency through a defined range of frequencies, and

(iii) a third mode consisting of scanning of the frequency through a number of specific frequencies stored in a frequency memory; and a stepping size memory for storing a magnitude of the first desired incremental frequency step size by which the tuner frequency is to be changed when the scan control is operating in the first scanning mode. These features provide versatility for the user in scanning the RF spectrum for signals. The tuner frequency select control is preferably responsive to input of the frequency change command by the user to change the frequency at one of two or more rates of change which is selectable by the user by a respective input via the input peripheral device, the control system further including a stepping size memory for storing a magnitude of a frequency step size by which the tuner frequency is to be changed when the frequency change command is input. This can enable the use of slower or faster movement through frequency ranges as the user decides.

Preferably the control system further includes: a receiver operating mode control operative to cause display on the display screen in real time of the current mode of operation of the tuner, the mode of operation including at least the current frequency band of the tuner operation; and a receiver power control operative to cause display on the display screen of an image of a power switch having an off condition and an on condition and between which the user can toggle by inputting a power command via the input peripheral device, the receiver power control being operative when the off condition of the power switch is selected firstly to cause display on the display screen of a quiescent image of a radio control panel with data presented on the display screen including the display of the current selected frequency being blanked and secondly to cause the tuner to be disabled, the receiver power control being operative when the on condition of the power switch is selected firstly to cause display on the display screen of an active image of the radio control panel with data being presented on the display screen including the current selected frequency and secondly to cause the tuner to be enabled.

To enable the user to directly change the tuner to a known frequency in one step, the input peripheral device preferably includes a set of numeric keys by means of which the user can input numeric data, the tuner frequency display on the display screen including a digital display of the numeric value of the current selected frequency, the tuner frequency display control being responsive to input of numeric data via the numeric keys to change the digital display of the frequency in real time as the numeric data is being input, and the tuner frequency select control being operative upon completion by the user of the inputting of the numeric data to cause the frequency selector to automatically change the current selected frequency of the tuner to the frequency represented by the input numeric data.

In addition to the invention comprising a radio receiver, the invention also provides a method of controlling the operation of a radio receiver, and a computer program for controlling the operation of a radio receiver, the method and program comprising operations to control the display of data and user selectable inputs to enable user monitoring and user control of the radio receiver's operation. The essential and optional features of the method and program will be understood from the preceding and following description of a radio receiver utilising the method and program. It is most convenient to describe additional preferred and optionally possible features of the present invention in relation to the accompanying drawings. Brief description of the drawings

Fig. 1 is a schematic diagram of a radio receiver according to the present invention;

Fig. 2 is a functional block diagram of a card which is useable in a PC to provide the tuner and other operations;

Fig. 3 is a possible screen display for presenting data and enabling user selection of receiver functions;

Fig. 4 comprises schematic flow charts for some main functional operations of the control system implemented by computer program; and Fig. 5 shows additional screen display panels for a radio receiver providing additional functional capabilities. Detailed description of the exemplary embodiments

The receiver includes a tuner 10 which can be provided on a card for fitting to an expansion slot of a conventional PC. The tuner 10 may be, for example, a superheterodyne receiver. The card assembly 1 1 comprises a backplane 12 and shielded module 13, and is

5 designed to be plugged into a standard PC bus. All user I/O connections can be at the rear of the card, to be accessible from the outside of the PC.

The hardware connections can comprise: a. jacks 15, 16 for the connection of antenna 20; b a jack 25 for the connection of a speaker or headphones; 10 c. a multi-pin connector 30 containing for example the following signal lines:

( 1 ) a audio output for driving a tape recorder or other audio device;

(2) an open collector DC line, for activating an external audio device such as a tape recorder;

(3) data I/O line, to enable the PC to exchange data with an external device; 15 (4) a audio input, capable of accepting audio from an external audio source;

(5) DC power output.

The tuner 10 in Fig. 2 includes in the shielded module 13 a frequency synthesiser 17 and an RF front end circuit 18 (which respectively operate as the tunable local oscillator and mixer of the superheterodyne receiver) and which together function as a frequency selector

20 19 of the tuner for determining the current selected frequency. Processing circuit 21 receives the intermediate frequency signal and in conventional manner processes it, e.g. by filtering, amplification, demodulation and audio processing. Suitable power and interface circuits 22 are also provided for conventional purposes. Outside the shielded module 13, but on the card 1 1, are a microcontroller 26, A D and D/A converters 27, and external interface circuits 28

25 all for conventional purposes or for functioning as will be readily understood to the person skilled in the art.

The backplane 12 will accept an optional DSP module 80 to provide additional signal processing capabilities, such as audio filtering, demodulation, and signal recognition described later.

30 The control system 100, which is preferably a programmed PC computer in which the tuner 10 is connected, controls the operation of the tuner including operation of the frequency selector 19. A display screen 200 such as the VDU of the PC is also coupled to the control system 100 and the control system controls the presentation of data and the presentation of user selectable inputs by the display screen. An input peripheral device 101, shown as a computer keyboard 1 10 and mouse 120, is coupled to the control system 100 to enable the user to input data, information, and commands to the control system. 5 Because the radio receiver operates through a wide frequency range, e.g. 500 kHz to

1.2 GHz, RF noise generated by operation of electronic equipment forming part of the radio receiver (or being used in the proximity) can interfere with discrimination of wanted RF signals at many frequencies, or can cause spurious identification of signals e.g. when scanning, there is provided a background antenna. This comprise two individual antennas, a

10 CPU antenna 38 located inside the metal casing of the computer constituting the control system 100 to receive RF signals generated by the computer's CPU, and a peripheral antenna 39 located adjacent the computer monitor constituting the display 200 to receive RF signals generated by the monitor (and other local equipment such as printers, etc.). The RF signals are input from CPU antenna 38 and peripheral antenna 39 to the tuner 10 which subtracts this

15 background RF from the signals received from the main antenna 20, e.g. by reversing the phase, suitable scaling, and addition to the input from antenna 20.

Fig. 3 shows a possible presentation of data and user selectable inputs to be presented on the display screen 200 by operation of the control system 100. The displayed image 201 is shown being displayed as a Windows ™ application with information, icons and function bar

20 202 being provided at the top of screen. The image 201 is a simulation of the display of a sophisticated radio receiver so that the presentation of data to the user is readily identifiable and understandable. The image 201 also includes images of objects, particularly switches and knobs, which a user can identify and select for the purpose of inputting data or commands to the control system and hence to the tuner 10. The invention can be most readily understood

25 by describing the operation of the control system in conjunction with the presentation and operation of the user interface constituted by the display image 201.

The control system includes a receiver power control 130 (Fig. 4A) operative to cause display on the display screen 200 of an image of a power switch 210 having an off condition and an on condition and between which the user can toggle by inputting a power command 0 via the input peripheral device 101. The image 210 of the power switch is an image of a push button switch, the display screen 200 showing an image of the push button switch in a depressed position when in its on condition and in a projecting position when in its off condition

The receiver power control 130 is part of a computer software which implements most of the functional operations of the control system 100 When the software is first loaded or when the off condition of the power switch 210 is selected, the program means 131 cause the display of a quiescent image in which all of the simulated hardware features of the image 201 are displayed, but data displays (e g display of the frequency to which the tuner is set) and status of the radio receiver (such as the particular mode currently selected) are not displayed l e are blanked However, if desired, a user can configure the system via the menu item 203 so that there are some or all data displays active upon initial loading This quiescent image therefore simulates the user being presented with a radio receiver which is not yet switched on The tuner 10 is also maintained off or is disabled by program means 132

By user selection of the switch image 210, e g by pressing a hot key combination and/or by moving a cursor on-screen via the mouse 120 onto the on/off switch image 210 and clicking the mouse button 121, the control system is commanded by program means 133 to turn on the tuner 10 Also the program means 134 changes the image 201 to display an active image as shown in Fig 3 in which data displays and status displays are illuminated, so as to display the current frequency, the current selected mode of operation, etc The display therefore simulates a radio receiver which is turned on, displaying data and current receiver status

Data displays as shown in Fig 3 include a power on lamp 21 1 which is extinguished in the quiescent image but illuminated in the active image, a time and date display 212 (denved from the computer's internal date and time clock), output volume and squelch level displays 213, a memory display 230 having a currently selected channel indicator 231 indicating a channel identifier from memory (if a memorised channel is selected) and images 232 or 233 of "Store" and "Retrieve" switches which are user selectable to respectively pop up a menu for stoπng the currently selected frequency for future retrieval and to pop up a schedule of pre-programmed and/or user programmable frequencies, e g for radio stations, enabling user selection of a frequency or channel to which the receiver is instantly switched, a step display 240 including a step size display 242 for frequency stepping, a frequency display 220 to show the frequency to which the receiver is currently tuned.

The control system 100 includes program means functioning as a tuner frequency display control 140 (Figs. 4B to 4D) operative to cause the display 220 on the display screen

5 200 in real time of the current frequency being passed by the tuner 10; and a tuner frequency select control 141 responsive to input of a frequency change command by the user via the input peripheral device 101 to cause the frequency selector 19 of the tuner 10 to change the current selected frequency of the tuner in accordance with the frequency change command.

The frequency display 220 comprises a digital frequency display 221 and an analogue 0 dial display 222 although only one may be provided if desired. Below 1 MHz, the frequency may be displayed in kHz. At 1 MHz and above, it may be displayed in MHz.

The analogue frequency display 222 is in the form of an image of a graduated scale 228 and which is caused to move in real time past a fixed current frequency marker line 229 in response to input of the frequency change command to thereby indicate the current 5 selected frequency by the relative location of the marker 229 along the graduated scale 228. The tuner frequency display control 140 is also operative to cause display on the display screen 200 of a scale zoom control 224 which is user selectable via the input peripheral device 101 and which when selected initiates either magnification or reduction of the scale depicted by the image of the graduated scale 228. The illustrated zoom control 224 comprises magnify and reduce scale buttons selected by cursor positioning and clicking the mouse 120.

The image 201 includes user selectable tuner frequency modifiers 223 and 225 The modifiers 223 are arrow buttons selectable by positioning of the screen cursor on the button and clicking the mouse key (and/or pressing a hot key combination) to increment or decrement the frequency in certain step sizes.

The tuner frequency modifier image 225 comprises an image of an analogue tuning dial having markings 226, 227 to indicate a simulated rotational position of the dial. When the user selects the dial 225 and inputs the frequency change command via the input peripheral device 101 to cause the frequency selector 19 of the tuner 10 to change the current selected frequency, the tuner frequency select control 141 causes display on the display screen 200 in real time of an animation of rotation of the dial 225 for as long as the frequency change command is being input (see upper part of Fig. 4C). The image of the tuning dial is an image of a circular dial 225 having a marking 227 which occupies different angular positions relative to the centre of the circular dial in response to user selection of the dial and input of the frequency change command so as to thereby simulate rotation of the dial. The image of the dial 225 simulates rotation in a clockwise direction for a frequency change command to increase the current selected frequency and vice versa. The user selects the dial 225 by entering commands on the input peripheral device 101 so as to move a cursor 205 on the display screen 200 to position the cursor on the image of the dial and the user then inputs the frequency change command while the cursor is positioned on the image of the dial. The computer mouse 120 has a left mouse button 121 and a right mouse button 122, and as shown in Fig. 4C, user depression of the left mouse button 121 while the cursor 205 is located in the upper half of the image of the dial 225 initiates a decrement of the frequency and simulated rotation of the dial in a counter clockwise direction, depression of the right mouse button 122 while the cursor is in the upper half of the image of the dial initiates an increment of the frequency and simulated rotation of the dial in a clockwise direction, depression of the left mouse button 121 while the cursor is located in the bottom half of the image of the dial initiates an increment of the frequency and simulated rotation of the dial in a clockwise direction, and depression of the right mouse button while the cursor is located in the bottom half of the image of the dial initiates a decrement of the frequency and simulated rotation of the dial in a counter clockwise direction. As shown in Fig. 3, the control system 100 is operative to generate a cursor 205 on the display screen 200 having the shape of an arcuate double headed arrow when the cursor is positioned in the image 225 of the dial, the arcuate double headed arrow being concave downwardly when the cursor is positioned in the upper half of the image of the dial and being concave upwardly (as shown) when the cursor is positioned in the lower half of the image of the dial. The step size memory 145 stores desired incremental frequency step sizes by which the tuner frequency is changed when the user inputs the frequency change command. The stepping size memory 145 stores at least two incremental frequency step sizes, the smaller of which (e.g. a value of 1 kHz, or 10 kHz if in FM-W mode) is used by the control system 100 to determine the step size by which the tuner 10 changes the current selected frequency when the user selects the analogue tuning dial 225 and inputs the frequency change command whereby the tuning dial is selectable for enabling a fine tuning of the selected frequency. Faster stepping may be selected by the user. The tuner frequency select control 141 is responsive to input of the frequency change command by the user to change the frequency at one of two or more rates of change which is selectable by the user by a respective input via the input peripheral device 101. The keyboard 1 10 has auxiliary keys 1 1 1, such as the "Ctrl", "Shift", and "Alt" keys on a computer keyboard, the user selection of the different rates of change of the frequency being effected by depressing one of the auxiliary keys 1 1 1 of the keyboard 1 10 simultaneously with inputting the frequency change command. The inputting of the frequency change command without depression of one of the auxiliary keys 11 1 causes the frequency selected to change at a base rate of change, inputting of the frequency change command simultaneously with depression of a first one of the auxiliary keys 1 1 1 such as the "Shift" key causes the frequency selected to change at ten times the base rate, and inputting of the frequency change command simultaneously with depression of a second one of the auxiliary keys 1 1 1 such as the "Alt" key causes the frequency selected to change at one hundred times the base rate. The selection of different rates of frequency change is available with both systems for issuing the frequency change command, i.e. (1 ) manipulating the mouse 120 to position a cursor 205 on a screen image of a frequency modifier 223, 225 and then depressing the mouse button 121. and (2) depressing either the "up" or "down" arrow key 1 12, 1 13 on the computer keyboard 1 10.

In addition to selecting and activating frequency modifiers 223, 225 in the image 201 and using the "up" and "down" arrow keys 1 12, 1 13, the frequency may also be changeable by typing in a new frequency on the keyboard 1 10. The keyboard 110 includes a set of numeric keys 1 15 by means of which the user can input numeric data. As shown in Fig. 4D the tuner frequency display control 140 is responsive to input of numeric data via the numeric keys 1 15 to change the digital display 221 of the frequency in real time as the numeric data is being input, and the tuner frequency select control 141 is operative upon completion by the user of the inputting of the numeric data to cause the frequency selector 19 to automatically change the current selected frequency of the tuner 10 to the frequency represented by the input numeric data. The keyboard 110 includes alphabetic keys 116 including at least K and M keys which, when selected after at least one numeric key 1 15 has been used to input numeric data, indicate that the numeric data represents frequency measured in kHz and MHz respectively. The keyboard 1 10 has an Enter key 117 which, when selected after entry of numeric data by means of the numeric keys 1 15, constitutes the frequency change command. If the user attempts to enter a frequency outside the allowable limits (as determined by the currently selected mode to be described later) the control system 10 can be operative to an error signal such as a beep, briefly display "Invalid frequency" or the like on the screen and either abort the process or make an assumption of the desired frequency value, e.g. assuming MHz if a frequency less than the capability of the tuner is entered.

To permit quick setting of the receiver to channelised frequencies, it is possible to select a step size, which is any number resulting in permissible frequencies. If the arrow keys 1 12, 1 13 or frequency modifier images 223 are selected, the radio should step by the selected increment. If the radio is tuned to such a frequency that the next step would be to a frequency which is outside the available range, stepping should cease and the PC should issue an appropriate alert to the user.

The user is able to select an option whereby the step size is automatically adjusted according to frequency band, unless another step size has been selected. For example, the initial defaults may include: a. 531 - 1620 kHz (AM band): step = 9 kHz (or 10 kHz in North America) b. 87.5 - 108 MHz (FM-N band): step = 50 kHz The user is able to add new ranges, and edit or delete existing ones. The control system 10 includes a scan control 160 (Fig. 4B) selectively operable to cause the frequency selector 17 of the tuner 10 to change the current selected frequency of the tuner by a first desired incremental frequency step size, and a receiver operating mode control 170 operative to cause a display 250 on the display screen 200 in real time of the current mode of operation of the tuner, the mode of operation including at least the current frequency band of the tuner operation. The step size memory 145 stores a magnitude of the first frequency step size by which the tuner frequency is to be changed when the scan control is operating and for storing a second desired incremental frequency step size by which the tuner frequency is to be changed when the user inputs the frequency change command to step up or to step down from the instantaneous selected tuner frequency. Program means 175 functions as a mode and step size switch responsive to the tuner frequency select control 141 and to the scan control 160 and operative if the current selected frequency enters a different band when it is being changed to automatically change the tuner 10 to the appropriate mode of operation for the different band by operation of the band change program means 176 and to automatically retrieve from the stepping size memory 145 the appropriate first or second frequency step size for the different band for use in controlling incremental frequency changes of the current selected frequency. The control system 100 further includes program means 177 operating as an auto stepping switch which, upon user selection of an auto stepping switch image 241 displayed on the display screen 200, is operative in determination of incremental changes in the current selected frequency. When the user inputs the frequency change command, the frequency selector 19 operating in response to the frequency select control 141 changes the current selected frequency by the second incremental frequency step size and when the scan control 160 is operated the frequency selector 19 changes the current selected frequency by the first incremental frequency step size. The frequency step size when the frequency change command is input or when the scan control 160 is operated and when the auto stepping switch 241 is not selected is a system default step size able to have a different value to the first and second frequency step sizes.

The first and second incremental frequency step sizes and the system default step size are each independently user programmable. The first frequency step size can be equal to the second frequency step size, so that user initiated frequency stepping or automatic frequency scanning both use the same frequency increments.

The mode and step size switch 175 is responsive to both the tuner frequency select control 141 when user initiated and the scan control 160 so that, if the current selected frequency enters a different band, the appropriate mode of operation of the tuner 10 is automatically commenced and also the relevant first or second incremental frequency step size is automatically retrieved from the stepping size memory 145 for controlling the frequency increments.

The possible frequency bands of the tuner operation include the SSB band (including LSB and USB), AM band, wide-band FM band, and narrow-band FM band. The receiver further includes a beat frequency oscillator (BFO) 180 operative to re-establish at the receiver the suppressed carrier frequency of an SSB signal received, the receiver further including a BFO offset control which is user operable by selection of a BFO offset image 262, 263 generated on the display screen 200 by the control system to adjust in small frequency increments the frequency of the BFO above or below the current selected frequency of the tuner 10 so as to thereby fine tune the reception of the SSB signal received.

The control system 100 further includes a receiver operating mode select control 182 (Fig. 4E) operative in response to input of a mode change command by the user via the input peripheral device 101 to switch the current operating mode from the mode determined by the mode and step size switch 175 for the band in which the current selected frequency falls to the mode selected by the user.

In operation, to change step sizes, the user can position the cursor on the select switch 5 241 in the step display 240 and by clicking on the select switch 241 can toggle between an "Auto-step" mode of stepping and scanning as described above, and a "Fixed step" mode of stepping and scanning using default step sizes. The step sizes, whether pre-programmed or user input, may be the same or different for different frequency bands. For example in AM broadcast bands, the frequency allocations to broadcasters are separated by internationally or nationally standardised intervals. These intervals can be different for different countries so that user alternatives to the default stepping intervals is provided for more efficient scanning.

A "fixed step" mode can provide for steps of 1 kHz. Conventional receivers often use 5 or 12.5 kHz steps. However, the present invention can provide high accuracy and simulated analogue (continuous) tuning by tuning in 1 kHz steps by way of a programmable 5 phase locked loop which has separate numerator and denominator inputs and using the computer to determine which numerator and which denominator will allow closest tuning at the selected frequency Therefore upon each increment of frequency, many divisions, comparisons and other calculations may be undertaken by the computer in iterative steps to calculate the closest quotient to the selected frequency whilst still having real time display and operation.

The control system causes a display 250 by the display screen 200 in real time of the current mode of operation of the tuner which includes the mutually exclusive operating modes of the receiver. The user can select any of the modes, either by clicking on the appropriate button 252-255, or hotkey combination (e.g. alphabetic key B, N, W, or A 5 respectively) The current mode is displayed, e.g. by highlighting or illuminating, or showing the selected button as an image of a depressed push button switch - see FM-N switch 253 in Fig. 3

As shown in Fig. 4E, the control system is operative when a new mode switch is selected by the user to de-highlight the previously selected mode switch and to highlight the newly selected mode switch. If SSB mode switch 252 is selected, the BFO offset display 260 can be illuminated, this image section 260 being quiescent if AM or FM mode is selected The BFO offset can be user adjusted e.g. in 5 Hz steps by selection and operation of the arrow icons 261 while the BFO offset value is displayed in the display window 262. Selectable Reset switch image 263 is also provided for resetting a default BFO offset e.g. zero Hz. The offset may be an integer between predefined upper and lower frequency limits. When the user is changing the offset, the frequency offset displayed by the window 262 is continuously updated in real time. Direct numeric keyboard entry of the offset value is also possible by locating the cursor on window 262 and inputting the desired value.

As previously described the control system includes a scan control 160 to cause the frequency selector 19 of the tuner 10 to change the current selected frequency of the tuner by scanning through different frequencies. The scan mode control is operative to cause display on the display screen 200 of an image of a user selectable scan mode modifier 310, the control system 100 being operative, in response to user selection of the image of the scan mode modifier via the input peripheral device 101 to enable the frequency selector 19 of the tuner 10 to commence to automatically scan through frequencies different from the current selected frequency of the tuner when the scan control is operated. The scanning mode can be selected by the user from the modes:

(i) a first mode consisting of scanning of the frequency up or down from the current selected frequency in steps of the first desired incremental frequency step size, stored in memory 145 as described previously; (ii) a second mode consisting of scanning of the frequency through a defined range of frequencies, and

(iii) a third mode consisting of scanning of the frequency through a number of specific frequencies stored in a frequency memory. The scan control 160 is operated in the first scanning mode by selecting either the scan down button 31 1 or the scan up button 312. For scanning in the second mode, the user selects the Range scan button 313. The user is presented with a menu which enables access to a scan range memory 167 which can store at least two user definable ranges of frequencies through one or more of which the scan control 160 can scan the current selected frequency of the tuner 10.

For scanning in the third mode, the user selects the Memory scan button 315 and the system presents a menu to enable selection of options, such as defining a group or groups of memorised frequencies through which to scan. The frequencies are stored in a frequency memory 168 which may comprise a data base of both known listed allocated transmitting frequencies and user stored frequencies (stored previously e.g. via memory store button 232). During scanning in the third mode, the respective channel identifier stored in memory is displayed by indicator 231 as such frequency is selected.

The control system 100 is operative to generate for the user upon selection of the Setup button 314 a scanner configuration menu which presents scanning options selectable by the user, the scanning options including at least two and preferably all of the following options:

(a) stop scanning when an input signal is detected,

(b) pause upon detection of an input signal and remain indefinitely at that frequency unless that input signal disappears, whereupon resume scanning,

(c) pause upon detection of an input signal for a predetermined (user programmable) pause time and remain at that frequency even if the input signal disappears in the pause time, and

(d) pause upon detection of an input signal for the predetermined pause time, but resume scanning if the input signal disappears in the pause time. The selected scanning option is consulted and followed whichever mode of scanning is active.

When the scanning stops or pauses upon detection of an input signal, the control systems may have program means operative to generate on screen a menu of user selectable options, including an option to write the current selected frequency to memory for later retrieval and tuning to the same frequency. Other otpiosn can include "stop scanning" (if pause only is otherwise operative) and "resume scanning" (for immediate resumption of scanning).

The control system also includes a scan rate memory 169 in which a scan rate value is stored determining the number of frequency changes per second effected by the frequency selector when the scan control is operated, the value in the scan rate memory 169 being programmable by the user through the menu presented on selection of the Setup button 314. The user can select two levels of sensitivity to reduce overloading or distortion when strong signals are present or to improve reception of weak signals by selecting maximum sensitivity switch 271 or local switch 272 of Sensitivity display 270. The user can change the volume by clicking on up/down buttons 214, or by pressing the left and right arrow keys on the keyboard, or if desired by hotkeying and entering a number. The volume should change simultaneously with the button 214 or arrow key being pressed.

When an FM mode is selected, the user may change the squelch level by clicking on up/down buttons 215 or, if desired, by hotkeying and entering a number. The squelch level should change simultaneously with the buttons 215 being pressed. An additional Mute button 213 is provided to instantly suppress the audio output.

The radio receiver embodying the present invention may provide additional functions in a more sophisticated embodiment, the screen displays of data and user selectable inputs being illustrated in Fig. 5. An auto calibrate mode can be provided to enable the radio receiver to be calibrated to compensate for frequency drift particularly due to temperature variations of components. When the AutoCal mode switch 257 is selected and activated, as shown in Fig. 4G the control system 100 causes the tuner to tune to a standard frequency transmission such as an accurately known radio station, measure the frequency error between the received standard frequency and the synthesised frequency of the tuner (using the digital signal processor described later), record the temperature measured by the temperature sensor 58 provided inside the module 13, and store in memory the data relating to frequency corrections subsequently to be used during RF signal reception at various different temperatures.

The display section 290 includes selectable "Identify" switch 291 which the user can select to cause a screen to pop up providing, for example, further identification information concerning the selected frequency band, e.g. "FM broadcasting band" or other stored descriptions of bands. The screen may also provide for example a list of transmitting stations within a particular range, e.g. + or - 5 kHz of the instantaneous frequency. The user can delete or edit identified stations. If desired, once selected, a map can be displayed showing transmitting stations located on the map. Stored longitude and latitude for each station can enable such display. During set up of the system, the user can input the site of use. e.g. "Melbourne", and the program can automatically highlight stations within a certain radius of the site when the identify screen is popped up.

The "Record" switch 292 upon user selection starts an external tape recorder or can, with signal compression, create a computer file where the received signal (demodulated or not) is stored. User selection of the "Repeat" switch 293 enables replay of the signal received for example within a preceding time interval For example incoming signals can be automatically stored in a buffer where the received signal from a programmable time interval, e g 20 seconds, is continuously stored The "Repeat" switch 293 replays this 20 seconds of signal e g to enable the user to attempt again to discriminate faint or noisy signals

The control system provides a user selectable log facility which when selected by the user operation of log button 294 automatically stores in a memory log the current selected frequency and the current date and time, and provides the user with a prompt for optional user entry of user comments concerning the radio signal received The memory log is retrievable by the user at a later time

The scale display 295 indicates in real time a measure of the accuracy of tuning or the strength of the signal, e g by a luminous bar, the length of which is proportional to the signal strength

The PLL display 218 comprises an illuminated display active when the phase locked loop is operating

It is possible for the control system to control the radio reception and receive and process the signal that is received by the radio For example, the output of tuner 10 becomes the input of control system 100 and the output can be displayed on display 200 or processed for other uses The receiver preferably further includes a digital signal processor (DSP) module 80 which may be an additional card connected to the card assembly 1 1 The DSP module is operative under the control of the control system to digitally process the audio output from the module 13 The displayed image 201 includes a DSP data display and selectable input display 280 By selecting the filter switch 281, the receiver can process the received signals in the DSP module 80 by digital filtering enhancement procedures so as to reduce noise and interference for improved signal clarity

By selecting the decode switch 282, the receiver can monitor a signal being received and can recognise and decode certain signals such as morse code, radio teletype, and other digitally encoded signals automatically in real time The decoded text can be displayed on screen as it is being received and decoded and/or can be stored to a file on the computer or can be output for other storage or processing For example the receiver can be programmed to monitor particular frequency bands continuously search for key words specified by the user (for example "SOS" in morse code), and in response initiate such further action as has been specified by the user, for example raising an alarm and/or storing the signal on the PC's hard disk or a tape recorder. The DSP can also be operated to compress and store analogue signals for later decompression for listening or processing. Operation of the display switch 283 causes the control system to instruct the DSP to analyse signals, e.g. for real time signal spectrum display by the display window 284.

In particular, when the DSP functions as a spectrum analyser it is operative when selected by the user to initiate a scan through a range of frequencies and a display on the display screen 284 of a spectrum comprising a plot 285 of received input signal strength through the range of frequencies. The input peripheral device 10 including a cursor moving means 120 operable by the user to position a cursor on the display screen 200 on any peak in the displayed spectrum 285, the control system being operative in response to entry of a tune command by the user when the cursor has been positioned on the selected peak (e.g. a click of the mouse button 121 ) to cause the frequency selector 19 to shift the current selected frequency to the particular frequency represented by selected peak in the displayed spectrum 285.

The control system 100 can be operative to display the present squelch level, e.g. as a proportion of the signal strength, as a bar graph similar to signal strength display 295. Because of absolute value changes in signal strength, as well as changes in signal strength relative to the background level, the control system can be programmed to automatically vary the squelch level e.g. as a function of both background level and instantaneous signal level. Thus, if a strong signal is being received much stronger than background noise around that frequency, the squelch level may shift to a relatively high level. One possibility is to automatically adjust the squelch level to a level higher than the average noise level by a (user programmable) percentage of the signal strength above the average noise level. The automatic squelch level variation may be operative while tuned to a particular frequency and/or while changing frequencies (e.g. when scanning).

The status of the receiver can be saved in a configuration file when exiting to be recalled when the next sessions commences.

Claims

CLAIMS 1 A radio receiver comprising: an RF tuner which is operative to receive an input RF signal from an antenna, the tuner including a frequency selector for determining the current selected frequency so that the tuner produces an output signal derived from the selected RF frequency and which can be supplied to a peripheral output device; a control system coupled to the tuner so as to control the operation thereof including operation of the frequency selector; a display screen coupled to the control system, the control system being operative to control the presentation of data and the presentation of user selectable inputs by the display screen; an input peripheral device coupled to the control system and by means of which the user can input data or information or commands to the control system; the control system including: a tuner frequency display control operative to cause display on the display screen in real time of the current frequency being passed by the tuner; and a tuner frequency select control responsive to input of a frequency change command by the user via the input peripheral device to cause the frequency selector of the tuner to change the current selected frequency of the tuner in accordance with the frequency change command.

2 A radio receiver as claimed in claim 1, the control system further including: a scan control selectively operable to cause the frequency selector of the tuner to change the current selected frequency of the tuner by a first desired incremental frequency step size; a receiver operating mode control operative to cause display on the display screen in real time of the current mode of operation of the tuner, the mode of operation including at least the current frequency band of the tuner operation; a stepping size memory for storing a magnitude of the first frequency step size by which the tuner frequency is to be changed when the scan control is operating and for storing a second desired incremental frequency step size by which the tuner frequency is to be changed when the user inputs the frequency change command to step up or to step down from the instantaneous selected tuner frequency; and a mode and step size switch responsive to the tuner frequency select control and/or to the scan control and operative if the current selected frequency enters a different band when it is being changed to automatically change the tuner to the appropriate mode of operation for the different band and to automatically retrieve from the stepping size memory the appropriate first or second frequency step size for the different band for use in controlling incremental frequency changes of the current selected frequency.

3. A radio receiver as claimed in claim 2, wherein the control system further includes an auto stepping switch which, upon user selection of an auto stepping switch image displayed on the display screen, is operative in determination of incremental changes in the current selected frequency, whereby when the user inputs the frequency change command the frequency selector changes the current selected frequency by the second incremental frequency step size and when the scan control is operated the frequency selector changes the current selected frequency by the first incremental frequency step size, the frequency step size when the frequency change command is input or when the scan control is operated and when the auto stepping switch is not selected being able to have a different value to the first or second frequency step size.

4. A radio receiver as claimed in claim 2 or 3 wherein the first frequency step size is equal to the second frequency step size.

5. A radio receiver as claimed in any one of claims 2 to 4 wherein the mode and step size switch is responsive to both the tuner frequency select control and the scan control so that, if either is operated, and the current selected frequency enters a different band, the appropriate mode of operation of the tuner is automatically commenced and also the relevant first or second incremental frequency step size is automatically retrieved from the stepping size memory for controlling the frequency increments.

6. A radio receiver as claimed in any one of claims 2 to 5 wherein the first and second incremental frequency step sizes are each independently user programmable

7. A radio receiver as claimed in any one of claims 2 to 6 wherein the possible frequency bands of the tuner operation include the SSB band, AM band, wide-band FM band, and narrow-band FM band, the receiver further including a beat frequency oscillator (BFO) operative to re-establish at the receiver the suppressed carrier frequency of an SSB signal received, the receiver further including a BFO offset control which is user operable by selection of a BFO offset image generated on the display screen by the control system to adjust in small frequency increments the frequency of the BFO above or below the current selected frequency of the tuner so as to thereby fine tune the reception of the SSB signal received.

8. A radio receiver as claimed in any one of claims 2 to 7 wherein the control system 5 further includes a receiver operating mode select control operative in response to input of a mode change command by the user via the input peripheral device to manually switch the current operating mode from the mode determined by the mode and step size switch for the band in which the current selected frequency falls to the mode selected by the user.

9. A radio receiver as claimed in claim 1 wherein:

10 the tuner frequency select control is operative to cause display on the display screen of an image of a user selectable tuner frequency modifier, the control system being operative, firstly, in response to user selection of the tuner frequency modifier image via the input peripheral device, to cause the frequency selector of the tuner to change the current selected frequency of the tuner in accordance with the user selection, the tuner frequency modifier

15 image comprising an image of an analogue tuning dial having markings to indicate a simulated rotational position of the dial and, secondly, when the user selects the dial and inputs the frequency change command via the input peripheral device to cause the frequency selector of the tuner to change the current selected frequency, the tuner frequency select control causes display on the display screen in real time of an animation of rotation of the dial for as long as

20 the frequency change command is being input: the control system further including a stepping size memory for storing a desired incremental frequency step size by which the tuner frequency is to be changed when the user inputs the frequency change command to step up or to step down from the instantaneous tuner frequency.

25 10. A radio receiver as claimed in claim 9 wherein the image of the tuning dial is an image of a circular dial having a marking which occupies different angular positions relative to the centre of the circular dial in response to user selection of the dial and input of the frequency change command so as to thereby simulate rotation of the dial.

1 1. A radio receiver as claimed in claim 10 wherein the image of the dial simulates rotation

30 in a clockwise direction for a frequency change command to increase the current selected frequency and vice versa.

12. A radio receiver as claimed in claim 1 1 wherein the user selects the dial by entering commands on the input peripheral device so as to move a cursor on the display screen to position the cursor on the image of the dial and the user then inputs the frequency change command while the cursor is positioned on the image of the dial.

13. A radio receiver as claimed in claim 12 wherein the input peripheral device comprises a computer mouse having a left mouse button and a right mouse button, user depression of the left mouse button while the cursor is located in the upper half of the image of the dial initiates a decrement of the frequency and simulated rotation of the dial in a counter clockwise direction, depression of the right mouse button while the cursor is in the upper half of the image of the dial initiates an increment of the frequency and simulated rotation of the dial in a clockwise direction, depression of the left mouse button while the cursor is located in the bottom half of the image of the dial initiates an increment of the frequency and simulated rotation of the dial in a clockwise direction, and depression of the right mouse button while the cursor is located in the bottom half of the image of the dial initiates a decrement of the frequency and simulated rotation of the dial in a counter clockwise direction.

14. A radio receiver as claimed in claim 13 wherein the control system is operative to generate a cursor on the display screen having the shape of an arcuate double headed arrow only when the cursor is positioned in the image of the dial, the arcuate double headed arrow being concave downwardly when the cursor is positioned in the upper half of the image of the dial and being concave upwardly when the cursor is positioned in the lower half of the image of the dial.

15. A radio receiver as claimed in any one of claims 9 to 14 wherein the stepping size memory stores at least two incremental frequency step sizes, the smaller of which is used by the control system to determine the step size by which the tuner changes the current selected frequency when the user selects the analogue tuning dial and inputs the frequency change command whereby the tuning dial is selectable for enabling a fine tuning of the selected frequency.

16. A radio receiver as claimed in claim 1 wherein the control system further includes: a scan control selectively operable to cause the frequency selector of the tuner to change the current selected frequency of the tuner by scanning through different frequencies; a scan mode control operative to cause display on the display screen of an image of a user selectable scan mode modifier, the control system being operative, in response to user selection of the image of the scan mode modifier via the input peripheral device to enable the frequency selector of the tuner to commence to automatically scan through frequencies different from the current selected frequency of the tuner when the scan control is operated, the scanning occurring according to a mode of scanning selected by the user from the modes: 5 (i) a first mode consisting of scanning of the frequency up or down from the current selected frequency in steps of a first desired incremental frequency step size, (ii) a second mode consisting of scanning of the frequency through a defined range of frequencies, and 10 (iii) a third mode consisting of scanning of the frequency through a number of specific frequencies stored in a frequency memory; and a stepping size memory for storing a magnitude of the first desired incremental frequency step size by which the tuner frequency is to be changed when the scan control is operating in the first scanning mode. 15

17. A radio receiver as claimed in claim 16 wherein the first frequency step size is stored in the stepping size memory for a particular frequency band, a different first frequency step size being stored in the stepping size memory for a different frequency band whereby when the scan control is operating and the current selected frequency of the tuner shifts to a different frequency band, the frequency step size automatically changes to the appropriate magnitude 0 for the new frequency band.

18. A radio receiver as claimed in claim 17 wherein the first frequency step size for at least one frequency band is user programmable.

19. A radio receiver as claimed in any one of claims 16 to 18 wherein the control system includes a scan range memory which stores at least two user definable ranges of frequencies 5 through one or more of which the scan control can scan the current selected frequency of the tuner during the second mode of scanning.

20. A radio receiver as claimed in any one of claims 16 to 19 wherein the frequency memory stores channel identifiers for respective stored specific frequencies and the control system is perative to generate on the display screen in real time the respective channel 0 identifier for the selected one of the stored specific frequencies during the third mode of scanning.

21. A radio receiver as claimed in any one of claims 16 to 20 wherein, upon user selection of the third mode of scanning, the control system is operative to present on the display screen a menu of memory scanning options including a user selectable option of scanning through a user defined portion only of the memory contents. 5

22. A radio receiver as claimed in any one of claims 16 to 21 wherein, when scanning in the first and/or second modes and an input signal is received causing a stop or pause in scanning, the control system is operative to present to the user on the display screen a user selectable menu of options including an option to write the current selected frequency to memory for later retrieval and tuning to the same frequency.

10 23. A radio receiver as claimed in any one of claims 16 to 22 wherein the control system is operative to generate for the user a scanner configuration menu which presents scanning options selectable by the user, the scanning options including at least two of the following options:

(a) stop scanning when an input signal is detected,

15 (b) pause upon detection of an input signal and remain indefinitely at that frequency unless that input signal disappears, whereupon resume scanning,

(c) pause upon detection of an input signal for a predetermined pause time and remain at that frequency even if the input signal disappears in the pause time, and

(d) pause upon detection of an input signal for a predetermined pause time, but 0 resume scanning if the input signal disappears in the pause time.

24. A radio receiver as claimed in any one of claims 16 to 23 wherein the control system includes a scan rate memory in which a scan rate value is stored determining the number of frequency changes per second effected by the frequency selector when the scan control is operated, the value of the scan rate value in the scan rate memory being programmable by the 5 user.

25 A radio receiver as claimed in claim 1 wherein the tuner frequency select control is responsive to input of the frequency change command by the user to change the frequency at one of two or more rates of change which is selectable by the user by a respective input via the input peripheral device, the control system further including a stepping size memory for 0 storing a magnitude of a frequency step size by which the tuner frequency is to be changed when the frequency change command is input.

26. A radio receiver as claimed in claim 25 wherein the input peripheral device includes a keyboard having auxiliary keys, the user selection of the different rates of change of the frequency being effected by depressing one of the auxiliary keys of the keyboard simultaneously with inputting the frequency change command.

27. A radio receiver as claimed in claim 26 wherein the auxiliary keys are chosen from the "Ctrl", "Shift", and "Alt" keys of a computer keyboard.

28. A radio receiver as claimed in claim 26 or 27 wherein the inputting of the frequency change command without depression of one of the auxiliary keys causes the frequency selected to change at a base rate of change, inputting of the frequency change command simultaneously with depression of a first one of the auxiliary keys causes the frequency selected to change at ten times the base rate, and inputting of the frequency change command simultaneously with depression of a second one of the auxiliary keys causes the frequency selected to change at one hundred times the base rate.

29. A radio receiver as claimed in any one of claims 25 to 28 wherein the input peripheral device also includes a computer mouse having a mouse button and the frequency change command is issued by the user manipulating the mouse to position a cursor on a screen image of a frequency modifier icon and then depressing the mouse button.

30. A radio receiver as claimed in any one of claims 26 to 28 wherein the frequency change command is issued by the user by depressing either the "up" or "down" arrow key on the computer keyboard.

31. A radio receiver as claimed in claim 1 wherein the control system further includes: a receiver operating mode control operative to cause display on the display screen in real time of the current mode of operation of the tuner, the mode of operation including at least the current frequency band of the tuner operation; and a receiver power control operative to cause display on the display screen of an image of a power switch having an off condition and an on condition and between which the user can toggle by inputting a power command via the input peripheral device, the receiver power control being operative when the off condition of the power switch is selected firstly to cause display on the display screen of a quiescent image of a radio control panel with data presented on the display screen including the display of the current selected frequency being blanked and secondly to cause the tuner to be disabled, the receiver power control being operative when the on condition of the power switch is selected firstly to cause display on the display screen of an active image of the radio control panel with data being presented on the display screen including the current selected frequency and secondly to cause the tuner to be enabled.

32. A radio receiver as claimed in claim 31 wherein the input peripheral device comprises a computer mouse having a mouse button and wherein the user inputs the power command to

5 toggle between the on and off conditions of the power switch by manipulating the mouse to position a cursor on the image of the power switch and then depressing the mouse button.

33. A radio receiver as claimed in claim 31 or 32 wherein the image of the power switch is an image of a push button switch, the display screen showing an image of the push button switch in a depressed position when in its on condition and in a projecting position when in its

10 off condition.

34. A radio receiver as claimed in any one of the preceding claims wherein the input peripheral device includes a set of numeric keys by means of which the user can input numeric data, the tuner frequency display on the display screen including a digital display of the numeric value of the current selected frequency, the tuner frequency display control being

15 responsive to input of numeric data via the numeric keys to change the digital display of the frequency in real time as the numeric data is being input, and the tuner frequency select control being operative upon completion by the user of the inputting of the numeric data to cause the frequency selector to automatically change the current selected frequency of the tuner to the frequency represented by the input numeric data.

20 35. A radio receiver as claimed in claim 34 wherein the input peripheral device includes alphabetic keys including at least K and M keys which, when selected after at least one numeric key has been used to input numeric data, indicate that the numeric data represents frequency measured in kHz and MHz respectively.

36. A radio receiver as claimed in claim 34 or 35 wherein the input peripheral device 25 includes an Enter key which, when selected after entry of numeric data by means of the numeric keys, constitutes the frequency change command.

37. A radio receiver as claimed in any one of the preceding claims wherein the tuner frequency display control is operative to cause display on the display screen of an analogue frequency display in the form of an image of a graduated scale and which is caused to

30 relatively move in real time past a current frequency marker in response to input of the frequency change command to thereby indicate the current selected frequency by the relative location of the marker along the graduated scale.

38. A radio receiver as claimed in claim 37 wherein the tuner frequency display control is operative to cause display on the display screen of a scale zoom control which is user selectable via the input peripheral device and which when selected initiates either magnification or reduction of the scale depicted by the image of the graduated scale.

39. A radio receiver as claimed in any one of the preceding claims wherein the control system includes a spectrum analyser operative when selected by the user to initiate a scan through a range of frequencies and a display on the display screen of spectrum comprising a plot of received input signal strength through the range of frequencies, the input peripheral device including a cursor moving means operable by user to position a cursor on the display screen on any peak in the displayed spectrum, the control system being operative in response to entry of a tune command by the user when the cursor has been positioned on the selected peak to cause the frequency selector to shift the current selected frequency to the particular frequency represented by selected peak in the displayed spectrum.

40. A radio receiver as claimed in any one of the preceding claims wherein the control system provides a user selectable log facility which when selected by the user automatically stores in a memory log the current selected frequency and the current date and time, and provides the user with a prompt for optional user entry of user comments concerning the radio signal received, the memory log being retrievable by the user at a later time.

41. A radio receiver as claimed in any one of the preceding claims and further including a background antenna for receiving background RF signals from local RF sources, the background antenna being connected to the tuner, the tuner being operative to compensate the input RF signal by subtracting the background RF signals so as to enable better sensitivity of the receiver to a wanted signal at the selected RF frequency.

42. A radio receiver as claimed in claim 41 wherein the background antenna is located so as to receive and input to the tuner background RF signals generated by electronic equipment which forms part of the radio receiver.

43. A radio receiver as claimed in claim 42 wherein the control system includes a programmed computer inside a metal casing, the background antenna including a CPU antenna located inside the metal casing to receive RF signals generated by the CPU and other computer components during operation of the computer.

44. A radio receiver as claimed in claim 42 or 43 wherein the display screen comprises a computer monitor, the background antenna including a peripheral antenna located in proximity to the monitor so as to receive RF signals generated by the monitor during operation thereof.