US3769575A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Metal detector using radio receiver and r-f probe
Assignee: Tanner Electronics Systems Technology Inc
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Filing: 1971-06-30
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Granted: 1973-10-30
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Expires: 1991-06-30
Abstract
Abstract A metal locating system is disclosed wherein a unitary R-F oscillator is disposed on a probe board including all necessary electrical components thereof and its power supply. The oscillator is operated at a frequency such that a harmonic thereof falls within the range of and is beat against the local oscillator signal of a typical inexpensive superheterodyne broadcast radio receiver. The receiver is used as a detector and produces an audible heterodyne whistle or beatnote. When the probe board is brought in proximity to a metallic object the R-F oscillator frequency is varied to produce an audible change in the beatnote frequency. The radio may be located remotely from the probe as, for example in the user''s pocket.
Inventors
- 👤 B Rist
- 👤 J Tanner
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 07:42
CPC Classifications
G; G01; G01V; G01V3/00; G01V3/15
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
166 words
A metal locator system comprising: a probe mounting member; an oscillator probe attached to sAid member and having an oscillator disposed thereon for generating and radiating a radio signal of a frequency within the capture range of a common radio receiver''s intermediate frequency amplifier, the frequency of said radio frequency signal varying as a function of the proximity of said probe to a metallic object; and a superheterodyne radio receiver including at least a local oscillator and a second detector positioned proximate said probe, said receiver being tunable to a frequency such that said local oscillator signal is heterodyned by a suitable harmonic of the radio frequency produced by said oscillator probe to produce an audible whistle from said receiver, said harmonic being generated in said second detector; whereby when said oscillator probe is positioned proximate to a metallic object, the radio frequency being radiated thereby is changed to produce a change in the frequency of said whistle to indicate the presence of the metallic object.
Claim 2
Dependent Claim
166 words
A metal locator system comprising: a probe mounting member; an oscillator probe attached to sAid member and having an oscillator disposed thereon for generating and radiating a radio signal of a frequency within the capture range of a common radio receiver''s intermediate frequency amplifier, the frequency of said radio frequency signal varying as a function of the proximity of said probe to a metallic object; and a superheterodyne radio receiver including at least a local oscillator and a second detector positioned proximate said probe, said receiver being tunable to a frequency such that said local oscillator signal is heterodyned by a suitable harmonic of the radio frequency produced by said oscillator probe to produce an audible whistle from said receiver, said harmonic being generated in said second detector; whereby when said oscillator probe is positioned proximate to a metallic object, the radio frequency being radiated thereby is changed to produce a change in the frequency of said whistle to indicate the presence of the metallic object.
Claim 3
Dependent Claim
127 words
A metal locating system comprising: a probe mounting member; oscillator probe means disposed on said probe mounting member for generating a radiating radio frequency signal the frequency of which is within the capture range of a common radio receiver''s intermediate frequency amplifier and varies as a function of the proximity of said probe to a metallic object; a heterodyne receiver located proximate said probe means and having its local oscillator tunable to a frequency differing from a harmonic of said probe radio frequency signal by a frequency difference within the audible range, whereby when said probe means is moved proximate a metal object said heterodyne receiver will produce an audible signal which varies in pitch due to the interaction of said metal object with said probe means.
Claim 4
Dependent Claim
127 words
A metal locating system comprising: a probe mounting member; oscillator probe means disposed on said probe mounting member for generating a radiating radio frequency signal the frequency of which is within the capture range of a common radio receiver''s intermediate frequency amplifier and varies as a function of the proximity of said probe to a metallic object; a heterodyne receiver located proximate said probe means and having its local oscillator tunable to a frequency differing from a harmonic of said probe radio frequency signal by a frequency difference within the audible range, whereby when said probe means is moved proximate a metal object said heterodyne receiver will produce an audible signal which varies in pitch due to the interaction of said metal object with said probe means.
Claim 5
Dependent Claim
30 words
The system of claim 2 wherein said oscillator in said probe means comprises: a printed circuit board having the oscillator circuit components and the battery power supply therefor positioned thereon.
Claim 6
Independent Claim
148 words
The method of producing an audible signal to identify the presence of metal, comprising the steps of: generating a radiating R-F signal at a frequency such that said signal is within the frequency range of a common radio receiver''s intermediate frequency amplifier capture range; generating a local oscillator signal in a superheterodyne radio receiver at a frequency differing from a harmonic of said R-F signal by a frequency difference within the audible range; detecting the local oscillator signal and generating the harmonic of said R-F signal in the second detector part of the I-F amplifier of the superheterodyne receiver to produce an audible beat note signal in the audio amplifier of said superheterodyne receiver; and changing the frequency of the R-F radiating signal and the harmonic thereof as a metallic object is approached to produce a change in the frequency of the audible frequency in said audio amplifier.
Claim 7
Independent Claim
148 words
The method of producing an audible signal to identify the presence of metal, comprising the steps of: generating a radiating R-F signal at a frequency such that said signal is within the frequency range of a common radio receiver''s intermediate frequency amplifier capture range; generating a local oscillator signal in a superheterodyne radio receiver at a frequency differing from a harmonic of said R-F signal by a frequency difference within the audible range; detecting the local oscillator signal and generating the harmonic of said R-F signal in the second detector part of the I-F amplifier of the superheterodyne receiver to produce an audible beat note signal in the audio amplifier of said superheterodyne receiver; and changing the frequency of the R-F radiating signal and the harmonic thereof as a metallic object is approached to produce a change in the frequency of the audible frequency in said audio amplifier.
References Cited (Backward Citations)
US3492564A
Cited
US3626279A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-10-29 | 1977-04-30 | 1977-10-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-10-29 | 1981-04-30 | 1981-10-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-10-29 | 1985-04-30 | 1985-10-30 | $7700.00 | Window Closed / Lapsed |