| 摘要 |
<p>1,166,977. Detecting RF fields; locating leaks in waveguides. UNITED STATES ATOMIC ENERGY COMMISSION. May 20, 1968 [June 26, 1967], No. 24016/68. Heading G1U. [Also in Divisions G4, H3 and H4] A circuit for producing a chirp note when an RF field is present comprises a coil L tuned by CI to the RF field, e.g. 200 MHz, (continuous or pulsed) the picked-up signal being rectified by DI to change C2. At a predetermined level depending on the setting of P the unijunction Q1 will fire and apply pulses to transistor Q2 at a frequency depending on the RF level. At each pulse capacitor C4 changes and turns on Q3, the time constant of C4 and R2 determining the duration of the chirp. When Q3 conducts, capacitor C5 alternately changes through R3 and discharges through a second unijunction Q4 to produce a chirp A. F. signal at a frequency depending on R3. This signal is amplified and fed to a Piezo-electric or other loudspeaker S. Diodes D2 and D3 prevent the associated transistors from being cut off by large signals. The circuit may be used as a personnel monitor for dangerous R. F. fields or for locating leaks in waveguides or cooling lines.</p> |
