Receiver preamplifier with tuned circuit adapted for Loran recep

Details Receiver preamplifier with tuned circuit adapted for Loran recep Receiver preamplifier with tuned circuit adapted for Loran recep

1988-07-21

1989-10-17

Mottola, Steven

Amplifiers

With semiconductor amplifying device

Including frequency-responsive means in the signal...

330300, 330306, H03F 3191, H03F 316

Patent

active

048750190

ABSTRACT:
A preamplifier system adapted for a Loran receiver includes a buffer amplifier receiving the signal from the antenna at its input and a tuned circuit connected between the input of the buffer amplifier and ground. The tuned circuit includes a parallel combination of a resistance, capacitance and inductance with values selected such that a resonant frequency is provided substantially at or near the carrier frequency of the Loran signal to pass it while higher and lower frequencies, constituting extraneous noise signals, are substantially attenuated. In particular, low frequency, e.g. 60 Hz signals and DC from sources such as precipitation static, are shunted to ground through the parallel inductor in the tuned circuit so that these low frequency components do not affect the performance of the receiver. A secondary filter section is connected to the output of the buffer amplifier and has components that may be selected in value such that the overall transfer function of the preamplifier, including the tuned input circuit, has a desired bandpass characteristic. Thermal noise contributed by the parallel resistor in the tuned circuit may be reduced by feeding back the output of the buffer amplifier through the resistor to effectively reduce its noise contribution while leaving the effective input resistance the same. Notch filters may be incorporated with the input tuned circuit to reject strong extraneous signals within the passband.

REFERENCES:
patent: 4559503 (1985-12-01), Camand et al.
patent: 4814771 (1989-03-01), Bahr et al.
DeMaw, Doug, "Preamp for 80 & 160 Meter Loop and Beverage Antennas", QST, Aug. 1988, pp. 22-24.
A. E. Gaunt et al., "The AN/ARN-101 Loran Receiver", paper presented at W. G. A. Technical Symposium, Oct. 9, 1975.
Durk van Willigen, "Hard Limiting and Sequential Detecting Loran-C Sensor," Delft University Press, 1985, pp. 6-17 to 6-20.
Antenna Circuit Diagram for "PAL" Loran Receiver on the market in the United States prior to the filing date of the present patent application.
R. W. Burhans, "All About VLF Active Antennas," Radio-Electronics, Feb. 1983, pp. 63-66.
R. W. Burhans, "All About VLF Active Antennas--Part 2," Radio-Electronics, Mar. 1983, pp. 65-67, 72.
R. W. Burhans, "Build This VLF-HF Active Antennas--Part 3", Radio-Electronics, Apr. 1983, pp. 132-135.
R. W. Burchans, "Build This Passive Antenna Tuner for VLF-LF, Part 4", Radio-Electronics, May 1983, pp. 73-76.
E. H. Nordholt et al., "A New Approach to Active Antenna Design," IEEE Transactions on Antennas and Propagation, vol. Ap.-28, No. 6, Nov. 1980.
Radio Receiving Principles, p. 12-13, in The ARRL Handbook for the Radio Amateur, American Radio Relay League, 64th Edition, 1987.

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