Digital Marine Electronics Corporation

Other

Sheldon B Michaels

Mark J Giubardo

Jeffrey M Morris

Jeffrey Scott Morris

Otis Philbrick

A scanning receiver channel identification apparatus and method comprising a scanning receiver, means for generating annunciations to be associated with the channels to which the scanning receiver is tuned, means for associating annunciations with the channels to which the scanning receiver is tuned, and means for incorporating the annunciations into the detected output of the scanning receiver for the purpose of overcoming the limitations imposed by conventional alphanumeric displays of the channel to which the receiver is tuned.

Scanner with audible identification of tuned channel

Undesired, interfering narrow band received signals in a Loran-C receiver are automatically rejected and the resulting distortion of the received Loran beacon signals caused by this rejection is automatically compensated for. The received Loran-C beacon signals in the band 90 to 110 KHz are fed through a narrow band, variable reject filter that rejects the undesired signal and is controlled by a feedback circuit in response to an interference detector in the receiver, so that the reject filter is automatically set at the interfering signal, rejecting it. Meanwhile, distortion of the received Loran beacon signals caused by the rejection is compensated for by an automatic circuit that varies a delay and add circuit in the Loran receiver to compensate for the distortion.

Radio receiver with automatic interference and distortion compensation

In a Loran Receiver that receives radio frequency (RF) signals from a master beacon and at least two slave beacons (also called secondary transmitters) and converts the received signals into hyperbolic coordinates that locate the position of the receiver with respect to the beacons and a programmed computer controls modes and sequences of operation of the system, these modes being generally the beacon pulse search mode, front edge/zero crossing location mode and the zero crossing track mode, received beacon pulses are searched and identified by the following technique: all received signals are repeatedly sampled at the beacon group repetition interval (GRI) in a regular sampling pattern in which the sampling rate is greater than the beacon pulse rate, each sample interval being only a small portion of a beacon pulse RF excursion; the samples are hard limited and assigned a value of plus or minus, depending upon whether they exceed a threshold, and these plus-minus patterns are accumulated over many GRIs and stored; the stored accumulation is analyzed according to the computer program and compared with a reference pattern; and when there is correlation within programmed conditions, the front edge/zero crossing location mode is then pursued to locate the samples at the zero crossing of a particular RF excursion of the tracked beacon pulses.

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Sudbury, MA, United States of America

Sheldon B Michaels