Radio receiver monitoring and testing apparatus

Claim 1

Monitoring and testing circuitry for attachment to a radio receiver to monitor and test a detected intermediate frequency (IF) signal and an audio signal from a demodulator portion of said radio receiver to determine if a radio signal received from radio transmitting equipment is within permissible transmitting frequency tolerances, said circuitry comprising: input signal conditioning means having a high input impedance characteristic for minimal loading of said demodulator, filtering means for filtering audio frequencies from the detected signal to obtain any DC component present therein, said input signal conditioning means providing an output signal related to said DC component, and said input signal conditioning means further comprises level shifting means for shifting the DC level of the detected signal from a signal which is nominally zero volts, and can deviate to either plus or minus polarities, to an output signal which is shifted in DC level such that the output signal will remain a single polarity despite any deviation; an upper voltage reference related to magnitude to the maximum permissible frequency deviation of the radio signal in one direction from the nominal transmitting frequency; upper level comparator means for comparing the output signal of the input signal conditioning means to said upper voltage reference, said upper comparator means changing output state whenever the output signal of the signal conditioning means exceeds said upper voltage reference; a lower voltage reference related in magnitude to the maximum permissible frequency deviation of the radio signal in another direction from the nominal transmitting frequency; lower level comparator means for comparing the output signal of the input signal conditioning means to said lower voltage reference, said lower comparator means changing output state whenever the output signal of the signal conditioning means is below said lower voltage reference; and alarm means responsive to a changed output state of either the upper or lower level comparator means to indicate that said transmitting equipment is not within permissible transmitting frequency tolerances.

Claim 10

The method of monitoring and testing a radio frequency signal to determine if the signal is within permissible transmitting frequency tolerances by monitoring and testing a detected intermediate frequency (IF) signal from a demodulator portion of a radio receiver which is tuned to the desired transmitting frequency, said method comprising the steps of: conditioning said detected intermediate frequency (IF) signal to recover the DC component thereof and filtering the AC component therefrom; comparing the recovered DC component of the detected IF signal to a voltage reference indicative of the maximum permissible frequency deviation of the transmitted radio frequency signal from the nominal transmitting frequency in a first direction; comparing the recovered DC component of the detected IF signal to a voltage reference indicative of the maximum permissible frequency deviation of the transmitted radio frequency signal from the nominal transmitting frequency in an opposing direction; controlling an alarm in response to an out-of-tolerance frequency condition found in either comparison step; and the additional step of level shifting the recovered DC component of the detected IF signal before comparing said DC component to said voltage reference.

Claim 11

The method of monitoring and testing a radio frequency signal to determine if the signal is within permissible transmitting frequency tolerances by monitoring and testing a detected intermediate frequency (IF) signal from a demodulator portion of a radio receiver which is tuned to the desired transmitting frequency, said method comprising the steps of: conditioning said detected intermediate frequency (IF) signal to recover the DC component thereof and filtering the AC component therefrom; comparing the recovered DC component of the detected IF signal to a voltage reference indicative of the maximum permissible frequency deviation of the transmitted radio frequency signal from the nominal transmitting frequency in a first direction; comparing the recovered DC component of the detected IF signal to a voltage reference indicative of the maximum permissible frequency deviation of the transmitted radio frequency signal from the nominal transmitting frequency in an opposing direction; controlling an alarm in response to an out-of-tolerance frequency condition found in either comparison step; and the additional step of level shifting the recovered DC component of the detected IF signal before comparing said DC component to said voltage reference.