Radio receiver monitoring and testing apparatus

Details Radio receiver monitoring and testing apparatus Radio receiver monitoring and testing apparatus

G - Physics

01

R

324/38

G01R 23/14 (2006.01) H04B 17/00 (2006.01)

Patent

CA 1082775

ABSTRACT OF THE DISCLOSURE Circuitry for attachment to a radio receiver to monitor and test a detected intermediate frequency signal and an audio signal from a demodulator portion of the receiver to determine whether a transmitted radio frequency signal is within frequency tolerances and modulation limits and to provide an alarm, either visual or audio, when the limits or tolerances are exceeded. An off frequency monitor tests the DC component of the radio de- modulator detected IF signal and includes input signal conditioning circuitry for filtering the audio signal, high impedance for minimal loading of the radio, and level shifting. Upper and lower level voltage references indicate maximum permissible fre- quency deviation from the nominal transmitting frequency. Upper and lower level comparators compare the conditioned direct current (DC) signal to the respective voltage references and provide a changed output state upon an out of tolerance transmission. An over modulation detector, generally in parallel with the off fre- quency monitor, provides a changed output state of a minimum time duration whenever the modulation limits are exceeded, and includes AC coupling to block the DC component of the radio detector signal, a voltage reference indicative of the maximum modulation level, a comparator for comparing the audio signal to the voltage reference, pulse stretching circuitry to provide a minimum time duration output for intermittent over modulation conditions. The frequency monitor and modulation detector independently control switching of alarm circuitry to enable either a light emitting diode, or a volume controlled audio oscillator.

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