Abstract: A technique for the automatic alignment and tuning of the front end of a vehicle radio. A tuning voltage is applied to a multiplying digital-to-analog converter before being applied to a front end tuning circuitry of the radio. A tuning voltage antenna number is applied to the tuning voltage at the converter to scale the tuning voltage, and adjust the center frequency tuning of the front end. During alignment, the tuning voltage antenna number is used to modulate the tuning voltage around a mean by reprogramming the tuning voltage antenna number a few values higher and lower in sequence. This modulation of the antenna tuning voltage creates an AC modulation component on the signal strength indicator signal passing through the front end. The signal strength indicator signal is measured and compared to its value before the tuning voltage antenna number was changed.

Abstract: An improved current monitor for measuring current over a wide dynamic range. The current monitor includes a low current channel, a high current channel, and a switch for selecting the low current channel if the measured current is below a predetermined level and the high current channel if the current is above the predetermined level. The output of the high current channel is voltage encoded by adding a fixed offset. The current monitor determines that the measured current is from the low current channel if the reading is below the offset and from the high current channel if the reading is above the offset. A current level output device automatically outputs a decoded current reading based on this determination. The current monitor also incorporates a low current error compensation circuit to compensate for parasitic current when the current monitor is using the high current channel.

Abstract: Wow and flutter of a tape player is measured by playing a recording of a constant frequency test tone, digitally sampling and storing each period of the tone over a test interval, subtracting the average period from each period to obtain deviation data, calculating the FFT of the deviation data, and then calculating power magnitude and wow and flutter. The apparatus includes an interface board which squares the signals from the player, and a desktop computer having a timing board for gating a counter for each square wave pulse to sample the periods, a memory for storing the samples, and a CPU programmed to analyze the samples according to the test method.

Abstract: A desktop computer having stereo audio input and output ports is used with an interface board to supply test tones to an audio device being tested. The interface feeds back the test device outputs to the computer audio input ports. The interface, under control of the computer, selects any two of several inputs from the device and attenuates the two signals to the optimum amplitude for analysis. The computer digitizes the audio inputs and simultaneously analyzes the signals by software operations in either time or frequency domain along with appropriate filtering to quickly obtain results according to standard test specifications.