Abstract: A tester for multiple types of radios has a first group of generic test elements common to all types of radios to be tested and second groups of test elements specific to each one of the multiple types of radios. Each of the second groups of test elements is mounted within a pluggable module for insertion into the tester where it couples to a common bus accessed by all of the other test elements and by the controlling computer. Each pluggable module contains a specific identifier which, when accessed by the controlling computer initiates a stored program which causes the computer, via the bus, to couple the various test elements into a configuration required to test the radio type associated with that identifier. The system is very compact and conveniently uses a lap top computer as the controlling element.

Abstract: A method and apparatus for a sweep oscillator and a spectrum analyzer containing the sweep oscillator having a precisely determined center frequency includes a sweep circuit having a sawtooth waveform, a reference oscillator, a microprocessor controller and a modified phase-locked loop. The modified phase-locked loop further includes a control signal summer, a voltage controlled oscillator coupled to the control signal summer, a sweep oscillator output, and a sample and hold circuit including a switching circuit.

Abstract: Test apparatus designed to be coupled to a transmitter including a local oscillator and mixer for reducing the received carrier frequency, a frequency counter for counting the IF cycles, a subtractor for subtracting the counted value from the actual value of the desired frequency, time averaging circuitry for finding the average error in a plurality of counts and display means for displaying the average error. The frequency counter is a gate time counter which normally counts for a one-tenth second period but increases the counting time to one second when the error is reduced below .+-.10 Hertz.