1972 Heathkit Model AJ-1510A Digital FM Stereo Tuner

This is a Heathkit Model AJ-1510 Stereo FM tuner. This was one of the first digital FM stereo tuners made. It has good sensitivity, loss cross modulation, and no overload on strong signals. It claims to have a frequency accuracy of better than +/- .005%. It uses a digital frequency discriminator rather than the Foster Sealy or ratio detector discriminators that use inductors and will drift in their tuning. Harmonic distortion is quoted at less than 0.3%. Two, five-pole IF filters provide excellent selectivity. Station selection is made using either the keyboard or by inserting up to 3 plastic cards with notches cut out for favorite stations. The receiver has no built-in memory to store frequencies - the storage is accomplished with the cards. The receiver will also search for the strongest station or for only stations that are stereo. A signal strength meter is included. Oscilloscope outputs are provided to observe multipath effects. The frequency readout uses 4 DR2100 vacuum flourescent tubes, one of which has a defective segment.