Ramsey Electronics HR20 manual Speaker Operation

SA602 audio output at the volume control, and switch in a pleasant oscillator pitch (keying sidetone) which is amplified to listening level by LM386. The Ramsey Electronics Universal timer kit No. UT-5 is easily adapted as a sidetone oscillator.

•SPEAKER OPERATION

A fifty cent, two inch diameter speaker, lying naked on your workbench will give you a fair test of the speaker output capability. Speaker quality and well- designed enclosures have their clear purposes! A reasonable speaker in a box delivers a pleasant listening volume. On the other hand, the LM386 indeed can deliver more audio output punch than is developed in our HR- series kits. For example, our FM receivers, using the same LM386 audio IC, deliver more volume. These receivers, however, take advantage of IF amplifiers, drift-compensation and crystal controlled oscillators built into mass production sophisticated FM receiver ICs. A heavier drain on the HR20’s battery by stronger audio will quickly result in chirpy signals and oscillator drift as well as the need for frequent battery replacement. Remember the SA602 circuits similar to the Ramsey HR-series generally call for sets of C or D cell batteries! For Experienced Builders more information regarding audio output is in the general notes.

The simple design of the audio stage of the Ramsey HR20 receiver assumes preference for headphone or small speaker operation, low battery drain and general economy.

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