The EICO Model 324 RF Signal Generator is intended for general radio and television servicing and for other applications requiring a modulated or unmodulated r-f signal of sine waveform from 175kc to 420me. The r-f output from the Model 324 may be modulated internally by a 400 cps audio oscillator or may be modulated externally by an audio signal fed into a connector on the front panel. The internal 400cps modulating signal is also available separately at a front-panel connector. Selection of external modulation rearranges the audio oscillator stage as an amplifier operating on the external modulation signal. Asa result, up to 30% modulation is possible when the output of the external a-f source is as low as 3.0 volt. Percentage modulation by either an Internal or external a-f source, as well as a-f output voltage, is adjustable by a single panel control. Six tuning bands are employed to cover the fundamental frequency range from 150kc to 145mc. Calibration ofthe third harmonicof thehighest fundamental band (FI) 37 me to 145 me is also given on the tuning dial to provide a seventh tuning band (F2) from 1Ί1 me to 435 me. The particular band desired is selected by the band selector switch which acts, therefore, as a coarse output frequency selector; the 6 to 1 vernier tuning dial control is for fine tuning and permits exact setting of the output frequency. Construction of the dial and tuning assembly is unusual ly fine. A heavy gauge, deep-etched, aluminum tuning dial is fastened to the shaft of the tuning capacitor behind the panel and rotates with the tuning knob. The dial is viewed through twin plexiglass windows, four complete scales appearing in one window and four in the other, so that, despite the large number of scales, they are well-spaced and not easily confused. The plexiglass not only affords protection for the tuning dial, but, due to its unique light-conducting property, permits the use of an Illuminated hairline, which is engraved in the plexiglass and edge-lit by a panel lamp to permit maximum ease of reading. The illuminated hairline also serve as a pilot. Other important construction points include the use of turret mounted, slug-tuned coils for maximum accuracy, copper-plated chassis for minimized interference, line filters, shielded r-f output cable and }ack-top binding posts for audio in/out. The Model 324 incorporates both coarse and fine r-f attenuators for smooth, efficient control of the r-f output signal. The coarse attenuator provides two steps of coarse attenuation of approximately 20 db each. The Model 324 employs a Colpitts-type r-f oscillator and a Col pitts-type audio oscillator of proven design for efficient and trouble-free operation. The r-f oscillator is plate modulated by a cathode follower for improved modulation. Maintenance is simplified by an uncrowded chassis and easy access to all internal alignment adjustments for the six fundamental r-f bands. The characteristics of the Model 324 render it extremely flexible. It may be used in the radio and television service shop or in the field for such applications as alignment and signal tracing of am and fm radio receivers, alignment of both high and low frequency i-f amplifiers in television receivers, and signal tracing and troubleshooting almost all sections of tv receivers. The Model 324 is equally suitable to bench or portable applications, being provided with an uncluttered, professional satin aluminum panel that will add to the appearance of any test bench and a rugged steel case that will withstand "car trunk" abuse.