T-100F FM RF Amp

The National Panasonic T-100F has a separate FM antenna input facility where the signal passes through the first stage FM RF amplifier consisting of 2SA241 germanium transistor. Consequently, the FM reception has good sensitivity, and it rejects RF noise well. This stage then feeds the heterodyne mixer consisting of 2SA71. They clamp the mixer output with an OA70 diode to produce the FM automatic gain control (AGC). The 2SA71 performs the FM oscillator function in a straightforward circuit design; however, they use a SC-15 diode to perform the automatic frequency control (AFC), which is very clever.

This Article Continues...