Page 246 - Build Your Own Transistor Radios a Hobbyists Guide to High-Performance and Low-Powered Radio Circuits

at 1,000 kHz, there can be a problem of oscillator-frequency stability. Therefore,

the RF signals whose frequencies are close to the oscillator's frequency can cause
the oscillator to lock onto or synchronize with the incominQl RF signal via injection
locking.
Figure 14-10 also can be used as a harmonic converter. If this is desired, the
oscillator's signal should be increased by increasing the DC collector current to
provide a "reasonable" conversion gain. This can be done by increasing the bias

voltage at the base of Q1 by increasing V bias and/or by decreasing the resistance of
emitter bias resistor RE.
Figure 14-11 shows a differential-pair oscillator with an emitter tail current source
that also amplifies the RF signal source. Thus the emitter current is a combination

of a DC current and the amplified RF signal current. The IF signal is extracted via
the collector of Q2. This is not as common a configuration for a mixer oscillator
circuit compared with the one-transistor circuit in FiQlure 14-10 but nevertheless is
workable. Care should be taken as to the RF level connected to the base of Q3.