Ten-Tec SSB-CW-AM Instruction Manual page 100

processing. This is illustrated with some example spectrum plots
in Figure 2R.
Fig. 2R: Spectrum Plot examples
The stage of selectivity and gain that follows the mixer is called
the intermediate frequency (IF) amplifier. Notice how the
position of the local oscillator determines which part of the
incoming spectrum falls within the bandwidth of the IF amplifier.
As the LO is tuned, individual signals can be separated out for
amplification and detection.
The typical receiver will use at least two mixers and two of these
intermediate frequency stages to convert an incoming signal
down to audio. The desired tuning range of the receiver and the
availability of certain standard filter frequencies is usually what
determines the selection of the IF frequencies.
Let's now study the Block Diagram of the Model 1254 receiver
shown in Figure 3R. We will follow the signal path from antenna
to speaker, and explain the reasoning behind the design of each
stage.
1254 Reference - 7