HYT TC-500, Service Manual, Page: 10 / 77

TC-500 Service Manual
9
Circuit Description
Frequency Configuration
The receiver utilizes double conversion superheterodyne. The first IF is 21.4MHz and the second is
455KHz. The first local oscillator signal is supplied from PLL circuit. Frequency needed in the transmitter
is supplied from PLL circuit. Figure 1 shows the frequency configuration.
Frequency Range: 136-150MHz 150-174MHz 350-370MHz
370-390MHz 400-420MHz 450-470MHz
Figure 1 frequency configuration
Receiver
The receiver utilizes double conversion superheterodyne.
1. Front-end RF Amplifier
The input signal from antenna is amplified in RF amplifier (Q27) after passing through the
receive/transmit switch circuit and a 3-stage LC band pass filter. The amplified signals are
filtered by a band pass filter (a 3-stage LC BPF) to eliminate unwanted signals before they
go to the first frequency mixer.
Figure 2 receiver section configuration
2. The First Mixer
The signal from RF amplifier is mixed with the first local oscillator signal from PLL frequency