RED PT500-2, Service Manual

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PT500-2 Service Manual
17
Figure 5. 1 Frequency configuration
5.2 Receiver
（
Rx
）
The receiver is double conversion superheterodyne, designed to operate in the frequency
range of 400 to 470MHz,The frequency configuration in Fig 2
Figure 5.2 Receiver section configuration
Front End of Receiver
Signals from the antenna are filtered by BPF which consists of C235 C236 C233 C604 C252
C951 C234 C255 C260 L211 L209 L208 D201 D202 and D204 via RX/TX switch (D101
D102 and D103). After being filtered out the useless out-of-band signals, the signals are
amplified by LNA consisting of Q203 and external components.
Signals from LNA are filtered again by BPF which consists of C228 C226 C238 C229 C227
C239 C947 C259 C948 L214 L204 L203 D905 D206 and D206 before entering the 1st mixer
(Q202).