sangean: Sangean ATS-909 RF bands variant configuration

According to the service manual, six signal diodes (like 1N4148) are used to set up the RF Bands coverage at the production stage, depending on the target market.

These diodes are soldered at the MCU Control PCB assembly.  

This ATS-909 chassis used on several other brands was very popular among the aficionados and modders around the globe. Among the modifications are the RF band coverage, but other more invasive procedures change the AGC circuit response, the Muting disabled, and sensibility improvement on telescopic antenna (an identified issue with impedance mismatch between the high value of the telescopic antenna and the low value of the two RF Front-End FET's common gate design).

 

Partial MCU Control schematics:

 

Partial MCU Control PCB layout:

 

Partial MCU Control PCB picture:

Note: As far as I know, on a common to find radio version marketed in USA and large part of European countries, none of the above six diodes are installed from factory. As such, it would cover FM from 87.5 to 108 MHz with 100 kHz channel steps, LW from 153 to 519 kHz, MW from 520 to 1710 kHz, and SW from 1711 to 29999 kHz.

 

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