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Date: 19-11-02 Page 3 of 8
1 Introduction
1.1 Purpose of this document
This document describes how to modify a Sony ICF-SW77 short wave receiver to be able to
receive a DRM signal. Therefore the DRM – Miniature Mixer Unit from Sat-Service
Schneider is used, to mix down the 455 kHz IF of the receiver to a 12 kHz IF. This 12 kHz IF
is feed to a PC sound card.
Please note that the manufacturer's warranty will be discarded if you do this modification.
1.2 Organization of this document
Chapter 1 provides an introduction to the document.
Chapter 2 provides an overview of the system.
Chapter 3 describes how the IF filter of the ICF-SW77 has to be changed.
Chapter 4 describes how the DRM Miniature Mixer Unit has to be connected to the receiver.
2 System overview
The 2. IF (455 kHz) of the ICF-SW77 receiver is feed to the miniature mixer unit and down
converted to a 12 kHz IF. This IF signal is then connected to the input of a PC sound card.
This PC decodes the DRM signal with a decoder software.
ICF-SW77
mixer
unit
455 kHz
PC
12 kHz
3 Change of 455 kHz IF filter
The bandwidth of the ICF-SW77 receiver is too small to receive a DRM signal. Therefore the
IF filter has to be changed.
3.1 Schematic
The following diagram shows the schematic of the SW 77 IF section.