Sony Receiver ICF Sw77 Drm Modufication Operation Instructions

  
  
Date: 19-11-02  Page 1 of 8   
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Modification of Sony ICF-SW77 
for DRM Software receiver 
 
 
 
 
 
 
 
 
 
 
 
 
 
  

  
  
Date: 19-11-02  Page 2 of 8  Table of Contents 
1 INTRODUCTION.........................................................................................................................................3 
1.1 PURPOSE OF THIS DOCUMENT...................................................................................................................3 
1.2 ORGANIZATION OF THIS DOCUMENT........................................................................................................3 
2 SYSTEM...

  
  
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 manufacturers warranty will be discarded if you do this modification. 
1.2 Organization of this document 
Chapter...

  
  
Date: 19-11-02  Page 4 of 8 wide band filternarrow band filterZF inGND
 
The IF section has two IF filters, a narrow band filter and a wide band filter. One of these 
filters has to be replaced by a wider filter with appr. 10 kHz bandwidth. The filter ‘W’ is 
active if the receiver is in ‘wide’ mode, the filter ‘N’ is active if the receiver is in ‘narrow’ 
mode.  

  
  
Date: 19-11-02  Page 5 of 8   
3.2 Filter bandwidth 
The with the receiver supplied wide band IF filter has a bandwidth ob appr. +/- 3 kHz. The 
bandwidth is shown in following diagram:  
The recommended replacement filter is a Murata CFWM455GY, which has the same 
footprint as the original filter, but a bandwidth of appr. +/- 4,5 kHz. The bandwidth is shown 
in following diagram:  

  
  
Date: 19-11-02  Page 6 of 8  
3.3 IF Filter types 
The following Murata filter types are fitting into the IF filter footprint in the SW77 receiver: 
Part Number 6 dB bandwidth CFWM455G +/- 4.5 kHz CFWM455F +/- 6.0 kHz CFWM455E +/- 7.5 kHz  
4 Connection of DRM Miniature Mixer Unit 
The IF frequency is 455 kHz in the SW77 receiver. Therefore the mixer unit with a 467,0 kHz 
oscillator is needed. It is recommended to use the mixer unit with the crystal oscillator.  

  
  
Date: 19-11-02  Page 7 of 8  
4.1 Power supply 
The mixer unit needs a power supply with 7-20 V DC. Unfortunately the receiver supplies a 
maximum voltage of 6 V. Test showed that it is possible to use the 6V instead of the 7-20 V 
to run the mixer unit. An other possibility is to remove the voltage regulator on the mixer unit 
and replace it with a diode (e.g. 1N4007). 
The 6V power lines of the mixer unit can be connected to the connector at the right side of the 
PCB (back view). The +6V line is...

  
  
Date: 19-11-02  Page 8 of 8