Sony ICF 7600D User Guide
Dietmar Adolf (info@asystec.de)
DRM Reception With
SONY ICF-7600D/DS (ICF-2002/2003)
v1.02 2004-02-09 first released version
v1.10 2004-02-14 external antenna connector, EMI suppression, AC harmonics suppression
v2.00 2004-02-17 compact version with lowres pics
This report is intended to help others, but no absolutely no warranty is granted, if any damages result from following these steps.
This popular vintage receiver from 1983 should be modified to support DRM radio transmissions
while all other operation should remain unchanged.
The receiver has a PLL synthesized tuning basis, but largely relies on analog circuitry for AM
reception, using double conversion with IF1 = 55.845 MHz and IF2 = 450 kHz. We want to
integrate the widely used DRM down mixer (manufactured and sold by Sat Schneider www.sat-
schneider.de).
A first inspection of the receiver reveals the challenge: the case is packed, but it is still possible to
install the DRM mixer circuit, hook up an output jack and install an external antenna connector:
The 12 kHz DRM output signal will be hooked to the “line out” jack socket labelled with a tape
symbol. The original audio output signal will be disconnected, as it is not of much use anyway. The
signal is far below specs for “line out”.
This is how to proceed:
IF Tapping
Looking at the circuit diagram, we identify two possible IF tap points for the DRM down mixer
input:
a) Pin 14 of IC1: This is the input pin of the AM IF amplifier. Here, the signal has passed the
450 kHz ceramic filter CF3, then has been amplified by transistor Q12 and DC-decoupled
by C69. As the IF filter is reported to be a CFW450H, we expect an AM bandwidth of +/- 3
kHz only. If the specs are strictly met, this will not be enough for DRM reception.
b) Between T9 and R68: This is just after the IF LC-oscillator and prior to the 450 kHz ceramic
filter. SONY uses a very similar circuit setup to the Sangean ATS-803A, described by David
M Pratt. We may expect a IF signal with bandwidth of at least 10..11 kHz
The DRM down mixer gain is adjustable: we should be able to account for the differring signal
levels of both options.
Removing the front cover and the control board,
we can inspect the IF components actually installed:
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