Pozosta JRC-NRD-535-mod-DRM User Manual
Modification of JRC NRD-535 HF Receiver for the reception
of DRM signals
V1.02 - 11-April-2003
Summary
A JRC NRD-535 HF Receiver has been modified to make DRM reception possible with
the DRM decoding software available at http://www.drmrx.org/
darmstadt.de/fb/et/uet/fguet/mitarbeiter/vf/DRM/DRM.html
The 455 kHz Intermediate Frequency (IF) available within the NRD-535 is mixed down
to 12 kHz with the LC-mixer available at:
http://home.t-online.de/home/sat-service/sat/DRM/DRM.htm
The necessary power to supply the LC-mixer can also be derived within the NRD-535.
The resulting 12 kHz IF is available on an extra 3.5mm connector mounted on the
backpanel of the NRD-535. Via a standard 3.5 mm stereo cable the 12 kHz signal is fed
into the line input of a soundcard in a computer. The software installed on this computer
decodes the signal and the audio is audible via the computer loudspeakers.
The computer used is a Compaq Deskpro EN with a 1GHz CPU, 128 MB RAM, onboard soundcard and Windows 2000 Professional.
and at http://www.tu-
Disclaimer
Attention!
This modification is done at your own risk! The author is not responsible for any damage
to your receiver or anything else. You may also loose vendor warranty and liability.
Modfication
The LC-mixer circuitboard is fixed with double sided tape on one of the NRD-535 cards
called “CFH-36A IF filter”. The blockdiagram of this IF filter is given in Annex I.
Ub
The power to supply the LC-mixer is available on pin 1 of connector P30 (10.8V) on this
card. The connection between P30-1 and inductor L8 is used. (red wire on photo)
ZF
There are various ways to derive the 455 kHz IF within the NRD-535.
Method 1:
In our case the “CFH-36A IF filter” board has an additional filter on the “FL5 NARR”
position and no additional filter on the “FL6 AUX” position. This means we can use the
bandwidth setting in AUX-mode for DRM reception. Other bandwidth settings are not
adequate as these attenuate the DRM signal too much.
The 455 kHz is available at pin 22 of connector P30 and ground is available at pin 21 of
the same connector. These signals are fed into ZF and ground (near ZF) of the LC-mixer.
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