JRC Nrd-535 Hf Modification Modification 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 athttp://www.drmrx.org/
and athttp://www.tu-
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...

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...

Method 2:
This method is independent of the available filters and can therefore be used in most of
the cases.
The 455 kHz signal is derived just after the LC filter (C19 parallel with L3) but before
the FL3-FL6 filters.
NF
The 12 kHz signal (NF) is fed to a special 3.5mm chassis part mounted on the rear panel
of the NRD-535.
A standard 3.5 mm stereo cable is used to connect the soundcard of the computer to this
chassis part. Please note that both the left and right pin of this chassis part must be...

Reception results
The NRD-535 has been used during many analogue years and it has always proven to be
a good quality receiver in terms of sensitivity, selectivity and dynamic range. These
receiver characteristics will still be very important during the DRM era: They can make
the difference between good reception or no reception at all.
Reception of DRM signals have been performed on 10 kHz wide DRM transmissions
within Europe in April 2003. Both software packages have been used to decode the DRM...

Annex 1: Block diagram of CFH-36A IF Filter unit 

Annex II: Screenshots of open source DRM software receiver