Making space for the DRM Interface

C56 and C102 on the IF-AF Amp board of the NRD525 were moved to the solderside in order to make some space for the DRM-Interface.

Input to the DRM I/F is TP1.

The output is connected to pin 15 of motherboardconnector P28.

The 10.8 Volt DC is obtained from L3.

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Output of the DRM I/F

The black (RG174) coax connects one of the Scope outputs (bottom right) to the output of the DRM I/F via pin 15.
This can only be done if the RTTY I/F is not fitted!

Extended filter switching

A new firmware (V1.5) in combination with some simple hardware modification results in bypassing the 455 kHz filters FL1 - FL4 resulting in a 455 kHz bandwidth of about 12 kHz necessary for the DRM I/F.

For more details:
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New backpanel connectors

The SO239 type bulkhead connectors for the VHF / UHF were replaced by N-type bulkheads.

The original RS-232 connector was replaced by an DB9 type.

RS232 connector