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Software Defined Radio

DiRaGen 30

Shortwave DRM Exciter

Successful field tests

Middle of February 2009 the first devices were delivered.

Meanwhile we have received only positive feedbacks. First test transmissions as exciter for broadcast applications were also successful.

Official DRM Supporter (Digital Radio Mondiale).


Documents (PDF):

Data Sheet DiRaGen 30 (2 pages)

Instruction Manual DiRaGen 30 (2 pages)


Optional accessory:

PostAmp 1-150

Ultra linear broadband post amplifier 1-150MHz with 30dB gain & eff. output power 100mW (> 55dBc) RMS for DRM


USB DAC 48 ( External USB DAC with max. 48KHz sampling rate)



Generating Shortwave DRM Radio Signals

drm transmitter diragen-30

The importance of the digital shortwave radio standard DRM (Digital Radio Mondiale) continues to grow rapidly. With the DiRaGen 30 we introduce an exciter which converts a PC-generated DRM signal to the shortwave range.

What is needed ?

1. DRM-Transmitter Software

Actually the following transmitter software is available for generating a DRM signal via PC & sound card:

- DREAM (Transmitte Mode)

- SPARK DRM Transmitter

DREAM the pioneer for DRM open source software contains an additional DRM-transmitter module which allows transmission of text & image files.

SPARK is an actual real-time software modulator developed by Michael Feilen. The software is very comprehensive and a free (non commercial) version is available on request from the author.

This software offers numerous possibilities and supports all code rates, bandwidths and robustness modes. A comprehesive documentation is also available.

Besides pure audio transmission basing e.g. on a WAVE file source additional transmission of text & image files is also possible.

There is also a commercial version with additional features available.

2. PC

A PC or notebook equipped with a standard (AC 97) sound card allows the generation of a DRM signal.

The low-frequency DRM Baseband signal is available at the line output of the sound card as OFDM (Orthogonal Frequency Division Multiplex ) signal.

The standard center frequency of the OFDM signal is 12KHz.

3. DiRaGen 30

The sound card OFDM signal is connected to the audio/IF input and converted in the shortwave range.

Any output frequency can be seleted within 130KHz to 30MHz directly via the integrated keyboard. The last selected frequency is stored automatically and permanently visible at the front display.

Generating a DRM radio signal according to standard:

Output signal of the DiRaGen 30 generated in combination with DREAM ransmitter and received via SoDiRa & direct conversion receiver on 10MHz test frequency

DRG30-49dB DRM Spectrum

(Robustness Mode B, MSC Protection Level 0, MSC Interleaver Mode 2s, Bandwidth 9KHz, IF 12KHz)

Highest linearity and easy to operate

In order to achieve the highest possible signal-to-noise ratio (SNR) the conversion must be absolutely linear. Overloading or compression degrades the SNR severly.

The DiRaGen has an easy-to-read integrated overload control (red LED) at the rear panel. Adjust the PC volume (audio level) control settings until the LED starts just to flicker. This is the optimum level to reach the highest possible SNR.

Due to a high performance design with triple frequency conversion in combination with efficient filtering very good unwanted sideband rejection and carrier suppression values are achieved.

All internal frequencies are derived from a stable crystal clock generator (master clock) to prevent odd frequency drifting effects.

A Direct Digital Synthesizer (DDS) acts as VCO combining good phase-noise and short time stability. We use this reliable principle already for our PC-controlled shortwave receivers.

Please note. In case of further amplification of the RF output signal additional selective filters must be inserted.

Furthermore the legal regulations shall be observed.


- Testing of DRM receivers, laboratories & testing facilities

- Generating a standard DRM signal for demonstration purposes

- Education

- DRM test transmissions & DRM transmitter

Technical Data:

Tuning Range: 130KHz - 30MHz (continous)
Smallest Tuning Step: 1Hz
RF Output Connector / Impedance: BNC socket / 50Ohms
Output Level: -10dBm eff. +/- 3dB typ. (thermal measurement)
Audio / IF Input Level: 0.1Vss @ 1KOhm via 3.5mm stereo phone jack socket

DRM Output SNR: MER>40dB, typ. 45dB (mean value / measured via SoDiRa 072 & DREAM Transmitter)

Unwanted Sideband Suppression ( -112KHz): > 60dB
Carrier Suppression (-56KHz): >50dB; typ. 65dB (0.5 - 27MHz)
Harmonics Suppressions: 0-30MHz >40dB; over 30MHz >60dB
Spurious Signals Suppression (0-30MHz): >35dB

Frequency Stability (15min. warm-up period): +/- 1ppm typ. (20°C)

Max. Baseband Bandwidth (Audio/IF): 15KHz @12KHz IF center frequency
Power Supply / Connector: 12 - 15V DC max. 250mA / 2.1mm DC power socket (positive inner)
Operating Temperature: 0 - 40°C
Dimensions / Weight: 125 x 71 x 31mm / 0.20kg

What`s included ?

DiRaGen 30

Please note: Plug-Power Supply, application software and connecting cables are not included !

Premium Edition

Selected DiRaGen 30 with DRM-SNR >45dB guaranteed

Please ask for availability !

Customer feedback:

As a DRM-Brasil founder member and as a DRM researcher I can say that NTi
plays a very important role in pushing DRM forward providing affordable
equipment for demonstration and trials.
The DiRaGen 30 together with the PostAmp provides an incredible portable
equipment for DRM demos.

Not to forget the great DRM software modulator - SPARK, that works
perfectly with the NTi chain.
I do recommend to anyone who is interested in trying DRM here in Brazil and worldwide,
talk to Rudolf of NTi.

Rafael Diniz / Brazil