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Software Defined Radio

DiRaGen 30 USB

Multimode Shortwave Exciter

1, 2, 3, ... ON AIR

with SPARK Modulator & DiRaGen 30 USB

With this unbeatable combination of software and hardware it is possible to generate all commonly used kinds of shortwave broadcast signals.

The DiRaGen 30 USB unit is completely remote controlled via USB.

1,2,3 On Air


Documents (PDF):

Instruction Manual DiRaGen 30 USB (2 pages)


More informations about the DiRaGen 30 USB:

Analog AM modulation

AMSS (Amplitude Modulation Signalling System)

SPARK Modulator Software


Accessories (optional):

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)


Official DRM Supporter (Digital Radio Mondiale)



Generating shortwave DRM and analog broadcast signals very easy

DiRaGen30 USB Shortwave Multimode Exciter

With the DiRaGen 30 USB we introduce a further variety of our shortwave exciter.

In close coorporation with Michael Feilen, the developer of the leading DRM modulator software SPARK, we created a symbiosis with unique features:

- Direct frequency setting via USB

- Full compatiblity to the DRM30 standard

- Compatible to all analog broadcast signals with 20KHz maximum bandwidth


DRM or analog modulation - Why not use both ?

In combination with the SPARK modulator software it is possible to generate either DRM or any analog broadcast signal.

This guarantees a maximum of flexibility. It is possible to change the modulation mode and time automatically -For instance DRM trial transmissions over a certain period of time in change with standard AM modulation.

The following broadcast signals could be generated in combination with the SPARK transmitting software:

- DRM according DRM 30 with 4.5KHz to 20KHz bandwidth

- Analog modulation modes with 20KHz maximum bandwidht:

AM with or without supressed carrier

AMSS with added informations timestamp, languagel,transmtting label, service Identifier, modulation mode

Single-sideband modulation LSB & USB with or without supressed carrier

It is also possible to implement other or new modulation modes which offers a flexible solution for upcoming developments.

What is needed ?

1. Transmitter Software SPARK

Michael Feilen had developed the early version of the SPARK modulator software already for his master thesis at the university of applied sciences in Kaiserslautern. The software was continuously optimized and includes now all actual used and scheduled broadcast modulation modes.

Besides pure audio transmission basing e.g. on a WAVE file source, MP3 playlist or soundcard input additional transmission of text & image files is also possible.

2. PC

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

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

As an alternative to the PC soundcard it is also possible to use our new developed USB DAC 48.

3. DiRaGen 30 USB

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 SPARK.

Standard DRM radio signal with 9KHz bandwidth:


Well prepared for the future - Extended DRM signal with 20KHz bandwidth:


AM modulated radio signal with 10KHz bandwidth:


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 30 USB 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 transmission & DRM transmitter

Technical Data:

Tuning Range: 130KHz - 30MHz (continous)
Smallest Tuning Step: 1KHz via SPARK (1Hz. eff.)
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)

Suppression of unwanted carriers referred to maximum output level (PEP):

Unwanted Sideband Suppression ( -112KHz): > 60dB
Carrier Suppression (-56KHz): >55dB
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)

USB connector: USB-B (socket) USB 2.0 (backward-compatible)

Operating Temperature: 0 - 40°C
Dimensions / Weight: 125 x 71 x 31mm / 0.20kg

What`s included ?

DiRaGen 30 USB

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

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