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Software Defined Radio

DiRaSelect 300

USB-controlled 3 Way Active Antenna Swich and Mixer
9KHz - 300MHz


  • USB controlled and powered

  • Wide frequency range (VLF - VHF)

  • High IP3

  • High isolation between inputs

  • High reverse isolation

  • No distribution losses

  • Inputs ESD protected



Official DRM Supporter (Digital Radio Mondiale).


Selecting and combining three different receiving antennas via USB




With the DiRaSelect 300 we expand our product range of receiver accessories by an additional component. Via USB up to three different receiving antennas from 9 kHz - 300 MHz can be switched loss-free to one output socket.

Additionally it is possible to combine all three input channels according to your individual needs. The selected channels are added as in-phase signals. Hereby it is possible to find always the best combination of antennas when receiving conditions are difficult.

Due to the elemination of mechanic components like relays, channel switching is purely elctronic switching using active components. So above average intermodulation values (IP3:+40 dBm at 7MHz typical) and extremely high reverse isolation values are achieved. The electronics are installed in strong aluminum profile housing.

The HF-inputs are BNC and are protected against short and pulse-shaped voltage surges with complex ESD protection circuits. Because the voltage supply is integrated via USB, there is no need for an additional power supply, which makes the ASM300 ideal for portable operation.


- Radio Monitoring



- Receiver Comparisons Tests

- Laboratory and Research Applications



DiRaSelect 300 Rear Panel

Control software AJ10Mini:

DiRaSelect 300 Software

The small control panel allows switching between the three antenna inputs (Antenna Swich) and also individual combining (Antenna Mixer).

This software is freely available and registration is not necessary. It is equally suitable for the NTi DiRaRelect 300 as well as for the technically identical AntennaJet ASM300 from Bonito.


Technical Data:

Input frequency range: 9KHz - 300MHz (-1dB)
Output connector / impedance: BNC / 50 Ohms (DC blocked max. 50V)
ESD input protection: 30KV; max. pulse power 350W (8/20µs)
Max. allowed input power: 0dBm
INput connectors / impedance: BNC / 50 Ohms (DC blocked max. 50V)

Isolation between inputs:

80dB typ. <0.3MHz

70dB typ. <1MHz
55dB typ. < 30MHz
45dB typ. <100MHz
40dB typ. <300MHz

Isolation between output and input (reverse isolation):

110dB typ. <0.3MHz

100dB typ. <1MHz
80dB typ. <30MHz
65dB typ. <100MHz
40dB typ. <300MHz

Amplitude frequency response: (300KHz - 300MHz): max. 1dB typ.

Amplitude difference between inputs: max. 0.5dB typ.

Third-order intercept point IP3:

+40dBm typ. <10MHz
+20dBm typ. >100MHz

Power supply connector: Type-B USB jack

Current consumption: max.50mA (5V DC)

Working temperature range: 0 - 40°C (without condensation)

Height / Weight: 115 x 90 x 32mm / 0.30kg

Conformity: CE

Standard accessory:

USB A/B cable (shielded with ferrite cores)

The control software AJ10Mini for Windows 7 & 8, Vista & Windows XP can be downloaded directly.

It is also available on CD-ROM on request.

Other items you might find interesting:

DiRaWave 032 ( Semi-professional USB-controlled Shortwave Receiver 40KHz - 30MHz )

DiRaSplitt 300 ( 3 Way Active Antenna Splitter 9KHz - 300MHz)