Based on the popular SDR transceiver ‘SunSDR2-Pro’, the Russian manufacturer Expert Electronics offers the ‘SunSDR2-DX’. This transceiver works as a direct scanning Software Defined Radio (SDR) with a high resolution 16 bit A/D converter. All amateur radio bands from 160 to 6m as well as the 2m VHF band are supported. The transmission power is 100W on HF bands, 50W on 6m and 7W on 2m.
The higher transmission power requires a larger output stage and thus a larger housing in contrast to the SunSDR2-Pro. At the same time, the thermal concept has been changed, resulting in a lower overall heat generation. An external fan is supplied, which can be mounted on top of the large cooling fins of the case if required (continuous operation in the contest, very warm environment). Further changes compared to the ‘Pro’ concern the filter possibilities. A new high pass filter from 100 MHz is available, which leads to VHF for better sensitivity. For HF, there are still 9 individual bandpass filters or a single low-pass filter from 65 MHz. This combination is supplemented by a permanently inserted low-pass filter from 70 MHz, which improves the dynamic range on short wave and 6m.
The receiver of the SunSDR2-DX is based on the fast 16-bit ADC LTC 2209, which is operated at 160 MS/s. The receiver is equipped with a low-pass filter from 70 MHz. This achieves an excellent blocking dynamic range of up to 130 dB. The already mentioned 9 bandpass filters for short wave result in a receiver that is very large signal stable with very good sensitivity and high dynamic range. Together with the ExpertSDR software, two independent main and two independent sub-receivers in the same bandwidth range are possible. In addition, a wide spectrum of up to 80 MHz can be displayed.
The transmitter is designed completely independent of the receiver with its own quadrature oscillator and thus enables flexible half or full duplex operation. Thus, the SunSDR2-DX can also be used as a measuring and spectrum analyzer with suitable software. Independent output stages for short wave and VHF generate the 100 (6m: 50) or 7 Watt transmission power. Two switchable antenna connections are provided for short wave, the connection for VHF is designed separately. Other connections are intended for transverter operation or the connection of an output stage. Eight freely programmable switching outputs enable the automatic (frequency-dependent) selection of antennas or external band filters or the connection of external preamplifiers and sequencers.
New is a connection for an external tuner! In the future, the manufacturer plans to offer a suitable automatic tuner which can be controlled via this connector.
Another special feature is that the fast FPGA of the transceiver processes the key signals of a Morse key directly on the device. Thus it becomes possible that the transmitter keying takes place without noticeable delay, even QSK operation at higher speeds is possible. A microphone can also be connected directly to the radio. Here the transceiver even has two sockets, an RJ45 socket for connecting a Yaesu hand microphone and a 3.5 mm jack socket, e.g. from the microphone of a headset. The decoded audio signal is output locally via a very low-distortion 24Bit DAC to a headphone output, as well as digitally transmitted to the computer. This opens up many possibilities for use directly in the shack or as a remote-controlled transceiver.
The SunSDR2-DX is connected to the computer via an Ethernet port. Skilful programming enables a direct connection between transceiver and PC as well as integration into the home network via a switch or DSL router. Particularly convenient is the possibility to remotely control the SunSDR2-Pro completely via the LAN. In addition to the connection to the device itself, the NF is also transmitted digitally and thus enables operation “on the couch”, for example with a simple PC headset…
A 10 MHz input for a reference clock replaces the signal of the internal OCXO, which also offers a very good stability of ± 0.5 ppm.
The freely available software ExpertSDR is continuously being developed and will always be available free of charge for owners of the transceiver in the future. The operating systems Windows XP, Win7, Win8 and Win10 are supported, a port to MacOS and Linux is planned. The operation of the software is kept relatively clear and offers also functions for the contest operation or the integration with multimode programs for example for RTTY or PSK31. A virtual CAT interface allows the use of other programs, for example for the contest.
The SunSDR2-DX represents the consistent further development of the successful SDR transceivers from Expert Electronics. This new hardware together with the continuously improved ExpertSDR2 software over the years shows that this manufacturer is a serious competitor on the market and plans long-term. Due to the compact dimensions of the SunSDR2-DX of 190 x 170 x 80 mm and a weight of approx. 2kg, it is not only suitable for shacks, but also for portable and holiday use (power supply 8-14.8VDC, max. 24 A).