The developer of the well-known SDR Airspy-R2 has announced a new receiver, developed in collaboration with ITead Studio and one of the leading semiconductor manufacturers: Airspy HF +.
Airspy HF +
The Airspy HF + receives from 9 kHz to 31 MHz and from 60 to 260 MHz. The new design of the SDR receiver is based on the "Zero-IF" concept, in which the received signal is mixed directly in the baseband range. This technology avoids many of the problems of classic receiver architectures, but presents developers with new challenges. The Airspy HF + meets these challenges using three analog tuners with fixed and tunable band filters. The mixers are designed as harmonic rejection mixers, thus ensuring extraordinarily good linearity and spectral purity of the mixed signal. This is important for good sensitivity, because the cleaner the signal, the less likely a weak signal will be lost in the noise. Two very powerful AD converters are used to digitize the baseband signal. The subsequent decimation steps (DDC) work with different methods to reduce (decimate) the flow of data. The result is a very effective anti-aliasing filter that provides an attenuation of around 108 dBc. The resulting signal has a resolution of 18 bits, which is then scaled to 16 bits for transmission via the USB 2 interface.
Such a receiver architecture requires a very precise AGC to obtain the best possible sensitivity and a high dynamic range. The software of the Airspy HF + microcontroller controls the amplification in every phase of the tuner, of the filters and of the successive amplifiers. The result is a theoretical dynamic range of 113 dB, reaching almost 110 dB (on short waves). This is an excellent result for such a compact receiver and this price range. The user benefits from excellent linearity and high dynamic range as the received spectrum is much cleaner and spurious. Manual gain control is not necessary, nor is the use of attenuators, preamplifiers, selective band filters, etc.
In addition to the excellent RF characteristics, the developers have achieved equally impressive noise reduction at the AF level. Here, the interfering noise in a desired signal is largely attenuated, without the signal itself suffering from intelligibility and without too much distortion in the AF. The best way to listen to the effect is to listen to the sample available below.
Another peculiarity of Airspy HF + is the free "SpyServer" software, which provides an easy-to-configure remote server. Here, a small calculator (an economic Raspberry PI or similar) can take on the function of a server to which Airspy HF + is connected. It is therefore possible to access the receiver via the network in the usual way, even with multiple listeners at the same time. The difference from other web-based projects is that the transferred data is actually an IQ signal, which can then be processed by the usual SDR software with all plug-ins. You are not hampered by the limitations given by a web browser used as SDR software.
|HF||0.009 - 31 MHz|
|VHF||60 - 260 MHz|
|MDS||@ 500 Hz, 0-31 MHz||-140 dBm|
|MDS||@ 500 Hz, 60-108 MHz||-141.5 dBm|
|MDS||@ 500 Hz, 118-136 MHz||-142.5 dBm|
|MDS||@ 500 Hz, 136-174 MHz||-140.5 dBm|
|MDS||@ 500 Hz,> 175 MHz||-140 dBm|
|IIP 3||0-31 MHz||+15 dBm|
|IIP 3||60-260 MHz||+13 dBm|
|BDR||0-31 MHz||110 dB|
|BDR||60-260 MHz||95 dB|
|Width of the spectrum / waterfall||48, 96, 192, 384 & 768 kHz (up to 660 kHz alias-free)|
|Oscillator Accuracy||0.5 ppm|
|Antenna connectors||2x SMA (HF, VHF)|
|Temperature range||-45 - + 85 ° C|
The Airpy HF + can be used with many programs on different operating systems. SDR # is probably the most suitable, since it comes from the same developer.
- SDR # (Windows)
- SDR-Console (Windows)
- GQRX (Linux, MacOS)
- All programs that can use the ExtIO.dll library (HDSDR, Studio1, Elad FDM-SW2 and others)
Here is the source code for an ExtIO.dll library suitable for the Ayrpy HF + . The website itself also shows a compiled image, but it is probably not sufficiently tested. With a wider deployment of Airspy HF + SDR, this DLL will become more stable or other versions will be available.
Here is source code for libairspyhf on Github , an open source library for various platforms such as Linux, MACOS etc.
More information on the Harmonic Rejection Mixers
To better understand how a Harmonic Rejection Mixer works, refer to the following technical documents (both in English):