The KiwiSDR is a wideband HF software defined radio that is designed to receive the entire 10 kHz – 30 MHz spectrum all at once. It works together with a BeagleBone single board computer and uploads it’s wideband radio data to the internet via the OpenWebRX SDR web interface and control software. Examples of KiwiSDRs shared publicly on the web with OpenWebRX can be found at sdr.hu.
Back in April of last year the KiwiSDR was successfully crowd funded on Kickstarter, and was later released for general ordering in October from SeeedStudio. Normally the KiwiSDR kit including KiwiSDR, BeagleBone, enclsoure, GPS antenna and SD card costs $299 USD.
Currently a Massdrop is underway for KiwiSDR (it seems that the link only works for logged in users). If you didn’t already know, a Massdrop is an organized group buy effort. Buy grouping several individual orders together and making a bulk order, the manufacturer is likely to give a discount. Currently the price for the KiwiSDR kit on the Massdrop is $249.99 USD ($50 saving on the regular price), with only 2 days remaining to join in. Once finished, the estimated shipping date is April 24, 2017.
Over on YouTube Jon, head of SDRplay marketing has uploaded a video showing how the SDRplay RSP2 can be used for accurate RF power measurements. In the video he shows how well calibrated the RSP2 is by comparing how well the power measurements in SDRuno match with a signal generator at various frequencies and power levels.
Later in the video he shows how RF power measurements can be used in a field situation by using the RSP2 and SDRuno to compare the performance of two different whip antennas.
Last month we saw news of the Airspy HF+, which is a yet to be released software defined radio with a focus on high performance reception in the HF bands. Some preliminary specs were unofficially released back then on the Airspy Yahoo forums.
Now over on the Airspy website, the official specifications have been released and they are pasted below. The specs suggest that the Airspy HF+ will have extremely high performance when it comes to strong signal handling. This means that there should be little to no chance of overloading, and thus no intermodulation or spurs.
The goal pricing is to be below $200 USD. If this is true, then it will compete heavily with the $249.95 USD ColibriNANO which is another new HF specialty radio with similar specs.
The Airspy team write:
Airspy HF+ is a paradigm shift in high performance HF radio design. It is a joint effort between Airspy, Itead Studio and some famous chip maker to build a state of the art SDR for HF and VHF bands.
Like most high-end HF receivers, the HF+ uses very high dynamic range ADC’s and front-ends. But unlike the current offerings in the market, it also brings more frequency agility by using high performance passive mixers with an excellent overtone rejection structure. Both the architecture and level of integration achieved in this design allow us to bring top performance reception at a very affordable price.
HF Tuner
Airspy HF+ achieves excellent HF performance by mean of a low-loss band filter, a high linearity LNA, a high linearity tunable RF filter, an over-tone-rejection (OTR) mixer that rejects up to the 21st harmonic and an IF filter. The 6 dB-stepped AGC gain is fully controlled by the software running onto the DSP which optimizes the gain distribution in real time for optimal sensitivity and linearity. OTR is a key issue in wide band HF receivers because of the large input signal bandwidth. The output of the IF-filter is then digitalized by the IF ADC for further signal processing.
VHF Tuners
Excellent VHF performance is also achieved by using optimized signal paths composed by band filters, high linearity LNAs with a stepped AGC and an over-tone-rejection mixer and IF filters optimized for their respective bands. The amplifier gain is switchable in 3 dB-steps and is fully controlled by the AGC processing running onto the DSP. The RF signal is converted to baseband by a high linearity passive mixer with overtone-rejection structure. The low-IF signal is then converted into the digital domain by the IF ADC for further digital signal processing.
IF Digitalization
The IF digital to analog converter has a 4th order multi-bit topology; it features very high dynamic range and linearity. The IF-ADC sampling frequency is determined by a control algorithm running on the DSP. This advanced technique changes the sampling frequency depending on the tuning frequency with the goal of avoiding the disturbances generated by the switching discrete-time sections of the IF-ADC.
Digital Down Converter
Once the IF signal is digitalized, the high sample rate I/Q stream is then frequency translated and processed with cascaded CIC and FIR decimation stages. After every stage, the sample rate is reduced and more the resolution is increased. The final signal at the output has 18bit resolution and the alias rejection performance is 108 dBc. The data is then scaled to 16bit and sent to the Micro-Controller for streaming over USB.
Use it over the network!
Connect as many SDR applications as needed to the HF+, over the Internet or in your own local network with near zero latency thanks to the new SPY Server software. This setup basically brings all the flexibility of Web based SDRs while still benefiting from the full power of desktop applications. The IQ data is processed in the server with state of the art DSP and only the required chunk of spectrum is sent over the network. What is sent is the actual IQ signal, not compressed audio. This means you can use all your favorite plugins to process the IF, eliminate noise and perform heavy lifting of the signals as you are used to do with locally connected SDR’s. We have a tradition of building multi-tools, so we made sure the SPY Server runs on 32/64bit Windows and Linux on Intel and ARM processors without any compromises. Low cost Raspberry Pi 3 and Odroid boards are in the party.
This software decoder appears to be an excellent choice for those people who want to perform their reception and decoding of Meteor M satellites all in Linux. Previously as explained in this previous post, you were able to receive the QPSK data in Linux with an RTL-SDR and a GNU Radio program, but then you’d still need to boot into Windows or run Wine to run LRPTofflinedecoder in order to generate the image. Now it appears that the image generation can be performed natively in Linux too with meteor_decoder. This help with creating portable automated Raspberry Pi based Meteor M decoder servers.
Meteor M is a class of Russian weather satellites that transmit live weather images of the earth as they pass over your location. They are somewhat similar to the NOAA satellites, although the Meteor satellites transmit higher quality images via a digital LRPT signal, rather than the analog APT signals used by NOAA. With an RTL-SDR, an appropriate antenna and decoding software they can easily be received.
An Example LRPT Image Received with an RTL-SDR from the Meteor M-N2 Satellite.
Back in September 2015 we made a posted that discussed how some amateur radio astronomers have been using RTL-SDR’s for detecting pulsars. A pulsar is a rotating neutron star that emits a beam of electromagnetic radiation. If this beam points towards the earth, it can then be observed with a large dish antenna and a radio, like the RTL-SDR.
In their work they showed how they were able to detect and measure the rotational period of the Vela pulsar, one of the strongest and easiest to receive pulsars. They also noted how using several RTL-SDR dongles could reduce the required satellite dish size.
Antenna: 7.3m homemade offset dish, OE5JFL tracking system Feeds: 70cm (424 MHz) dual-dipole with solid reflector, 23cm (1294 MHz) RA3AQ horn Preamplifiers: 23cm cavity MGF4919, 70cm 2SK571 (30 years old!) Line Amplifier: PGA103+ Interdigital filter: designed with VK3UM software, 70cm 4-pole, 23cm 3-pole Receiver: RTL-SDR (error <1ppm), 2 MHz bandwidth Software: IW5BHY, Presto, Tempo, Murmur
Furthermore, from looking at the Neutron Star Group website, it seems that the majority of amateur radio astronomers interested in pulsar detection are currently using RTL-SDR dongles as the receiver. Some of them have access to very large 25m dishes, but some like IW5BHY, IK5VLS and I0NAA use smaller 2.5m – 5m dishes which can fit into a backyard.
If you are interested in getting into amateur pulsar detection, check out the Neutron Star Group website as they have several resources available for learning.
OE5JFL’s 7.3m pulsar detection dish with an RTL-SDR receiver.
Over on YouTube user ElPaso TubeAmps has uploaded a video showing his tests on our broadcast AM (BCAM) high pass and broadcast FM (BCFM) band stop filters. These two filters are designed to block broadcast radio signals which in some locations can be extremely strong. If they are very strong then they can overload your SDR which causes very poor performance, even on other frequencies.
Some possible solutions for reducing overloading include:
Attenuation – reduce all the strength of ALL signals coming in.
Increase SDR dynamic range – purchase a higher end SDR with more ADC bits as these can handle strong and weak signals coming in together much better.
Filtering – reduce the signal strength on the problematic frequencies that are causing overload, or only allow your frequency of interest to pass.
Antenna tuning – use a narrowband, directional and/or differently polarized antenna which reduces the unwanted signal’s strength.
In the video he uses his signal generator and a spectrum analyzer to analyze the output of the filters. His results closely match our VNA results which are posted on the BCFM and BCAM filter product release posts.
Over on YouTube user Danny Shortwave And Radio DX has uploaded a video showing an overview and tutorial about setting up the Soft66IP RTL-SDR. The Soft66IP is a custom RTL-SDR that is made in Japan by JA7TDO. It is an RTL-SDR with upconverter and LNA built into a box together with an embedded computing platform. We’re not sure what the computing platform is, but it is likely to be something similar to a Raspberry Pi. The computing platform is then used to run an rtl_tcp server, and so via a network cable or WiFi connection the device can be accessed by a remote PC.
On the video Danny gives an overview on what the Soft66IP is, and what features it has. Then later in the tutorial he shows how to SSH into the Linux server on the Soft66IP, set it up for your local network, and then later how to connect to it from a remote PC.
How to setup Soft66IP for your Local Area Network with SDRSharper
RPiTX is a piece of software that you can run on your Raspberry Pi unit, which with no additional hardware turns it into a full radio transmitter, capable of transmitting FM, AM, SSB and other signals anywhere from 5 kHz to 500 MHz. Of course remember that the methods used to do this emit a lot of harmonics, so to be legal and safe filtering should be used on the signal output.
Over on Twitter Cyril @kotzebuedog has been experimenting with RPiTX and his radio controlled toy car. From the videos and images, it appears that he’s used GNU Radio to create the required control signals which then transmits the data to the RC car via RPiTX. With this he’s been able to create a program to control his RC car with his computer gaming joystick.
