A few months ago the popular SDRTouch software for Android added support for the SDRplay RSP. The RSP is a $149 USD software defined radio with a tuning range of 100 kHz to 2 GHz and a 12 bit ADC.
Over on YouTube user Mile Kokotov has uploaded a video showing the SDRplay RSP running in SDRTouch. He uses it to listen to the 14 MHz ham band in SSB mode and finds that reception is clear and that it is fairly easy to tune around.
In order to use the RSP with an Android device you will need a fairly modern phone and a USB OTG cable. Ideally try to get a USB OTG cable with an external power port as the battery can drain quite fast when using the SDR. SDRTouch also supports the RTL-SDR.
Over on YouTube user Veryokay has uploaded a video showing how he was able to receive WSPR (Weak Signal Propagation Report) signals at 14 MHz with his direct sampling modified RTL-SDR. WSPR is a HF mode designed to be received even if the signal is very weak. It is used to help determine radio propagation conditions. Direct sampling mode allows you to receive HF signals on an RTL-SDR without the need for an upconverter, but it is more difficult to implement and get good results with. To get the best results Veryokay built an add on PCB that fits onto the RTL-SDR which contains and LNA and single ended to differential operational amplifier to amplify and get correct impedance matching on the input.
His video mainly shows how to calibrate the receiver correctly to receive WSPR as incorrect calibration is the most common error when trying to receive WSPR for the first time. In the video he also explains that he is transmitting WSPR himself using his Raspberry Pi and a QRPi WSPR filter shield for use with Rpitx.
Receiving WSPR with the RTL-SDR in direct sampling mode and WSPR-X.
Receiving WSPR mode at 20m with RTL-SDR dongle in direct sampling
Over on YouTube user Mile Kokotov has uploaded a video showing him receiving a WPX CQ CW (morse code) contest on his SDRplay RSP. The SDRplay RSP is a $149 USD software defined radio with a tuning range of 0.1 – 2000 MHz, 8 MHz maximum bandwidth and 12-bit ADC.
In the video Mile shows that the SDRplay is capable of receiving many strong closely spaced CW signals at the same time as weaker ones without overloading. He uses the HDSDR software and a large 43.1m long delta loop antenna strung up in his backyard.
In the HF region between about 0 – 30 MHz it is common to see and hear “chripers” – signals which quickly sweep through the HF frequency band and produce an audible chirp. These chirps are actually signals from Ionosondes which is a type of radar system used to monitor the Ionosphere. The Ionosphere exists about 50km above the surface of the earth and is the atmospheric layer responsible for a large part of long range HF communications. In a previous post by Mario Filippi we also discussed Ionosondes.
Usually it is scientists who transmit and monitor these Ionosondes, however if you have wide band radio that can cover a majority of the HF spectrum then you can also monitor these chirpers yourself. Over on his blog Fabrizio Francione has created a post showing how to use a USRP, together with a GNU Radio Program called GNU Chirp Sounder to create his own amateur Ionogram monitoring station. The USRP is a fairly expensive SDR with a bandwidth of 25 MHz, but we add that we think that next generation of low cost wide band SDRs like the up and coming LimeSDR should also be able to do the same job.
The Ionograms show at what frequencies HF propagation is currently optimal for a specific distance (or number of signal bounces from the Ionosphere). Below is an example Ionogram animation showing the reception of Ionosondes taken over time. Video from the GNU Chirp Sounder page.
The KiwiSDR is a software defined radio with 30 MHz of bandwidth and a tuning range that covers 0 – 30 MHz (VLF to HF). It is intended to be a low cost web based SDR that can be accessed from all over the world via a browser interface. It is designed as a cape for the BeagleBone Black mini embedded computer, and uses a LTC 14-bit 65 MHz ADC and Xilinx Artix-7 A35 FPGA. It also has an integrated SDR based GPS receiver which is used to automatically compensate for any frequency drift from the main 66.6 MHz oscillator. It runs on the OpenwebRX web based software, which many RTL-SDR users have already been using to stream live radio to the web.
In a previous post we mentioned that the KiwiSDR project had some ethical issues attached to it. The creator of the OpenWebRX software, Andreas, was upset over the fact that the KiwiSDR had forked his open source project and had said that they would not share any profits. However, it appears that KiwiSDR have now struck a deal with Andreas, with both sides being happy, thus resolving any ethical issues.
Over on the SWLing Post blog contributor Mike Ladd has posted up a review of the Soft66RTL3 software defined radio. The Soft66RTL3 is a fully enclosed SDR unit that consists of a standard mini RTL-SDR dongle, a selectable upconverter circuit, several switchable bandpass filters for HF and a UPC1688 RF amp which is enabled in HF mode and is controllable through a trimmer pot. The selectable bandpass filters are from 0.4 MHz to 1.2 MHz, 1.2 MHz to 5 MHz, 5 MHz to 15 MHz and 15 MHz to 30 MHz. The unit also comes enclosed in an aluminum box with an SMA input connector and Micro-B USB port.
The Soft66RTL3 is custom produced by Kazunori Miura (JA7TDO) who is based in Japan. The Soft66RTL3 sells for $40 USD shipped, or $46 USD shipped with registered air mail.
In the review Mike shows us the insides of the Soft66RTL3 and discusses its features. Later he also shows an installation and user guide.
Over on YouTube user London Shortwave has uploaded a video showing a comparison of the FunCube Dongle Pro+, Airspy with SpyVerter upconverter and SDRplay on shortwave reception. The Funcube, Airspy and SDRplay are all $150 – $250 USD software defined radios that have much higher performance compared to the RTL-SDR.
In the video he tests the reception of Radio New Zealand International (RNZI) at 9400 kHz using a 6m copper wire dipole and 9:1 matching balun raised 2m off the ground. He did not use any external antenna preselectors. The RNZI station is weak and appears to be almost blocked by a stronger station so reception of the station is difficult.
In his results it appears that the FunCube and Airspy/SpyVerter are able to clearly receive the RNZI station, but the SDRplay has trouble with images of other stations mixing into the signal.
Differential GPS (DGPS) are signals that exist between 285 – 325 kHz and are used to enhance the accuracy of GPS receivers. The system can improve GPS accuracy from 15m down to 10cm in some cases. It works using a network of ground stations at a very accurate known location that continuously measure the GPS error they receive. They then broadcast this error to DGPS capable receivers. The receiver can then use this error knowledge to correct their own readings.
