Chipset-based Radios

Digital Television Chipset-based SDRs

Shortly after the year 2000, a number of specialty chips were developed to support new digital television standards, DVB-T (Europe, Africa, Asia) and ATSC (North America, South America and South Korea).  Eventually radio, hardware, and software hobbyists figured out how to repurpose these chips for use as general purpose SDR communications receivers.  These chipsets have enabled the production of very inexpensive, yet capable, radios.

One of the earliest and most popular series of such SDRs are the many variants of RTL-SDR.   These are based on a variety of chips such as  RTL2832U ,Elonics E4000, Rafael Micro R820T/R860/R828D, FitiPower  FC0012/FC0012, and the FCI FC2580.  Many RTL-SDRs are implemented in the USB-dongle form factor, similar to a USB memory stick.  The basic chips have 8-bit analog-to-digital converters, which does limit their dynamic range.  More detail about RTL-SDR can be found at RTL-SDR.COM.

Another popular digital Radio/TV chipset from Mirics Semiconductor, the MSi001 tuner chip and the MSi2500 USB interface/ADC chip, are used in the SDRPlay series, the FUNCube Dongle Pro+ and many Chinese "MSI-SDR" or "RSP1" clones. 

SDRs based on digital television chipsets almost always require a separate computer to operate.

Self-Contained Chipset Radios

More recently, the Silicon Laboratories/Skyworks Solutions Si47xx, the NXP TEF6686/TEF6688 and KTMicro KTM09XX radio chipsets, have become very popular.  These chipsets were designed specifically for radio service.  Many of these radios use an embedded ESP-32 microprocessor or other CPU to control the display and user interface, and do not require an external computer for normal operation.

Si473X Radios

TEF668X Radios

KTM09XX Radios

The latest wrinkle is dual self-contained chipset radios that have both a Si4732 and a TEF6686.  These radios have not just two radio chipsets, but two separate ESP32 microcontrollers, and two separate user interfaces - buttons and touchscreen for the TEF6686 part, and touchscreen and combination push-switch/rotary encoder for the Si4732 part.  A single button switches between radio chipsets, showing the appropriate boot up screen for each set of firmware.  There are  3 radios with similar form factors - the Si4732-based ATS-120, the TEF6686-based ATS-125, and the dual chipset ESP-138.

The overall quality of reception depends greatly on the external components and circuitry used in the builds.   Most serious reviews of the chip-based radios reinforce the judgement that these are suitable only for "casual" listening.  

The DeepSDR 101 and Clones

The DeepElec DeepSDR 101 is a portable receiver covering 100 kHz to 149 MHz with a spectrum analyzer display that can cover up to 192 kHz centered on the receive frequency.  It can receive CW, USB, LSB, AM and wideband FM.  It uses a Silicon Labs Si5351 quadrature clock generator to an unnamed CODEC used as a Tayloe Zero-IF product detector.   The IQ signal output of the CODEC is processed by a ARM Cortex-M4 CPU.

The DeepSDR advertises an  AM sensitivity of 10 microvolts across the medium wave broadcast band, and 1 microvolt for HF shortwave (0.25 microvolts for SSB/CW).  There is only one processed bandwidth for each mode - 800 Hz for CW, 2.6 kHz for LSB/USB, 9 kHz for AM and 192 kHz for wideband FM.

The DeepSDR 101 clones are sensitive, and the advertised bandwidths are sound reasonable.  But the receivers are subject to strong out of band signals and images, as well as artifacts on the spectrum display.  Like the radio-on-a-chip models, an external preselector and step attenuator are almost a prerequisite for decent reception when using an external antenna.

The user interface is similar to that of the ATS-Mini radios - a single combination push button and rotary encoder is used to select radio parameters and then (via rotary encoder) to change the values.  Not very user friendly....

The DeepSDR 101 is no longer in production, as DeepElec is developing new models.  That has not stopped numerous clone makers from issuing their own very similar versions.  The clones do not support the uploading/modification of either the firmware or memory presets  that the authentic DeepSDR supports, but this can be corrected by adding missing surface mount resistors in the universal serial bus section of the circuit.  DeepSDR actually warns about the clones in their firmware update documents.  The original DeepSDR uses a BNC connection on the left side; most clones use an SMA connection on the top left.