The QS1R Communications Receiver

Disclosure: AB9IL.net is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program such that this site earns advertising fees by linking to Amazon.com. If you make a qualifying purchase after clicking a link on this website, the associate affiliated with this site may earn a comission at no cost to you.

#Advert: Unleash your powers with a Razer laptop.

New Features: Global Quick Tune Internet SDR List Improve Your Radio Knowledge at "YouTube SDR School"
Article Index --- click here to unfold ---
Newest Pages NEW: Texas is the Valu-Jet of States
NEW: Ubuntu PPAs for Alacritty
NEW: Trumpists Kicking the Hornets Nest
NEW: Introduction to Catbird Linux
NEW: Skywave Linux Updated to ver 4.1
i3wm: Using i3-ipc to Float Windows
How to Record from WebSDR and OpenWebRX Sites
Programmatic RTL-SDR Frequency Claibration
Public KiwiSDR Lists
Malaysia Airlines Flight MH17: Simply Mass Murder
The Anonymous Cathay Pacific Employee Letter to Hong Kong
For For Cathay Crews Crossing Borders With Electronics
Photo Gallery 9: The New Life Movement in China, 1944
E Pluribus Unum: From Many, One, Dammit
HFGCS Quick Tune SDR List
The Robert Mueller Iron Triangle Speech
A Rant About One Party Rule
Best OpenWebRX and WebSDR Servers
SDR School via YouTube
ADALM-PlutoSDR on Linux Systems
MOFO Linux: Defeating State Censorship and Surveillance
Linux: Distros, Code, and Nifty Software NEW: Ubuntu PPAs for Alacritty
NEW: Introduction to Catbird Linux
NEW: Skywave Linux Updated to ver 4.1
NEW: i3wm: Using i3-ipc to Float Windows
Skywave Linux: HPSDR, WebSDR, and RTL-SDR ready to run.
Siduction Linux with the Cinnamon Desktop
Siduction Linux with the LXQT Desktop
Andy's Ham Radio Linux 15 and QtRadio
Booting Multiple Linux Disc Images with Grub2
Porteus Linux Hard Drive Installation
UPDATED: MOFO Linux - For Unrestricted Internet
Aptosid with LXDE
Asus EeePC 1215N with Linux
Autostart Tweaks for KDE3 and KDE4
Broadband Speed Tweaks For Linux
Fixing the Firefox 3 Rendering Bug
Linux on Solid State Drives
Linux Wireless Interface Driver Updates
Setting Polkit to Automount USB Devices
Sidux with LXDE
Fixing Skype Inverted Video
SLAX Remix - kernel upgrades
Flash Drive Linux - Introduction
Flash Drive Knoppix 5.3 - Part 1
Flash Drive Knoppix 5.3 - Part 2
Flash Drive Knoppix 6.0 - Part 1
Flash Drive Knoppix 6.0 - Part 2
Flash Drive SLAX - Part 1
Flash Drive SLAX - Part 2
Flash Drive Bluewhite64 - Part 1
Flash Drive Bluewhite64 - Part 2
Flash Drive Linux - Basic Customization
SLAX Customization - Part 1
SLAX Customization - Part 2
Bluewhite64 Customization - Part 1
Bluewhite64 Customization - Part 2
Long Range Wi-Fi Basics of Long Range Wireless Networking
Linear Focus Parabolic Wi Fi Antenna
High Gain Wi Fi Dish Antenna
High Gain Helical Wi Fi Antenna
High Gain Yagi Wi Fi Antenna
High Power Wireless Adapters
Wi Fi Extender Antenna for Routers
Belkin F5D7050 External Wi Fi Antenna
Linksys WUSB54GC External Antenna Mod
Compat Wireless Linux Drivers
Installing WPA_Supplicant for Wi-Fi Security
Linux Wireless Interface Driver Updates
Linux Wireless Interface Driver Support
NetworkManager and Consolekit
RT73 Wireless Drivers for Linux Kernel 2.6.27+
RT2860 Wireless Drivers for Linux Kernel 2.6.27+
Radio: Amateur Radio, Aero Radio, Shortwave, etc NEW: Programmatic RTL-SDR Frequency Claibration
NEW: Public KiwiSDR Lists
NEW: GHFS Quick Tune SDR List
UPDATED: Best OpenWebRX and WebSDR Servers
UPDATED: Skywave Linux: HPSDR, WebSDR, and RTL-SDR ready to run.
CubicSDR on Debian, Ubuntu, and Linux Mint
Dump1090 for Linux Mint 17.1 and Siduction 2014.1
Software Defined Radio - An Introduction
QS1R Direct Sampling SDR
Chaining SDR Audio Interfaces
FLEX-6000 Direct Sampling SDR
RTL2832 Software Defined Radio
WebSDR Digimode Reception
Enabling FLASH in Jack Audio
Realtime Software Audio Processing
Liberation Technology MOFO Linux - For Unrestricted Internet
Veracrypt Encryption for Linux
Veracrypt Encryption for Windows
Using Google Within China
Popcorn Time and Flixtor for Uncensored Streaming Media
DNS Encryption using DNSCrypt
Galaxy Nexus Privacy and Robustness Enhancements
Galaxy SIII Privacy and Robustness Enhancements
Flash Drive Encryption for Linux
Flash Drive Encryption for Windows
Multihop VPN Connections for Strong Internet Privacy
Open and Free DNS Server List
OpenVPN Cloaking against Deep Packet Inspection The Serval Mesh Phone Project
Skype's Robust Security
Man in the Middle Wireless Security Risks
Wireless Security and Surveillance
Digital Audio Adjusting Audio Dynamics in VLC
Backing Track Prep Guide
Ipod Music Processing Guide
How To Record Record Live Music Performances
Realtime Software Audio Processing
Chaining SDR Audio Interfaces
Aerospace Radio, Aviation, Pontification, and Opinion NEW: Texas is the Valu-Jet of States
NEW: Trumpists Kicking the Hornets Nest
NEW: The Anonymous Cathay Pacific Employee Letter to Hong Kong
NEW: For For Cathay Crews Crossing Borders With Electronics
NEW: E Pluribus Unum: From Many, One, Dammit
NEW: HFGCS Quick Tune SDR List
NEW: The Robert Mueller Iron Triangle Speech
NEW: A Rant About One Party Rule
Captains Authority Versus Autocratic Airline Management
Malaysia Airlines Flight MH17: Simply Mass Murder
Malaysia Airlines Flight MH370 - A Media Circus
High Gain Air Band Antennas
Apollo Unified S Band Communications
Chinese Anti-Stealth VHF Radar
Oceanic Communications - Procedures, Equipment, Voice and HFDL
Boeing 737NG Radio Equipment
Boeing 767 Radio Equipment
NAOC-TACAMO Monitoring
My Flight on 9/11
Joshua Chamberlain's Leadership Tips
Special Operations Forces Truths
TWA 800: Just Give Me Some Truth
Photo Gallery Aviation Photo Gallery 1: Snapshots From My Journeys
Aviation Photo Gallery 2: On the Road With ATA Airlines
Aviation Photo Gallery 3: More ATA Airlines
Aviation Photo Gallery 4: Southwest Airlines is the Borg Empire
Aviation Photo Gallery 5: Starting Over, Moving On...
Aviation Photo Gallery 6: More Viva Macau
Aviation Photo Gallery 7: Mainland China Airline Flying
Aviation Photo Gallery 8: Chinese Smog and Fog
NEW: Photo Gallery 9: The New Life Movement in China, 1944
Broadcasting BBC Radio Blooper - Adolf Merckle
TV DXing the World Trade Center
New York TV after 9/11
Live Music Recording Adjusting Audio Dynamics in VLC
Backing Track Prep Guide
Ipod Music Processing Guide
How To Record Record Live Music Performances
Radio Poetry and Arts In Distress, by David Wagoner
Just A Radio Operator, by Robert A. Wallace
Radio Circuit Modifications ATS-909 Modifications
ATS-909 Manuals
ATS-909 Alignment Procedure
ATS-909 Alignment Spectrograms
Very Low Frequency (VLF) Radio Internet Based VLF Radio Listening
Windows Tips Windows Performance Enhancement Tips
A Faster Windows 7
Windows 7 SSD Setup

UPDATED 09/02/2017: Refined and expanded comments regarding factors affecting dynamic range in QSD versus direct sampling radios.


The bleeding edge of radio technology was initially manifested in projects using quadrature sampling detectors feeding studio quality audio interfaces. Also known as "zero IF SDRs," these devices exhibited characteristics far superior to superheterodyne radios in the following categories:

  1. Dynamic range, thanks to superior "H mode" mixers.
  2. Stability, when the local oscillator is oven stabilized and / or GPS disciplined.
  3. Signal purity, due to high quality high bit depth audio ADCs..
  4. More signal purity made possible with direct digital demodulation.
  5. Panoramic spectrum display, implemented in the software interface.
  6. Point and click tuning, implemented in the software interface.

For example, the Softrock, Flexradio, and RTL SDRs easily outperform most superhet radios in those five aspects. Innovative software makes these radios versatile and easy to use, but ultimately it is RF hardware with the first critical job: capturing a clear enough signal for manipulation in the digital domain.

#Advert: Get your CPUs, GPUs, and Motherboards from GigaParts.

Though the QSD based software defined radios are obviously an advancement beyond superhets, they do have some limitations related to bandwidth, dynamic range, and tuning range. These SDR's operating range is limited by the bandwidth of the A/D converter - often an audio sound card. The QSD based SDR hardware, samples chunks of spectrum in 48, 96, or 192 kHz segments, and relies on a crystal oscillator, phase locked loop or direct digital synthesizer for setting its center frequency. Noise and distortion are introduced during mixing in the QSD due to oscillator phase noise, spurs, filtering, and mixer limitations. Superior signal purity and low noise performance, therefore, is tough design challenge in SDRs. That is why radios like the Flex-3000 or Flex-5000 are not quite as simple as they first appear.

M0RZF has recently (3/2014) published an improved circuit design advancing the popular Mobo QSD based software defined radios. His work has very nicely improved the sensitivity, dynamic range, and useful bandwidth to the point that full HF coverage is possible without the need for a preamplifier. His Unity SDR also has better I/Q balance than the earlier designs, making overall performance MUCH better without the need for tweaks and adjustments after the circuit is built. He also makes a valid point that QSD based SDRs can be smaller, simpler, less expensive, and more energy efficient than their direct sampling counterparts.


Consider a more advanced SDR design: eliminate the mixer and oscillator by directly sampling the entire spectrum of interest, and implement all modulation, demodulation, fuliltering, and processing functions within a virtual transceiver. Very wide bandwidth A/D converters can digitize spectrum from near DC through VHF range, and feed the data stream to a processing engine. This methodhas fantastic potential! Consider a modest list of possibilities:

  1. High dynamic range due to elimination of hardware mixers, diode switched roofing filters, and oscillators.
  2. Very high performance multimode operation.
  3. Versatile multifrequency operation.
  4. Any manner of spread spectrum and high rate digital modes.
  5. Multiple virtual transceivers using one or many antennas.
  6. Synthetic phasing / beam forming for antennas.
  7. Streaming RF data to remote receiver interfaces via internet protocol.
  8. Very high definition reception and recording, limited by user's computing and storage hardware.
  9. Numerous possibilities for RADAR, radio astronomy, and other special modes.

There are some limitations to performance in direct sampling software defined radios. For high bandwidth sampling, the data flow is enormous - enough to stress the limits of modest desktop computers. Internal latency is a factor, and systems must be tweaked to minimize it. Also, while oscillator and mixers are removed from the RF signal path, the ADC clock absolutely must be accurate and steady to prevent distortion and noise due to clock jitter. One issue which seems to NOT be a problem, especially when the operating range is sampled at a far higher minimum sampling rate: ADC overload. Flexradio experience has shown that when the HF range is sampled at a rate five times higher than the theoretical minimum, the summing of many strong signals rarely results in ADC overload. Simulations indicate that overloads would involve single samples and have no significant effects on a received signal.

A group of nearly 1000 talented radio amateurs and short wave listeners have been working on a "High Performance Software Defined Radio (HPSDR)" project with the goal of ceating the sort of direct sampling SDR under discussion here. In fact, the HPSDR group is creating hardware and software which greatly advances radio's state of the art. Their Mercury module is an early example of movement toward direct sampling SDR designs.


Quicksilver 1R SDR
Quicksilver 1R SDR

SDRMax 3D Waterfall
SDRMax 3D Waterfall

SDRMax on 40 Meters
QS1R on 40 Meters

A ready-to use SDR currently available outside of military / government circles provides fantastic performance and very advanced features: the QS1R receiver (and soon a QS1T transmitter), made by the Software Radio Laboratory LLC. This radio is the result of intense brainstorming among numerous talented people, and more specifically, the work of a team led by Philip Covington (N8VB).

The QS1R has excellent specifications, and an in its most basic form, covers the range from 10 kHz to 62 Mhz, and through 300 MHz using undersampling techniques. With proper front end equipment, it can receive VHF, UHF, or microwave signals in a manner far more advanced than conventional communications gear. The unit uses a USB 2.0 interface for connection to the user's computer, and companion software is available for Linux, MAC, and Windows. SDRMax is the open source software for the QS1R. SDRmax may be examined, analyzed, modified, and evaluated by the end user community. With each update, more capabilities are added, and the Quicksilver SDR system continues to improve. Another excellent software interface for the QS1R is HDSDR Both of these software packages give the radio operator the ability to find and use radio signals in an intuitive and effective manner unimaginable in the past.


For radio listeners curious about the Quicksilver SDR, graphical interface software makes it the best web controlled receiver on the internet. The QS1R can be remotely tuned throughout its range, in any mode, and with easily configurable settings. The panoramic display is excellent, and the audio quality is limited only by the end user's soundcard. It is possible to connect to an SDRMAX server on the other side of the world, using a modest broadband connection, and enjoy great sounding signals from the remote QS1R receiver. ESSB signals, for example, seem to jump into the foreground and hardly seem to originate hundreds or thousands of miles away.

Note that presently, when changing servers for SDRMAX, the server IP address should be manually set by editing the "GUILocalSettings.xml" file. It may be possible in the future to select servers from a dropdown list. It all depends on popular demand. If you think these remotely operated QS1Rs are fabulous, be sure to write to the hams hosting them and let them know.

Online QS1R Receivers
Ken, N9VV, Chicago KenN9VV 43065
Tilman, SM0JZT, Stockholm sm0jzt 43065


Frequency Coverage:	10 kHz – 62 MHz
Modes:			LSB, USB, CW, AM, SAM, FMN, FMW
Sensitivity:		0.56 uV SSB (S+N)/N= 10 dB
Selectivity:		120 dB
Image Rejection:	90 dB Input IP3 >42 dBm
Dynamic Range:		101 dB (SSB, 2.4 kHz BW) 104 dB (CW, 500 Hz BW)
SFDR:			112 dB
BDR:			126 dB (CW, 500 Hz BW)
MDS:			-121 dBm (500 Hz BW)
ADC Clipping Level:	+9 dBm ( 8 mW )
Ext. Encode Clock:	60 - 130 MHz, +10 dBm max.
ADC:			16 bit, 125 MSPS
FPGA:			Altera Cyclone II EP3C25
Audio DAC:		TI 24 bit stereo, 50 kSPS
Interface:		USB 2.0 High Speed ( typ. 32 MB/S Max )
Sampling Rates:		25, 50, 125, 250, 500, 625, 1250, 1562, 2500 (kSPS)
Output Bandwidth:	20, 40, 100, 200, 400, 500, 1000, 1250, 2000 (kHz)
Output Signal:		32 bit/sample I-Q pair
Power Supply :		+5 to +6 Volts @ 1000 mA typ.
Cabinet:		Anodized Aluminum 103 x 53 x 160 mm (W x H x L)
Operating Temp:		0 – 40 C
Frequency Accuracy:	+/-1 PPM after calibration

Direct sampling software defined radio is certainly where the bleeding edge is found, and the QS1R reflects that state of the art quite nicely. The QS1R does have new competition in the Flex-6000 direct sampling software defined radio. Evolution, like rust, never sleeps - so expect the Software Radio Laboratory people to further advance their product and show new performance and capabitities in the coming months and years.


©2005 - 2021 AB9IL, All Rights Reserved.
About, Contact, Privacy Policy and Affiliate Disclosure, XML Sitemap.