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SDR Cube Transceiver
The SDR Cube is a totally self-contained, embedded SDR transceiver for CW & SSB using a Softrock for the RF front end and a pc board implementation of an HF modem. PC is not needed for using the SDR Cube, as all DSP processing is accomplished by an embedded DSP processor on the three internal pc boards. The Cube is designed to fit into an optional 4” x 4” x 4” pre-cut black powder-coated aluminum enclosure containing all controls, a blue graphic display showing the transceiver settings and an exciting 8 kHz-wide band scope of spectrum signals, and the popular Softrock RXTX v6.3 board. The SDR Cube may also be used with any of the 11,000 other Softrocks in the field today! Sold as a kit or as a fully assembled & tested transceiver, Cube kits are currently available and fully assembled & tested Cubes will be ready for shipping by the end of January. We presented on the SDR Cube at TAPR's annual "Digital Communications Conference" in Portland, Oregon, and the DCC Proceedings containing our paper is available from TAPR. Many details are already presented here on this website, and active email discussion occurs in the SDR-Cube Group in Yahoo Groups
Standalone SDR transceiver ... No PC required, portable, compact
Self-contained single/multiple bands/module ... Based on the I/Q RF front end
Softrock-compatible ... Designed to interface with SR v6.3 RXTX, etc.
Low Power ... 90ma (Cube), plus 100 ma (Softrock Rx) or 400 ma (Software Tx)
Add-on RF Amp & Attenuator ... Good control of incoming RF, optimize some SR features.
Quadrature Sampling Clocking options ... DDS, Si570, or I2C to target Softrock
Built-in Keyer ... 1-100 wpm, Iambic A, B, or straight key
Popular HF modes ... SSB, CW, Digital (with special interface to NUE-PSK for digital modes)
Special interface to NUE-PSK Modem ... Digital interface provides best quality
Graphic LCD Display ... Provides clear indications of the many status and options
Bandscope ... Provides +/- 4 kHz spectrum visibility for Rx, signal monitor for Tx
Audio filtering ... Low corner 200Hz, high corners 700, 1500, 2400 or 3600Hz
Audio Output ... Headphones or amplified speaker, binaural audio
Beeper ... User interface clicks, code practice oscillator, and more
Frequency agile ... Fast/Med/Slow tune, dual VFOs, memories, RIT/XIT
Menus ... Calibration, all settings, system gain, sidetone frequency, etc.
Software Upgradeable ... Bootloader enables user to load new software versions
Open Source ... Take the source code and add your own features
(See complete Features list at Features)
3-PCB BOARD SET
Click on images for larger views
I/O BOARD DSP BOARD CONTROLS BOARD
The heart of the SDR Cube Transceiver is comprised of three mating PC boards, as shown above. The board set is designed to conveniently connect to each other by means of edge connectors that may be configured in a number of ways. When using the optionally-purchased enclosure, the Controls board fits up against the back of the front panel, with the controls and display accessible by the user. The DSP board connects at a right angle to the Control board to sit in along the left side of the enclosure. And the I/O board connects to the DSP card by means of a short flat ribbon cable to sit parallel to the rear panel. This arrangement maximizes the space inside the SDR Cube such that one can place a Softrock front end or even a battery in the remaining volume of the enclosure.
The Cube board set may also be arrange in other ways for other enclosures, or perhaps in a flat, side-by-side manner, as we have used in our development arrangements, as shown below ...
Softrock RXTX v6.3 Components
SR-BASE with TXPA and RXAMP plug-ins
(Click photo to see larger image.)
SDR Cube Transceiver is able to use any of the 11,000 Softrocks in the field today as its "RF front end". The SDR Cube may be interfaced to the very popular Softrock RXTX 6.3 merely by dropping it into the shielded compartment of the Cube. Or if the model of Softrock you have doesn't fit, such as the current "Ensemble" series, you may interface it externally with a custom wire harness that connects to the back panel of the Cube.
If you do not already have a Softrock, don't worry! We have a good supply of the RXTX 6.3 Softrock transceiver kits with the 80m, 40, and 20m plug-in modules available for sale with the SDR Cube. We even have an enhanced BPF plug-in card for the receive side of the RXTX, and we provide RX and Tx plug-in modules for other bands as well.
The Softrock RXTX 6.3 "RF Front End" is an option in the SDR Cube pricing matrix on the Ordering page.
X-LPF ... an "Extra LPF"
An additional Low Pass Filter for use between the Softrock and the antenna
(Click photos to see larger image.)
This is the "eXtra Low
Pass Filter" that the Softrock RXTX 6.3 designers
recommend using to reduce harmonics when operating on 80m and 30m.
Softrock owners have classically needed to provide this extra LPF in
some way for themselves in the past ... but we include it when when
SR-Base softrock option is purchased with the SDR Cube. The X-LPF
board dimensions are 1/2" x 1" and it mounts on the back of the BNC
connector. The short RF output cable from the SR-Base board
connects over to the nearby X-LPF board and plugs into one of
several pinheader connectors, as determined by the band on which one
intends to operate: 80m or 30m. Then a shunt (jumper) is placed
across another pinheader to route the RF to/from the BNC connector.
But if the Softrock is going to be used on some other band that
doesn't need an extra LPF, the RF cable from the SR-Base gets
plugged into another pinheader on the X-LPF board at the RF is
routed directly to the BNC, effectively bypassing either of the two
extra LPF filters needed for Softrock operation on 80m and 30m.
So again, the X-LPF kit is being provided with all SR-Base
purchases. You do not need to order this item if you already
have an SR-Base option ordered; but SDR Cube owners may order the X-LPF
item for use with their external Softrocks (see order page for
this). The X-LPF schematic is
(BTW, the need for an extra LPF is an example of the Softrock design limitations, not a limitation of the SDR Cube design. We've previously mentioned some challenges of using the Softrock as our "RF front end", and this is another such challenge. We are currently building up other RF decks to see how well the SDR Cube performs with a less-compromised design ... RF decks such as the Genesis Radio 2030, WB6DHW's UHFSDR, the FlexRadio SDR-1000, and some others. Albeit more expensive than the Softrocks, these more encompassing designs have the potential to let the SDR Cube shine with regards to RF performance characteristics.)
TXPA Plug-in Band Module
A band-specific 2.5W RF power amp and low pass filter for the transmit side of the Softrock RXTX 6.3
Kit and assembled version of two modules are available: TXPA-80/40 and TXPA-30/20/17. These modules enable the SDR Cube to operate on three bands: 80m or 40m (with the TXPA-80/40 module) and 20m (with the TXPA-30/20/17 module)
(Click photo to see larger image.)
RXAMP Plug-In Band Module
A band-specific "pre-selector" plug-in for the receive side of the Softrock RXTX 6.3
What is the RXAMP?
The "Rx Amp" is a
higher-performance plug-in module that replaces the standard RX
BPF plug-in provided when the Softrock RXTX 6.3 was previously
available on the market.
What has been improved? To help make the Softrock perform better, we used a different bandpass filter, a pair of relay-controlled attenuator pads, and a 20 dB amplifier. With the RXAMP, greater front end sensitivity is able to be achieved, with greater user control over the wide-ranging signal levels encountered in a communications radio.
Choose TXPA and RXAMP modules for desired band coverage.
The SDR Cube is able to transceive on 5 ham bands with the correct modules in place, as illustrated below. Additionally, the Cube is able to receive across the 2-30 MHz HF spectrum, again with the correct modules in place, enabling it to perform as a general coverage receiver.
Mating "Accessory" Enclosure
Blank-painted aluminum enclosure the same size as the SDR Cube but with no holes, other than a 15-pin "D" connector on the rear panel. Perfect for holding an external Softrock, an RF power amp, speakers, power supply, antenna tuner, SWR/power meter, or what ever else you might like to build up for your "Cube line".
"Accessory Enclosure" shown to the left of the SDR Cube.
Will be black powder coated to match the Cube.
Now an orderable option.
(Click photo to see larger image.)
Copyright 2012 Midnight Design
Solutions, LLC. All Rights Reserved.
Page last updated: December 12, 2012