First of all, a massive thank you to everyone who backed the campaign, supported us with messages, reported issues, helped fix them, ported their apps to support XTRX, and shared their test results with us.

We’ve gathered a lot of feedback from our backers and other industry players, and while this may disappoint some of our backers, we decided to replace XTRX CS (Crowd Supply) version with XTRX Pro - a higher spec but also more expensive revision of XTRX. We believe that this will ultimately help us achieve our goal - a widely available, high-quality embeddable SDR.

At the same time, we’re always happy to create customized, price optimized versions of XTRX for customers with high volume orders. We also intend to introduce more XTRX versions with different specs depending on feedback and demand.

XTRX Pro vs XTRX CS

Software drivers will automatically detect the XTRX hardware version, so there should be no difference from an application perspective - unless you use a feature only available in the Pro version.

XTRX CS is the version initially offered during the Crowd Supply campaign. If you placed an order before this update was published, you will be receiving the XTRX CS version. You can always check which version you ordered by logging in to your Crowd Supply account. If you would like to change your order, you can do so by contacting Crowd Supply. Be sure to include your order number.

FPGA Size and DSP Acceleration

A bigger FPGA is a frequent request we get from backers who want to pre-process samples on the FPGA before sending them to the computer. The Artix 7 50T on XTRX Pro gives you a good deal of space for DSP processing. We will publish a detailed FPGA utilization report a bit later when we publish the FPGA code.

One thing few people accustomed to USB-based SDRs realize is that, with a PCIe bus, there is plenty of bandwidth to move data back and forth between an XTRX and a PC. Even better, the latency of the PCIe bus is much lower than the latency of USB 3. This means you can have DSP accelerators on the XTRX FPGA!

A DSP accelerator is an FPGA block which can be accessed from the PC as a function call. As an example, one could implement an FFT DSP block. You would then get raw samples from an SDR, preprocess them on a CPU, then move them back to the XTRX FPGA for FFT and get frequency domain samples back to the CPU again. This allows you to combine the best of both worlds — the flexibility and simplicity of CPU programming with the high performance of FPGA processing.

What else does a larger FPGA allow us to do? We can, for example, put a RISC-V softcore onto the XTRX. Combined with DSP accelerators on the FPGA, this opens even more possibilities.

We plan to offer a set of DSP accelerators for the most popular cases. Please share your ideas of which accelerators would be most useful.

Note that the FPGA code will be released under a permissive open source license, which will allow you to create both open source and proprietary extensions to the baseline FPGA image.

Temperature Range

While intuitively understandable, this parameter is worth some explanation. First of all, please make sure you don’t confuse "temperature range" with "operating ambient temperature."

Temperature range specifies the hottest and coldest points on the hottest and coldest chips on the PCB, respectively.

The ambient (environmental) temperature at which your system will be able to operate will always be more restrictive than the temperature range. Exactly how much more restricted is determined by the temperature gradient of your heat dissipation/cooling solution, which is normally at least 10°C.

We paid a lot of attention to heat dissipation and made sure the hottest chips (RFIC and FPGA) are both on the bottom side of the XTRX PCB to make it easy to dissipate the heat into a carrier PCB. At the same time, the metallic cage on the top side of the XTRX PCB serves a dual purpose of RF shielding and additional heat dissipation because it’s well thermocoupled with the RFIC chip. If you can’t dissipate heat into the underlying PCB or if you just want some extra heat dissipation, you can put a heatsink onto the cage.

Reference Clock

Most, if not all, other low-cost SDRs available on the market use TCXOs with a frequency stability of 1-2 ppm, or even 20 ppm. This means that at a frequency of 1 GHz, you will tune +/- 1-2 kHz or +/- 20 kHz respectively. Your sampling clock will be similarly off as well. This works fine for a lot of use cases, but some important use cases we’re targeting require much better reference frequency stability. For example, cellular applications require 50 ppb accuracy for macro cells and 200 ppb for small cells. Radar and some other applications require very stable clocks as well. This is where XTRX’s 100 ppb / 500 ppb TCXO will make a lot of difference - running a GSM/UMTS/LTE base station with XTRX will "just work."

XTRX Pro Availability and Early Access

We plan that XTRX Pro units ordered now will ship before January 31, 2019. The exact shipping date will be announced later when we go into production.

For a limited time, pre-orders of XTRX Pro will be offered at a special price of \$550, after which the retail price of \$599 will take effect. Meanwhile, if you want an XTRX Pro right away, we have several samples of the XTRX Pro ready for immediate shipping at an Early Access price of $2,500 per unit.

Deluxe Bundle, Octopack, and Accessories

As we transition from XTRX CS to XTRX Pro, the Deluxe Bundle and Octopack pledge levels will make similar transitions, effective immediately. If you’ve already placed an order for the Deluxe Bundle or Octopack as of the time of this update being published, you will be getting XTRX CS versions of those products. The Antennas + Cables, USB 3 Adapter with Aluminum Enclosure, and PCIe x2 Front End Adapter will remain unchanged for now, but will likely increase in price once production is complete and they are in stock.

XTRX CS Version End-of-Life Timeline

If you want to have the lower cost XTRX CS, they will be available for sale either until Nov 6 or until we sell out the remaining 250 pieces.

At the same time, we want to assure you that the XTRX CS version will enjoy software and firmware support for the foreseeable future.