Davide Cavion Opens Pre-Orders for the High-Spec, Modular RFNM Software-Defined Radio Platform

Davide Cavion has officially opened orders for the RFNM, a high-performance software-defined radio (SDR) motherboard which uses a choice of radio-equipped daughterboards to deliver a tuning range from 1MHz up to 3,500MHz or 7,200MHz and up to 122.88MHz of streaming bandwidth over USB.

"The RFNM motherboard is a new concept, so it's worth taking a few seconds to understand it," Cavion writes of his project, which has gone from concept to an open crowdfunding campaign in just nine months. "In a nutshell, the most complicated parts are consolidated into a single block, the motherboard, and all of the interesting and fun bits are exposed via the RFNM Interface to daughterboards."

These daughterboards hold the actual tuning hardware, with two planned for the launch: the Lime, based on a Lime Microsystems LMS7002M and offering a single full-duplex transmit-receive channel and tuning between 1MHz and 3,500MHz; and the Granita, based on an Arctic Semi Granita chip and offering two receive-only or one full-duplex receive-transmit channel tunable between 10MHz and 7,200MHz. The RFNM motherboard, meanwhile, is built around NXP's LA9310 programmable baseband processor and a Skyworks Si5510 clock synthesizer — giving it a high-accuracy timing source, an NXP i.MX8MP processor, 4GB of LPDDR4 RAM, and 64GB of eMMC storage.

Those specifications allow the board to shuffle an impressive amount of data to a host machine — though not quite the full 153.6MHz promised by the LA9310's spec sheet. "As we learned, USB 3.0's 5Gbps bandwidth is a marketing lie," Cavion writes. "8/10b encoding lowers that to 4Gbps, and when going through hubs or having any overhead, the limit to what can be had reliably is closer to 3.5Gbps (430MBps). Add in a buffer for slower computers and a good guess is that 400MBps is the number you can design your system against."

That gives the RFNM a still-impressive 122.88MHz of real-time bandwidth, equating to 368MBps of throughput unpacking to 491MBps — or 983MBps using the CF32 format. "To stream the full 153.6MHz the LA9310 is capable of, we need 460MBps @ 12 bit, 422MBps @ 11 bit or 384MBps @ 10 bit. We could split the stream over multiple USB connections (the i.MX has two USB ports), or USB and Ethernet, but it’s probably more reasonable to just use those options for a second stream."

Cavion's latest update on the project, brought to our attention by RTL-SDR.com, opens crowdfunding for the boards, priced at $299 for the RFNM motherboard, $179 for the Lime daughterboard, and $249 for the Granita daughterboard — plus $19 for a breakout board designed for testing the motherboard. "We are happy with the performance of the Lime chip, not so much with the Granita," Cavion admits. "Hopefully it’s just a growing pain, because Granita does come with what seems to be a much lower noise PLL than the Lime."

Pre-orders for the boards are now open on the RFNM website; Cavion recommends buying the Lime daughterboard for a smoother experience, while promising that a daughterboard designed for operation in ham radio frequency bands is in the works.