NUE-PSK Digital Modem

An easy and portable way to get on the air with PSK-31, RTTY and CW ... no computer required!

The NUE-PSK is a small 7" x 4" x 1" standalone, battery-operated digital modem using a graphic display for transmit and receive text data, as well as for showing band spectrum and tuning. Just plug in a standard PS2 keyboard and connect to an SSB-capable transceiver like the FT-817 or the PSK-xx transceivers from Small Wonder Labs, and you'll have an effective digital mode station that goes absolutely anywhere.

The NUE-PSK modem is an "open" design, with published hardware details and software source code. What this means is that many others can contribute to the modem's capabilities and modes of operation. Already we have a "USB add-on option" that maintains the current time and date, and lets you record the QSO (with a timestamp) to a USB stick for archival or EmComm use.

Further, the modem has the ability to be "field upgraded" by using a serial port (or USB thumb drive) to load new versions of the modem software. The NUE-PSK Modem supports BPSK (PSK-31), QPSK, RTTY and CW. Just download the latest-and-greatest modem software from this website and send it to the modem over the serial port. It's the modem that keeps on growing ... new modes, new features, new add-on accessories!

MODEM NEWS
Updated: December 31, 2013

> Version 5.03d Software Available ... We added External Monitor (MON) feature to send the modem�s Tx and Rx data characters to the modem�s type �B� USB serial port (square jack on the side of the modem case), in addition displaying them on the modem�s LCD. This feature, toggled on/off by the ctrl-E keystroke, shows �MON� at the right side of the modem LCD when active, and allows modem data to be sent to a terminal emulator program running on a PC, and thus may allow the operator to more easily view the incoming and outgoing modem data. Notes: (1) The PC�s serial port must be set to 115 Kbps N81, no flow control. This may be set in the terminal emulator application running on the PC; and (2) A USB flash drive containing a new �ftrfb.ftd" file must be inserted to the modem upon initial power-up in order that the modem�s USB controller chip is updated to the correct version. (See Latest Software files below for this ftrfb.ftd file. Thanks to Milt W8NUE for this great feature!

> SDR Cube Transceiver ... an SDR transceiver that is optimized for digital mode operation with the NUE-PSK Modem � Want another easy way to take your digital mode operation to the field? Check out this companion to the NUE-PSK modem: a portable, Software Defined Radio transceiver that also does not need a PC to work! It's a fully self-contained CW/SSB/AM transceiver with some amazing features that make it great for the digital modes when used with the NUE-PSK.

Overview
PSK31 is one of the latest communications modes to capture the interest of hams worldwide. Its inherent ability to dig out low, near-inaudible signals is ideally suited for low power QRP enthusiasts. The PSK31 digital modem engine, however, requires intense DSP processing that is only commonly available in PC sound card. Thus the PSK operator desiring portability for field operation is locked into using a laptop computer as a controller, which results in a cumbersome station. But there�s hope!

The NUE-PSK is a standalone, battery-operated digital modem using a Microchip dsPIC33F microcontroller. The project uses a single graphic display showing transmit and receive text data, band spectrum, and tuning indication. When coupled with an SSB-capable transceiver and a standard PS2 keyboard, the NUE-PSK Digital Modem forms an effective, compact, and portable station for working the digial modes on the amateur bands.

> Standalone, half-duplex modulator/demodulator for amateur radio digital mode communications

> 128 x 64 pixel graphic LCD displays audio signal spectrum 500 Hz to 2.5 kHz (with backlight)

> Tx and Rx buffers and menu system displayed in lower half of LCD using four 20-character lines of text

> Standard PS2-style or dual-mode USB/PS2 keyboard (user-supplied) provides text input for Tx entry, command/mode selection and modem frequency adjustment

> Connection to SSB transceiver: 8-pin mini-DIN (audio in, audio out, PTT, power)

> Powered by two internal 9V batteries (not included) or an externally-applied supply via 2.1mm coaxial jack

> Power requirements: 9-18V DC. Current at 12V is 60 ma without backlight, 80mA with backlight. The current decreases as input voltage is increased.

> Aluminum enclosure provides for rugged portable use while shielding transceiver from digital EMI

> Cable assembly provided (plug and shielded cable) for connection to the SSB transceiver
> Optional USB Card provides ability to record transmit and receive text from QSOs for archival and printing. Also serves as serial adapter port for connection to PC for upgrading modem software, and for uploading/editing/downloading file with modem settings and macro text strings.

As illustrated below, a dsPIC33F is at the heart of the project design. This highly-integrated dsPIC33F device employs a powerful 16-bit architecture that seamlessly integrates the control features of a Microcontroller (MCU) with the computational capabilities of a Digital Signal Processor (DSP). The resulting functionality is ideal for applications that rely on high-speed, repetitive computations, as well as control � just perfect for the NUE-PSK Digital Modem.