AmQRP products supplied by MIdnight Design Solutions

NUE-PSK Digital Modem

A digital modem for PSK31 field operation ... without using a PC!

Try out the IW7EHC "Menu Reference Label"
Just print, cut it out and paste to the top of your modem!
(Click for larger view)

NUE-PSK Digital Modem

Pre-Fab Modem Cables also available ...
- Type 1 cable (6-pin miniDIN) supports ... Yaesu FT-817, FT-857 and FT-897, ICOM IC-703, IC-706, IC-7000 and Kenword TS-480
- Type 2 cable (8-pin DIN) supports ... Icom IC-756 and IC-746 families (including PRO models), and the IC-707

Technical Resources

Software:
- Source Code: dsPIC  MC908 -- All the source code useful for developers
- Full Binaries: dsPIC  MC908 -- The actual binaries that get programmed into blank microcontrollers
- Boot-Loadable Binary: dsPIC  -- The binary used for the "Field Programming" updating process

Video Clips:
- Prototype Operation (5 minutes, 47 MB .wmv file)
- Video Clip: Battery Installation  (2.5 minutes, 20 MB .wmv file)

Tips on Installing the Batteries -- (web page)

Articles:
- QST --  March 2008
- QEX --  Mar-Apr 2008
- ARRL/TAPR 2007 Digital Communications Conference -- Article and Slides

Manuals:
- Operator's Manual (normal  small)  
- QuickStart Guide   
- Radio Cable Guide   
- Kit Assy Manual
- SDK Manual -- for developers of custom software

IW7EHC "Menu Reference Label"-- (PDF or DOC) -- Just print, cut it out and paste to the top of your modem!

Important Notes:
- Power Supply Modification -- Modems first into production can benefit by applying these simple mods to allow powering the unit from an external supply without removing the batteries.
- Radio Cable Documentation Correction -- See the linked page here for information concerning the 3-foot radio cable supplied with your modem. It is important to understand if you have a Type A or Type B cable so you know how to attach the connector for your SSB rig.
- Supplying Power to/from the Modem -- This is a caution note for use in wiring your own connector for the cable to your transceivers ... be careful how you handle the +V line on the end of your cable.

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.

Specifications

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

>    Handheld unit ... no PC required

>    Menus select operating modes, Squelch Thresh, PGA Gain, CW ID

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

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

>    Tune controls modem position along audio spectrum

>    Modes currently supported: BPSK31, QPSK, QPSK reversed

>    External keyboard jack: 6-pin mini-DIN, PS2-compatible

>    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.

>    Field reprogrammability of internal microcontroller to allow software updating in the field by the owner

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

>    Enclosure dimensions: 7" x 4" x 1"

>    Single 3.75" x 5.25” pc board contains all components and connectors

>    Lightweight: < 1 lb with batteries.

>    Control for precise audio level control to transceiver 

>    Cable assembly provided (plug and shielded cable) for connection to the SSB transceiver

Schematic

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.

A complete description of the NUE-PSK Digital Modem design and operation is provided in our cover article in QEX for March-April 2008.

(Download full-resolution PDF version of the schematic)

Parts List for Homebrewers:

Download BOM as Excel Spreadsheet

User Interface