American QRP Club NUE-PSK User manual

NUE-PSK Digital Modem Operator’s Manual, ver 1.20 1 Copyright 2008, American QRP Club
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The NUE-PSK Digital Modem is a standalone, battery-operated digital
modem using Microchip dsPIC technology. Weighing about 12 ounces and
requiring only 60ma at 12V DC, the modem is easily taken to the field. For
easy visibility in high or low ambient light, the NUE-PSK modem’s backlit
graphic LCD displays transmit and receive text data, as well as band
spectrum and tuning indicator. When coupled with a standard PS2 or USB
keyboard and an SSB-capable transceiver, you can have an effective
portable PSK31 station.

NUE-PSK Digital Modem Operator’s Manual, ver 1.20 2 Copyright 2008, American QRP Club
CONTENTS
1) Introduction ............................................................................................................ 3
2) Connections ........................................................................................................... 3
3) Specifications......................................................................................................... 4
4) Power ...................................................................................................................... 5
5) Signal Connections................................................................................................ 5
6) Keyboard ................................................................................................................ 5
7) Operation ................................................................................................................ 6
8) Macros .................................................................................................................... 7
9) Configuration Menu ............................................................................................... 8
10) Updating Modem Software .............................................................................. 10
11) Tips & Techniques, and “Things to Watch Out For” ..................................... 12
12) Technical Support ............................................................................................ 13
Appendix A: The Radio Cable ................................................................................... 14
Appendix B: Schematic ............................................................................................. 15
Appendix C: Release Notes....................................................................................... 16
Caution:
Shortly after going to production status and starting to ship the first round of modems,
we discovered a problem in the "power supply" area of the pc board. The arrangement
we use with two internal 9V batteries (yielding 18V) was conflicting with an external
power supply when connected to the J1 power connector. Current would flow from the
batteries back to the nominally lower voltage external supply, causing the batteries to
heat up and fail in pretty short order.
Most modems in Round 1 were fixed before being shipped, but some of the earliest
ones were not.
One solution to this condition is to remove the batteries whenever an external
power supply is being used.
A better solution is to make a few simple modifications on the pc board, as
described and illustrated on the NUE-PSK website at www.nue-psk31/batt_mod
Neither the earlier “EBS” modems nor the later modem kits have this problem. And the
coming Round 2 modems will be okay too.

NUE-PSK Digital Modem Operator’s Manual, ver 1.20 3 Copyright 2008, American QRP Club
1) Introduction
PSK31 is one of the latest communications modes to capture the interest of hams
worldwide. Its inherent ability to dig out weak, nearly-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 Digital Modem offers a unique way for hams to get on the air using the
digital modes. No PC is required, thus enabling one to communicate using PSK31. This
self-contained, hand-held modem connects to your SSB transceiver and allows you
send and receive text data using the PSK31 digital mode.
PSK31 is actually one-of-many modulation techniques within the “phase shift keying”
family of communication. PSK31 operates at 31.25 bits/second, while other speeds may
be achieved using variations to the software algorithm. PSK is perhaps more accurately
termed BPSK, for bi-phase shift keying, whereby two distinct phase states separated by
180 degrees are used to convey the information. Four states may also be
encoded/decoded, as is done with QPSK (quad-phase shift keying), in order to provide
higher speeds with greater error correction ability.
The NUE-PSK digital modem can currently support the digital modes of BPSK and
QPSK, and will soon support MFSK and RTTY. In fact, the field updating capability –
that is, the ability to download new/improved programs from the Internet and simply
program them into the modem – will allow users to stay current with new features and
modes for years to come!
2) Connections
Ideally, you just need to connect up two cables:
a) Connect the modem’s “Radio” cable to the “data” jack on the back of your SSB
transceiver. Most radio manufacturers today provide this way for getting audio
modulated tones to/from the rig.
b) Connect a standard PS2 keyboard, or a PS2/USB combination keyboard, to the
“Kbd” jack on the modem.
You are now ready to rock & roll using PSK31 … read on and enjoy!

NUE-PSK Digital Modem Operator’s Manual, ver 1.20 4 Copyright 2008, American QRP Club
3) 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

NUE-PSK Digital Modem Operator’s Manual, ver 1.20 5 Copyright 2008, American QRP Club
4) Power
Install two standard 9V alkaline batteries in the battery compartment, or connect a 9 to
18 volt supply to the coaxial power connector (2.1mm) on the right end of the modem.
The two 9V alkaline batteries nestle tightly against the pc board in the compartment.
One battery lies flat and over to one side in the compartment, with the other battery
sitting up at an angle with its connector overlapped with that of the first. The screw-on
cover holds them firmly in place.
5) Signal Connections
Install a connector, or connectors, to the end of the cable which has an 8-pin mini-DIN
connector. Most modern HF rigs have a mini-DIN Data or AUX connector which
provides for PTT, fixed level audio from the receiver (independent of the volume control
on the rig), and a line-level (approx 100mv rms) audio input to the transmitter. On the
Yaesu FT-817/857/897 this connector is a 6-pin mini-DIN. On many Kenwood HF rigs
there are 6-pin and 13 pin mini-DIN connectors that may be used. See Appendix A for
wiring details.
6) Keyboard
The modem requires an AT/PS2 style keyboard for character entry. The keyboard also
provides for entry and playback of macros. Use the 6-pin mini-DIN connector on the
end of the modem to connect to the keyboard. A USB keyboard may be used if it has
built-in PS2 support. Most USB keyboards that are sold with a USB to PS2 adapter will
work, using the adapter.