Midnight design solutions Nue-psk User manual

NUE-PSK Digital Modem

Operating Manual

(For software version 5)

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

digital mode station for PSK31, RTTY and CW modes, with a special Keyer mode for

“headless operating”! Optional internal USB card provides for saving QSO text files,

easy software updates, and real time clock.

SECTION 1: Basic Modem Operation

1) Introduction .....................................................................................................4

2) Connections....................................................................................................4

3) Specifications..................................................................................................5

4) Power..............................................................................................................6

5) Signal Connections.........................................................................................6

6) Keyboard.........................................................................................................6

7) Operation ........................................................................................................7

8) RTTY Operating Details..................................................................................8

9) Using the “Download Config” and “Upload Config” Features ........................10

10) Real Time Clock Calendar (RTCC)...............................................................14

12) Macros ..........................................................................................................14

13) Configuration Menu.......................................................................................16

14) Updating Modem Software............................................................................18

15) Capabilities and usage of the optional internal USB Card.............................20

16) Tips & Techniques, and “Things to Watch Out For” ......................................23

17) Technical Support.........................................................................................25

SECTION 2: CW Mode Operation

SECTION 3: CW Mode QuickStart Guide

SECTION 4: RTCC Operation

SECTION 5: Keyer Mode Operation

SECTION 6: Keyer Mode QuickStart Guide

Section 7: APPENDICES

Appendix A: The Radio Cable

Appendix B: Modem Schematic

Appendix C: Optional USB+RTCC Card Schematic (rev B2a)

Appendix D: Recognized Prosigns

Appendix E: Morse Encoding with Prosigns and ASCII Equivalents

Appendix F: New Configuration Options and Hot Keys

Appendix G: EEPROM Contents

Appendix H: Config.txt

Appendix I: Hot Key Map

VERSION HISTORY

The version number of this manual corresponds to the software version running in the modem,

which is displayed in the display’s “splash screen” when the modem is initially turned on. (The

small letter after the version number in the splash screen differentiates minor fixes for the

specific version.)

ver 1.15 –Initial production release.

ver 1.20 –Improved speed tuning, F10 for Tx mode, Ctrl-S char, backspace and CWID fixes,

and improved displaying/saving/loading of configurable modem settings.

ver 1.30 –Initial support for the optional USB add-on hardware and improved text entry

keyboard sequences and commands.

ver 1.33 –Full USB support adds PC Bootload and Flash Bootload capabilities.

ver 1.34 –Beacon Operating Mode added.

ver 2.10 –RTTY Operating Mode added.

ver 2.33 –Added: Upload / Download Config, spectral display improvements, Beacon Counter.

ver 3.00 –Added: Real Time Clock Calendar feature (RTCC).

Ver 4.00 –Added: CW Operating Modes (Normal, Direct, Practice) and Morse Reader

Ver 5.00 –Added Keyer Modes (for headless operating: user interface with Keyer input, Morse

output)

SECTION 1: BASIC MODEM OPERATION

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 now also support RTTY. The modem may soon support other modes such

as MSFK and even CW. 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 –allows users to stay current with new features and modes for years to come!

2) Connections

Ideally, you just need to use 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 ‘n roll using the digital modes … read on and enjoy!

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, Beacon, more

> 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

> “Tune” dial controls modem position along audio spectrum

> Modes currently supported: BPSK31, QPSK, QPSK reversed, and RTTY

> 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, 80 mA

with backlight. The current decreases as input supply voltage is increased.

> Field reprogrammability of internal microcontroller allows 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.

> “Tx Audio” control for precise audio level control to transceiver

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

transceiver

> Optional USB plug-in card provides ability to Record QSO text and save to USB

flash memory device. The USB port also can be used for easy software upgrades.

The USB option includes an independently powered Real Time Clock Calendar.

> Beacon Mode provides auto-repeating message buffer for far-signal measurement

experiments.

4) Power

Install two standard 9V alkaline batteries in the battery compartment, or connect an

external 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.

Use of internal batteries is not possible when optional USB card is in place.

5) Signal Connections

Install a connector(s) to the unterminated end of the cable provided with the modem.

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. See the website Ordering page for a list of pre-assembled modem cables

accommodating over 50 different rigs.

6) Keyboard

The modem requires an AT/PS2 style keyboard for character entry. The keyboard also

provides for entry and playback of macros. Connect the keyboard to the 6-pin mini-DIN

connector on the right-hand side of the modem. 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 this adapter.

7) Operation

Once you have the cable between the modem and the rig connected, keyboard

attached, and power available, you are ready to operate. But first, some additional setup

may also be desired, as described next.

Turn on the modem. If the cabling between the rig and modem is wired correctly, you

should see evidence of signals and/or noise on the top half of the display (the spectrum

area). Tune your rig to one of the PSK sub-bands. These are typically 70-to-74 kHz

above the lower band edge on 40 and 20 meters. If there is digital activity on the band,

you should see peaks on the graphic display. The horizontal location of the peaks

corresponds to the audio frequency of each signal relative to the tuned frequency of the

rig. For example, if the rig is tuned to 14070 kHz, the display shows audio frequencies

from 500 Hz to 2500 Hz, or actual RF frequencies from 14070.5-to-14072.5 kHz.

Now for the fun ... tuning! Turn the “Tune” dial clockwise, or counterclockwise, to move

the cursor to a higher or lower frequency. The cursor is the small triangular icon just

below the spectrum display. The audio frequency is displayed when turning the dial.

Try to align the cursor with one of the peaks on the display. Don’t worry if it is not

exactly aligned. Once close to the peak, stop turning the encoder. The modem now

attempts to “lock” onto the signal and fine-tune the frequency if needed. If the modem is

able to lock onto a PSK signal, it will very shortly begin decoding the signal, and then

display characters on the screen. The time it takes for decoded characters to appear

depends on the ability of the modem to estimate the center frequency of the incoming

signal and the signal to noise ratio. Tuning can also be done by using the arrow keys on

the keyboard. The right and left arrow keys provide finer tuning, while the up and down

arrow keys provide faster tuning. The tuning rate of the encoder on the modem can also

be selected from a menu setting. Note: When tuning in receive mode, the spectral

display is frozen - this is intentional.

Now on to setup for transmission. If you have a dummy load for your rig, connect it

now.

Since PSK signals generated by the modem contain simultaneous multiple frequencies

(over a very narrow bandwidth), it is imperative that the audio output from the modem

not overdrive the input to the rig; otherwise very poor signal quality will result. To

facilitate setting the audio drive to the rig, a potentiometer on the modem may be used

to adjust the level. In addition, the modem includes provision for “measuring” the

position of the potentiometer so that it can be easily reset to the same setting in the

future. More on this later.

We have found that the best way to set up for PSK operation is to initially set up the

transceiver for normal SSB operation, including whatever power setting you usually

employ. For example, if you have a 100 watt PEP rig, set it up for 100 watts on SSB.

Switch to Digital mode if your rig provides that option; otherwise retain the SSB mode.

Then press F8 on the keyboard. This places the modem in the TUNE state, which is

denoted by “TUNE” at the top left of the display. The modem is now generating a

continuous single tone, which is fed to the audio input of the rig. The PTT signal from

the modem should also cause the transceiver to switch to Transmit. At this point, the

“Tx Audio” control on the modem just to the right of the display can be adjusted to set

the power level of the transceiver. A transmit power of 15%-to-40% of the rig’s rated

power is recommended. (That is, 15-to-40 Watts with a 100 Watt rig). Keeping the

power at this level does two things. First, it minimizes distortion due to clipping.

Second, it avoids excessive heating in the rig finals since PSK is a 100% duty cycle

mode. A power meter is very handy for making this setting. Once the Tx Audio control

has been set, press F8 again to return to RECEIVE mode.

You should now be ready for transmitting PSK.

Pressing F10 will place the modem in TRANSMIT mode, but with a PSK idle tone being

generated, unlike the single tone used in TUNE. If you are ready to give it a try, Press

F10. At this point anything that you type on the keyboard will be converted into Varicode

characters and transmitted using PSK modulation. Pressing F10 again, will toggle back

to RECEIVE. When in TRANSMIT mode, “TX” will appear at the top left of the display.

8) RTTY Operating Details

Starting with software version 2.10, the NUE-PSK Digital Modem is now able support

full RTTY transmit and receive. Use of the modem for this older-yet-still-popular digital

mode is very similar to the other modes we support (PSK, QPSK), and is great for long

ragchews, sending “brag files” describing equipment, and contesting. Decoding

sensitivity is a bit less than with PSK31 (a mode that has been optimized for low power

operation), but tuning in someone calling CQ is a bit easier and some people say there

are more RTTY-capable hams around for potential contact, continuing the age-old

enjoyment of the hobby.

We are initially supporting 45 baud operation with 170 Hz shift between mark and space

frequencies, which classically tends to characterize the majority of RTTY use over the

years –especially with the older and original TTY equipment. We also simplify the

upper/lower sideband confusion that can exist these days by allowing the user to flip the

order of the mark and space frequencies, thus accommodating a variety of users over

all the bands.

RTTY Specs:

45 Baud, 170 Hz shift. (Other speeds and shifts may be supported later.)

Normal operating convention is to use USB for RTTY. In the event that the

station that you are attempting to connect with is instead using LSB, you may

“reverse” the Mark and Space frequencies to allow this “cross-mode” connection.

Normal mode, with the lower Mark frequency, is indicated by an N in the upper

right corner of the LCD.

Reverse mode, with the higher Mark frequency, is indicated by an R in the upper

right corner of the LCD.

Normal and Reverse may be toggled by typing Ctrl-R while the modem is in

Receive mode. Typical usage of this toggling is to help the modem decode when

the transmitter is on a different sideband.

Generally, Normal mode is used when both transmitting and receiving stations

are on the same sideband. (USB-USB or LSB-LSB.) When the stations are on

different sidebands (USB-LSB or LSB-USB), type Ctrl-R to toggle to Reverse

mode in order to enable proper transmit and receive.

An L or F is also displayed in the upper right portion of the LCD, corresponding to

LTRS or FIGS being received by the modem. The L and F may be toggled by

typing Ctrl-C, which is useful if the corresponding LTRS or FIGS character is

missing from the incoming data stream. Thus the user can correct such an error

condition.

Setting the Modem for RTTY Operation:

Select the Mode item in the Config menu. (Press the Select pushbutton for about

2 seconds, release and rotate the Tune encoder one position clockwise.)

Rotate the Tune dial until the RTTY menu item is shown. Press the Select

pushbutton to change to that mode. The press the pushbutton again to exit back

to normal modem operation.

Notice that the spectral display now shows two cursors. These cursors are used

when tuning to a RTTY signal that has two characteristic spectral peaks

separated by 170 Hz. When the frequency is properly adjusted, each cursor will

point to a spectral peak.

Two techniques may be used for adjusting the frequency to place the cursors

beneath the two spectral peaks of the desired incoming signal. The modem’s

Tune dial may be used in the conventional manner to slide over to the received

signal. Otherwise, the receiver’s frequency dial may be adjust to move the

spectral peaks of the desired signal such that they are positioned over the two

cursors.

If the modem does not immediately start properly decoding the incoming data

stream, try pressing Ctrl-R to reverse the mark-space frequencies as described

above. The sending operator might be on an opposite sideband from what you

are using, and the mark-space frequencies would need to be the same for proper

decoding.

RTTY Operating Tips:

When using RTTY with your transceiver set to USB, the actual RF frequency is

simply the addition of the transceiver setting plus the display frequency on the

NUE-PSK modem. Further, most Digital modes (with the exception of RTTY) are

usually run in USB.

It should be noted that RTTY will not decode weak signals as well as PSK31.

This is because the filters for RTTY are not as narrow. The modem will decode a

PSK signal that is about one S-unit lower than what can be decoded with RTTY

Macros work just fine in RTTY mode –same as in other modes, and is quite

convenient for the “brag files” that are commonly used in RTTY.

Beacon Mode works well with RTTY as well.

If you wish to use RTTY mode exclusively for a while, it may be convenient to

select Save Config from the Configure menu, thus saving your current mode

(RTTY) so it comes up by default when you next turn on the modem.

Some typed characters do not appear on the LCD. The older, 5-bit “Baudot code”

used in RTTY communications is limited in the number of characters that are

supported. Thus, only capital letters are able to be transmitted, and the only

supported “FIGS” include: -, ?, :, &, !, &, #, ‘, (, ), /, “, comma, semicolon and

period. (Characters not transmitted or displayed on the modem LCD include: %,

@, ^, *, {, }, [, ], |, \, +, =, ~, `, _, -, <, and >.) So be careful not to use these

characters when doing RTTY communications … otherwise your messages may

be received in an unusual manner. (For example: “My email is george

verizon.net”, “It costs 23.44”, “The Dow is up 2.1”, “John I went home”, etc.)

We have implemented the US version of Baudot character representation. For

example, someone on a mechanical TTY keyboard (such as the Teletype Model

19) who types a FIGS key followed by the H key, a pound sign (#) will be sent

and displayed on the NUE-PSK display. Correspondingly from the NUE-PSK

modem keyboard, pressing the # key will transmit the FIGS code followed by the

H code (or just the H code if the FIGS code was previously sent) and the #

character will be printed on the receive side.

9) Using the “Download Config” and “Upload Config” Features

This new feature pair, accessed from the modem’s CONFIG menu (beneath the Select

pushbutton), allows the operator to send (Upload) the modem’s current “configuration

settings” (user settings and macro strings) to a text file on the USB Flash Drive; edit this

text file on a PC; and then load (Download) that modified text file into the modem. This

is a great way to create macro strings offline and save them for later reminder or

modification. This is a very convenient way to ...

Send the modem's current configuration parameter settings and the current

macro strings (found under the Function keys F1-thru-F7) as a text file to the

USB thumb drive;

Edit all of the above on the PC by plugging the USB thumb drive into the PC; and

Load the modified text settings back to the modem by plugging the USB flash

drive into the modem and "Downloading" the config.txt file.

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