Pulsar EME, FSK441, JT65, JT6M User Manual

WSJT 4.6 User’s Guide

WSJT is a computer program for VHF/UHF communication using state of the art digital techniques. It can decode signals propagated by fraction-of-a-second reflections from meteor trails, as well as steady signals 10 to 20 dB weaker than those needed for conventional CW or SSB.

Operating Modes

• FSK441 for high speed meteor scatter

• JT6M for meteor/ionospheric scatter on 6 meters

• JT65 for extremely weak troposcatter and EME

• EME Echo for detecting your own echoes from the moon

System Requirements

• SSB transceiver and antenna for one or more VHF/UHF bands

• Computer running Microsoft Windows

• 200 MHz or faster CPU

• 32 MB of available RAM

• Monitor with 800 x 600 or higher resolution

• Windows compatible sound card

• Computer-to-radio interface using a serial port to key your PTT line (or use VOX)

• Audio connections between transceiver and sound card

• A means for synchronizing the computer’s clock to UTC

Quick-Start Installation and Setup

1. Download WSJT from http://pulsar.princeton.edu/~joe/K1JT or the European

mirror site,

2. Execute the downloaded file to install WSJT to a directory of your choice.

3. If you have not already done so, print a copy of this manual and keep it handy.

4. Connect appropriate interface cables between your computer and radio. (For help with

the hardware interface, refer to one of the many descriptions of other sound card modes such as PSK31.)

5. To start the program, double-click on the desktop icon for WSJT.

6. Select Options from the Setup menu (see picture on next page) and enter your callsign,

grid locator, and UTC offset. Click Done to dismiss the Options screen.

7. Select Setup | Set COM Port and enter the number of the serial port you will use for

T/R control. Enter 0 if you will use VOX control.

8. Indicate on the Setup menu whether you wish to use the DTR or RTS line for PTT

control. (If not sure, check both.)

These settings should be adequate for learning your way around the program. If you are new to WSJT, work through the examples at the top of page 3 and then continue reading this manual, stopping to experiment with the program when it seems appropriate.

http://www.vhfdx.de.

Decoded Text Box

Main Screen

FSK441A mode

Setup | Options

Screen

Example Files

To gain some familiarity with the operation of WSJT, use the program to decode some example files provided with the standard installation. Hit function key F7 to choose FSK441A mode, and select Open from the File menu. Navigate to the folder in your WSJT home directory and open the file recorded from W8WN. When this file has been decoded, the top of your screen should look like the picture on page 2. With a speaker or headphones connected to the soundcard output, listen to the recording by clicking the Play button. You will hear static crashes at the beginning of the file and a moderately strong ping from W8WN about 18 seconds later. Try clicking around the ping with both left and right mouse buttons, and observe the decoded text that appears. Click the Big

Spectrum button to see what these signals look like on the large waterfall display. Click Erase on the main screen to clear the text and graphical areas.

Next, select JT6M from the Mode menu and open the sample file from AF4O. Nothing decodes automatically in this file—the signal is very weak—but try right-clicking on the green line at about t = 12.9 s, as displayed on the green label at lower left of the plot area. You will find that AF4O was calling K1JT. Try listening to this file: the signal is audible some of the time, but only barely. Finally, switch to JT65A mode and open the recording from OH7PI. The graphics window and decoded text boxes on your screen should look like the picture on page 5. Listening to this file, you will hear only random noise. OH7PI’s 144 MHz EME signal was much too weak for CW communication at this time, but he was solid copy in JT65.

RxWav\Samples

Adjusting Signal Levels

1. Turn on your radio and tune it to a clear frequency so that only background noise is sent

to the sound card.

2. Press F9 to select the EME Echo mode.

3. Select Setup | Adjust RX Volume control to bring up the sound card input mixer.

4. Click Measure to start a sequence of noise measurements

5. Adjust a slider on the audio mixer and/or your receiver gain control(s) so as to bring the

signal level close to what WSJT calls “0 dB”. The signal level is displayed numerically and illustrated by a green line in the plot area. The green curve should be approximately aligned with tick marks on the left and right border.

6. Press F7 to enter FSK441A mode.

7. Click Record to start a receiving period. The program will record noise for 30 seconds

and then attempt to decode it. This should produce a jagged green line in the large plot area, along with a waterfall-style spectrogram. The green line is a graph of received noise power vs. time. The waterfall is a time vs. frequency spectrogram in which frequency increases upward, time to the right.

8. Select Setup | Adjust TX Volume control to bring up the sound card output mixer.

9. Turn off your final amplifier (if any). Click one of the four Tune buttons A, B, C, or D

to be sure that T/R switching works and an audio tone is sent from the computer to your radio.

10. Adjust the slider on the audio mixer to get the proper audio signal level for your

transmitter. Watch the transmitter power output while sending each of the four tones A, B, C, and D. Variations of 10% or even 20% among the four tones are acceptable, but 50% differences will degrade your signal. You may find it useful to experiment with the setting of a speech processor or ALC control.

Basic Operating Instructions

Note: further details on commands in boldface may be found in the alphabetical list starting on page 15.

WSJT uses timed intervals of transmission and reception. By convention FSK441 and JT6M use 30 s periods, while JT65 always uses 60 s intervals. To prepare for making a QSO, enter the other station’s callsign in the To radio box and click Lookup and Gen Std Msgs to generate a sequence of commonly used messages. If Lookup does not find the callsign in the database file Decide whether you or the other station will transmit first, and check or uncheck TX First appropriately. Click Auto to start an automatic sequence of transmission and reception intervals.

At the end of each receiving period, WSJT displays various properties of a received signal graphically. A green line illustrates signal strength vs. time, and other lines or images display spectral information and synchronization results, depending on the mode. Decoded text appears in the large box near center screen. Refer to the pictures on pages 2, 4, and 5 for examples in the FSK441, JT6M, and JT65 modes.

When an FSK441 or JT6M reception period has finished the program looks for signal enhancements produced by short-lived reflections from meteor trails. You can often hear such “pings” when they occur, and they can be seen as spikes on the green line and brighter colors in the waterfall spectrum. One or more lines of decoded text may result from each ping. By clicking on the green line with the mouse, you can force decoding of a particular spot in a record.

CALLSIGN.TXT, you may enter the grid locator manually.

WSJT attempts to compensate for relative mistuning between transmitting and receiving stations. By default the frequency search range is ±400 Hz (±600 Hz in JT65). You can reduce the range by setting the value of Tol (for “tolerance”) to a lower value. Several other decoding parameters can be adjusted, as well. In FSK441 mode W sets the minimum width and S the minimum strength (in dB) for acceptable pings. Adjustments can be made at any time by clicking on spinner controls next to the parameter labels, and all parameters can be reset to default values by clicking the Defaults button.

JT6M mode

In addition to the green line for overall signal strength, JT6M produces a yellow line showing the detected strength of a synchronizing tone. JT6M attempts to decode both individual pings and an “average message” based on the entire transmission (or selected portions thereof). An average message is flagged with an asterisk at the right end of the text line. Clicking with the left mouse button decodes a 4 s block of data near the mouse pointer, while the right button decodes a 10 s segment. You can also drag the mouse pointer with the

button down to select any desired region. As in FSK441, with marginal signals you should

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experiment as necessary for best decoding. JT6M can work with signals many dB weaker than those required for FSK441. You will sometimes find that clicking on a smooth green line, even where nothing was heard and nothing can be seen, causes callsigns or other information to pop up out of the noise.

Sync tone detected

at DF=43 Hz

red line

Time synchronization

at DT = 1.9 s

blue line)

DF: –600 –400 –200 0 200 400 600 Hz DT: –1 0 1 2 3 4 5 s T: 0 10 20 30 40 50 60 s

Graphics Window

Sun/Moon

Data

Decoded Text Box

TX Messages

Main Screen JT65A mode

JT65 requires tight synchronization between transmitter and receiver, so in this mode the only way to initiate a transmission or reception interval is by toggling Auto to ON. As in other WSJT modes, an incoming signal is analyzed after a full receiving sequence is complete. The resulting graphical display includes red and blue lines along with the green line. The additional curves summarize the program’s attempts to synchronize with the

Average Text Box

received signal, a necessary step toward decoding the message. Proper synchronization is indicated by a sharp upward spike in the red curve and a broader peak on the blue curve. Horizontal locations of the peaks correspond to the frequency and time offsets, DF and DT, between transmitter and receiver. EME QSOs have propagation delays of about 2.5 s and can have significant Doppler shifts. Along with clock and frequency errors, these effects contribute to the measured values of DT and DF.

Message Formats

Standard messages in FSK441 and JT6M are generated with the aid of templates defined on the Setup | Options screen (see p. 2). Default templates are provided conforming to standard practice in North America and Europe, and you can edit the templates to suit your own requirements. Normal FSK441 and JT6M messages can contain any arbitrary text up to 28 characters. The supported character set is 0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ.,/#?$ plus the space character.

FSK441 provides a special shorthand format to transmit a few simple messages in a highly efficient way. Check Sh Msg to activate shorthand messages. The supported messages are R26, R27, RRR, and 73. FSK441A sends pure tones at 882, 1323, 1764, or 2205 Hz to convey them, while FSK441B and C use alternating two-tone sequences with the lower tone at 861 Hz and the upper at 1206, 1550, 1895, or 2240 Hz.

JT65 messages are more constrained and must have one of three basic formats:

1. Four alphanumeric fields with specific contents as described below.

2. Any arbitrary text, up to 13 characters

3. Special shorthand messages ATT, RO, RRR, and 73

The four fields of a type 1 message usually consist of two legal callsigns, an optional grid locator, and the optional signal report OOO. CQ or QRZ can be substituted for the first callsign, and CQ may be followed by a space and three digits to indicate a desired callback frequency. If K1JT transmits on 144.140 and sends “CQ 113 K1JT FN20”, it means that he will listen on 144.113 and respond there to any replies. A country prefix preceded by “/” or a signal report of the form “–NN” or “R–NN” may be substituted for the grid locator. For example, –24 might indicate that signals were received at –24 dB. The minus sign is required, and NN must lie between 01 and 30. A list of supported country prefixes is given in Appendix A. The following are all examples of legal messages of type 1:

F9HS K1JT F9HS K1JT FN20 F9HS K1JT FN20 OOO F9HS K1JT OOO F9HS K1JT /KP4 F9HS K1JT /KP4 OOO VK7MO K1JT –24 K1JT VK7MO R–26 CQ K1JT CQ K1JT FN20 CQ 113 K1JT CQ 113 K1JT FN20 QRZ K1JT QRZ K1JT FN20

The JT65 shorthand messages are powerful because they can be decoded at signal levels some 5 dB below those required for standard messages. They do not use tight time synchronization, so they provide no information on DT. The ATT message (for “Attention”) is intended to help two stations find each other before a normal QSO begins. If a message starts with ATT, RO, RRR, or 73, the shorthand format will be sent. If it satisfies the requirements for message type 1, the full message of up to 22 characters will be compressed and sent. With any other entry, 13 characters of arbitrary text will be sent.

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