Getting Started With Digital Modes

1. Getting Started With Digital Modes Tommy Brough, KB5TB July 17, 2018

2. Introduction This presentation covers station and computer setup for the popular HF ham radio digital modes FT8, JT65, PSK31, and RTTY using asoundcard. However, the vast majority of setup and operating principles for these modes apply to many, lesser-known modes, as well (Olivia, Hellschreiber, Contestia, MT63, etc.).

3. FT8 was a joint developmentbySteve Franke, K9AN, Dr. JoeTaylor,K1JT, and Bill Somerville, G4WJS, in June2017 for weak signalcommunications. Uses 15-secondsequences, (13 seconds transmit, 2 seconds decode) and structured messages. Exchanges the minimum information needed for a QSO (Call Signs, Grid Squares, Signal Reports). Multi-decoder finds and decodes all FT8 signals in the passband – not just where you have the receive marker set. What isFT8?

4. Modulation is 8-FSK, tone spacing 5.86 Hz. Waveform is continuous phase with a constant envelope. Bandwidth is 47Hz. Decoding threshold is -24 dB, sometimes lower. This means decoding sometimes takes place when you hear nothing and see nothing on the waterall! Accurate computer time, within twoseconds, isrequired (more on this later). Sound ofFT8: More aboutFT8

5. JT65 was developed byDr. JoeTaylor,K1JT, in late2003for EME (earth-moon-earth)communications on VHF. Uses 60-secondsequences, (48 seconds transmit, 12 seconds decode) and structured messages. Exchanges the minimum information needed for a QSO (Call Signs, Grid Squares, Signal Reports). Digital signal processing and redundancy allow up to 80% ofthe message to be lost and still be decodedcorrectly. What isJT65?

6. During 126 intervals of 0.372 sec the waveform is one of 65 pre-definedtones. Bandwidth is 177.6Hz. Accurate computer time, within twoseconds, isrequired (more on this later). Sound ofJT65: More aboutJT65

7. PSK31 was developed by Peter Martinez,G3PLX, in December 1998. Allows real time keyboard chat between twooperators. A great “ragchew” mode! Other stations see your typing immediately. PSK31(Phase Shift Keying, 31 baud)modulates the phase of acarrier, not by using different tones, such as RTTY. What isPSK31?

8. Typing speed is 50 wpm. Bandwidth is 62.5 Hz (about the same as 25 WPMCW). Uses varicode, frequently used characters are shorterthan others. Sound ofPSK31: More aboutPSK31

9. After WWII, hams began using surplus RadioTeleTYpe equipment. Allows real time keyboard chat between two operators. Another great “ragchew” mode! Other stations see your typingimmediately. RTTY uses a five-bit code (Baudot) to represent all the letters of the alphabet, the numbers, some punctuation, and some control characters. At typical 45baud speed, each bit is 1/45.45 seconds long,or 22milliseconds. Typing speed is 60WPM. What isRTTY?

10. Bandwidth is 250Hz. The standard mark and space tones are 2125 Hz and 2295Hz. RTTY can be sent using either FSK (on/off keying using radio circuitry, typically controlled bya COMport) or AFSK (audio from a soundcard). Sound ofRTTY: More aboutRTTY

11. The equipment needed to connect your rig to a computer is very modest, can be purchased at low cost, or can be homebrewed (Google is your friend!). The software needed is free or lowcost. FT8, JT65, and PSK31work well with low power and simple antennas. RTTY is a popular mode forcontests. Many hams use digital modes on HF, and contacts canbe made anytime. Why Use DigitalModes?

12. HF transceiver capable of SSB and monitoring of ALC (can be an older rigor beginnerrig). Computer running Windows, Linux, or MacOS. Soundcard interface between the computer and the transceiver. Can be purchased commercially, orbe homebrewed;manynewer rigs have built-in USB interface. HF antenna. Software (free or low cost software isavailable). Optional hardware: CAT (computer aided transceivercontrol) What Equipment isNeeded?

13. CommercialInterfaces RIGblaster http://www.westmountainradio.com/rigblaster.php SignaLink USB http://www.tigertronics.com/slusbmain.htm

14. For Windows and Linux, a minimum 1.5 GHz dual core processor with 3 GB memory is recommended. An external USB sound card or second internal sound card is recommended to avoid sending OS sounds over the air, and to allow ham software to use computer speakers. 16 bit (or higher) sampling rate recommended for sound card. WSJT-X recommends setting the sound card to 16 bit, 48000 Hz (DVDQuality). TheComputer

15. Ham Radio Deluxe (HRD) is integrated software offering modules for digital modes, radio and rotor control, logging, and satellite work. Digital modes, including PSK31, RTTY (both varieties), and a host of others are supported via the module Digital Master 780 (DM-780). https://www.hamradiodeluxe.com fldigi supports PSK31, RTTY, CW, and many otherless-used digital modes for Windows, Linux, and MacOShttp://www.w1hkj.com WSJT-X supports FT8, JT65, and JT9 for Windows, Linux, and MacOS.http://physics.Princeton.edu/pulsar/K1JT/wsjtx.html Dimension 4 synchronizes the computer clock with internet and atomic time servers. This is critical for FT8, JT65, andJT9. http://www.thinkman.com/dimension4/download.htm Software

16. Several popular logging software programs support these modes: Ham Radio Deluxe DXKeeper (part of DXLab Suite) https://www.dxlabsuite.com Logger32http://www.logger32.net/index.html N1MM Loggerhttp://n1mm.hamdocs.com Amateur ContactLoghttp://www.n3fjp.com/index.html Software (otherchoices)

17. When operating FT8, JT65, and JT9, JTAlert(http://hamapps.com) interfaces with WSJT-X and provides audio and visual alertsfor: Your callsign decoded (someone callingyou). Stations calling CQ. Wantedcallsigns, grids, US States, DXCCs, and CQ Zones. Stations you have worked before. Will also automatically log to the most popular logging software programs on the market (Ham Radio Deluxe, DXLab, ACLog (N3FJP), Log4OM, and many others). The logging software programs can be configured to then upload, in many cases automatically, to many of the popular online QSL websites (QRZ, eQSL, LoTW, etc.). RecommendedSoftware

18. RecommendedTool – PSK Reporter https://www.pskreporter.info

19. Right-click the white colored speaker icon located in the lower-right corner of your desktop and select "Recording Devices" from the pop-upmenu. In the new window that opens, click one time on the "Microphone - USB Audio Codec" sound card to select itand then click the "Properties"button. In the Properties window that opens, click the "Levels"tab.Right-click the percentage display to the right of the Levelslider and then select"decibels." Lower the Level slider to "0db" or as close as you can. This is "-0.4db" in Windows 7. It might be slightly different in Vista, Windows 8 and 10, but in any case, the closest value to 0db will work just fine. Note that you can use the left/right arrow keys to move the slider once you've clicked on it. This might be easier than using yourmouse. Click OK, then click OK on the Recording Devices window. Soundcard LevelSet (50/50)

20. Too much audio output from your soundcard will distort your signal. Typically, set RF power from the transceiver to 100%, then adjust audio output from soundcard to achieve desired power output. ALC (Automatic Level Control) should be zero.Make sure that speech compression is off. With my wire antenna, typical power output for FT8 and JT65 is 25 to 50 watts,PSK31 15 to 40 watts, andRTTY from 50 to 100 watts. Your power output will vary depending upon the efficiency of your antenna. TuningUp

21. For FT8, JT65, and PSK31, set your AGC (automaticgain control) tofast, and turn NB (noise blanker) and NR (noise reduction) off. ***YMMV*** Setting receiver filter to widest possible. Using any notchfilteris very helpful when working weaksignals. ReceiverSettings

22. Suggested OperatingFrequencies