FT-8 Weak Signal Digital Rob Hall KV8P kv8p@arrl.net
Why are we talking about FT-8? Developed by Steven Frankie (K9AN) and Joe Taylor (K1JT) and offered in mid- 2017, FT-8 took off where JT-65 and JT-9 started! (Making something good, even better!) Since its launch in mid-2017, FT-8 has taken off like a rocket, with about ½ of today s HF QSOs being on FT8. - Data courtesy of Club Log
What is FT8? FT-8 stands for Franke-Taylor design, 8-FSK modulation. FT-8: The numeral designates the mode s 8-frequency shift keying format. Tones are spaced at 6.25 Hz, and an FT8 signal occupies just 50 Hz. Transmissions are 4X shorter than JT-65 (full QSO takes less than 2 minutes instead of 5-6min). One transmission takes 15 seconds. Early releases allowed for reception down to -20db, but recent changes now allow depth down to -24db.
Specifics? Very similar to JT-65! Sounds like Music Transmissions last 15 seconds to transmit approx. 13 characters. Station clocks must agree with within 200ms. Stations take turns odd vs. even time slices NOT a ragchew mode short exchange Exchange = callsign, signal report and grid square Weak signal mode = perfect for restricted antennas
Interface Same used for fldigi As with FLDIGI Modes such as PSK31, you interface your HF rig to a computer, and send out text encoded by your computer over the amateur bands. Most use the exact same interface. Some items I have learned (the hard way): Turn off your Automatic Gain Control Turn off any auto notch filters and noise filters Set the levels in windows to 0.0db on the sound input Freeware sound card o-scope Make sure you aren t clipping/square edging your signal.
Software Needed WSJT-X (Free on the internet) Version 1.8.0 https://physics.princeton.edu/pulsar/k1jt/wsjtx.html https://sourceforge.net/projects/wsjt/files/?source=navbar
Exchange 00:01 CQ KV8P EN81 00:02 KV8P JA1JNY PM95 00:03 JA1JNY KV8P -16 00:04 KV8P JA1JNY R-18 00:05 JA1JNY KV8P RRR 00:06 KV8P JA1JNY 73 00:07 JA1JNY KV8P 73 00:08 00:09 CQ KV8P EN81
Time sync is required! We re not talking within 30 seconds here. 200 mili-seconds off is barely acceptable. 200ms is ok. In reality, you ll want it to be less than 0.2 seconds off. http://dimension-4.en.softonic.com/ D4 time sync http://www.meinberg.de/english/sw/ntp.htm Meinberg time sync
What does it look like? TX and RX Location Waterfall us, calling CQ N4LHY answering us Turns on transmitter function Immediately stops the TX Note: this bar at bottom is actually JT- Alert! (very handy)
What is different from JT-65? Hold tx where you want it, and click on a user.. Only rx moves to them. If someone calls you, the program will take over from there! Program will answer the first station decoded. No signal reports exchanged. Takes too long and not really needed!
Don t be a part of the QRM mess! FT8 Franke Taylor, 8 FSK Modulation Differences from JT-65 Explained: 1. Auto Sequencing 2. Operating Split on waterfall = standard (hold tx freq) Standard = old way New = Operate split!
Differences from JT-65 Explained (continued): Call 1st - automatically responds to your first decoded caller literally, the first one whose message is decoded. If you would rather have responded to someone else, too bad if you had Call 1st selected unless you are quick: within the first second or so of your transmission, you can hit F4 to clear the callsign of the first decoded caller, then double-click the decode that you want to respond to which picks up his callsign and puts it into the generated messages. The F4 step is necessary, unfortunately: it would be easier if we could just double-click the decode to respond to that one, even with Call 1st selected, but without F4 the double-click is ignored by WSJTX v1.8.0
TMRA 2017 Antenna Discussion UTC db DT Freq. RX stn TX stn exchange UTC When the signal was received db Signal strength of the received signal in db. +19 is about the best you will get, down to about -24dB. DT Calculated offset of the received signal from your local clock. Values above.3 are not good. Freq frequency (Hz) of the received signal
Additional Info You will find 1. You will lose your spot on the waterfall quite often using FT8 Be patient. Move often if (ok.. when) you need. Because of split calling, open spots open up every minute of so. Because of this, you may very well find more operators to be rude, transmitting over top of you. However, most of it isn t intentional. 2. There is a tendency to not finish the QSO with RRR and 73 for many. (changing) Many Europeans, in particular, don t follow standard format 3. Because it can be SO difficult finding a spot to transmit (due to popularity of the mode), I ll often call a station, in split for a couple minutes while they complete QSOs with others. If I stop, I ll definitely lose my transmitting spot. Being split causes nobody and issue during that time. 4. Time sync. issues will cause you to not decode properly 5. If you leave your rig on and you select report to PSK Reporter, rarer overseas stations will call you even though you weren t transmitting!
PSK Reporter Option FT8 Franke Taylor, 8 FSK Modulation
PSK Reporter: https://pskreporter.info/pskmap.html Punch in your call at the top and see who can hear you!
FT-8 Frequencies 1840 khz 3573 khz 7074 khz 10.136 khz 14074 khz 18100 khz = (awesome DX during the day!) 21074 khz 24915 khz 28074 khz 50313 khz
TMRA 2017 Antenna Discussion Where do I get additional help? Guide: http://www.g4ifb.com/ft8_hinson_tips_for_hf_dxers.pdf Lastly: This is what can be done