ft-8 weak signal digital• weak signal mode = perfect for restricted antennas interface – same...

FT8 – Franke Taylor , 8 FSK Modulation

FT-8 Weak Signal Digital

Rob Hall– [email protected]

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 1.8.0https://physics.princeton.edu/pulsar/k1jt/wsjtx.htmlhttps://sourceforge.net/projects/wsjt/files/?source=navbar

https://physics.princeton.edu/pulsar/k1jt/wsjtx.html

https://sourceforge.net/projects/wsjt/files/?source=navbar

Exchange


00:01 CQ KV8P EN8100:02 KV8P JA1JNY PM9500:03 JA1JNY KV8P -1600:04 KV8P JA1JNY R-1800:05 JA1JNY KV8P RRR 00:06 KV8P JA1JNY 7300:07 JA1JNY KV8P 7300:08 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 synchttp://www.meinberg.de/english/sw/ntp.htm Meinberg time sync

http://dimension-4.en.softonic.com/

http://www.meinberg.de/english/sw/ntp.htm

What does it look like?


Note: this bar at bottom is actually JT-Alert! (very handy)

Waterfall

TX and RX Location

us, calling CQN4LHY answering us

Turns on transmitter functionImmediately stops the TX

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!

Differences from JT-65 Explained:


Standard = old way

1. Auto Sequencing 2. Operating Split on waterfall = standard (hold tx freq)

New = Operate split!

Don’t be a part of the QRM mess!

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 – 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

UTC dB DT Freq. RX stn TX stn exchange

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 properly5. 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


Punch in your call at the top and see who can hear you!

PSK Reporter: https://pskreporter.info/pskmap.html

FT-8 Frequencies


1840 kHz3573 kHz7074 kHz

10.136 kHz14074 kHz

18100 kHz = (awesome DX during the day!)21074 kHz24915 kHz28074 kHz50313 kHz

Where do I get additional help?

TMRA 2017 – Antenna Discussion

Guide:

http://www.g4ifb.com/FT8_Hinson_tips_for_HF_DXers.pdf

Lastly:

This is what “can be done”

http://www.g4ifb.com/FT8_Hinson_tips_for_HF_DXers.pdf

ft-8 weak signal digital• weak signal mode = perfect for restricted antennas interface – same...

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