Category: Digital Modes

FT8 – The Basics

FT8 – The Basics

FT8.
It has been around for a while now and the protocol itself has undergone some radical changes recently so what’s all the fuss about, and is it actually worth bothering with?

Ham Radio digital modes are a bit like Marmite, you either love them or you hate them and FT8 is no exception to this rule, well that’s not strictly true because FT8 has come in for it’s fair share of stick over recent times due to it’s quick and dirty QSO method. Basically FT8 has a very stripped back QSO exchange that only actually comprises of CQ Call, a signal strength exchange and a confirmation.

FT8 was developed by Joe Taylor K1JT and amateurs typically use it as part of the WSJTX software package which can be downloaded from here

Here is a typical conversation over FT8:

“CQ G0SBN IO95”  CQ call from G0SBN
G0SBN 2E0EFP IO95” 2E0EFP replies with their location
2E0EFP G
0SBN +06” G0SBN responds with a signal report
G0SBN 2E0EFP R-02”
2E0EFP confirms signal report & replies with his own report
2E0EFP G0SBN RR73” G0SBN
 says Reception Report Received, Goodbye
G0SBN 2E0EFP 73” 
2E0EFP says Best regards

Each message of up to 13 characters takes 13 seconds to send. There are 4 slots per minute, and your transmission  block lasts for 15 seconds, then the software listens for any replies for 15 seconds, and so on. A typical exchange above takes around 90 seconds to complete. Great ! You’re thinking I can get loads of DX in a short window, and that is indeed a fact but it’s quite devoid of any user interaction. This is where some amateurs seem to have an issue because it’s basically M2M (Machine to Machine) transactions and can actually be automated so the operator needn’t even be in front of his radio / shack PC to stack up a load of QSO’s

Is that cheating ? You decide !

So I am guessing by now the burning question is how do I get into this brave new world and make some QSO’s ?

Now this isn’t going to be a full on guide on how to setup your radio for FT8 but I will share some details on some tips I have found during my setup etc. As a minimum you will need the following:

A shack PC, (WSJTX Can be ran on Windows, MAC OSX, Linux)
An audio interface from your shack PC to you radio
Optional CAT Control of radio from shack PC

As well the above you should check the following settings on the radio, AGC is off, Data mode is ON and the SSB mode is USB. Most FT8 or digital modes in general users normally say the ALC should not be invoked by the radio when transmitting.

Now there is a little bit of PC jiggery pokery required here to ensure your shack PC can hear the signals coming from your radio (via the mic input) and can also send the data signals to the radio via the speakers output. Withregards to the ALC invocation, I would normally set the sound card input level on the radio to a fairly low setting and then set the shack PC speaker volume manually when transmitting to make sure the ALC is not being triggered.

Similarly with the reception of signals, you don’t want the RF from the radio overloading and clipping the audio into the PC, so again check your Mic level on your sound card and monitor the received signal on WSJTX to ensure that the reception signal is around -60dbm.

Have a look at the bottom left on the image to see the received signal strength.

 

 

 

 

As well as the operating system tweaks for the audio output and recording levels there are some settings in WSJTX that need to be completed to tell the software which audio interfaces on the shack PC to use.

WSJT-X Settings screen (audio)
WSJT-X Settings screen (audio)
  • RIG – Radio interface settings – most common models of radio already have their comms settings built-in to WSJT-X, so simply select your radio.
  • CAT CONTROL – Connecting to the radio’s CAT/DATA port for controlling the radio. Typically the interface will appear as a serial COM port.
  • PTT – So that the PC can put the radio into transmit, the software needs to know how to trigger Transmit. Often this will be a separate COM port that needs setting up in the software
WSJT-X Settings screen (radio / PTT)
WSJT-X Settings screen (audio)

As well as the audio settings, Your computer’s clock does have to be very accurate with FT8. I use the Dimension 4 for keeping my clock accurate. This runs in the background and uses NTP to keep your clock in-sync to one of the online atomic clock servers periodically.

Anyway give it a shot, even if you are a foundation licence holder you can make some great contacts using 10w and a modest antenna!

Enjoy your radio !

2E0EFP