Getting More From FT8 – Do YOU have Blinders On?

A lot of people operate FT8 digital mode. In spite of the negatives, it does quite well during poor propagation and band conditions. Unfortunately, a lot of FT8 operators are not getting the best out of their radio, because “They have blinders on”! I believe this to be a widespread problem. What do I mean by that? Well let me explain.

Most radios have a 3 Kilohertz passband capability. The passband is the range of frequencies or wavelengths that can pass through a filter. The passband is basically the spectrum coming into your radio from your antenna that you can actually hear when you are tuned to a particular frequency. Now, many times it is a good idea to limit the passband based upon what you are doing with your radio. For example, for CW, you might only want the passband to be 500 Hertz or even 100 Hertz to mute other CW signals that would interfere with you hearing the one you want to QSO with. Most radios have multiple different filters that allow you to limit the passband of your radio for these very reasons.

Now, in the case of FT8, the passband from your radio is being sent to your computing device as audio, and the WSJT-X program decodes the entire passband that it receives, and displays the decoded messages as well as the signals themselves in its waterfall window. You might notice that you can stretch the WSJT-X waterfall window out as wide as 3000 Hz. Well, that’s because most radios can pass that much, so it made sense to the WSJT-X authors to decode that much. That’s why you are able to see signal traces from 0 through 3000 in that waterfall window.

I say are able, because in my experience many FT8 ops have their radio’s passband configured improperly for FT8 mode, and they don’t hear the entire 3 KHz of spectrum, but instead only a fraction of it on either side of their red transmit cursor. How can that be? Well it’s because many radios come from the factory with a filter setting that reduces the 3 KHz passband to something much less. I am constantly saying out loud to myself that “There’s another ham who has his FT8 blinders on!”

I know this because I transmit a lot from the edges of the passband where there is less QRM, and I call people who have these blinders on and they are “deaf” to my signal, until I move my TX signal closer to or on top of theirs whereupon magically they hear me! I see this many times a day, so I decided to write this article make people aware of this “blinders’ phenomenon and learn how to correct it.

To illustrate what this looks like, I set a filter on my radio to allow the frequencies between 1000 and 2000 in the passband to pass through, but filter 0-1000 and 2000-3000. This is what you see on the WSJT-X waterfall:

You will NEVER decode/see a signal to the left of 1000 or the right of 2000, even though they are there! So, do you see something like this when you operate FT8? If you do, you are really missing out! It is because your radio has a narrowing filter in action. Every radio is different, and you will need to read your radio’s manual to find out what its passband is, and what the default width the default filter is set to. And after you set the passband filter to its maximum width, you will then see something like this:

So much better, and you will make so many more QSOs if you have your radio’s filter set properly when you operate FT8 digital mode. I will also pass on from experience that both the Icom IC-7100 and Yaesu FT-891 radios have a default filter width less than 3000. When I helped a friend set a proper width for Filter 1 on his IC-7100, he was amazed at what he had been missing. The same for the friend with the FT-891.

So, read your radio’s manual and make sure you don’t have “Blinders On" when you are operating FT8.

73 all, and good DX! Bob Hensey – K4VBM (Very Bad Memory)