Deciphering and Using F/H and SuperFox

1) SuperFox is asymmetrical. When the SF is transmitting, he uses the entire spectrum between 750 and 2250 Hz. This looks (and sounds, if you listen) very different from the ordinary 50 Hz-wide FT8 signal. Also, if the DX is running SF, you won’t be able to decode him at all unless you set your station to SuperHound mode. And in SuperHound, you won’t be able to decode any ordinary FT8 in the SuperFox’s slot.

2) You can observe ordinary F/H by noting two things: Stations in Hound mode will get their transmitted signal frequency moved down to the Fox’s frequency (under 1000 Hz) once the Fox has called them. Also, no Hound will get a call from the Fox if they are transmitting at a frequency less than 1000 Hz.

3) Of course, you can always work an ordinary Fox (not a SuperFox) without setting your station into Hound mode. The only difference is that your signal frequency will not be moved down during the QSO, but you can complete the QSO perfectly well. For that reason, many ops never set their station to Hound mode, since ordinary FT8 works both with Foxes and non-Foxes. The only (supposed) advantage of Hound mode is that your frequency is moved down to what is (presumably) a clear channel during the Hound slot. That may or not be true, depending on whether someone is trying to call the Fox on their own frequency (which will never work, but people do it anyway).

4) MSHV can run multiple streams, AND does not require that you call above 1000 Hz. This is one of the reasons it is often preferred by DXpedition operators (besides the fact that it can run unattended, which isn’t SUPPOSED to be done, but nonetheless often is). But the transmitted signal (in both directions) is ordinary FT8, and no special mode needs to be invoked at the non-DXpedition’s end.

So you can figure things out by observing how QSOs are completed. If station frequencies are being moved down to the low end during a QSO, it’s assuredly ordinary F/H. If the waterfall looks totally different between the DXpedition transmission and the callers, and you can’t decode an FT8 signal during the DXpedition’s transmit slot, it’s SuperFox. You can verify that by setting yourself to SuperHound mode to see if you get a decode of the DXpedition signal.

One other note: For ordinary FT8, and even for FT8 F/H, the radio frequency (dial or display) setting is not critical. You can be off by hundreds of Hz, or even a KHz or more, and still make QSOs. All of the audio frequencies will shift, so YOU might think you are transmitting at 1500 Hz, while the other station sees you at 2500 Hz because one of you has tuned your radio off by 1 KHz. But you can complete the QSO without even realizing this. Not so with SuperFox. You must have your radio tuned to the proper frequency within a few 10s of Hz. The base frequency of the SuperFox signal starts at 750 Hz from the radio’s display frequency, and if you are too far off, you won’t be able to decode him.
Rich KE1B

Additional Comments by AA6YQ (edited)

You do not need to use Hound mode to work a Fox.
Especially when the DX is rare and in view of the number of misguided or
inexperienced people calling on the DX station's frequency instead of above
1000 Hz, you might well be better off sticking with the frequency the DX
copied your Tx1 call on.

Second, in Hound mode WSJT-X only moves you to the DX station's frequency for
the initial Tx3 response. If that does not garner an RR73 from the Fox, the
normal Hound mode behavior is to then move you away from the Fox's frequency
to another frequency below 1000 Hz for repeat attempts with Tx3. If it didn't
do that, in difficult conditions there would soon be a pileup of callers on
the DX frequency all trying to send Tx3 to the DX on the same frequency - not
a good idea.