I often see questions of many operators in the chats, mailing lists, WhatsApp groups, etc. requesting whether a certain DXpedition is using FT8 in Fox/Hound or using the Multistream feature provided by MSHV.
Unfortunately I also often see many answers from other operators that are not correct !
IMPORTANT: Due to recent changes in the implementation of the Multistream in MSHV, it is now impossible to distinguish it from Fox/Hound just seeing the transmissions of the DX station. In former versions of MSHV it was possible and here it was explained how to do it.
The new MSHV implementation of Multistream:
Allows to send two different messages in the same audio frequency (frame), as Fox/Hound already did before.
Forces stations using Multistream to transmit on the even periods, as Fox/Hound already did before.
With this "confusion" created by the new implementation of the Multistream in MSHV you will have to relay on the information provided by the own DX operators in order to know whether they are going to use Fox/Hound or Multistream during their operation. There is no way to do it just watching to their signals/messages.
Some important considerations:
In case of doubt always use Fox/Hound and call the DX in audio frequencies above 1000 Hz. Doing it in that way it will work even if the DX is using Multistream.
If you don't enable the F/H mode and the DX is actually using Fox/Hound then you will possibly not be able to be make the QSO.
Calling the DX in frequencies below 1000 Hz will only work if they are using Multistream, never if they are using Fox/Hound.
If DX station is answering stations that call him below 1000 Hz, it means that he is using Multistream, not Fox/Hound.
If the DX station is answering to a caller with R+report, it means that he is using Multistream, not Fox/Hound.
So is it better for DXpeditions to use the WSJT-X in Fox mode or to use the MSHV in Multistream mode?
The answer is not simple and depends on each case, but the latest implementation of the Multistream in MSHV will possibly have more advantages than disadvantages. Anyway let's discuss the advantages and disadvantages of each:
WSJT-X in Fox mode:
Advantages:
Callers must use frequencies above 1000 Hz, while the ongoing QSO take place always below 1000 Hz (WSJT-X/JTDX automatically change the audio frequency when the DX answers your call). In this way the callers can't interfere the ongoing contacts, making easier for the DX to complete the contacts.
Disadvantages:
It requires prior knowledge by the callers (the "hound") on how to configure the program and use the special Fox/Hound protocol. This is easy and it is explained here, but it is true that you have to be able to spend ten minutes to read it and be able to understand it, what seems to be not within everyone's reach.
It should only be used by true DX expeditions, not for special events, activations, etc.
Callers (Hounds) must transmit above 1000 Hz in order to be decoded by the Fox. This restricts the bandwidth that callers can use and also create trouble for those that don't know the Fox/Hound protocol.
MSHV in multistream mode:
Advantages:
Callers do not have to make any configuration changes or have any knowledge beyond knowing how to use the standard FT8 mode.
It can be used not only for true DX expeditions, but also for other smaller events, such as special events, activations, etc.
Callers can use any frequency to call the DX, so more bandwidth is allowed.
Disadvantages:
Callers can use any frequency to call the DX, even frequencies already being used for the ongoing contacts of the DX, causing him trouble to complete the contacts.
IMPORTANT: In no case, under any circumstances, should the FT8 standard frequencies be used, neither for Fox/Hound, nor for multistream.
You could also be interested to read the articles "How to make good enemies in FT8 / FT4" and "How to make a QSO in FT8 Fox/Hound (F/H) mode"