FT roundup rule:7.14 Multiple, parallel QSOs are permitted If the technique does not cause excessive IMD QRM to other stations. (Current WSJT-X DXpedition mode, DigiRite Streams and MSHV Multi Answering implementations are prohibited because they do produce excessive IMD in current amateur radios.) Note that the total power transmitted on all frequencies is limited to the power specified in these rules.
From the digi-com site:
Q: What is multi-streaming?
The term “multi-streaming” refers to conducting QSOs in parallel where one transmission contains QSO information for 2 or more QSO partners. For example, if two stations answer your CQ, multi-streaming would allow one transmission to contain the signal reports back to each of the two stations. This is a natural consequence of the inherent multi-channel characteristic of the FT mode.
Q: How is multi-streaming done?
As of the 2019 WW Digi DX Contest, there is no satisfactory method available for conducting multiple parallel QSOs in a contest environment.
Q: Isn't the WSJT-X Fox and Hound mode "multi-streaming"?
Yes, but only for a single fox working split frequency. Thus, it is not suitable in a contest where there are many foxes. A large DXpedition is the target user of Fox and Hound mode with the "hounds" being all the DXers striving to work the single DX station.
Q: Why can't there be multiple foxes in a contest?
The current implementation of Fox and Hound mode divides the transmit voltage among 2 or more audio frequencies, one for each QSO partner. This creates two problems in a contest.
First, each contest fox would take up ‘n’ times as much bandwidth as a single audio signal for the ‘n’ parallel QSO partners. In rough terms, this would expand the total contest bandwidth required from a few kHz to over 100 kHz, similar to current RTTY contests. In contrast, FT8 contests to date have used less than 4-6 kHz per amateur band despite high activity.
Second, the on-the-air RF signal is considerably wider than even the multiple audio frequency signal created by the FT8 software. While the multiple audio frequency waveforms are each narrow and distortion free, the RF transceiver creates IMD products from the multiple audio signals, much like the classic Two-Tone SSB transmitter test. The result is a signal with very wide skirts, similar to a typical RTTY signal.
It doesn’t make sense to degrade the clean, narrow FT8 signal into a signal as bad or worse than a RTTY signal. Hopefully, in the future, different implementation techniques will be developed to conduct multiple parallel QSOs while maintaining the inherent clean, narrow signal characteristics of the FT mode.
Food for thought...
It is allowed but not with the technique we have available now...
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