> From: Black Michael via wsjt-devel [mailto:wsjt-devel@lists.sourceforge.net] > Sent: sunnuntai 7. toukokuuta 2023 19.35 > That's why I put 3 definitions of split in there. It means different things > in > different contexts.... Hi Mike and Sam, I have had a lot of private discussion with Adrian and we have not yet reached final agreement. I am not going to repeat that discussion here.
Let's look first why we have any split action? I have spotted two independent issues. #1 WSJT-X uses split to keep audio to RF mixing at sweet point inside radio. - Transmitted power is as constant as possible independently of the location of the red goalpost on waterfall. Technically it means that internally audio frequency is kept in range 1500 to 2000 Hz and rigs VFO frequency is shifted to keep the transmit frequency intact. - The audio frequency range 1500 to 2000 Hz shifts the harmonics of the audio signal outside Tx SSB filter passband and the transmitted signal is kept clean. - For this WSJT-X uses terminology *Split operation*. This means the radio is controlled via CAT using split function of the radio. - This split operation is not detectable at the output (antenna connector) of the radio. #2 The second is the 'classical' split working. That simply means that for set up and during a QSO stations communicating are using different frequencies. - Split is used to minimize QRM especially on the transmission frequency of the DX station. - Usually the split frequency difference is more that signal bandwidth as that minimizes QRM. In WSJT-X both signals are normally within rig's audio bandwidth. - WSJT-X FT8 tolerates a certain amount of QRM and can decode overlapping signals. But there is a limit and a pile-up on the DX station transmission frequency (= single frequency operation) would be less effective than using *split working*. I do remember when Joe K1JT sent free text messages USE SPLIT PSE. - WSJT-X supports split working very well as it has built-in skimmer function by decoding all signals inside the waterfall. - In WSJT-X the *split working* is supported by the Hold Tx Freq and by the independent selections of reception and transmission frequencies. e.g. using green and red goalposts. - On the radio frequency point of view the green and red goalposts behave as VFOs. (The conversion from audio FT8 to radio frequency FT8 is just a frequency translation.) - There is no real difference between *split working* in CW, SSB and FT8/FT4 (or almost all WSJT-X modes). In CW operator may use a CW skimmer to help in tuning reception frequency, in WSJT-X that is built-in. #3 Those two splits are independent of each other. - #1 depends only on the red goalpost location. - #2 is a user selection. I do recommend that this issue will be added in some form into the User Guide. The current wording seems to generate a lot unnecessary confusion, including me at my FT8 novice time. 73, Reino OH3mA _______________________________________________ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel
