Hi Adrian, Sam and all interested parties, I also disagree, but that's not fair as we have not defined terminology for this discussion! Warning: this takes a bit bandwidth, sri.
Behind there may be two issues. The first is what is meant by the transmission frequency in FT8? The second is of course what split means? Let's first take the FT8 transmission frequency, RF frequency. Before that we need to agree that an FT8 signal is 50 Hz wide eight level frequency shifting modulated (constant amplitude) signal and for the purposes of WSJT-X nominal frequency is the same as the lowest tone of those eight tones. [Quite often the center of the transmission is defined as the signal frequency, but it is irrelevant for this discussion.] We need to look what is radiated from the antenna, RF frequency. That is the only point an observer e.g. official frequency monitoring unit will see. When FT8 is generated in the typical manner, then it is rig's carrier frequency + audio frequency. It is irrelevant what are the carrier and audio frequencies, only the sum of those has a meaning. [In some rigs the carrier frequency is the same as VFO frequency, but in older rigs there are additional mixing stages with band frequency generators.] Actually it is possible to generate the FT8 signal directly on the RF frequency as well. So what you see at antenna is the transmission frequency. [Please note that voice signal is a wide signal typically 300 Hz to 2800 Hz or so. The RF frequency is defined as the carrier frequency that is zero Hz at audio level. That is a modulation type based definition. It is the same as for Amplitude Modulation, just only one sideband is sent and no carrier in SSB. Although FT8 signal is generated or actually moved to radio frequency using an SSB rig, still it is not an SSB transmission. Some rigs generate CW in the same manner, but nobody calls CW as SSB in that case. The same is valid for (ASK) RTTY.] The second is 'split'. WSJT-X uses 'Split Operation' or 'Split Mode' internally. By internal I mean that you cannot tell from the antenna radiated signal whether that 'internal split' is used or not. [Well, no rig is perfect or operator may misuse it and the unwanted radiation can tell how the signal is generated. But that's not an issue for this discussion.] So that 'Split operation' in only an internal RF signal generation issue. There is another 'split' mentioned in the User Guide. In that context word 'split' is not used, but indirect expression such as the recommendation to avoid QRM on the DX Rx frequency by using 'Hold Tx Freq' and selecting another 'free' Tx frequency on the waterfall. Radio amateurs usually call that way of working 'split'. Perhaps 'split working' could be used in that context. Coming back to the RF frequency. the 'split working' is seen at antenna as the Rx frequency is different than the Tx frequency. I could say it is an external split. Now with those definitions the internal 'Split Operation' does not change radio frequency. It changes VFO frequency, but that's irrelevant on the antenna radiation point of view. On the other hand having the Rx green goalpost at a different (audio) frequency that the Tx red goalpost is classical split working (in short 'split') as at the antenna there are different Rx and Tx frequencies. Perhaps we could add some note into the User Guide on that issue. Currently terminology seems to lead to unnecessary disagreements and move discussion to irrelevant arguing instead of discussing the original item (a random frequency selection for CQ). My 2 cents. 73, Reino OH3mA > -----Original Message----- > From: Adrian via wsjt-devel [mailto:wsjt-devel@lists.sourceforge.net] > Sent: sunnuntai 30. huhtikuuta 2023 11.03 > To: WSJT software development <wsjt-devel@lists.sourceforge.net> > Cc: Adrian <vk4...@gmail.com> > Subject: Re: [wsjt-devel] Fwd: Enhancement suggestion - 30 second cycles > > I disagree with below. > > Sam explained it well. Keeping the same Pan TX location the RF frequency is > shifted to maintain and audio frequency suitable for the best passband > performance and level > > continuity. It is split. The TX VFO adjust to 500, 1000 below the RX RX VFO > frequency when pan TX marker is set ~ 500 or 1000 below the mid mark. and > opposit when set above so the TX vfo raises frequency 500, 100 Hz and so on. > The same effect of changing frequency changing the pitch of a received > voice/signal is the same effect used to get the audio frequency in the > sweetspot > while maintaining pan position for stations listening. Any frequency shift > between TX and RX is split operation. > > Fake (split) is changing the same (TX/RX) vfo frequency between TX and RX for > the same effect. > > > vk4tux > > > > When using sideband modulation (USB/LSB) the RF frequency is tied to > > audio slot frequency. That is: dumped RF carrier +/- audio frequency > > depending on sideband used. If we change audio slot we change RF > > frequency that means we are using "split" in means what is in Ham radio. > > > No it means you are altering audio frequency in line with the pan > marker, carrier point frequency remains the same, and unless it is > forced to shift then audio passband become an issue. > > > > Using the thoughtlessly named "split operation" of > > wsjt-x/settings/radio has NO effect to RF frequency that is produced. > > It is always the same as "split operation", when used, adjusts the > > ratio of RF carrier to audio frequency to keep the produced RF > > frequency always the same while centering the audio frequency in > > middle of AF filter passband. > > > Rubbish, The split operation shifts RF frequency on TX vfo in 500Hz > increments to suit the audio marker more than 500Hz off center. > > > _______________________________________________ > wsjt-devel mailing list > wsjt-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/wsjt-devel _______________________________________________ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel
