Interesting discussion but I find it a bit confusing so I've gone back to
basics:
The transmission is in the form of amplitude modulation using single
(upper) sideband suppressed carrier. That means the RF may not be a single
frequency but a band of frequencies with the bandwidth defined by the
normal USB filter width - the sideband. The carrier and lower sideband
aren't there in usable form.
The USB filter width is about 300Hz to 2800Hz, depending on rig settings,
so a single tone of exactly 1500Hz will produce RF at 1500Hz into the
sideband width and for all practical purposes nowhere else in that sideband.
A lower tone of 500Hz will produce RF 500Hz into the sideband but also
probably some harmonics every 500Hz up to 2500Hz.
If there is no audio signal at a particular frequency within that filter
width there will be no RF in that part of the sideband either.
A WSJT-X signal is generated as a narrow band of frequencies about 50Hz
wide. On transmit RF will be present within the sideband only for that
50Hz width.
WSJT-X by default begins that 50Hz wide signal at 1500Hz. If we move the
TX marker to say 1200Hz the 50Hz wide RF signal will begin at at 1200Hz
into the sideband width, not 1500Hz.
WSJT-X in receive sees and displays all of the signals within the USB
filter width.
We pick one signal that will have a particular position within the received
sideband, let's say 400Hz up from the lower bound and reply to it.
Without split our transmission would occupy RF between 400Hz and 450Hz into
the sideband. This is non-optimum for WSJT-X.
If we have split set then on our reply WSJT-X will change the rig VFO to
put our transmission back into the optimum location in the sideband for
reception.
If we have fake it set then WSJT-X shifts the transmit audio so that the
resultant RF is again in the optimum location within the sideband.
The location of RX and TX signals within the sideband are different, so the
RF frequencies involved are different.
That's the definition of split frequency operation, but it all occurs
within a single USB sideband width, so may not be immediately obvious.
The important thing to remember is that in USB mode the frequency shown on
the rig is not a single transmit frequency. Its the start of a band of
frequencies, the upper sideband produced by amplitude modulation.
Does that all make sense?
In the context of WSJT-X it might be better to use something like "Hardware
AHS" and "Software AHS" with AHS meaning audio harmonic suppression rather
than split?
Alan G0TLK, sent from my mobile device
On 1 May 2023 12:18:59 Adrian via wsjt-devel
<wsjt-devel@lists.sourceforge.net> wrote:
Too funny, as the rx of both stations covers the entire pan bandwidth,
the fact they are transmitting on a different pan slice within,
does not qualify as 'audio split' in my book. If both were running 300Hz
rx filters then it might qualify on matching tx/tx placement between two
stations
not running rig/fake split.
Both stations can be running very similar audio frequencies and have the
TX offset between then controlled mainly by the RF split frequency offset,
which is what we are talking about. I can work 100Hz to 2900Hz in the
pan keeping audio within 1500 - 2000 HZ , again what Rig split is
designed for.
I often do that re 300Hz Rfil RX with DX peditions, which gives a 20dB
gain on the FTDX101MP here @! 300Hz , while taking out the callers.
Using TX hold should be default behavior, jumping around the pan on
target , has many competing for the same tx marker/timeslot whereas
spread-out calls using the space, work much better for everyone.
73
vk4tux
On 1/5/23 20:52, Jim Shorney wrote:
Apparently this is really hard to understand. When the audio offset of your
QSO partner and your TX audio offset are different your are running audio
split.
On Mon, 1 May 2023 15:58:55 +1000
Adrian <vk4...@gmail.com> wrote:
There is no 'audio split' in WSJTX' TX audio is determined by mode, RF
frequency and the TX marker.
RX audio decode covers the pan bandwidth, with the RX marker filtered
for the right pane display.
vk4tux
On 1/5/23 14:45, Jim Shorney via wsjt-devel wrote:
audio split in WSJTX
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