On 16/10/2021 16:01, Virginia Greene via wsjt-devel wrote:
As Bill wisely pointed out:
2) many rigs have considerable roll-off in receiver gain towards the
bottom end of the expected receiver pass-band, the K3 is one of those
BTW.
This seems not to be well understood or appreciated.
My own KX-3 rolls off rather sharply starting at about 400 Hz when set
for DATA-A mode, which is what most people set their Elecraft radios
to for operating under WSJT-X. I know the same situation exists with
the KX2, and may with the various K3 models. You can see this for
yourself if you look at the WSJT-X waterfall display on a dead band
with the gains turned up and the Flatten and Ref Spec buttons turned
off. I think this was a deliberate choice by the radio designers, who
are big RTTY fans. They must think that there is some performance
advantage to doing this.
The solution I take is to use USB mode while operating with WSJT-X.
With the PBT control set to maximum bandwidth, the frequency response
extends from below 200 Hz to about 3500 Hz.
Of course, if you also operate SSB, you need to turn off the
compressor, turn off the equalizers, and so on when switching to
WSJT-X operation. A way around that is to place the radio in ESSB
mode when using WSJT-X, which does all that for you. I added a Macro
that allows me to switch between normal SSB and WSJT-X modes with a
press of a Programmable Function switch.
Other radios have the same issue. Not all, of course, but enough.
This is really a problem for DXpeditions using F/H mode. The default
start frequency for a single TX channel in F/H mode for a Fox is 300
Hz, as clearly stated in the documentation. But, if the Fox has a
radio that cuts signals off below 400 Hz, even a loud Hound that gets
a +10 report when calling above 1000 Hz may now be in the mud when
s/he responds at 300 Hz. This inevitably leads to the “three strikes
and you’re out” outcome for a Hound.
The two solutions are to use a radio that receives down to at least
300 Hz, or to set the Fox TX frequency to above maybe 500 or 600 Hz.
But, how many DXpeditions know this?
Just this morning I was monitoring a moderately rare DX station
operating as a Fox. His TX channel was set to the default of 300 Hz.
He’d give Hounds reports of +00 and above, and then not complete the
QSO. There were times when he was running five streams and not
completing any QSOs for several decode periods in a row. Then, to his
credit, he figured out his mistake and started at 700 Hz. Voila! The
rate skyrocketed.
For Hounds who have radios that roll off at low frequencies, if the
Fox isn’t that loud and there’s QSB, the Fox might fall into the noise
right when you’re trying to complete the QSO. How much fun is that?
You can always offset your VFO setting by a few hundred Hz and be
sure to transmit above 1000 plus that few hundred Hz, but that’s easy
to forget or mess up. That’s why I researched this and made and use
the Macro.
I haven’t a clue how to popularize this message. I don’t think most
DXpeditioners follow mails on SourceForge.
Or, maybe I’m just all wet!
Clarke K1JX
HI Clarke,
since the K3 has the ability to us a 4,000 Hz Rx filter, I would instead
recommend tuning the VFO down 200 Hz or 300 Hz as a far better solution.
You can even adjust the working frequencies to those offsets. I suggest
this for a couple reasons:
* Switching between data modes and SSB will be much simpler as SSB is
used for SSB and DATA A is used for data modes,
* Using the ESSB option is likely to allow any unwanted audio
harmonics to be transmitted, the WSJT-X Split Operating relies on a
Tx filter cut-off at just below 3,000 Hz which will not be the case
if you select ESSB transmit.
You say that you might forget to do the setup for a slightly shifted VFO
frequency, yet you suggest several other settings changes that are
needed to operate the way you suggest. Simply change the working
frequency values in "Settings->Frequencies" and you are done with my
recommendations, there's no down side IMHO.
73
Bill
G4WJS.
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