Re: [wsjt-devel] Some questions related to the MSK144 operation

[Bill S. <g4...@cl...>]

Hi Claude,

comments in line below.

On 09/04/2017 13:43, Claude Frantz wrote:
> Please allow me you ask some questions about the MSK144 operation and
> the related settings, especially in relation to the FT-2000. But the
> operation is probably similar with other Xcvr's.
The FT-2000 and a couple of other recent Yaesu rigs have some minor 
issues when used with WSJT-X. The main issue is that the aerial 
selection and some other Rx settings are not recalled when switching 
bands using CAT frequency set commands. This is a nuisance when 
switching between HF and 6m where it is likely that different aerial 
sockets are in use. For now you will have to remember to select the 
correct aerial socket, AGC and pre-amp settings, likewise when returning 
to HF.
>
> In the main WSJT-X window, there is a settings "RX 1500 Hz", which is
> probably the default. What is the TX frequency ? Is it the same as the
> RX frequency or is it always 1500 Hz ?
The MSK144 modulation can be viewed in different ways, it is synthesised 
as binary frequency shift keying with the two frequencies being 1000 Hz 
and 2000 Hz and the keying rate is 2000 baud. The notional 1500 Hz 
centre frequency is chosen to lie near the middle of a standard SSB Tx 
filter. The same modulation scheme can be viewed as offset quadrature 
phase-shift keying (OQPSK) which is convenient for analysis. The raw 
modulation envelope is constant amplitude and continuous phase like all 
the other current modes in WSJT-X but that is only the case if the full 
width of the signal including side bands is included. In reality the 
side bands and a sliver of the main lobe are truncated by the rig's SSB 
filter so the signal does have a resulting small amplitude modulation 
component. It should be clear that only by centring the modulation 
around 1500 Hz is the signal information maximized. WSJT-X expects to 
only Tx or Rx one signal at a time.
>
> I do not understand exactly which are the right settings to use. Please
> allow me to consider the 6 m band as an example.
>
> If I understand right, the calling frequency is 50.280 kHz. How to
> change to the operation frequency after I have got a response from the
> other station ? How do I known about this operation frequency ? I have
> seen that when WSJTX switches from TX to RX mode, the TX offset setting
> of the XCVR is reset to zero. If I select the split mode, in the WSJTX
> config, the frequency of the second VFO is reset to the frequency of the
> main VFO when WSJTX switches from TX to RX mode.
If you are used to the way that WSJT-X uses split operating on HF then 
MSK144 operating is a little different. Normally split is unnecessary as 
only a pairs of stations communicate on a single common frequency and 
because of the above both should reasonably well centred on that single 
frequency. WSJT-X does provide an "FTol" frequency  tolerance adjustment 
and the usual Rx DF adjustment to allow for small offsets between 
stations but both should be looking to be on the same frequency and 1500 
Hz centre frequency for optimum communications.

6m MS activity varies throughout the day and from day to day, both are 
due to variations in the number of meteor impacts on the ionosphere. In 
general mornings are better and during the peaks of the well know 
showers the rates increase significantly. Notionally 50.280 MHz is both 
a centre of activity and a calling frequency in region 1 & 2 as far as I 
know, I am not sure about procedures and band plans in region 3. There 
is nothing wrong with having QSOs on 50.280 when reflections are very 
sparse but most of the time stations will either pre-arrange QSOs on 
Ping Jockey, ON4KST chat or elsewhere on a pre-determined frequency or 
by calling CQ on 50.280 MHz and including a listen frequency as a 3 
digit number. The number given is a kiloHertz offset into the current 
MHz, so a call of "CQ 295 G4WJS IO91" would state my intention to listen 
for and have QSOs on 50.295 MHz. WSJT-X directly supports this style of 
operation if you have CAT control. You must enable 
"Settings->Radio->Split Operating" (preferrably "Rig" but "Fake It" 
works too) and you simply select your working dial frequency on the rig 
or in WSJT-X. You can also add your favourite working frequency as in 
"Settings->Frequencies" if you wish but simply typing "295k" into the 
WSJT-X band drop down entry will work just as well once you are on 6m. 
WSJT-X will automatically make CQ calls with the correct listen offset 
number when the option box next to the "Tx CQ NNN" spin box is checked. 
The CQ calls will be on the calling offset you have set, all you need do 
is dial in the correct calling frequency for your region, for example 
"Tx CQ 280" in my case.

WSJT-X will also do the right thing when you are listening for calls. In 
this case having the calling frequency in "Settings->Frequencies" is 
advisable so that you can drop right onto the calling frequency when you 
start listening for calls. If you have CAT control then double clicking 
a "CQ NNN ..." format decode will shift your rig to the correct working 
frequency ready to reply to the caller on their next Rx period.
>
> How can I add the calling frequency to the working frequency list of the
> settings ?
Go to "Settings->Frequencies" and right-click the table of working 
frequencies then select "Insert ...". Add the MSK144 mode and the 
desired frequency in MHz. You should also drag and drop the new 
frequency row down onto the "Station Information" table then insert your 
station details in the 6m row, this information is sent to PSKReporter 
so other stations can see what you are running.
>
> I have not found these information in the operating manual. Will this
> information be added later ?

Yes.

73
Bill
G4WJS.