Australian Ham Radio Discussion Forum ( AHRDF )

Seemed like a good idea to start a thread where people can share their favorite digital mode hot tip...  I will start us off, please add your own

In WSJT-X / JDTX and other variations from the WSJT-X code platform there are many options in the settings menu that may puzzle some people. One that appears to be not well understood is on the RADIO tab of the Settings menu.

On there is an option called "Fake It" (no it is not sponsored by Donald Trump) that helps you transmit the best possible audio on any of the modes in WSJT-X.  What this does when enabled, it looks at the frequency value of your TX tones, if the centre of you tones is below 1500Hz or above about 2200Hz, then the program will alter BOTH your actual on air RF frequency to a lower value and your TX tones to a higher or lower value (as appropriate) all auto-magicially, not user intervention needed.

The online help can be seen here: WSJT-X Manual

Okay I know that sounds confusing, so here is an example, say I am on 18.100 MHz FT8 with Fake-it enabled and my TX tones are at 1600 HZ (mid passband) then when I go to TX, nothing needs to be changed on the radio to ensure the 2nd harmonic of my tones is outside the 300-3000Hz TX passband of my radio so the software makes no changes.

BUT if my TX tones are down at 700Hz working a new station, then the 2nd Harmonic of my tones is now 1400Hz and would be transmitted as well as my proper tones at 700Hz  Arrghh not the best look for those who see you as a strong signal.

With "Fake it" turned on, as I go to transmit, the program alters my on air RF frequency down to be 18.099 and sets my tones to be 1700Hz so they appear in the far end receivers as if I am transmitting a set of tones at 700Hz. When the transmit cycle ends the radio is commanded back to 18.100 Mhz so my receiver is back to where it should be.  This change of the TX tone frequency is NOT displayed to the end user, it is all done under the hood of the software. 

End result, my second harmonic or third harmonic tones are no longer in the TX passband and do not make it past the rigs SSB filters WooHoo one less thing to worry about on-air.  A lot of what people think is ALC overdrive is actually 2nd harmonic tones..  Do not get me wrong there are still plenty of people overdriving radios but enabling "Fake It" could be the easy step you take to make your TX signal that little bit cleaner.

This feature was built into the software for this exact reason as the authors understood that the TX tones are never going to be 100% pure and there will ALWAYS going to be 2nd and 3rd harmonic content.

When Fake It is enabled, the green dot next to the frequency display on WSJT-X will now have an "S" in it to tell you your running 'split'

Now, some brands of rigs do not allow the TX frequency to be set after the PTT is on so you may need to check if yours is compatible with "Fake It" (Note: All Icom's do allow this to occur)

I admit I may have not done the best at explaining it but please do some of your own googling and see if there is a better explanation out there but for your own peace of mind if you can, enable this feature in your digital software and have a cleaner TX signal for no cost.

Peter,

Following the appearance of your tip, I set Fake It on and found that the rig (both 7300 and 7400) did not ALWAYS return to the likes of 50.313 after the TX period.  The wide graphs would show the sigs moved too.  Probably 90-95% it was OK but it was the odd time when I wasn't looking at the digital display or the WSJTX freq that it seemed to occur (maybe I should just keep a better eye out ??)

I will try the actual Rig Split option shortly (Icoms, so should be supported ok) and see what it does with that option set, but in the meantime have set it back to None.  The best option then (none) is to always set the TX freq above 1500Hz to minimise harmonics in the audio passband. { Post note :  actually make that 1KHz, as the predominant harmonic is 3rd, and then those occur at 3KHz or higher.)

Another comment : it is amazing to see people txing down near 200Hz where the receiver IF dropoff is happening even on Wide USB filter settings (even with Fake It set, the receiver still has bandwith limitations). Not sure how well the USBD mode handles such frequencies though..

Doug

Hi Doug,
have never seen one of my two rigs ever not come back from a Fake-It move.  Been using this for 18 months now and chewed up a LOT of TX time on 28, 24 and 18 MHz chasing single band DXCC there.  Unsure why your particular setup would cause a problem.  As I know you generally have a lot going on your PC's it might be a driver library from an experiment or the like but that is just a stab in the dark.

Peter

You could be correct about a driver library but it is more likely that OmniRig can't handle the commands fast enough.

The Icoms are set at 19200 (OmniRig settings, rigs actually set to Auto baud rate) but have two rigs plus a support package that provides access to extra CIV features all running.

Just to be safe, am leaving it to None for now and may come back to it later.

Doug

Great tip Peter, also like the improved version of WSJT-X with the red and green bars and better layout.

73 Mark VK5LO

In my original post, I neglected to include that the a similar QSY of the TX RF frequency and the baseband audio when you go high in the passband, so when you set your TX tone frequency up near the top of the normal SSB passband or beyond, the RF frequency will move UP and your tone frequency DOWN to keep things near the optimum spot in the SSB passband, all without you needing to think about it.

Do you hate having to gather up all your saved ADIF files from multiple JTDX or WSJT-X installs so you can import to your logging program?

I love to experiment and trial new version of WSJT-X and JTDX, most recently a variant called JTDX-Improved (worth a google search) and because of this I have multiple folders where an ADIF file might get stored, which is a real pain in the ar$e.

DOS / Windows like linux has the ability to create symbolic links in the file system folders, think of these as pointers to where the real file is.  In this case I have these 'pointers' or symbolic links in each of the JTDx / WSJT-X folders that point to a master ADIF file.

to create the links, you will need a list of all the installed copies of the software and select a single destination file that you then import to your log program.  The command to create a symbolic link is called 'mlink' in the Windows world and you can either do it one at a time with a command like this:



or you can put many lines into a BATCH file and store all your needs there, you can run the Batch file multiple times with no ill effects.



do not be confused by seemingly complicated folder names yours will be a bit simpler as I use some long names in my config setups.

This gives me one MASTER ADIF file located at : C:\ham_radio\ADIF-FILES\wsjtx_log.adi  that I tell my log program to import.

Now one important note, before you go to create the links in each folder, you MUST gather up / MOVE all the original wsjt_log.adi files as the symbolic link cannot be overwrite a real file if still there.

Here is one that is topical : do you have the "Hold TX Freq " box ticked ??  There are (as always) two sides to this one.

Using Wide Graph to find a clear audio frequency on BOTH periods and putting your transmit frequency there (Control + left mouse click for WSJT-X and its ilk) is the one I prefer. That hopefully means that your transmissions will be on a clear frequency... maybe.  But then what signals don't you see on Wide Graph that your target station does see ? Is that frequency really busy in his/her propagation zone ?  You "takes your chance" and try it.   BUT if you keep calling and the other station does not respond, that might be a clear indication that the chosen frequency is busy in that locality and it is probably time to select another transmit audio frequency.

The other side says that you should leave it unticked so that you respond on their transmit frequency however that often does not work. Have you ever listened to the pileup that occurs when LOTS of stations call a rare DX callisgn on their frequency ?  It is a mess, and it you analyse who the DX responds to, it is most likely to someone NOT on their own transmit frequency !

SO, KEEP IT TICKED !!

I find that lots of stations respond to CQ calls with level reports down below -15dB, and on a busy band that usually results in no QSO.  On a quiet band (activity-wise), I often have two-way contacts down in the -20dB area.  So before you call that elusive DX, see how strong he really is.  It might not be that you are using a busy frequency, just that you are not putting enough signal into their QTH...

On that same topic, it is useful to compare sent and received reports.  Many stations are using 100W rigs, and theoretically if you are too, then the exchanged reports should be quite similar.  After all, antenna gains work together to give a composite value so it doesn't matter if you have 10dB of antenna gain and him 3dB, the total transmit-to-receive path losses are the same.  Going further, if you give a send report of +3 then you should expect something similar back.  But so many times the report back is below -15 thus indicating that they do not have transmit/receive performance equivalency OR they have a very noisy environment.  Maybe something they can fix - or - you can if it is the other way around ?

Something to contemplate !