No I am not a pirate!

Not a pirate!

A friendly HAM sent me an email today kindly noting that someone is pirating my call.

The reason being that on WSJT-X he decoded two transmissions on the same minute from OH3T.

That was not a pirate, that was my development version of WSJTX-multi running one signal on JT65 and another on JT9.

Lets take two steps back..

My Vision

I have university background in signal processing and software sciences. I love digital modes, but I hate RTTY. RTTY is inefficient, breaks easily in congested band, and usually is frustrating mode to work. No pun intended, that mode is just not for me.

I also love working DX. 300+ DXCC in the log.

What if we could make working digital mode DX fun again. I think we can. What I particularly like in JT modes is the structure, powerful encoding in tough band conditions, tolerance to aurora, and the fact that anyone can work DX with JT modes. You do not need massive antennas or linear amplifiers to make a contact with a distant station. This mode is a great equalizer! For example, past 8 days in a row I have logged a VK station on every single day. On the best day 10+ VKs in the log. Most of the stations via long path during the early morning my time.

One of the biggest issues regarding JT9 of becoming de-facto DX digital mode is that it is slow. If we omit sending the grid information we can have one complete QSO in four (4!) minutes. For DX purposes that is way way way too slow QSO rate. Now.. what if we could run multiple QSO at the same time, with one rig?!

I did my first tests roughly 5 months ago. I tediously constructed an audio file of 16 JT9 transmissions. I recorded my CQ calls with virtual audio cable (VAC) and Audacity. I mixed them together in Audacity and then played the audio back to my KX3 and by remoting the local club station OH3NE I was able to see what my transmission looked like. And voila, 16 complete messages decoded. So the concept works.

The maximum simultaneous transmissions so far I have tested the software with (generated by WSJTX-multi) is 40. Again, receiving with the clubstation while the 10 meter band was closed. 10 meter band is a very nice local QSO band here in OH land.

Past few months I have been modifying the JT code and during the past few weeks I have been also testing the software with one transmission only. Now I have added second one, but in another mode. I am trying to avoid confusion, but apparently still generating it. I am sorry for the trouble, but I need to test the software somehow in "production", as software engineers like to say...

Vision Becoming Reality

Still quite a bit of work to be done...

• Dynamic power output control. 5 watts per signal is reasonable. 20 signals equals 50 watts out. With 200 watt rig or with linear amp the duty cycle is fine. One signal with 50 watt out is bad, so dynamic control is needed.
• Current user interface is suitable only for one QSO per GUI instance. New user interface is needed for effective multi QSO use.
• The internal mixer seems to be working fine, but more headroom is needed. Maybe 24bit audio instead of 16bit should be employed.
• I decided NOT to increase threads in the system. The modulator is looping, generating and mixing the tx signals one by one.
• Software is prone to errors, the whole QSO concept should be implemented as an object structure to clean up the software semantics.
• Logging to central DB need to be also included.
• Better split algorithms needs to be written.

Thanks for reading, CU on the bands!

Toni oh3t