Digital Modes with the Sudden Transceiver
When I design something I often think "down the road" which drives the rig construction using modules and access to the various circuit boards. I also think about using the rig itself as an experimental platform.
My thoughts also consider where the "hobby is" relative to what I am building. If you open a new buggy whip factory you must think seriously how many would actually be sold/used.
For a variety reasons many in our hobby have moved from the standalone rig to one that is mated with the power of a computer. I recently heard a big time 160 Meter DXer who lamented there were no longer DX SSB/CW ops on that band--all of his friends are now on FT8. The digital modes can be done at QRP power levels and modest antennas. The playing field is "leveled" with the digital modes!
The Sudden Transceiver fits in the framework just outlined and thus the decision to test the Sudden Transceiver using the digital modes. In my mind the Si5351 PLL gives the needed stability to "do digital". I have serious reservations that with an analog VFO it would be possible to operate the digital modes. There are those who will tell me --you are wrong -- but just yesterday the Sudden Transceiver started operating digital when the garage was a cool 68 F and worked flawlessly with no frequency movementt when it hit 100F late in the afternoon. Try that with an anlog VFO!
The beauty of my approach is that the Sudden Transceiver remains in tact and all the Digital Stuff is outboard. The $10 addition of a digital sound card interface plus some connectors and cables from the junk box is all that was needed. For the digital program I used WSJT-X which has a menu of optional digital modes. We now will cover:
But first how well does this work? Bottom line it does digital and this morning I was spotted in Australia running 5 watts to a droopy dipole. (VK2ALR)
Then of course there are those who want to do FT8 --well it does it just FB. Here is a snap from 8/23 at 8 AM in the morning using a droopy dipole. So the receiver side is quite good for this mode. Keep in mind this is 40M with a less than ideal antenna.
The external harware consists of digital inteface to the computer sound card. This sounds really exotic but is nothing more than three diodes, three resistors, two capacitors, two modem transformers, an optical coupler (4N25). This is something that could be homebrewed but I bought a kit for less than $10 delivered to my door.
Essentially this kit provides a somewhat isolated interface to the computer and provides a means of using the transmit command from the program to "turn on" the transmitter for sending the digital information. Hidden in the interface are various methods for causing the TR and these are selected in the WSJT-X program. I am using COM 1 and DTR. You also enter into the WSJT-X program your call sign and grid square location (WSPR, JT8) and power level for WSPR. Variants in the program for other digital modes (FT8) let you create custom messages such as your qth, name etc.
Here is the link to purchase this kit.
The are sveral sets of connections to/from the interface board.
I could spend hours and hours trying to describe the set up of the software but an easier way for both you and ME, just visit youtube and type in FT8. Just watch the videos and you will see what you need to do.
Just a couple of things:
Final Digi Box