Just a heads up on a modular build of the BiTX40. If you haven't seen it, a young ham in Belgium (ON6RF) laid out a set of pc boards to build a modular version of the BiTX and placed the project on Hackaday - <https://hackaday.io/project/20067-puzzle-radio-building-blocks>. Since I've been giving classes to some local hams on working with surface mount components, this looked like an excellent class project. I had already built three BiTX4Ver3 units as well as a BiTX20A and a G6LBQ MK1 so I was fairly certain I knew what to expect. After reviewing all of the board layouts I ordered 10 pc boards from PCBWAY for a cost of $32.00 ($5.00 for the 10 boards and $27 shipping via DHL which arrived 5 days after placing the order). After laying out a 100X140 mm "motherboard" for the modules to plug in to, I assembled two prototypes using Si5351 VFOs to present to the class. Both prototypes worked as expected with no surprises with the exception that I had NO birdies other than the notorious one at 7.2 MHz and that one you have to listen closely to hear.
What makes this a great group learning project is it breaks down the transceiver into functional blocks, perfect for an easier understanding of how everything works. It also allows the builder to make modifications to particular parts of the circuit easily without having to disassemble the entire rig. Because the cost of the pc boards is so low the plan for the class is to give each builder 2 sets of boards. The first set will be built as designed. When that build is completed and working the second set of boards can be used to build separate blocks to try some of the modifications available. This way, if a mod isn't successful or an improvement over the original design, the rig can be restored to operational condition by simply removing and replacing the module with the original.
As a caveat, there are two things to mention. First, the pc board layout only has one bi-directional amp module and, of course, the rig requires three. I simply made a new gerber file containing two more amps and had 10 pc boards made. Second, the only thing that was over looked in the original layout is there is no provision for connecting M1 and M2 from the PA board relay to the audio amp board. This was overcome by adding a plug on the motherboard to make the connections.
If anyone is interested in the project you may email me and I'd be happy to share my notes and my gerber file for the motherboard. All credit goes to ON6RF for doing all of the heavy lifting:-)
--73-- Mike -- W0MNE