All very good observations.
First of all the credit for the original design goes to Erik Kaashoek.? He developed it much further and much more polished than this project, producing the TinySA and recently the TinySA Ultra.? This was started before the TinySA became commercial, several of us took on the task of making our own version of Eriks original using the ESP32.? John WA2FZW contributed a lot of time improving the software, and Glen VK3PE created his own PCB design.? Unless you particularly want to make your own you would be better off buying a TinySA or TinySA Ultra from a reputable source.? Personally I like making things and on the way learning something.? It is rather boring if something just works first time!
I am not an electronic engineer and not trained in RF design - so all suggestions, improvements and even criticism are very welcome.??
The LPF in practice is closer to your second trace with real components, actually a bit worse.? It does affect results at those higher frequencies.? I don't use mine above 150MHz so I am OK with it.? If you can come up with a better design I would really appreciate the input.? The LPF is mainly there to suppress the LO leaking through the mixer when the port is used as signal generator as well as possible alias effects.? No doubt smaller parts would help, but then harder to solder.? I had the idea that this could become a club project so ease of soldering was important.? Even 1206 parts would be too too difficult for many unfortunately.
I have not come across RFSim99 before - will take a look at it - thanks.
The other limitation was using four of the pre-made Si4432 boards.? If starting from scratch it would be far better to not use these modules and fit the SI4432 directly to the PCB, saving space and allowing the use of one clock source as you suggest.? This would also remove the need to modify the modules with the removal of their filtering.? The separate resonators on each module is far from ideal as they all drift slightly differently to each other.
It should be understood however that the frequency resolution of the SI4432 is not that good, and the smallest RBW is 2.8kHz so it is not that critical in most circumstances.
I would say the software of this project is usable but still could do with some work.? For example there are no markers on the web page (they are there on the local display), it would be handy to be able to easily use the two outputs as independent signal generators, amplitude modulation of the signal generator would be nice, but it is useable especially with the encoder and sees frequent use on my test bench.? The hardware allows for these improvements but time available for coding does not.
I do seem to recall using the impedance calculator on the JLPCB web site for the four layer PCB to get the track width but may not have been consistent in applying it.
Which country are you in?
Dave M0WID
