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To find the root cause of the spurs, I worked in 2 steps: 1. I took the front panel board out of the case and connected it with jumper wires to the main board. My objective was to eliminate possible EMI from the Pi Pico into the RF board. This did not make a difference for the spurs, as they just went down by 0.5dB which is the resolution of the TinySA. 2. In the si5351v2.c code I changed 8MA to 2MA. This results in approximately 5dBm less output power (33.5 vs 38.1dBm) but also a relative reduction of the spurs by approximately 7.5dB from -28.1dBc to -35.6dBc: Reduced output power is most probably due to the fact that the zBitx uses a diode ring mixer instead of the KISS-Mixer used in the sBitx and the oscillator power to the ring mixer is provided directly by the SI5351 CLK2 output (in reality an MS5351). Also, the IF diode ring mixer gets its oscillator signal directly from the SI5351 CLK1, whereas in the sBitx there is a buffer amplifier with two 2N3904. It could be that the much higher load on the SI5351 outputs, results in some intermodulation in the SI5351, which finally shows up as spurs. Given that these spurs are a showstopper, to transmit with the zBitx as the spurs are not at least 40dB suppressed, I am looking forward to further investigation and direction by hfsignals. On Mon, Apr 14, 2025 at 11:39 PM, Ron, N6YWU wrote: -- 73, Joerg - DB2OO

I have a minor update to make zbitx work with wsjtx/fldigi/etc and fixed cw latency. You have to update just the raspberry zero. From a terminal window, type this: cd ~/sbitx ./update sbitx this should do it

Hi! More work following the path that Ashhar suggested. I have also bought an older Icom 810H that has full duplex VHF/UHF. I'm doing initial experiments on Windows PC, but I have already demonstrated full Doppler shift control of sBitx acting as the 10m transceiver to a transverter, so this can all move to the sBitx.... GPREDICT re-installed due to better location, tracking any satellite I like. Does all the trig and doppler MATH RIGCTLD - previously studied and working; receives tcp/ip commands from GPREDIT to do doppler shift adjustments of sBitx or Icom radio Today: ROTCTLD -- figured out how to run this on a windows machine. Receives trig output of GPREDICT. Converts (in this case) to Yaesu type rotator commands for Az/ elevation and sends out serial port (in my case, COM4, 9600 baud) K3NG Rotator Controller -- I havent made a board for this yet. So I took one of my homebrew WINKEYER ARDUINO simulators, and reprogrammed it using K3NG code to "act like" the controller, handling Az, El controls, reading the CW speed control as if it were an azimuth potentiometer; running the display and activating the "key" and "PTT" to rotate clockwise or counterclockwise. The reprogramming of my Winkeyer Arduino appeard to be a huge success. I properly set the pins to run the display, which worked FINE. It was reading the speed pot as an azimuth reading, and if I pushed "buttons" it would read different elevations. ROTCLD happily connected to it at 9600 baud, and the "rotator controller" accepted commands and displayed them. I was not able on the first test to monitor whether it activated simulated motor controls (key output, etc) -- but that will come. So huge success here and soon (days, weeks?) I should be able to lay out a board (many others have done so before me, but some just did crazy wiring between variuous "shields") to put all this in a neat little package with relay outputs, possibly with PWM output (dunno)., to control available rotators for real. 73 Gordon KX4Z

I've been digging through all the schematics and I don't see anything for the rotary encoder board? While the board that's in there is functional, I'm not a fan of how bent the board is. Seems like a quick easy task for me to design a board that fits properly, but I need to know which encoders are used and if there's any other devices on that board.

After my first successful FT8 QSOs with the zBitx, I switched it off. When I later switched it on again in FT8 mode, I was surprised, that I did not have any FT8 decodes, although I could clearly hear and see the FT8 signals. Connecting a monitor showed, that the time was off, i.e. the real time clock obviously does not work. I opened my zBitx (very nice concept of 3D printed parts for the case!) and took a picture of the mainboard: There is a 2 pin connector next to the RTC DS3231, which I guess is J7 from the schematics. Most probably this should be connected to a battery, but there is none!? Has this been an oversight during assembly and if yes, will a CMOS BIOS backup battery work? -- 73, Joerg - DB2OO

Hello, My sBitx v3 has killed next final MOSFET. Again, as previously, only one was dead: However, this time the failure wasn't caused by overheating (the fan was cooling the heatsink and its temperature was ca 30 C) but by SWR. I was operating my device remotely via WiFi in FT8 mode, and my ATU got crazy. Unfortunately, I could only see the increase of SWR on my laptop, and the connection got broken. I couldn't cease the transmission immediately. When I reached the sBitx, it already showed the output power 0W. Well, when replacing them, I have exchanged the mica insulators with AlN ones. Let's see how long is it going to survive now. BTW. Is it possible to replace IRF510 with other MOSFETs (maybe more expensive, but offering higher maximum voltage and better power at 28 MHz)? 73, Wojtek SP5DAA