Transceiver is pretty simple — it’s based on prebuilt modules from «60dbm» and trx-duo board from aliexpress with minor changes.
This post is about trx-duo board itself.
Stock TRX-DUO board:
I modified it with replacing stock clock generator (125MHz) with Crystek CVHD-950 (122.88Mhz) (It also requires to recompile binary for FPGA — redpitaya 122.88 binaries are for Xilinx 7020 chip, but TRX-DUO uses 7010.
As «extclk» is just a caption without any connections the only way to use different generator is just to replace stock clock with the new one:
All in place:
As it’s Red Pitaya clone — i’m using Pavel’s Demin project called «Red Pitaya Notes».
https://pavel-demin.github.io/red-pitaya-notes/
Also RX1 ADC died after few weeks of using — it looks like one input just shorted to the Vcm inside the chip.
I was able to fix it partially. It works with transformer central point on the ground instead of Vcm, with bias above 0volt and with lower sense.
And i just replaced stock LPF filter on RX1 with 7 order chebyshev LPF on the piece of textolite with 0805 smd components. Because it’s pretty complicated for me to work with small stock smd components:
Now RX1 is usable.
I have replacement for ADC, but not sure that i want to put it there. Will see…
