volker@muehlhaus
Advanced Member level 6
Hello,
there are some HAM radio operators around here, so maybe this is of interest.
In our multi operator VHF/UHF contest location, we had an issue with the 144 MHz fundamental (!) signal beeing picked up by the 70 cm antenna which was driving the 432 MHz LNA into nonlinearity. That’s why we decided to add an additional high pass filter in the 432 MHz receive path, which indeed solved that problem.
Starting from an existing design by VE2ZAZ, I created a modified 70cm high pass filter that requires no wirewound coils and no tuning. Detailed design and simulation report, including measurement results and PCB files:
https://muehlhaus.com/support/ham/hpf432
Enjoy!
Volker
there are some HAM radio operators around here, so maybe this is of interest.
In our multi operator VHF/UHF contest location, we had an issue with the 144 MHz fundamental (!) signal beeing picked up by the 70 cm antenna which was driving the 432 MHz LNA into nonlinearity. That’s why we decided to add an additional high pass filter in the 432 MHz receive path, which indeed solved that problem.
Starting from an existing design by VE2ZAZ, I created a modified 70cm high pass filter that requires no wirewound coils and no tuning. Detailed design and simulation report, including measurement results and PCB files:
https://muehlhaus.com/support/ham/hpf432
Enjoy!
Volker