Miernik SWR Arduino.
Hi!

I built the Arduino SWR Scanner with the software from SP3NYR and it works quite well. Thank You! Still, I noticed that the noise from the antenna could influence the measurements greatly, as the RF signal from the DDS is relatively weak. So I have just built a version with a 20 dB RF amplifier after the DDS and the existing op-amps demoted to voltage followers. It seems to be working as expected, but the calibration procedure does not work well for this version.

The "z" coefficient is calculated in the hidden I4 cell of the Excel sheet. Without the amplifier, it is usually a negative number, but it is presented as ABS() to the user and sent through the terminal to Arduino's EEPROM as a positive number. But, now, with the amplifier, "z" is sometimes positive in I4, so it should be written to the EEPROM as a NEGATIVE number, which is not possible through the terminal. Still I found a workaround. I read the EEPROM and saw that the coefficients were stored as LONGs. So I tried to send -94 through the terminal as 2^32 - 94 (i.e. "4294967202z"). And it worked! The Arduino program accepted this as setting "z" to -94.

Still it would be nice if SP3NYR would somehow correct this issue in his otherwise clever calibration procedure. It would help further improvements.

Thank You!

73s
Mire YU2ZZ

https://yu2zz.wordpress.com/2018/04/16/arduino-swr-scanner/


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